Caribbean - Central America Weather

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
451 AM AST Mon Jun 5 2023


.SYNOPSIS...
Another hot week is expected for the islands. Heat indices above 108
degrees are anticipated for many urban and coastal areas across
Puerto Rico, and from 102 to 107 for the U.S. Virgin Islands, each
day from 10 AM through 5 PM AST. Hazy skies due to Saharan dust is
also expected, with the highest concentrations today and Tuesday,
and again on Thursday. Rainfall activity will be limited at least
through the first half of the workweek. Tranquil marine conditions
will continue trough the week.

&&

.SHORT TERM...Today through Wednesday...

Since midnight, Doppler Radar indicated some passing showers across
southern and easternmost municipalities, including Vieques. A few
passing showers reached some more interior municipalities. No rain
was detected over the USVI. Notably, a brief thunderstorm managed to
form over waters north of Luquillo and Fajardo. Minimum temperatures
have ranged from the upper 60s at higher elevations of Puerto Rico
to the warm low 80s at lower elevations of the islands.

No major changes to the short term forecast. Current satellite
derived precipitable water (PWAT) values are up to 2.0 inches over
the region with drier air with around 1.7 inches filtering in from
the southeast. This drier air includes a Saharan Air Layer (SAL)
which will promote hazy skies over the region for most of the short
term period. A drier pattern will now start to dominate as this air
mass continues to filter into the islands lowering PWAT to below
normal values for this time of the year. Any available moisture
would mostly remain in the lower levels as a ridge and dry air will
remain in the mid to upper levels. Only passing showers are
expected, mainly over southern Puerto Rico, with weak afternoon
convection posible mainly across north-central to northwestern PR.

The deep layer high pressure system over the eastern Atlantic and a
deep layer trough are promoting breezy southerly winds over the
islands, with steering flow at 16-20 kts today. Backing is forecast
tomorrow with winds becoming more from the southeast as the trough
starts to lift. Available humidity and southerly winds will continue
to promote high heat indices today, humidity today shouldn't
decrease enough to affect apparent temperatures over the islands.
Maximum temperatures can reach the mid 90s across coastal and urban
areas of Puerto Rico, and the upper 80s to low 90s across the USVI.
An Excessive Heat Warning will be in effect from 10 AM to 5 PM today
for north-central municipalities, San Juan and Vicinity and Culebra,
with heat indices above 111 degrees. A Heat Advisory will be in
effect from 10 AM to 5 PM today for eastern, southeastern, eastern-
interior, northwestern and western municipalities, with heat indices
above 108 degrees. Heat indices above 102 can be observed across
other coastal areas of Puerto Rico, Vieques, and the USVI.

&&

.LONG TERM...Thursday through Tuesday...
Stable weather conditions are expected to prevail during the long-
term forecast period. A high pressure system at all levels will
continue to hold just northeast of the islands. This feature will
drive the winds from the southeast through Saturday. Breezy
conditions will persist throughout this period, with a low level
steering flow of 15-20 knots. A Saharan Air Layer will remain in
place too, with hazy skies expected. So far, the aerosol models have
the highest concentration lingering into early Friday. Due to dry
air aloft, shower activity will be limited during this period. ON
Friday, fragmented patches of moisture associated with old frontal
boundaries will be push into the islands from the circulation of the
high pressure. Moisture content will increase, and so will the
probability of showers, with passing activity expected to reach the
eastern coast of Puerto Rico and the U.S. Virgin Islands. This
activity is not expected to be significant.

For the weekend, another pulse of dry air and Saharan particulate
will approach the islands. The surface high will weaken a little,
allowing for the trade winds to resume from the east. However, this
will not last long, as the winds will veer from the southeast by
early next week. During this period, any rainfall activity will be
associated with small patches of moisture approaching the area.
However, the climatological outlook from the Climate Prediction
Center does favor below than normal precipitation for this period,
and since June is typically a dry month, little rainfall
accumulation is anticipated.

In terms of temperatures, 925 mb temperatures will drop a little by
Friday, and again on Monday and Tuesday. This may allow for just a
very small relief from the very high heat indices experienced so
far. Nevertheless, values are expected to remain around advisory or
warning criteria, especially for the urban areas of northern and
northwestern Puerto Rico, and between 102 to 107 for the Virgin
Islands. The users are advised to follow heat prevention guidance
during this prolonged hot forecast period.

&&

.AVIATION...
Mainly VFR conditions are expected across the terminals
during the next 24 hours. Low level southerly winds up to 15-20 kts
will continue today. Saharan dust will filter into the region
promoting HZ during the upcoming days.

&&

.MARINE...
Seas 1-3 feet and winds up to 9 kts were observed in the nearshore
buoys. No significant events are expected to impact the local
waters, and seas 2-4 feet will prevail throughout the forecast
period. The risk of rip currents will be low for all the local
beaches.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...Excessive Heat Watch through Tuesday afternoon for
PRZ001-005-008-012.

Excessive Heat Warning from 10 AM this morning to 5 PM AST this
afternoon for PRZ001-005-012.

Heat Advisory from 10 AM this morning to 5 PM AST this afternoon
for PRZ002>004-008-010.

VI...None.
AM...None.
&&

$$

SHORT TERM...MRR
LONG TERM....ERG

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
403 AM AST Tue Jun 6 2023

.SYNOPSIS...
Very hot conditions will persist for the rest of the workweek
across the urban and coastal areas of the islands. The highest
heat indices are once again expected for the northern
municipalities of Puerto Rico and Culebra. Skies will be hazy due
to Saharan dust today, and this particulate will gradually
diminish through the workweek. No significant rainfall event is
expected for the next several days.


&&

.SHORT TERM...Today through Thursday...

Since midnight, no rainfall accumulations were detected across the
islands with small showers only over the Caribbean Sea. Minimum
temperatures have ranged from the upper 60s at higher elevations of
Puerto Rico to the upper 70s to the warm low 80s at lower elevations
of the islands. Current satellite derived precipitable water (PWAT)
values show values up to around 1.6 inches over eastern PR and the
local islands, gradually decreasing to around 1.37 inches over
northwestern PR. Dry air with Saharan dust will continue to filter
into the islands, promoting hazy skies over the region. During the
next few days precipitable water values are expected to reach below
normal values for this time of the year. Any available moisture
would remain in the lower levels, mostly dry air will be present in
the mid to upper levels along with ridging. Only passing showers are
expected across windward sectors of the islands, weak afternoon
convection posible mainly across north-central to northwestern PR.

Winds are expected to back and become more southeasterly today as
the deep layer high pressure system over the eastern Atlantic
continues to influence the region. Overall dry and stable conditions
are expected to prevail. However, available moisture and windflow
will continue to promote high apparent temperatures over the
islands. Maximum temperatures can reach the mid 90s across coastal
and urban areas of Puerto Rico, and the upper 80s to low 90s across
the USVI. An Excessive Heat Warning will be in effect from 10 AM to
5 PM today for northwester, north-central municipalities, as well as
for San Juan and Vicinity and Culebra, with heat indices above 111
degrees. A Heat Advisory will be in effect from 10 AM to 5 PM today
for northeastern, eastern-interior, and western municipalities, with
heat indices above 108 degrees. Heat indices above 102 can be
observed across other coastal areas of Puerto Rico, Vieques, and the
USVI.

.LONG TERM...Friday through Wednesday...

A high pressure at all levels will continue to hold across the
central Atlantic. This high will drive the winds from the
southeast at speeds of 12 to 20 knots. This feature will also
maintain unfavorable conditions aloft for shower development,
although fragmented patches of moisture carried by the trade winds
will move in at times. Slight concentrations of Saharan dust will
be present with this flow, with skies looking hazy at times. On
Friday, a tropical wave moves over the Caribbean waters, but the
bulk of the moisture should stay over the waters. For the next
workweek, the high will move a little to the east, and the winds
will back from the east, but still enhanced, with speeds around 20
knots. Generally stable weather is expected through Monday, but
another low level disturbance will approach the northeastern
Caribbean on Tuesday and Wednesday. This could increase the
frequency of showers over the islands, but the high at the mid and
upper levels will act against strong shower development.
Additionally, the climatological outlooks from CPC also indicate
below than normal precipitation next week, and since June is
already a dry month, flooding rains are not anticipated.

The 925 mb temperatures will stay around two standard deviations
above the climatological levels through at least early next week,
meaning that above than normal temperatures will persist. With
tropical moisture at the low levels filtering from the Caribbean
Sea, the significant heat risk will persist, especially along the
northern coast and urban areas of Puerto Rico and Culebra. Other
urban areas of Puerto Rico, as well as the U.S. Virgin Islands
will experience heat indices of 102 to 107 during these days.


&&

.AVIATION...Mainly VFR conditions are expected across the terminals
during the next 24 hours. Saharan dust will continue filter into the
region and promoting HZ during the upcoming days. Winds will be more
southeasterly at up to around 17 kts with higher gusts.


&&

.MARINE...
Seas at 1 to 4 feet will persist for the next several days. Winds
will remain from the souteast at 10 to 15 knots. The risk of rip
currents will be low today.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
417 AM AST Wed Jun 7 2023


.SYNOPSIS...
Excessive heat conditions will persist through the end of the week
and the weekend for northern Puerto Rico, with heat indices over
112 degrees expected. Other urban and coastal areas along Puerto
Rico and the U.S. Virgin Islands will be above 102 degrees. Dry
weather will persist throughout the weekend, with increasing
chances for showers next Tuesday.

&&

.SHORT TERM...Today through Friday...

No rainfall accumulations were detected across the islands by the
Doppler Radar since midnight. Small showers were mostly seen over
the Caribbean Sea, with a few very weak ones reaching southern PR
near midnight. Lows have ranged from the upper 60s at higher
elevations of Puerto Rico from the upper 70s to the warm low 80s at
lower elevations of the islands.

No major changes to the forecast. A deep layer high pressure system
over the Atlantic east of the islands will continue to be present
throughout the period. This will promote overall stability and
subsidence over the region. Winds will be from the southeast and
will continue to bring dry air with Saharan Dust particles. Any
available moisture will be mostly confined to the lower levels with
mostly dry air above 850 mb. Current satellite derived precipitable
water (PWAT) values show around 1.5 to 1.6 inches over the coastal
waters, local islands, and eastern PR, and around 1.4 inches across
the rest of PR. Hazy skies will continue today due to the Saharan
Air Layer (SAL); dust particles will continue to linger through the
workweek. PWAT is expected to continue mainly at below normal values
for the period, with a slight increase on Friday as fragmented
moisture reaches the region. On Friday, a tropical wave will move
over Caribbean Waters but will have little effect on the islands.
With dry and stable conditions aloft, only some brief passing
showers are expected across windward sectors mainly during the
morning or night hours and only weak, shallow, afternoon convection
is possible over northwestern PR.

Available moisture and southeasterly winds will continue to promote
high heat indices over the islands during the period. Temperatures
at 925 mb will continue to be two standard deviations above normal
levels. Highs can reach the low to mid 90s across coastal and urban
areas of Puerto Rico, and the upper 80s to low 90s across the USVI.
An Excessive Heat Warning will be in effect from 10 AM to 5 PM today
for north-central municipalities, with heat indices above 111
degrees. A Heat Advisory will be in effect from 10 AM to 5 PM today
for San Juan and Vicinity and Culebra, with heat indices above 108
degrees. Heat indices above 102 can be observed across other coastal
areas of Puerto Rico, Vieques, and the USVI.


&&

.LONG TERM...Saturday through Thursday...
High pressure at all levels will continue to drive east southeast
winds at 15 to 20 knots throughout the weekend. Unfavorable
conditions for rain formation are expected to continue as the high
promotes dry air above 850 mb. By Monday, the high reposition a
little to the west and the winds will back from the east. This
chance in winds is expected to bring a slight relief to the
intense temperatures and heat indices that have been experienced
across the islands. However, the heat indices are still expected
to remain above 108 along some sections of northern Puerto Rico.

