Caribbean - Central America Weather

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
500 AM AST Sun Jun 24 2018

.SYNOPSIS...Locally induced afternoon showers and thunderstorms
are still expected across the northwest quadrant of the Puerto
Rico in the afternoon. A drier air mass will then encompass the
forecast area early the upcoming work week.

&&

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

Upper level ridge will continue to build from the east and upper
levels will not be as conducive for widespread shower and
thunderstorm activity as previous days. However, enough low level
moisture is expected to aid in the development of diurnally induced
convection over portions of western Puerto Rico. Also, streamers are
expected to form downwind of el Yunque and showers should move over
portions of the metropolitan area.

A surface high pressure over the Central Atlantic will generate
fresh to strong trade winds across the forecast area through at
least Tuesday. Therefore, breezy conditions are expected across the
islands. Drier air and Saharan dust moves in on Tuesday and
Wednesday, but diurnally induced afternoon showers are expected to
briefly develop over western Puerto Rico. Across the rest of the
islands, mostly fair weather conditions are expected to prevail
through the short term period.

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

Although trofiness will prevail across the eastern Caribbean
through the forecast cycle, the available moisture will determine
if organized convection develops. At this time, low level moisture
is still expected to remain below the normal range much of the
cycle except Friday and Monday when tropical waves are expected to
move across the eastern Caribbean. Expect temperatures near or
slightly above the normal values as a broad surface high pressure
across the central Atlantic yields easterly winds.

As a result, continue to expect a fair weather pattern across the
local islands with locally induced afternoon showers and thunderstorms
across western areas of Puerto Rico each day. However, on Friday
as the tropical wave interacts with the upper level trough, an
increase in intensity and areal coverage of showers and thunderstorms
is expected. Similar conditions on Monday as another tropical
wave moves across the area.

&&

.AVIATION...Mainly VFR conditions are expected to prevail during the
next 24 hours. However, between 16z-22z SHRA/TSRA is expected to
develop over west PR, impacting mainly TJBQ/TJMZ with tempo MVFR
conditions. Low level winds expected from the E-ESE at 15-25 kt. Sea
breeze variations and gusty winds at the surface expected after
14z.

&&

.MARINE...Surface high pressure across the west-central Atlantic will
tighten the local pressure gradient to result in moderate to fresh
east southeast winds. As a result, marine conditions will continue
to deteriorate throughout the day. Mariners should expect seas 5
to 7 feet across the Atlantic waters and ranging between 6 and 8
feet across the Caribbean waters and the Mona passage.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 78 88 78 / 40 30 10 20
STT 87 78 88 78 / 40 40 20 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
500 AM AST Sun Jun 24 2018

.SYNOPSIS...Locally induced afternoon showers and thunderstorms
are still expected across the northwest quadrant of the Puerto
Rico in the afternoon. A drier air mass will then encompass the
forecast area early the upcoming work week.

&&

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

Upper level ridge will continue to build from the east and upper
levels will not be as conducive for widespread shower and
thunderstorm activity as previous days. However, enough low level
moisture is expected to aid in the development of diurnally induced
convection over portions of western Puerto Rico. Also, streamers are
expected to form downwind of el Yunque and showers should move over
portions of the metropolitan area.

A surface high pressure over the Central Atlantic will generate
fresh to strong trade winds across the forecast area through at
least Tuesday. Therefore, breezy conditions are expected across the
islands. Drier air and Saharan dust moves in on Tuesday and
Wednesday, but diurnally induced afternoon showers are expected to
briefly develop over western Puerto Rico. Across the rest of the
islands, mostly fair weather conditions are expected to prevail
through the short term period.

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

Although trofiness will prevail across the eastern Caribbean
through the forecast cycle, the available moisture will determine
if organized convection develops. At this time, low level moisture
is still expected to remain below the normal range much of the
cycle except Friday and Monday when tropical waves are expected to
move across the eastern Caribbean. Expect temperatures near or
slightly above the normal values as a broad surface high pressure
across the central Atlantic yields easterly winds.

As a result, continue to expect a fair weather pattern across the
local islands with locally induced afternoon showers and thunderstorms
across western areas of Puerto Rico each day. However, on Friday
as the tropical wave interacts with the upper level trough, an
increase in intensity and areal coverage of showers and thunderstorms
is expected. Similar conditions on Monday as another tropical
wave moves across the area.

&&

.AVIATION...Mainly VFR conditions are expected to prevail during the
next 24 hours. However, between 16z-22z SHRA/TSRA is expected to
develop over west PR, impacting mainly TJBQ/TJMZ with tempo MVFR
conditions. Low level winds expected from the E-ESE at 15-25 kt. Sea
breeze variations and gusty winds at the surface expected after
14z.

&&

.MARINE...Surface high pressure across the west-central Atlantic will
tighten the local pressure gradient to result in moderate to fresh
east southeast winds. As a result, marine conditions will continue
to deteriorate throughout the day. Mariners should expect seas 5
to 7 feet across the Atlantic waters and ranging between 6 and 8
feet across the Caribbean waters and the Mona passage.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 78 88 78 / 40 30 10 20
STT 87 78 88 78 / 40 40 20 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
405 AM AST Tue Jun 26 2018

.SYNOPSIS...Hazy skies due to Saharan dust will continue today.
Limited shower activity is expected across the region for the next
few days. A tropical wave is forecast to move mainly south of the
region on Friday. Fair weather conditions return during the
weekend. Another tropical wave with better moisture is forecast
to move across the region on Monday.


&&

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

Clear skies prevailed across Puerto Rico and the U.S. Virgin
Islands overnight. No shower activity was observed across the
region. Local area remains under a very dry air mass which will
continue to dominate the local area through at least Thursday.
Upper level ridge and a surface high pressure will hold through
Thursday. By late Thursday into Friday, an upper level trough is
expected to dig southwest weakening the high pressure. As a
result, atmospheric conditions will destabilize creating better
chances for shower and thunderstorm development by the end of the
work week.

At the surface, a tropical wave is expected to pass mainly south of
the region Friday. However, an increase in low level moisture in
combination with the aformentioned upper level trough will increase
the chances for showers and thunderstorms on Friday afternoon.

LONG TERM...Friday through Wednesday...

A tropical wave is forecast to move mainly south of the region on
Friday. Also, an upper level low is forecast to move west of the
region and due to its proximity it could provide good dynamics
aloft. Although the best moisture associated to the wave is
expected to remain over the Caribbean waters, shower and
thunderstorm development is expected over western Puerto Rico
during the afternoon hours.

Drier air and Saharan dust will return quickly during the weekend
and this will create hazy skies and limit shower activity across
the region. Another tropical wave with better low level moisture
content is forecast to move across the region on Monday. This wave
is expected to bring better chances of rain across the region
than the previous one. Drier mid to upper levels return after the
wave passage and fair weather conditions are expected to prevail.


&&

.AVIATION...Mainly VFR conditions are expected to prevail during the
next 24 hours. Some hazy conditions are expected, but no restriction
to visibilities is expected. Sea breeze variations and gusty winds
at the surface expected after 26/14z.


&&

.MARINE...Seas will continue to improve during the rest of the
week. However, small crafts should exercise caution today due to
seas up to 6 feet, mainly across the Caribbean waters and
passages. Elsewhere, seas are expected to range between 3-5 feet.
Moderate east winds between 10-15 knots will prevail through at
least midweek. There is a moderate risk of rip currents for most
of the east, north and southern beaches of the islands.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 88 79 89 80 / 20 20 40 40
STT 90 79 89 79 / 20 20 40 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
450 