By late Monday and Tuesday, an area of enhanced moisture detached
from an old frontal boundary is expected to reach the islands,
increasing cloudiness and the frequency of showers. So far, this
feature is expected to only bring moderate rainfall amounts. Then,
the northern-most moisture field of a tropical wave will also
bring some moisture over the islands, with a few more showers
anticipated. Low concentrations of Saharan dust will be embedded
in the wind flow by the end of the period, with hazy skies
possible.


&&

.AVIATION...Mainly VFR conditions are expected across all terminals.
HZ due to saharan dust will continue but VIS will be greater than
6SM. Generally southeasterly winds will be at 10-15 kts with higher
gusts.


&&

.MARINE...
Seas 1 to 3 feet are being observed in the CariCOOS buoy network.
Marine conditions of 2 to 4 feet will persist through must of the
period, with increasing winds causing choppy seas next Sunday.
There is a low risk of rip currents for today.


&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...Heat Advisory from 10 AM this morning to 5 PM AST this afternoon
for PRZ001-012.

Excessive Heat Watch from this afternoon through Thursday
afternoon for PRZ001-005.

Excessive Heat Warning from 10 AM this morning to 5 PM AST this
afternoon for PRZ005.

VI...None.
AM...None.
&&

$$

SHORT TERM...MRR
LONG TERM....ERG

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
504 AM AST Thu Jun 8 2023


.SYNOPSIS...

Today, excessive heat conditions will persist across Puerto Rico
and the U.S. Virgin Islands. Hazy skies due to Saharan dust
particles will continue to gradually decrease through the
workweek. At this time, no significant rainfall event is expected
during the short-term period. However, early mid-week condtions
may be prone to moderate rainfall. A Heat Watch is now in effect
for Puerto Rico until Saturday afternoon.

&&

.SHORT TERM...Today through Saturday...

Mostly clear to partly cloudy skies were noted overnight into the
morning hours, with only light showers and minimal rainfall
accumulations were detected over parts of the south and east coastal
areas of Puerto Rico, as well as across portions of the Caribbean
waters and passages. Lows temperatures have so far ranged from the
upper 60s to low 70s in the higher elevations of Puerto Rico and
from the upper 70s to the low 80s at coastal areas of the islands.
Winds were generally calm to light and variable over land areas and
mainly from the southeast over the coastal waters.

Deep layered high pressure ridging continued across the region and
is forecast to persist through the entire period. This will
therefore promote strong subsidence aloft with a very dry and stable
airmass over the region. Prevailing low level steering winds will be
from the southeast and will therefore continue to spread relatively
hot and dry air along with a lower concentration of Saharan Dust
particulates across the forecast area. Moisture will be limited to
the low levels and will mainly that brought in by the prevailing
southeast wind flow. Overall dry and stable conditions will
continue in the mid to upper levels. Recent satellite derived
precipitable water values product (PWAT) suggest 1.0 to 1.5 inches
spread over the region with a slight increase to 1.50 to 1.80 inches
expected by Friday and Saturday mainly due to pockets of advected
moisture brought in by the prevailing wind flow and the passage of a
weak tropical wave moving mainly south of the region by Friday and
Saturday. As a result so far expect very little change in the
overall weather pattern and wind flow through the period,with only
brief passing showers expected to move across the windward sections
of the islands mainly during the overnight and early morning hours
with only shallow diurnally driven afternoon convection possible
over northwestern PR. Limited or no shower activity is expected over
U.S Virgin Islands as well as Culebra and Vieques where mostly hot
and sunny conditions will prevail with slight chance of isolated
showers possible mainly downwind of the islands.

The fairly moist and light to moderate southeast low level winds
will continue to promote high heat indices over the islands during
the period. Temperatures at 925 mb are still forecast to remain to
at two standard deviations above normal levels through Friday.
Therefore daytime high will continue slightly above normal reaching
between low to mid 90s across coastal and urban areas. An Excessive
Heat Warning will be in effect from 10 AM to 5 PM today for north-
central municipalities,San Juan and Vicinity with heat indices above
111 degrees. A Heat Advisory will be in effect from 10 AM to 5 PM
today for some of the west and northwest, and portion of the Caguas
and Gurabo area and Culebra, where heat indices are expected to
reach above 108 degrees. Heat indices above 102 can be observed
across other coastal areas of Puerto Rico, Vieques, and the USVI.
Based on the present and expected conditions, an excessive heat
watch will remain in effect through at least Saturday afternoon.

&&

.LONG TERM...Sunday through Friday...

No significant changes were introduced in the long-term forecast.
A high-pressure system at all levels of the atmosphere will continue
to drive moderate to locally fresh southeasterly winds around 15
and 20 knots through the end of the weekend. Therefore, expect
unfavorable conditions for rain development as the high promotes
dry air above 850 mb. By the beginning of the workweek, winds will
become easterly as the high pressure repositions slightly to the
west of the forecast area. This wind shift will bring a slight
relief in warm temperatures and the heat indices that people
across Puerto Rico and the U.S. Virgin Islands have been
experiencing. Nonetheless, heat indices over the tropical islands
will remain above 108 along some sections of northern Puerto Rico.

By late Tuesday into mid-week, expect a change in weather conditions.
Model guidance continues to suggest that an area of enhanced
moisture detached from an old frontal boundary will reach the
local islands, increasing cloudiness and the chance for afternoon
convection across the western quadrant of Puerto Rico and morning
activity across the eastern part of the island. At this time, we
anticipate moderate rainfall amounts. Also, moisture from a
tropical wave will bring some extra showers.

Last but not least, low concentrations of Saharan dust will be embedded
in the wind flow by the end of the period. Therefore, expect hazy
skies.

&&

.AVIATION...VFR conditions are expected at all terminals.
SCT lyrs nr FL022...FL040...SKC ABV. Isold SHRA mainly ovr Caribbean
waters btw PR and USVI. SFC Wnds calm to lgt/vrb, and generally fm
southeasterly btw 15-20kts blo FL120. No sig operational wx impacts
attm.

&&

.MARINE...Calm marine conditions will persist with seas at 4 feet
or less across most of the nearshore waters. Moderate to locally
fresh southeasterly winds will continue through at least Sunday.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...Excessive Heat Warning until 5 PM AST this afternoon for PRZ001-
005.

Excessive Heat Watch from this afternoon through Saturday
afternoon for PRZ001-004-005-008-010.

Excessive Heat Watch through Saturday afternoon for PRZ002-003-
006-007-009-011>013.

Heat Advisory until 5 PM AST this afternoon for PRZ004-008-010-
012.

VI...None.
AM...None.
&&

$$

SHORT TERM/AVIATION...RAM
LONG TERM....MMC

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
453 AM AST Fri Jun 9 2023


.SYNOPSIS...

Today, expect another hot day across the local islands. The
southeasterly wind flow will prevail through the short-term
period. Saharan dust will begin to gradually diminish across the
region. At this time, no significant or heavy rain is expected
during the short-term period.

&&

.SHORT TERM...Today through Sunday...

For Today...A mix of sunshine and partly cloudy skies will prevail
across the islands with limited shower activity expected during the
afternoon hours. Traces of suspended Saharan Dust particulates will
linger today but is to diminish and move away from the region over
the upcoming weekend. The dominant low level southeasterly wind flow
will persist with only pockets of shallow moisture expected to
affect the islands. This along with intense daytime heating may lead
to isolated to scattered shower development mainly across the
northwestern portions of Puerto Rico, in the east interior and
mainly downwind and south of the U.S Virgin Islands where hot and
sunny conditions will prevail.

Hot, humid and overall dry conditions will prevail each day through
the upcoming weekend. Recent blended satellite derived precipitable
water values were between 1.50 to 1.85 inches across the region,
suggesting a slight increase in low level moisture along with the
passing showers noted across the Caribbean waters and the Anegada
passage. A weak tropical wave is expected to pass well south of the
islands later today through Saturday, but still no significant
moisture transport and impacts are anticipated with this feature
across the islands. Therefore expect brief passing showers to
affect the coastal waters and south and east coastal areas due the
overnight and early morning hours, followed by locally and
diurnally induced showers mainly over parts of northwest Puerto
Rico, with lesser activity expected elsewhere and downwind of the
U.S Virgin islands.

Main Impacts during period. Once again, the low temperatures will
will vary between the mid-60s and low 70s in mountainous regions and
upper 70s to low 80 along the coastal and in urban areas. Maximum
temperatures will be in the low to mid 90s across the coastal and
urban areas, and in the mid to upper 80s in the higher elevations of
Puerto Rico through the weekend. Heat indices are expected to
exceed the low and mid 100 degrees Fahrenheit each day, with
Excessive Heat Warnings and Advisories likely through the weekend.
Overall rainfall activity and moisture transport is expected to be
will be suppressed and limited by the deep layered high pressure
ridge which will remain the dominant feature through the period.
Consequently shower activity if any will be focused along portions
of the south and east coastal areas during the overnight and early
morning hours, followed by limited afternoon shower development in
the northwest sections of Puerto Rico, downwind of the U.S Virgin
Islands and over the coastal waters.

The Excessive Heat Watch continues in effect for Puerto Rico,
particularly in the coastal and urban areas of northern Puerto Rico.
The high humidity and air temperatures will cause a continuation of
the hot and sticky weather conditions, with maximum heat indices
ranging from 105 to 115 degrees Fahrenheit or more in isolated areas
along the north coastal area of Puerto Rico. The U.S. Virgin Islands
may also experience another hot day with possible maximum heat
indices ranging from 102 to 105 degrees Fahrenheit especially the
island of St Croix.

An Excessive Heat Watch will now remain in effect until Sunday
afternoon across much of Puerto Rico, including Culebra and Vieques
and Portions of the U.s. Virgin Islands.

&&

.LONG TERM...Monday through Saturday...

This forecast period remains unchanged. Latest model guidance
continues to suggest moderate to locally fresh southeasterly winds
around 15 to 20 knots through the end of the weekend. This wind
flow is associated with a high-pressure system at all levels of
the atmosphere. This pattern will maintain unfavorable conditions
for rain development as the subsidence from the high pressure
promotes dry air above 850 mb. By the beginning of the workweek,
winds will become easterly as the high pressure repositions
slightly to the west of the forecast area. This wind shift will
bring a slight relief in the warm temperatures pattern and the
heat indices that people across Puerto Rico, Vieques, Culebra, and
the U.S. Virgin Islands have been experiencing. Nonetheless, heat
indices in the low areas will remain above 108, especially along
the northern sections of Puerto Rico.

At this time, Tuesday into mid-week continues to be the day when
the weather conditions will change slightly. This change is due
to an area of enhanced moisture that will detach from an old frontal
boundary and merge with a tropical wave heading into the forecast
area. The combination of these two weather features will increase
cloudiness and the chance for afternoon convection across the
western quadrant of Puerto Rico and morning activity across the
eastern part of the island. We anticipate moderate rainfall
amounts across the local islands. Nonetheless, expect the dry
pattern to return by the end of the workweek. Last but not least,
low concentrations of Saharan dust will be embedded in the wind
flow bringing hazy skies by the end of the period.

&&

.AVIATION...VFR conditions will continue. SFC wnds calm to
lgt/variable overnight, bcmg fm ESE-SE at 10-15 kt with ocnly hir
gusts aft 09/14Z. L/LVL wnds fm SE 15-20 kts BLO FL180. Few
-SHRA/SHRA may affect the regional waters btw E PR and USVI and
the surrounding Caribbean waters south of PR durg prd but no
significant wx impacts fcst at local terminals durg prd. Wdly SCT
lyrs nr FL022...FL040... mstly SKC ABV.

&&

.MARINE...Calm marine conditions will persist with seas at 4 feet
or less across most of the local waters. Seas are reaching the
Atlantic waters from the ENE. Expect the moderate to locally fresh
southeasterly winds to prevail across the region.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
419 AM AST Sat Jun 10 2023

.SYNOPSIS...

Expect warm conditions continue for the next several days across
the local islands. Passing showers will continue during the early
morning hours across the southeastern portions of Puerto Rico,
with no impacts anticipated. Saharan dust will continue to
diminish across the region through the weekend.

&&

.SHORT TERM...Today through Monday...

Overnight passing clouds with occasional showers affected the
coastal waters and portions of the east and southeast sections of
Puerto Rico as well as the U.S Virgin Islands and surrounding
waters. Estimated rainfall amounts ranged between a tenth of an inch
and half an inch with the heaviest rains. Most of the heavy rainfall
however was over the coastal waters just southeast of Puerto Rico
accompanying and easterly perturbation and low convergent band now
crossing the region.

For the rest of today...A mix of sunshine and partly cloudy to
variably cloudy skies can be expected with sufficient moisture
availability to combine with local effects and daytime heating to
promote isolated to scattered late morning and afternoon showers. A
prevailing southeast low level wind flow will persist today but is
forecast to become more east southeast by Sunday then easterly on
Monday, as a surface high pressure ridge will build just north of
the forecast area. This will result in a gradually increase in the
easterly trades by the end of the period. Patches of shallow
moisture will however continue be transported across the region but
is expected to be less frequent Sunday and into Monday. Afternoon
convection should be focused over parts of the east interior and
northeast Puerto Rico as well as sections of northwest PR during the
late afternoon hours today and Sunday, then over part of the west
interior on Monday as winds become more easterly. Over the U.S
Virgin islands, shower activity during the day will be mainly on the
west-end of the islands or just downwind, but again mainly hot and
mostly sunny to partly clouds skies will prevail with no significant
rainfall accumulations are expected.

Warm and humid weather trend will continue through the rest of the
weekend and at least into Monday. Recent blended satellite derived
precipitable water product suggested values between 1.50 to 1.90
inches now across the region accompanying the surge of moisture
crossing the region However by Sunday and Monday, the PWAT values
are forecast to diminish and range between 1.00 and 1.50 inches as
winds become more easterly.

Main Impacts during period will continue to be the excessive heat
conditions through the weekend and at least until Monday, with
temperatures expected to continue to reach the low 90s and above the
daily normals especially along the north coastal areas each day. The
warmer low temperatures will persist and vary between the mid-60s
and low 70s in mountainous regions and upper 70s to low 80 along the
coastal and in urban areas. Heat indices are expected to exceed the
low and mid 100 degrees Fahrenheit, with Excessive Heat Warnings and
Advisories now likely through Monday for portion of the islands. As
a result an Excessive Heat Watch will remain in effect for Puerto
Rico and portions of the U.S Virgin Islands, particularly St Croix.


&&

.LONG TERM...Tuesday through Sunday...

The latest model guidance suggests that Tuesday into mid-week will be
the best days for the weather to change slightly. This change
will be associated with an enhanced moisture area that will detach
from an old frontal boundary and merge with a tropical wave
heading into the forecast area. The combination of these two
weather features will increase cloudiness and the chance for
afternoon convection across the western quadrant of Puerto Rico
and morning activity across the eastern part of the island. We
anticipate moderate rainfall amounts across the local islands. On
Tuesday, expect the easterly flow to dominate as the high pressure
remains west of the forecast area. This wind flow will maintain a
slight relief in the warm temperatures pattern and the heat
indices that people across Puerto Rico, Vieques, Culebra, and the
U.S. Virgin Islands have been experiencing. Nonetheless, heat
indices in the low areas will remain above 108, especially along
the northern sections of Puerto Rico. By midweek, expect winds to
return from the southeast, meaning warm weather conditions will
return.

At this time, models suggest late Thursday into Friday as the
transitional days, where a combination of the residual moisture from
an old front and tropical wave continues to move away from the
area, and the dry air begins to filter once again. By the end of
the workweek into the weekend, expect the dry pattern to prevail.
Last but not least, low concentrations of Saharan dust will be
embedded in the wind flow, causing hazy skies through the end of
the period. Therefore, we suggest that people with respiratory
illness follow the necessary precautions established by health
experts.

&&

.AVIATION...VFR conds at all local terminals. SFC wnds calm to
lgt/variable, bcmg fm ESE at 10-15 kt with ocnly hir gusts aft
10/14Z. L/LVL wnds fm SE 15-20 kts BLO FL180 bcmg fm E ABV. SCT
-SHRA/SHRA ovr regional waters and en route btw eastern PR and the
USVI terminals as well as ovr the Caribbean waters just south of
the local islands. SCT ocnl BKN lyrs nr FL022...FL040 til
10/14Z...mstly SKC ABV FL100. No significant wx impacts fcst durg
prd.

&&

.MARINE...No changes to previous discussion. Calm marine weather
continues with seas at 4 feet or less across most of the region.
Today, expect moderate to locally fresh southeasterly winds
across the region. Small craft operator should exercise cautions
across most of the northern beaches of Puerto Rico.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
459 AM AST Sun Jun 11 2023


.SYNOPSIS...

The heat remains as the biggest threat for today. Expect, heat
indices around 108 to 112 degrees. Winds will become more
easterly. Nonetheless, moisture and southeasterly wind will
return by mid-week, resulting in a more humid day with warm
conditions. Seas should remain at 5 feet or less with a low to
moderate risk of rip currents during the period.

&&

.SHORT TERM...Today through Tuesday...

Fewer passing clouds and showers were noted over the coastal waters
and around the islands during the overnight hours. Very light
showers brushed some of the islands but no significant accumulations
were noted. Recent satellite imagery and the doppler weather radar
both suggest an even drier airmass now crossing the region as the
surge of moisture from the previous day exited the region. The TJSJ
11/00Z upper air sounding also suggests diminishing precipitable
water content to around 1.76 inches, while the upstream TNCM (St
Marten) sounding showed an even drier airmass with a precipitable
water value of 1.48 inches. This is all indicative of an even drier
airmass to filter today through Monday along with low level winds
having more of an easterly component versus the south to southeast
component in recent days. Thereafter, model guidance continued to
suggest increasing moisture and instability with a tropical wave and
also the erosion of the upper level ridge, as a short wave trough is
forecast to cross the enter the west and southwest Atlantic and sink
southwards just west of the region.

For the rest of today...Mostly sunny skies with another day of hot
conditions expected across the islands, except for some locally and
diurnally induced afternoon convection which should be limited to
the west to northwest quadrant of Puerto Rico, as well as the chance
for very isolated showers over parts of the east interior of Puerto
Rico and mainly downwind of the USVI, where and sunny and hot
conditions will also prevail. A prevailing east to southeast wind
flow will persist with some sea breeze variations expected to
briefly kick in today. By Monday, as a surface high pressure ridge
builds just north of the forecast area, winds will become more
easterly resulting in an increase in the easterly trades. Late
Monday through Tuesday a tropical wave will approach the region and
bring an increase in moisture to the forecast area. This along with
the aforementioned erosion of the upper level ridge, expect a better
chance for enhanced early morning and afternoon convection over
portions of the islands. Although there is increased potential for
shower activity by Tuesday, significant and widespread rainfall
accumulations are so far not anticipated.

The hotter than normal weather trend will persist the rest of today
and at least until Monday. Recent blended satellite derived
precipitable water product suggested values between 1.40 to 1.70
inches now across the region as the airmass continues to dry out and
PWAT values forecast to diminish. East to southeast winds will
continue through the period.

Main Impacts at least until Monday will be the excessive heat
conditions, with temperatures expected to continue to reach the low
90s and above the daily normals especially along the north coastal
areas each day. The warmer low temperatures will persist and vary
between the mid-60s and low 70s in mountainous regions and upper 70s
to low 80 along the coastal and in urban areas. Heat indices are
expected to exceed the low and mid 100 degrees Fahrenheit, with
Excessive Heat Warnings and Advisories now likely through Monday for
portion of the islands. As a result an Excessive Heat Watch will
remain in effect for Puerto Rico and portions of the U.S Virgin
Islands, particularly St Croix.

&&

.LONG TERM...Wednesday through Monday...

Expect the residual moisture associated with an enhanced moisture
area that detached from an old frontal boundary and merged with
the tropical wave heading to the forecast area to prevail by mid-
week. These two weather features will increase cloudiness and the
chance for afternoon convection across the western quadrant of
Puerto Rico and morning activity across the eastern part of the
island. We anticipate moderate rainfall amounts across the local
isles through Wednesday. Nonetheless, thunderstorms cannot be
ruled out in the afternoon, mainly across the west and
northwestern quadrant, as the east-southeasterly wind flow begins
to dominate the area. By mid-week, warm weather conditions to
return across Puerto Rico, Vieques, Culebra, and the U.S. Virgin
Islands. The heat indices are expected to remain around and
slightly above 108, especially along the northern sections of
Puerto Rico.

At this time, models suggest Thursday as the transitional day, where
a combination of the residual moisture continues to move away
from the area, and the dry air begins to filter once again. By the
end of the workweek into the weekend, expect the dry pattern to
prevail. Last but not least, low concentrations of Saharan dust
will be embedded in the wind flow, causing hazy skies through the
end of the period. Therefore, we suggest that people with
respiratory illness follow the necessary precautions established
by health experts.

&&

.AVIATION...VFR at all local terminals. SFC wnds calm to lgt/vrbl,
bcmg fm ESE at 10-15 kt with ocnly hir gusts between 20-22kts ft
11/14Z. L/LVL wnds fm SE 15-20 kts BLO FL120. Wdly SCT SHRA mainly
ovr the offshore Atlantic and Caribbean waters and en route btw E
PR and the USVI. SCT lyrs nr FL022...FL050.SKC ABV FL100. No
significant operational wx impacts durg fcst prd.

&&

.MARINE...Seas up to 4 feet, occasionally up to 5 feet. An
increase in winds will lead to choppy wind-driven seas, small
craft operators should exercise caution. Low to moderate risk of
rip currents will prevail in the waters near PR and the USVI.

[LarryWx]

Likely related to the record warm tropical Atlantic for this time of year, San Juan has just had its warmest June 1-11 on record, 86.9 F. Furthermore, it is the warmest by a good margin. The old record warmth was down at 85.3, set in 1988. The record coolest is 77.5, set in 1922, 1913, 1914, and 1939.

https://www.weather.gov/wrh/Climate?wfo=sju

They've had a mere 0.02" of rainfall so far this month, 1% of their normal of 1.87" for June 1-11.

The record warm tropical Atlantic is at least partially being blamed on near record low for this time of year Saharan dust being blown into the Atlantic.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
523 AM AST Fri Jun 16 2023

...New SYNOPSIS, AVIATION, MARINE...

.SYNOPSIS...
Issued at 428 AM AST Fri Jun 16 2023

Hot and hazy summer conditions will prevail under east southeast
flow with only limited sea breeze intrusions during the daylight
hours on the north coasts. Showers are possible in the western
portions of Puerto Rico each afternoon, with the best chances and
amounts on Monday and Tuesday. Isolated showers may also occur
during the overnight and early morning hours over the U.S. Virgin
Islands and the eastern sections of Puerto Rico. Marine conditions
remain choppy as moderate to locally fresh winds continue. The
risk of Rip Currents is moderate tonight into tomorrow for many of
the local Puerto Rican beaches and in the U.S. Virgin Islands,
Saint Croix.


&&

.Short Term...Today through Sunday...

Mostly clear skies prevailed across the local islands overnight with
a few sprinkles noted across the local waters. Temperatures dropped
to the upper 70s to 82 degrees near coastal areas under an east to
east southeast wind flow of 12 knots or less.

The short term forecast is still on track. No major changes were
introduced at this time. The mid to upper level ridge will continue
to promote dry and stable weather conditions during the forecast
cycle. Showers and isolated thunderstorms... if any...will be
focused across western areas of Puerto Rico during the afternoon
hours. As a mater of fact, the latest guidance continued to suggest
precipitable water values below to well below seasonal average under
an east to east southeast wind flow. Bit hazy today.

The daytime temperatures across the forecast area will remain in the
low to mid 90s mainly along the coastal areas and in the mid to
upper 82s at higher elevations under an east to east southeast wind
flow. The aforementioned east to east southeast wind flow will
continue to prevail during the next several days as a surface high
holds across the central Atlantic.

The major hazard continues to be heat indices in the Heat Advisory
(108-111F) and Heat Warning (>=112F) criteria at the lower
elevations, the worst heat being across northern Puerto Rico.

&&

.LONG TERM...Monday through Saturday...

At upper levels, a high pressure center continues to be indicated
for the east central Caribbean by Sunday. On Monday it begins a
northward migration over Hispaniola, and then slowly drifts west
northwest toward Florida between Cuba and the Bahama Islands
through Saturday of next week. At mid levels, high pressure over
the central Atlantic between 20 and 30 north splits, with half
aligning with the upper level high to the west and the other half
drifting eastward across the Atlantic. This split is partly due
to the cut-off low forming along 60 west east of the Carolinas. A
tropical disturbance being tracked by the National Hurricane
Center and now noted around 10 degrees north and 20 degrees west
is now being given a 40 percent chance of development during the
next 7 days and it should be evident by Monday, according to the
GFS run with the weak forecast for the local area, whether or not
this will develop as it crosses 40 degrees west longitude.

Otherwise the primary mover of our weather will be the slightly
cooler air mass from the east northeast that will be returning
back around the western side of the high pressure still in the
Central Atlantic at 700 mb. Depending on the development of the
tropical system previously mentioned, there could be a dry slot
moving through the area Tuesday night before the broad envelope of
moist air around the system moves in behind it from the east
southeast. Then, winds and showers will become highly dependent
on the track and development of the tropical system.

&&

.AVIATION...
(06Z TAFS)
Issued at 428 AM AST Fri Jun 16 2023

VFR conds will prevail today under ESE winds at 10 to 15kt. Sea
breezes variations and higher gusts are expected as well. Winds at
nor12 knots or less aft 16/23z. VCSH possible at TJMZ between
16/16 and 16/20z. Some haziness, but VIS will remain P6SM. Max
winds W 37-42 kts btwn FL415-435.

&&

.MARINE...
Issued at 428 AM AST Fri Jun 16 2023

Locally fresh winds for at least a few hours each day will
prevail across the waters of the northwest and southwest coasts of
Puerto Rico. Seas will occasionally approach 6 feet there.
Otherwise only choppy conditions with 3 to 5 feet are expected.
Both the ECMWF and GFS models have been erratic regarding the
track and intensity of a possible tropical depression/storm
moving toward the area late next week. Mariners will want to
monitor the development and progress of this feature.




&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...Excessive Heat Warning from 10 AM this morning to 5 PM AST this
afternoon for PRZ001-005-008-010.

Excessive Heat Watch from this afternoon through Sunday
afternoon for PRZ001-005-008-010.

Heat Advisory from 10 AM this morning to 5 PM AST this afternoon
for PRZ012.

VI...None.
AM...None.
&&

$$

SHORT TERM...OM
LONG TERM....WS
AVIATION...99

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
445 AM AST Sun Jun 18 2023

.SYNOPSIS...

Another hot day is forecast across the northern coastal areas of
Puerto Rico, where an Excessive Heat Warning and Advisory are in
effect from 11 AM AST through 5 PM AST today. Afternoon convection
is forecast each day, especially in the afternoon across the
interior and western sections. However, the flood threat should
remain limited across some sections of the islands. On Tuesday, a
drier patch will limit the rain; however, the islands can expect
an increase in moisture on Thursday. Uncertainty remains high
regarding the tropical wave tracked by the National Hurricane
Center. Residents and visitors should monitor the development of
this tropical wave.

&&

.SHORT TERM...Today through Tuesday...

Heat indices up to 114 degrees are expected today across the lower
elevations of north central Puerto Rico, and an Excessive Heat
Warning is in effect. Meanwhile, heat indices up to 111 degrees are
expected for the northwest, and San Juan and vicinity areas where a
Heat Advisory is in effect. Please refer to the latest heat
bulletin (NPWSJU) for more information.

Passing showers embedded in the trade winds moved through the night
across portions of the USVI and coastal sections of eastern PR. The
Doppler radar estimated over half an inch of rain in Patillas and
Maunabo. Lesser amounts were noted across the rest of the islands.
In general, minimum temperatures were from the mid 60s across the
higher elevations to the mid and upper 70s across the lower
elevations of the islands. For the rest of the short term period,
precipitable water content is expected to peak today around 1.75-
2.00 inches, while gradually decreasing on Monday and Tuesday
between 1.25-1.50 inches as a drier air mass arrives from the east.
At the upper levels, a weak ridge should remain in place through
Monday and a short-wave trough on Tuesday should provide some
instability aloft.

Therefore, patches of low-level moisture will reach the islands from
the east at times, promoting trade wind showers across the regional
waters and briefly over land areas across the USVI and eastern PR.
Then, in the afternoon hours, locally induced afternoon showers with
isolated thunderstorms should develop over western PR. At least
today, higher rainfall amounts are expected and this may lead to
urban and small stream flooding.

&&

.LONG TERM...Wednesday through Monday...

A broad surface high pressure extended from the western Atlantic
to the central Atlantic will be the dominant feature for the first
part of the long-term period. This surface feature will favor
east-southeast winds, increasing the presence of low-level
moisture content across the region from late Wednesday into
Friday. The available moisture will maintain a convective pattern
across the region, with the typical afternoon showers across the
interior and western sections of Puerto Rico. So far today and
according to the latest guidance, Thursday looks like the wettest
day.

Uncertainty increases as we move from Friday into the weekend. The
latest guidance from the global models disagrees with their
solutions for the tropical wave tracked by the Hurricane Center,
now more defined and with a 90 percent of formation chance in the
next seven days. The ECMWF shows a trend with the tropical
disturbance near the islands by Sunday. On the other hand, GFS is
still developing a low pressure, moving northward and merging with
a low over the northwestern Atlantic. As we mentioned, uncertainty
remains high at this moment, given the different solutions.
However, the forecast calls for a continued period of moisture
near or above the climatological normals. Therefore, the islands
can expect showers in the windward for the morning, followed by
afternoon convection each day. Residents and visitors should
monitor the development of this tropical wave using official
information from the National Hurricane Center and the NWS local
Weather Forecast Office in San Juan, Puerto Rico.

&&

.AVIATION...

Mainly VFR conditions are expected to prevail across all
terminals during the next 24 hours. However, SHRA/TSRA expected to
develop in and around TJBQ btw 18/17z-23z, this may cause tempo MVFR
conditions. Sfc winds ESE at 12-16 kt with higher gusts and sea
breeze variations after 18/14z.
&&

.MARINE...

A surface high pressure will continue to result in moderate to
locally fresh east-southeast winds across the local waters. Seas
should remain at 5 feet or less. Showers with isolated
thunderstorms may affect portions of the coastal waters of western
or northwestern Puerto Rico each afternoon. There is a low risk
of rip currents across all of the exposed beaches of Puerto Rico
and the U.S. Virgin Islands.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...Heat Advisory from 11 AM this morning to 5 PM AST this afternoon
for PRZ001-008.

Excessive Heat Warning from 11 AM this morning to 5 PM AST this
afternoon for PRZ005.

VI...None.
AM...None.
&&

$$

SHORT TERM & AVIATION...DS
LONG TERM & MARINE....LIS

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
517 AM AST Mon Jun 19 2023

.SYNOPSIS...East to southeast winds and good moisture along the
north and west coast of PR should continue to promote heat indices
between 100-110 degrees for most of the week. Diurnally induced
afternoon showers are expected each afternoon over western PR.
Moisture content is expected to increase by midweek. AL92 over the
far Tropical Atlantic is forecast to develop into a tropical
system later today or tonight, however, there is still high
uncertainty on the possible impacts, if any, across our local
area.


&&

.SHORT TERM...Today through Wednesday...

Moderate to heavy passing showers were observed across the local
waters and some coastal sections at night. However, rainfall
accumulations remain minimal. Overnight temperatures fluctuated in
the upper 70s to the lower 80s across the coastal areas and from the
low to mid 70s. Winds were from the southeast at 10 mph or less,
with land breeze variation and gusty winds near the showers. Passing
showers will persist for most of the morning hours.

A mostly stable pattern is forecast for the following days due to a
solid mid-level ridge prevailing during the period. At the surface,
a broad high pressure extending from the western Atlantic into the
eastern Atlantic will maintain a southeasterly wind flow. This wind
pattern will provide low-level moisture for the morning hours with
PWAT up to 1.63 inches, as the imagery from the derived Satellite
shows. As the day progresses, a drier air slot will filter into the
region and decrease the showers' frequency, at least until Tuesday
afternoon. Another band of moisture surge will reach the islands
embedded in the winds on Wednesday, enhancing the morning and
evening showers across the regional waters. Although variable
conditions are forecasted, in general, expected the development of
localized showers in the northwest and western interior each
afternoon, being Tuesday the driest day.

Daytime temperatures will range from the upper 80s to the lower 90s
in the coastal areas and the mid 70s across the interior. The
southeast wind pattern will keep heat indices up to 18 degrees
Fahrenheit each day. As a result, a heat advisory is in effect from
11 AM to 5 PM AST today across the west, northwestern, and north-
central coast of Puerto Rico.


.LONG TERM...Thursday through Monday...

Precipitable water content should increase between 1.75-2.00
inches of Thursday as a tropical wave is expected to move across
the local area. Therefore, expect showers and isolated thunderstorms
to increase in coverage, with an elevated threat for excessive
rainfall across western PR. Thereafter, the forecast confidence is
low in terms of possible tropical impacts associated to AL92, as
global models continue to diverge in their solution. Therefore,
will continue to carry a seasonal weahter forecast through the end
of the long term forecast, with trade wind showers favoring the
windward areas of the islands during the night and early morning
hours, followed by afternoon convection across western PR. The
forecast will be adjusted as needed during the next couple of
days. Regardless, we are already in the Hurrican Season, and
residents and visitors should always be prepared and have their
emergency plans up to date in case of any tropical development.


&&

.AVIATION...VRF conditions will prevail for all the TAF sites
during the period. VCSH will persist across most of the sites at
least until 19/14Z. The showers will diminish as the day progress;
however, afternoon showers might result in SHRA over TJBQ at
19/18Z. Winds will remain from the southeast at 8 knots or less
until 19/14Z, increasing up to 12 knots with sea breeze variation
and gusty winds.


&&

.MARINE...Seas should remain at 4 feet or less through much of the
workweek. East to southeast trades will continue between 10 and
15 knots today, and locally higher to 20 knots during the middle
of the week across the coastal waters and passages. There is a low
risk of rip currents across all beaches of PR and the USVI.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
537 AM AST Tue Jun 20 2023

.SYNOPSIS...Heat indices between 105-110 degrees are expected mainly
along the north central to northwest coast of Puerto Rico. Diurnally
induced afternoon showers and thunderstorms are expected each
afternoon over western PR. Moisture content is expected to
increase during the weekend due to the passage of Tropical Storm
Bret to our south.


&&

.SHORT TERM...Today Through Thursday...

Satellite and radar Imagery showed cloudiness and some light-passing
showers across the region. According to the derived GOES-16 imagery,
a drier slot of airmass moved into the region, limiting the shower
activity. Overnight temperatures were in the upper 70 to the lower
80s across the coastal areas and between the low and mid 70s across
the mountains. Winds were from the east-south at 10 mph or less,
with land breeze variation.

Drier conditions should prevail most of the day as the drier airmass
with a PWAT of 1.40 inches persists. Therefore, residents can expect
clear skies with mid to upper clouds for the morning hours and
minimal rainfall accumulation. Localized showers are still on the
forecast in the afternoon, mainly due to the local effects and the
diurnal heating. By Wednesday, as the broad surface high pressure
interacts over the Atlantic basin, it will induce a pressure tight,
resulting in breeze conditions over the CWA. Meanwhile, low-level
moisture associated with a tropical wave, now located just in front
of Tropical Storm Bret, will reach the local islands. This wave will
maintain enough water content for a more convective pattern.
Therefore, residents can expect an increase in showers by late
Wednesday into Thursday. According to the latest guidance, Thursday
looks like the wettest day of the period.

.LONG TERM...Friday through Tuesday...

Precipitable water content should increase gradually on Friday and
Saturday, as Tropical Storm Bret is expected to move mainly south
of the local area. However, there is still uncertainty in the
evolution of the system during the long term period, and the
forecast will be adjusted as needed. Having said that, based on
the latest forecast the track was adjusted a little bit south and
just outside of our CWA over the Caribbean Sea. Therefore, the
main impacts should be hazardous seas and life-threatening rip
currents across the southern waters and passages of the islands,
and along the southern beaches. In terms of rainfall, shower and
thunderstorm activity could increase across the islands from late
Friday and through Saturday. Thereafter, a seasonable weather
pattern is expected with trade wind showers favoring the windward
areas of the islands during the night and early morning hours,
followed by afternoon convection across western PR.

Regardless of the forecast, we are already in the Hurricane
Season, and residents and visitors should always be prepared and
have their emergency plans up to date in case of any tropical
development.


&&

.AVIATION...VFR conditions are expected for all the TAF sites
during the period. VCSH will persist for TIST at least until
20/14Z. Afternoon showers over the west will induce lower ceilings
and VCTS on TJBQ at 20/18Z. Winds will remain VRB at 8 knots or
less until 20/14Z increasing up to 15 knots from the E-SE with sea
breeze variations. No VIS obstructions are expected.


&&

.MARINE...Seas should remain at 5 feet or less through much of
the workweek. East to southeast trades will continue between 10
and 20 knots through workweek. There is a low risk of rip
currents across all beaches of PR and the USVI. Hazardous seas and
gusty winds are expected from late Friday and through Saturday,
as Tropical Storm Bret is forecast to pass south of the region.
Life-threatening rip currents are expected along the southern
beaches of the islands during this period.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
526 AM AST Wed Jun 21 2023

.SYNOPSIS...A tropical wave will increase showers across the
region today. Tropical Storm Bret is expected to pass south of the
area on Friday, creating hazardous seas and life-threatening rip
currents along the southern waters and coastal areas of the
islands. Shower and thunderstorm activity along with gusty winds
across the Caribbean waters should increase with the passage of
Bret. Hazy skies due to Saharan dust are expected during the
short-term period.


&&

.SHORT TERM...Today through Friday...

Clear to partly cloudy skies prevailed during the night and early
morning hours across the region. Some passing showers were observed
over the local waters and some coastal sections of St. Thomas.
Overnight temperatures were in the lower 80s across the coastal
areas and in the low to mid-70s across the mountains. Calm winds
prevailed with land breeze variations.

A variable pattern is forecast for the short-term period. At the
surface, a broad, high pressure over the central Atlantic will
promote an east-southeast wind pattern across the islands for the
period. Dragged by this wind pattern, moisture associated with a
tropical wave will filter in across the region. The bulk of the
moisture will reach the local islands in the afternoon into the
night. Given the expected conditions, the U.S. Virgin Islands can
expect more frequent showers during the late morning hours,
increasing in the afternoon across the interior and western
Puerto Rico. A drier air mass with a Saharan Air Layer will
filter in by Thursday, resulting in hazy skies, warm temperatures,
and limited shower activity. Drier conditions will not last long,
as on Friday, Tropical Storm Brett moves south of the islands
over the Caribbean Sea, increasing moisture across the area.
Although the center of the system will remain well to our south,
cloudiness and shower activity associated with the moisture field
of Bret will reach the local islands.

.LONG TERM...Saturday through Wednesday...

Precipitable water (PWAT) content should increase between
2.00-2.25 inches on Saturday, due to lingering moisture associated
to the passage of Tropical Storm Bret to our south of Friday.
Therefore, expect showers and isolated thunderstorms to increase
in coverage, with an elevated threat for urban and small stream
flooding across western PR, and ponding of water in roads and poor
drainage areas across the rest of PR and the USVI. Thereafter,
PWAT is expected to gradually decrease to around 1.75-2.00 inches
through midweek. Promoting a seasonable weather pattern each day,
with trade wind showers favoring the windward areas of the islands
during the night and early morning hours, followed by afternoon
convection across western PR. However, a tropical wave (AL93) is
forecast to approach the northeastern Caribbean by early next week
and the forecast will be adjusted as needed in the upcoming days.

A Saharan Air Layer should promote drier air intrusion and hazy
skies by midweek. Hot temperatures are expected to continue
through the long term period, mainly across the lower elevations
and urban areas of northern and western PR, with heat indices
exceeding 108 degrees Fahrenheit each day.


&&

.AVIATION...VFR conditions will persist for all the TAF sites until
21/16Z. Winds will prevail VRB at 8 knots or less, increasing at
21/14Z from the E-SE at 12-15 k knots. SHRA will increase during the
day across TIST, TISX, and TJSJ at 21/16Z due to moisture moving in.
Strong showers will briefly reduce the ceilings and VIS. PM showers
will affect TJBQ at 21/18Z with VCTS resulting in brief MVFR
conditions until 21/22Z.


&&

.MARINE...By the end of the workweek, hazardous seas up to 10
feet and gusty winds with showers and thunderstorms are possible
across the southern waters of the islands due to the passage of
Tropical Storm Bret. Meanwhile, moderate to locally fresh trades
will prevail for much of the period. There is a moderate risk of
rip currents across the southeastern beaches of PR, including
Vieques, and St. Croix.


&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...Heat Advisory from 10 AM this morning to 5 PM AST this afternoon
for PRZ001-002-010.

Excessive Heat Warning from 10 AM this morning to 5 PM AST this
afternoon for PRZ005-008.

VI...None.
AM...None.
&&

$$

SHORT TERM/AVIATION...LIS
MARINE/LONG TERM...DSR

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
552 AM AST Thu Jun 22 2023

.SYNOPSIS...

Hot conditions continue over the region. Heat indices of 112
degrees or higher are anticipated today for low-lying areas of
northern Puerto Rico. Heat indices of 105 to 112 degrees are
anticipated for portions of western Puerto Rico as well as some
areas of northeastern/eastern Puerto Rico. Saharan Dust is moving
over the region as well, bringing hazy conditions to the islands.
Still, some typical shower activity is likely, with showers and
isolated thunderstorms expected, particularly in interior and
western Puerto Rico this afternoon.

Tropical Storm Bret is moving westward towards the Windward
Islands and is forecast to enter the Caribbean by tonight. It will
pass by well south of the islands (at least 200 miles away at
closest) during Friday afternoon. An increase in moisture over the
region is possible, and increased winds and seas are anticipated,
particularly for over the waters south of the islands.

&&

.SHORT TERM...Today through Saturday...

A drier air mass with suspended particles from the African Deserts
will create hazy skies across the islands today. The mid-level high
pressure will continue to promote subsidence across the Northeast
Caribbean. Nevertheless, occasional showers embedded in the trades
will move across the windward sections of the U.S. Virgin Islands
and Puerto Rico. Afternoon convection will form, resulting in
showers and one or two thunderstorms across the interior and western
PR. The hot spell will continue over the region with heat index
values between 105 and 112 degrees Fahrenheit or even higher.

According to the latest National Hurricane Center forecast track,
Bret will continue its westward movement across the Caribbean Sea
well to the south of Puerto Rico and the U.S. Virgin Islands.
However, GFS and ECMWF suggest that the tropical moisture from the
northern part of Bret could potentially pool over the islands by
around Friday afternoon. In this scenario, unstable weather
conditions may be possible as early as Friday morning and most
likely by Friday afternoon. Bret's trailing moisture may continue
across the region on Saturday. The weather pattern is directly
related to the final behavior of Bret; therefore, any change in its
forecast track and intensity may affect the islands' weather
conditions. Consequently, we encourage the residents of Puerto Rico
and the U.S. Virgin Islands to monitor Bret's progress and the most
recent forecast.

.LONG TERM...Sunday through Thursday...

Moisture is forecast to decrease over the area on Sunday, as what
moisture may be pushed over the area by TS Bret will likely be
moving out of the region, and a dry slot is forecast to be in place
east and southeast of what is now Tropical Depression Four. Still,
model guidance suggests that precipitable water values will be
somewhere near normal, though on the far lower end of normal.
Similar conditions are likely for Monday, as well, though some areas
may see a modest increase in some moisture later in the day.
Gradually increasing moisture is then forecast for Tuesday, followed
by a marked increase in moisture for Wednesday into Thursday,
associated with the passage of a tropical wave. Drier air will then
enter the region behind this wave, and a drying trend is expected
during the day Thursday into Friday.

Aloft, an upper-level ridge will dominate for much of the forecast
period, though some weakness in the ridge, with the potential for
the development of a weak upper-level trough to the north of the
area, is expected around midweek. In the mid-levels, the features
are much more dependent on what happens with Bret and TD 4. Overall,
model guidance suggests what is likely to be, at best, neutral
conditions in the mid-levels for most of the next week, though some
troughing is possible depending on how strong the tropical systems
are as they pass by the area, and how far away/close they are. On
the whole, the best dynamics over the region looks to be for
Wednesday into Thursday.

Uncertainty in this forecast is relatively high. This is in large
part due to the influences of the two tropical cyclones that are
currently over the Atlantic, well east of the area. Tropical Storm
Bret is forecast to pass by the area well to the south at the end of
this week and then dissipate, with the potential for lingering
effects into early next week; overall, though, it is not expected to
have direct impacts to the area, and its indirect impacts will
likely be gone by early in the next workweek. As for Tropical
Depression Four, it is forecast to remain well north of the region,
but could have indirect impacts in terms of the pattern in place
over the region, particularly with the dynamics and moisture
pattern. Because of this, significant changes to the forecast
through the week are possible.

Generally speaking, the forecast is for the wettest day of next week
to be Wednesday. Thursday may be a little drier for much of the
region, though lingering moisture and instability in the west could
bring similar conditions to that area for Thursday afternoon as
Wednesday. Sunday and Monday will likely be among the driest days.
But, again, with the high level of uncertainty, significant
changes are possible.

&&

.AVIATION...
(6Z TAFS)

VFR conditions will prevail through most of the fcst period. Expect
hazy skies with VIS between 6-8 miles. SHRA and TSRA will develop
across the interior and W-PR aft 22/16Z. Winds will continue calm to
light/vrb til 22/13z, then will return from the E/ENE at 15-20 kt
with gusts up to around 30 kt.

&&

.MARINE...

Winds of up to around 20 to 25 knots are expected for the
nearshore waters of northern Puerto Rico during the day today,
with gusts of up to 30 to 35 knots. Elsewhere, winds of up to 15
to 20 knots are expected. Seas of up to 6 feet are possible during
the day today, with building seas expected late today into
tonight, particularly for the offshore waters, and moreso for the
southern waters. This is associated with the passage of Tropical
Storm Bret well to the south of the area. Seas of up to 7 to 8
feet are expected for portions of the waters tonight into
tomorrow.

There is a moderate risk of rip currents for beaches of St. Croix,
Vieques, Culebra, and northern and southeastern Puerto Rico.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
548 AM AST Fri Jun 23 2023

.SYNOPSIS...

Relatively dry and warm or hot conditions are expected during the
first part of the day today. Moisture will increase over the area
late today, associated with the passage of Tropical Storm Bret,
which is moving westward well to our south, which will help to
sustain some showers and isolated thunderstorms in a typical
pattern over the region. Hazardous marine conditions are expected
today into tomorrow, particularly for the Caribbean waters and
local passages. Drier conditions are forecast to return by early
next week.

&&

.SHORT TERM...Today through Sunday...

The trade winds brought showers across the windward sections of
Puerto Rico and the U.S. Virgin Islands overnight, and some of
them further inland across PR's northern and eastern interior. We
also noted hazy skies due to suspended dust particles from the
African deserts. Overnight low temperatures continue above average
across most coastal and urban areas, while the winds continue
from the east-northeast at 5 to 15 mph.

Subsidence ahead of Bret will result in mostly clear skies with
plenty of sun across the islands this morning. Additionally,
surface high pressure across the Central Atlantic will promote
windy east to east-northeast winds over the next few days,
sometimes pushing pockets of moisture. Although moisture from the
northern periphery of Bret will reach us later this afternoon into
the weekend, hostile environmental conditions associated with
mid-level high pressure may limit widespread heavy rain activity
over the U.S. Virgin Islands and Puerto Rico. Therefore, expect
warm to hot weather throughout the morning, with heat indices
mainly between 100-107 degrees Fahrenheit in the urban and coastal
areas. Then, afternoon convection will develop across the
surrounding waters of the USVI and E-PR and over the interior and
SW-PR.

NHC's latest track forecast moved Bret across the Caribbean Sea,
around 300 miles off to the south of Ponce. Nevertheless, warmer
waters, good tropical moisture, low-level convergence, and local
effects may result in unsettled weather conditions across eastern PR
and possibly near St Croix later tonight into Saturday morning.
Moisture content will slowly erode around Saturday evening into
Sunday, leaving the islands on the subsidence ahead of Cindy, which
NHC's latest track forecast puts off to the northeast (over the
Atlantic Ocean) at more than 220 miles off the northeast of St.
Thomas early next week. Therefore, calm weather conditions for
Sunday, with periods of sunshine and clouds in the morning,
followed by afternoon convection.

.LONG TERM...Monday through Friday...

Relatively dry conditions are expected for Monday into Tuesday,
though precipitable water values are likely to remain near the lower
end of seasonally typical values. Ridging is likely to dominate
in the mid- to upper-levels as well, providing decent stability
over the region. Even so, some showers and isolated thunderstorms
are likely.

The model guidance now suggests that the wettest day will be
Thursday, with the moisture from the tropical wave only pushing over
the region late on Wednesday. Both the Euro and the GFS indicate the
potential for a weak upper-level trough in the vicinity of the area,
with the Euro having a generally more believable scenario placing it
just west of the region during midweek into the latter half of the
week. The best instability will coincide with some of the best
moisture for late Wednesday and Thursday. Drier air is forecast to
move into the region during the day on Friday, and with the ridge
aloft re-asserting itself, instability is also forecast to decrease.

However, uncertainty with the forecast remains high. Much of the
forecast is reliant on the timing of a tropical wave and what
happens with Tropical Storm Cindy. Though there is good confidence
in the forecast for TS Cindy through the first 5 days, model
guidance, particularly the GFS, has some intriguing ideas on what
happens with the system beyond that point. The GFS lacks continuity
with other model guidance and between runs with itself. The 18Z run
had the system losing its strength and structure as is likely to
occur, but the 0Z run then resurrects it, restrengthens it, and
suggests it attains a minimum pressure of around 980 to 985 hPa
Friday into Saturday south of South Shore to Halifax, Nova Scotia
and east of Delmarva to Boston, before once again weakening, likely
suggesting a transition, as it heads for North Shore, Nova Scotia.
While, I suppose, I cannot fully rule this out (climatology does
indicate such a thing is possible during this time of year, after
all - see Hurricane Arthur of 2014, though that traversed the coast
and went up the Bay of Fundy), considering current conditions, the
lack of any corroboration from other model guidance, lack of inter-
run continuity, I think it best that we consider this potential far
from likely. But, this leads to some uncertainty with the exact
potential for the pattern aloft and some of the moisture pattern. It
also renders the rest of the solution from the GFS somewhat suspect.
Even so, and regardless of the disagreement from the Euro on the
fate of Cindy beyond 5 days, there is some agreement on conditions
over the region between the models, including similar timing of good
instability and moisture over the region. But with that timing
having been pushed another day out to ensure it remains in the land
of Day Seven does not provide much comfort in its believability. So,
on the whole, we may have good rainfall late Wednesday through
Thursday and possibly even into Friday, but also cannot really rule
out that no such event materializes.


&&

.AVIATION...
(06Z TAFS)

VFR conditions will prevail through most of the fcst period. Expect
hazy skies with VIS between 6-8 miles. SHRA and TSRA will develop
across the interior and SW-PR aft 23/16Z. Winds will continue from
the E-ENE at 10-13 kt til 23/13z, then they will be at 15 to 20 kt
with gusts up to around 30 kt (or higher).

&&

.MARINE...

Building seas of up to 8 to 10 feet are expected through the day
today, with hazardous conditions lingering into tomorrow,
associated with the passage of Tropical Storm Bret well to the
south. The system is moving to the west and will remain more than
200 miles south of the area, but still, increasing, gusty winds
are likely today, of around 20 to 25 knots, with gusts to 30 to 35
knots. Seas of up to around 7 feet will also affect the Atlantic
waters.

There is a high risk of rip currents for beaches of St. Croix
today and tonight, and for southeastern Puerto Rico starting
tonight.

&&

.FIRE WEATHER...

Dry conditions persist into this afternoon, despite increasing
moisture expected late in the day. The flow over the islands has
also become more east-northeasterly, meaning that the air over the
southern coastal plains during the day today will be off of the
mountains and not the Caribbean. Because of this, RH values are
likely to be similar, if not lower, than they were yesterday, when
the minimum was 39% at Camp Santiago and 51% at Cabo Rojo. Winds
will also remain around 16 to 22 mph, with stronger gusts
possible. Though some wetting rains are possible in the southwest,
so are thunderstorms. With dry soils and fuels, strong winds, and
RH values likely to fall to near or below critical thresholds, a
Red Flag Warning has been issued for the southern coastal plains
of Puerto Rico for today, with the highest risk occurring around
midday into the early afternoon.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...Red Flag Warning from 10 AM this morning to 6 PM AST this
evening for PRZ014-027.

High Rip Current Risk from this evening through Saturday
afternoon for PRZ003.

Heat Advisory from 10 AM this morning to 5 PM AST this afternoon
for PRZ005-008-010.

High Rip Current Risk from Saturday morning through Saturday
afternoon for PRZ007-011.

VI...High Rip Current Risk through late tonight for VIZ002.

AM...Small Craft Advisory until 2 AM AST Saturday for AMZ711.

Small Craft Advisory until 8 PM AST this evening for AMZ712.

Small Craft Advisory until 8 AM AST Saturday for AMZ723-726-733-
735-741.

Small Craft Advisory from 2 PM this afternoon to 8 PM AST this
evening for AMZ742.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
508 AM AST Sat Jun 24 2023

.SYNOPSIS...
Issued at 427 AM AST Sat Jun 24 2023

Today is the wetter day of the weekend. A typical weather pattern
will prevail through at least Tuesday. Heat index values will
range between 100-110 degrees each afternoon. An unsettled weather
pattern may evolve by the second part of next week with the
arrival of a strong tropical wave.

&&

.SHORT TERM...Today through Monday...

Passing showers have affected the region through the night, though
overall have gradually decreased in intensity and frequency through
the late night and early morning hours. They will linger into the
morning before giving way to midday/afternoon convection.

Looking at the pattern into early next week, a decrease in overall
shower activity is likely. Still, a typical shower pattern is
expected to be maintained over the region, with passing showers
overnight across the waters and onshore in windward portions of the
islands, and afternoon convection in the form of showers and
isolated thunderstorms in interior and western (and possibly into
northwestern on Monday) Puerto Rico, as well as some streamer
development in the east.

Patchy moisture is entering the region from the east/east-northeast,
which will help to sustain the typical pattern of showers over the
area. A modest increase in this patchy moisture is expected for
today into tomorrow, with a more marked increase in moisture likely
later in the day on Sunday. A little bit of moisture advection and
convergence is likely midday or early afternoon on Sunday into the
evening, with lingering moisture into Monday. This moisture will
move out of the area on Monday, followed quickly by another decent-
sized patch of moisture arriving at the islands during the second
half of the day on Monday. Overall, the moisture levels will remain
near seasonally typical values within the patchy moisture, with the
strongest patches generally having precipitable water values of
around 1.8 to 1.95 inches or so. That being said, some areas will
have moisture levels that are below seasonally-typical levels,
particularly late Sunday into Monday, in the dry slot ahead of the
southern extent of moisture associated with Tropical Storm Cindy.
The track for Cindy places the system well away from the area,
passing by to the northeast by over 300 miles to the northeast on
Monday.

Instability over the region is marginal, but sufficient to support
isolated afternoon thunderstorms. There is a weak upper-level trough
in the vicinity of the region that is likely to persist through the
weekend; its placement is likely to not be favorable for the
development of convection during that time period. Both the GFS and
the Euro now indicate that the trough will weaken modestly at the
start of the workweek, but also shift to just west of the area,
which could result in some improved ventilation over the area,
resulting in a small increase in instability. Weak troughing is
likely to persist in the mid-levels through the period. It could
become weaker and more neutral on Monday, which is more favored by
the GFS, but the Euro maintains, and suggests that there is even the
potential for a small increase in strength on the feature on Monday,
so there is some uncertainty with respect to the instability for the
day. On the whole, it is likely that with moisture conditions as
they are likely to be, conditions will overall be less favorable for
widespread shower activity on Monday than in previous days, but
there is the potential for a few of the showers that do develop to
be somewhat strong. Combined with a weakened steering flow that is
forecast for the day, this could result in locally higher rainfall
totals, and there is the potential for the development of some
hazardous conditions.

&&

.LONG TERM...Tuesday through Saturday...

There is high uncertainty in the long-term forecast due to the
track and intensity of Cindy. While it is not a direct threat to
the U.S. Virgin Islands and Puerto Rico, Cindy's final behavior
will significantly impact the weather in the area. The National
Hurricane Center track forecast has high confidence, and Cindy
will continue its movement far to the north and north-northeast of
the islands from Tuesday onward.

On Tuesday, the weather in Puerto Rico and the U.S. Virgin
Islands may follow a typical summer pattern. There could be
scattered showers in the windward areas in the morning, followed
by thunderstorms in the afternoon. Due to high humidity and
temperatures, heat index values could reach 112 degrees Fahrenheit
or more, particularly in urban and coastal areas. In addition,
suspended dust particles from the Saharan Deserts may result in
some haziness.

An unsettled weather pattern could be possible due to a robust
tropical wave arriving around Wednesday afternoon and remaining
near the region through early Friday morning. The GFS and ECMWF
Gálvez-Davison Index (GDI) predict a high likelihood of widespread
rain and scattered thunderstorms during this timeframe. Therefore
a wet and unstable weather pattern may produce beneficial rains
for the local islands.

A ridge pattern aloft may increase stability as it returns late
Friday into early Sunday. At the same time, a drier air mass with
a more significant concentration of suspended dust particles may
reach the region creating hazy skies. Under this weather pattern,
warm temperatures with less rain activity may reestablish one more
time across the islands. &&

.AVIATION...
(06Z TAFS)
Issued at 427 AM AST Sat Jun 24 2023

Generally VFR conds expected next 24 hrs. Passing SHRA across the
waters may push onshore from time to time over USVI/E PR; cannot
entirely rule out MVFR for TIST/TISX thru around 24/14Z, with lower
risk TJSJ. Afternoon convection for W/interior PR w/ SHRA/TSRA. VCTS
for TJBQ likely to mostly be S of aerodrome. Streamer in E likely to
remain W of TIST/TISX and S of TJSJ. Passing SHRA resume tonight, w/
fewer than last night/this morn, but still nonzero chance of impacts
TJSJ/TIST/TISX.

&&

.MARINE...
Issued at 427 AM AST Sat Jun 24 2023

Hazardous seas will continue to prevail today across the southern
waters of the islands. Therefore, mariners can expect seas
between 5 and 8 feet across the Caribbean Waters, Mona Passage,
and Anegada Passage today. While choppy seas will range between 3
and 5 feet across the Atlantic Waters. Winds will prevail from the
east to east-northeast at 1- to 20 knots. Seas will improve
Sunday onward, below small craft criteria. However, local effects
may create choppy seas each afternoon. A tropical wave will
deteriorate weather and marine conditions by the middle of next
week.

Showers and isolated thunderstorms are still expected across the
regional waters tonight, with gusty winds at times.

For beachgoers, life-threatening rip currents are also expected
along the south-facing beaches of Puerto Rico. The risk is
moderate for the majority of the other beaches. Therefore, please
exercise caution because life-threatening rip currents often occur
near groins, jetties, and piers. Please, exercise caution.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
455 AM AST Sun Jun 25 2023

.SYNOPSIS...

The western, northwestern, and north-central regions of Puerto
Rico and Culebra are expected to experience very hot temperatures
with heat indices ranging from 108-111 F. As a result, a Heat
Advisory has been issued for these areas. Meanwhile, the coastal
and urban areas of the U.S. Virgin Islands and Puerto Rico can
expect warm temperatures with scorching heat index values ranging
from 102-107 F. The upcoming workweek will see an atypical summer
weather pattern with scorching heat indices of 112 or more each
afternoon in the urban and coastal areas. However, an unsettled
weather pattern may develop from Wednesday to Friday due to a
robust tropical wave before returning to a more typical summer
pattern by the following weekend.

&&

.SHORT TERM...Tonight through Tuesday...

A typical pattern will continue over the islands. Decreased shower
activity is expected today, and an overall decrease is likely for
Monday. However, some locally high rainfall totals are possible in
some areas during Monday afternoon. On Tuesday, the morning is
forecast to be relatively dry, followed by an increase in activity
by around midday. There is decent confidence in the forecast into
Monday, but forecast confidence falls off a cliff through the day on
Tuesday.

An area of increased moisture is over the area, mostly in the
south, particularly over the Caribbean. Some of this moisture will
push up over the islands today into tonight, with additional patchy
moisture expected to enter the region during the day tomorrow; drier
air is anticipated to linger between these more moist airmasses.
Overall, though, moisture levels will remain within seasonal normals,
even within the strongest patches of moisture. In the pockets of
drier air between the patches of moisture, however, precipitable
water values will be below the normal range; based on model guidance
and satellite estimates from the Total Precipitable Water imagery
from GOES-16, PW values will be on the order of 1.25 to 1.45 inches.
Moisture levels are somewhat decreased compared to yesterday,
however; because of this, it is likely that there will be a modest
decrease in shower activity today compared to yesterday.

Aloft, there is a weak shortwave trough in the upper-levels over the
region; the impact of this today is likely to be limited, but it is
forecast to shift somewhat westward for tomorrow, which could aid in
increasing the instability over the region modestly. A deeper column
of moisture is forecast to be over the region, though some drier air
will likely persist in the mid-levels. There is the potential for
the development of stronger showers and thunderstorms during the
afternoon on Monday. However, the steering flow becomes weaker;
winds will also veer somewhat with height, though remain generally
less than 10 knots, so the direction is not wholly certain at this
time. Because of this, shower activity is likely to be strongest
over the interior of Puerto Rico, where locally high rainfall totals
are possible, which could result in some hazardous conditions,
mostly in the form of ponding of water, but some localized minor or
urban and small stream flooding is also possible.

A slot of dry air is forecast to push over the islands Monday night
into Tuesday, resulting in a decrease in shower activity. Additional
moisture may move into the area during the day on Tuesday, which
will help to support a typical shower pattern over the region. There
is significant uncertainty in the forecast for Tuesday onwards,
however. This is because of uncertainty with respect to the future
of Tropical Storm Cindy. The storm is forecast to weaken and
dissipate over the next 48 to 60 hours, with high forecast certainty
through that time period. After that, model guidance suggests that a
restrengthening of the system is possible. The GFS is quite bullish
on this, and has quite a bit of inter-run continuity at this point,
as well as agreement in part or in whole from nearly all other
models (the Euro had been a bit of an outlier in previous runs (even
so, it still had some regeneration, just had it occurring later -
though along a similar track that resulted in a fairly similar
outcome for the system (and by extension Atlantic Canada, as all
solutions push the system over mainland Nova Scotia) by the end of
the week), but it has a very similar solution to the GFS with the 0Z
run). The majority of the variation in solutions at this point is in
the form of details - how strong does the system get, how quickly
does it move, etc (to be honest, there hasn't even been much
variation in track, as its generally shape has not changed
significantly, and its final land destination has only varied by
maybe 100-200 miles). All of this to absolutely belabor the point
that there is some uncertainty in the circulation and conditions
induced around the tropical cyclone and its remnants. In particular,
the uncertainty in the moisture pattern, as moisture is or isn't
pulled up over the area by TS Cindy, and the mid- to upper-level
features, and therefore instability over the region, quickly
increases significantly through the day on Tuesday.

&&

.LONG TERM...Wednesday through Monday...

What may happen at the mid and upper levels of the atmosphere
(and therefore the degree of instability) and the low-level
moisture concentration that we could expect over Puerto Rico and
the U.S. Virgin Islands is highly tight to Cindy's final track and
intensification forecast. The National Hurricane Center had lower
confidence in Cindy's possible regeneration and, consequently,
her possible position after 72 hrs, encompassed between the end of
our Short Term and the beginning of the Long-term Discussion.

That said, GFS consistently suggests an unsettled weather pattern
due to a robust tropical wave arriving around Wednesday afternoon
and remaining near the region through early Friday morning. Also,
GFS Gálvez-Davison Index (GDI) predicts a high likelihood of
widespread rain and scattered to numerous thunderstorms during the
second part of the workweek. Therefore, we have a moderate chance
of observing a wet and unstable weather pattern if that tropical
wave moves across the U.S. Virgin Islands and Puerto Rico region.
It may produce beneficial rain for the local islands, especially
for St Croix.

Stability may increase as a ridge pattern builds over the
Northeast Caribbean late Friday into early next week. At the same
time, an African Easterly Jet may bring a drier air mass with a
more significant concentration of suspended dust particles around
late Saturday through Monday, resulting in hazy skies. Under this
weather pattern, warm temperatures with less rain activity may
reestablish one more time across the islands. &&

.AVIATION...
(06Z TAFS)

Generally VFR conds expected next 24 hrs for all aerodromes.
Passing SHRA cont this morn, mostly over the waters, with some
pushing onshore over the islands, mostly in the east, including vc
of TIST/TISX/TJSJ, with limited operational impacts likely at
terminals. Afternoon activity is likely to be over interior and
western PR, with SHRA/TSRA likely to remain S of TJSJ/TJBQ. Cannot
rule out TSRA vc TJBQ to the S, but direct impacts unlikely.
Passing SHRA resume this evening over the waters.&&

.MARINE...
Issued at 408 AM AST Sun Jun 25 2023

Seas will improve from today onward, with seas between 1 and 3
feet in protected areas and up to 5 feet across the offshore
waters, especially in the Mona Passage. However, local effects may
create choppy seas each afternoon. We cannot rule out
afternoon/evening thunderstorms daily, which may result in
dangerous conditions.

A tropical wave will cross the Lesser Antilles around Wednesday,
moving near the region through at least early Friday morning,
deteriorating weather and marine conditions.

For beachgoers, the risk is rip currents is low for most beaches.
However, please exercise caution because life-threatening rip
currents often occur near groins, jetties, and piers.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...Heat Advisory from 11 AM this morning to 5 PM AST this afternoon
for PRZ005-008-010-012.

VI...None.
AM...None.
&&

$$

SHORT TERM/AVIATION...CS
SYNOPSIS/LONG TERM/MARINE....CAM

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
335 AM AST Mon Jun 26 2023


.SYNOPSIS...
Winds will shift from the southeast today, contributing to
hot conditions once again. Showers and thunderstorms will develop
again this afternoon along the interior and western Puerto Rico,
with passing showers expected elsewhere. A tropical wave will
reach the islands on Wednesday, resulting in unsettled weather
into Friday. Saharan dust is expected for the weekend and early
next week, along with increasing winds.


&&

.SHORT TERM...Today through Wednesday...

Showers with isolated thunderstorm development could lead to
lightning and excessive rain hazard risk. Excessive heat hazard
risks are likely each afternoon.

A layer of upper-level clouds and pockets of low-level clouds
generated variably cloudy skies across the local islands. Showers
moved from the waters into northern, northeastern, and eastern
Puerto Rico during the overnight and early morning hours, producing
rainfall totals of up to a quarter of an inch across these areas.
Overnight low temperatures ranged from the upper 60s across higher
elevations to around 80 degrees across coastal areas of eastern
Puerto Rico and the US Virgin Islands. Winds were generally light
and variable.

A weak upper-level trough will remain west of the region today,
maintaining a weak trade wind cap inversion and favorable conditions
for deep convective development. At the lower levels, light
southeasterly winds, generated by the local pressure gradient's
relaxation and passage of Cindy's remnants well northeast of the
local islands, will steer tropical moisture over the region. In this
scenario, unstable conditions aloft and increased moisture levels,
with precipitable water as high as 1.9 inches, along with local
effects and diurnal heating, will likely induce shower development.
The expected shower activity will follow the seasonal pattern,
distinguished by early morning showers moving over eastern Puerto
Rico and the U.S. Virgin Islands from the local waters, followed by
afternoon showers with isolated thunderstorm development. Given the
expected weak southeasterly steering flow, moderate to heavy rains
resulting from the afternoon activity will likely cluster along the
central to the western interior sections of Puerto Rico, with some
showers spreading northward and westward into neighboring
municipalities. Rainfall totals of around 1-2 inches with isolated
higher amounts could lead to flooding of urban areas, roads, and
small streams. Isolated flash floods are possible. Elsewhere,
showers producing lesser rainfall totals are possible, mainly from
El Yunque and the local islands into the San Juan metropolitan area,
eastern Puerto Rico, and neighboring islands in the afternoon.

Satellite-derived precipitable water vapor data and model guidance
suggest drier air briefly moving over the forecast area between
Monday night and Tuesday morning, limiting shower development and
coverage. After that, a wetter weather pattern will follow as the
remnants of Cindy lift deep tropical moisture into the northeastern
Caribbean on Tuesday, and the moisture fields from a broad tropical
wave begin to move over the area by Wednesday into Wednesday night.
Although the upper-level trough will migrate eastward over the local
islands by Monday night and eventually dissipate on Tuesday, local
effects and diurnal heating with abundant tropical moisture should
boost showers with isolated thunderstorm development across the
local islands, thus, expect increased excessive rainfall hazard
risks.

Temperatures will range from the lower 90 degrees across lower
elevations and other urban areas in the daytime to the upper 60s
across higher elevations at nighttime. Southeasterly winds in a high
moisture environment could yield 102 degrees or higher heat indices,
mainly across western and northern Puerto Rico. Some areas may
experience higher heat indices, likely exceeding 112 degrees.

&&

.LONG TERM...Thursday through Monday...
The moisture field associated with the tropical wave will linger
into the islands on Thursday and early Friday. At the upper
levels, a trough will be in place over the Greater Antilles,
increasing divergence aloft. Due to the combination of this
features, the risk for urban and small stream flooding, as well as
mudslides will be enhanced, as well with the elevated risk for
lightning and gusty winds from the thunderstorms. After that, the
aerosol models show drier air filtering in late Friday into the
weekend, along with Saharan dust. Throughout the weekend, any
available moisture that arrives from patches of moisture dragged
by the trade winds will combine with local effects to generate
showers and isolated thunderstorms, especially over western Puerto
Rico. Winds will increase as well, due to a tighter pressure
gradient caused by a surface high pressure over the eastern
Atlantic. Finally, on Monday, conditions will become too hostile
for rainfall production, and skies will turn hazy as more Saharan
dust arrives.


&&

.AVIATION...TSRA/SHRA could result in brief MVFR conditions
across some terminals during the next 24 hours. For TJSJ and USVI
terminals, VCSH through 26/14Z and after 26/22Z. For TJSJ and TJBQ,
VCTS/VCSH between 26/16-22Z. Calm to light and variable winds
becoming more east-southeasterly with sea breeze variations and
increasing to around 5-15 knots with higher gusts by 26/18Z. Winds
again become light and variable after 26/22Z.


&&

.MARINE...
Seas 2 to 4 feet are anticipated for the coastal waters across the
islands, with seas up to 6 feet expected for the offshore
Atlantic. A tropical wave will deteriorate seas by the second half
of the workweek. The risk of rip currents is low for today.



&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...Excessive Heat Warning from 10 AM this morning to 5 PM AST this
afternoon for PRZ005.

Heat Advisory from 10 AM this morning to 5 PM AST this afternoon
for PRZ008-010-012.

VI...None.
AM...None.
&&

$$

SHORT TERM...ICP
LONG TERM....ERG

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
333 AM AST Tue Jun 27 2023

.SYNOPSIS...
Very warm conditions will prevail today. A tropical wave will
approach to the islands on Wednesday, enhancing the potential for
flooding for Puerto Rico and the U.S. Virgin Islands. The wave
will depart the islands on Friday, followed by hazy skies due to
Saharan dust. Some relief from the heat can be anticipated with
the increasing cloudiness from the wave, but the heat will return
Friday onward.


&&

.SHORT TERM...Today through Thursday...

Showers with isolated thunderstorm development could lead to
lightning and excessive rain hazard risk, with an increased risk
between Wednesday and Thursday. Excessive heat hazard risks are
likely today and on Wednesday.

Mainly fair weather conditions under clear to partly cloudy skies
prevailed during the overnight and early morning hours. A few
showers developed along the nearshore waters of southern Puerto Rico
and moved inland, producing minimal rainfall totals. Satellite and
radar imagery indicated thunderstorm development over the Atlantic
waters, with no impact over land areas. Overnight low temperatures
ranged from the upper 60s across higher elevations to around 80
degrees across coastal areas of eastern Puerto Rico and the US
Virgin Islands. Winds were generally light and variable.

The weak upper-level trough will continue moving eastward, crossing
the local islands, until it dissipates later tonight to our
northeast. In the meantime, a mid-level ridge will hold over the
region, keeping a weak trade wind cap near the 850-800 mbar layers.
Light to gentle east-southeasterly winds at 5-15 mph will continue
to steer tropical moisture into the area, with precipitable water
values peaking around one standard deviation above normal today.
Following the latest radar Doppler and GOES-16 satellite, showers
with possible isolated thunderstorms will move inland from the local
waters over eastern and southern Puerto Rico, Vieques, Culebra, and
the U.S. Virgin Islands. As the day progresses, with strong
influence from local effects and diurnal heating, expect an increase
in showers with isolated thunderstorm development over land areas,
mainly across the interior to the northwestern quadrant of Puerto
Rico. Considering the persistent weak steering flow and potential
for thunderstorm development, the resulting moderate to heavy rains
will likely lead to urban and small stream flooding across these
areas, where rainfall totals could peak in the 1-3 inches range with
isolated higher amounts. Isolated flash floods are possible,
particularly in areas affected by previous days' rains. Elsewhere,
showers producing lesser rainfall totals of up to an inch are
possible, mainly from El Yunque and the local islands into the San
Juan metropolitan area, eastern Puerto Rico, and neighboring islands
in the afternoon.

As the moisture field from a westward propagating robust tropical
wave spreads across the region, precipitable water values will
increase from this evening onwards, holding at around 2.2-2.3 inches
and within two standard deviations between Wednesday and Thursday.
The wave's interaction with another upper-level trough developing
west of the local islands will support a generalized risk for
significant showers and thunderstorms, boosting excessive rainfall
and lightning hazard risks. This threat will likely favor eastern
Puerto Rico and the US Virgin Islands on both days, but the threat
holds for the northwestern quadrant on Wednesday. Residents and
visitors should monitor the latest forecast, including advisories
and warnings issued by the National Weather Service, San Juan
office.

Temperatures will range from the lower 90 degrees across lower
elevations and other urban areas in the daytime to the upper 60s
across higher elevations at nighttime. Southeasterly winds in a high
moisture environment could yield 102 degrees or higher heat indices,
mainly across western and northern Puerto Rico. Some areas may
experience higher heat indices, likely exceeding 112 degrees.
Increased cloud cover and rains may result in lower temperatures and
heat indices on Wednesday and Thursday.

&&

.LONG TERM...Friday through Tuesday...

Friday is going to be a transition day from the rainy and cloudy
pattern caused by a tropical wave and drier conditions expected
during the weekend. First, the tropical wave will depart toward the
Dominican Republic, but leaving enough moisture to cause passing
showers, as well as the development of additional activity in the
afternoon for western Puerto Rico. Then, as the day progresses, dry
air will filter in. The aerosol models also shows a moderate event
of Saharan dust lasting into Saturday or Sunday, so hazy skies are
anticipated. A trade wind CAP at the low levels will, therefore,
maintain all the moisture trapped at the surface, limiting the
formation of showers. It will become breezy too, as a high pressure
in the Central Atlantic migrates closer to the area. For the first
half of the next workweek, a more significant dust event is
anticipated. Through this period, it will be hot, hazy, breezy and
with very limited shower activity.

&&

.AVIATION...
TSRA/SHRA could result in brief MVFR conditions across some
terminals during the next 24 hours. For TJSJ and USVI terminals,
VCSH through 27/14Z and after 27/23Z. For Puerto Rico terminals,
VCTS/VCSH between 27/16-23Z. Calm to light and variable winds
becoming more east-southeasterly with sea breeze variations and
increasing to around 5-15 knots with higher gusts by 27/18Z. Winds
again become light and variable after 27/23Z.

&&

.MARINE...
Seas 1 to 4 feet are expected to continue today. Seas could increase
a little by Wednesday as a tropical wave crosses the area. This wave
will cause locally hazardous seas due to increased thunderstorms and
showers. The risk of rip currents is moderate for the northern coast
of Puerto Rico and St. Croix.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...Heat Advisory from 10 AM this morning to 5 PM AST this afternoon
for PRZ001-002-005-008-010-012.

VI...Heat Advisory from 10 AM this morning to 5 PM AST this afternoon
for VIZ002.

AM...None.
&&

$$

SHORT TERM...ICP
LONG TERM....ERG

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
334 AM AST Wed Jun 28 2023


.SYNOPSIS...
An approaching tropical wave and a weak upper level trough will
increase instability across the islands, increasing the risk for
flooding and mudslides throughout the end of the week. Once the wave
departs late Friday and Saturday, skies will become hazy as Saharan
dust filters in. Hot summer temperatures will return on Friday and
will continue through the next workweek.

&&

.SHORT TERM...Today through Friday...

Showers with isolated to scattered thunderstorm development will
lead to lightning and excessive rain hazard risk, with an increased
risk today and Thursday. Excessive heat hazard risks are likely
today and Friday.

The interaction between the leading edge of a robust tropical wave,
with its axis now located around 65W, and a weakening upper-level
trough induced showers with isolated thunderstorms over the local
waters. Some moved over eastern Puerto Rico and the U.S. Virgin
Islands, producing rainfall totals of up to a quarter of an inch.
Overnight low temperatures ranged from the upper 60s across higher
elevations to around 80 degrees across coastal areas of eastern
Puerto Rico and the US Virgin Islands. Winds were generally light
and variable.

The weak upper-level trough will continue to weaken to our
northeast. Yet, another weak upper-level trough will develop today
and settle west of the local islands until dissipating on Friday.
The field moisture from a vigorous tropical wave will continue to
spread across the local area today, maintaining above-normal
precipitable water values between one and two standard deviations
around 2.0-2.3 inches through most of the period. As a result,
abundant tropical moisture and sufficient dynamical forcing from the
wave's and trough's interaction will promote unsettled weather
conditions through at least late Thursday night. After that, drier
air and another pulse of Saharan Dust particulate will gradually
move over the area, promoting fair and hazy weather conditions with
limited shower activity from Friday onwards.

As the tropical wave propagates eastward, east-southeasterly winds
at 5-15 mph will gradually veer from the southeast and increase to
10-20 mph through the cycle, with breezy conditions likely over
southwestern Puerto Rico and the local islands. For today, and
following the steering flow, the showers with isolated to scattered
thunderstorm activity will distribute following the seasonal
pattern. That is, favoring eastern Puerto Rico and the U.S. Virgin
Islands through the rest of the morning hours and clustering along
the interior to northwestern Puerto Rico in the afternoon, where
there is a threat of lightning and excessive rainfall. The afternoon
activity could affect other areas, particularly portions of the San
Juan metropolitan area, eastern Puerto Rico, and the local islands,
but with lower lightning and excessive rainfall hazard risks. From
tonight and continuing through Friday morning, the focus of the
showers and thunderstorms will shift to eastern and southern Puerto
Rico and the local islands, in this case, moving inland from the
local waters with limited afternoon convective development over land
areas. Daily rainfall totals of 1-2 inches with locally higher
amounts, mainly over northwestern Puerto Rico today and eastern
Puerto Rico tonight into Friday morning, could result in flooding of
urban areas, roads, and small streams, with isolated flash floods
possible.

Increased cloud cover and rains should result in lower temperatures
today and Thursday, ranging from the upper 80s across lower
elevations in the daytime to the lower 70s across higher elevations
at nighttime. However, limited excessive heat hazard risks are
expected today across lower elevations and other urban areas of
western, northern, and eastern Puerto Rico and Culebra, where heat
indices of 102-107 degrees are likely. Once weather conditions
improve and become more seasonal on Friday, expect higher (lower)
maximum (minimum) temperatures with excessive heat hazard risks.

&&

.LONG TERM...Saturday through Wednesday...

Moisture from a departing tropical wave will continue to decrease on
Saturday. At the same time, Saharan dust will continue to filter in,
resulting in hazy skies. Additionally, the trade winds will be
enhanced due to a low-to-mid level high pressure system migrating
closer to the region. The steering flow will be from the southeast
at 14-18 kts. The high will also create a trade wind cap inversion,
so shower activity will be limited. On Monday, a weak tropical wave
will cross the region, increasing shower activity a little. Just
after the wave departs, an even denser cloud of Saharan dust will
reach the region, hence hazy skies will continue.

As we move into July, normal high temperatures are in the range of
86 to 92 degrees Fahrenheit, with warm nights too...mainly in the
upper 70s. Due to seasonal warmer temperatures and enhanced humidity
levels at the surface, elevated to significant heat indices will
persist throughout the period.

&&

.AVIATION...
TSRA/SHRA will result in brief MVFR conditions
across most terminals within 24 hours. For TJSJ and USVI terminals,
this scenario will prevail throughout the cycle. For TJPS and TJBQ,
this scenario is likely after 28/16Z and between 28/17Z and 29/02Z,
respectively. Calm to light and variable winds becoming more east-
southeasterly to southeasterly with sea breeze variations and
increasing to around 5-15 knots with higher gusts by 28/18Z. Winds
again become light and variable after 28/23Z. Higher winds and gusty
conditions are possible near the TSRA/SHRA.

&&

.MARINE...
Seas 1 to 3 feet are observed in the CariCOOS buoy network around
Puerto Rico and the U.S. Virgin Islands. However, seas 3 to 6 feet
are anticipated, with winds at 20 kts or locally higher as a
tropical wave moves in. This wave will also increase the frequency
of showers and thunderstorms throughout Friday. After that, rain
will decrease, but the trade winds will remain fresh, and choppy
seas are anticipated.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...None.
VI...None.
AM...None.
&&

$$

SHORT TERM...ICP
LONG TERM....ERG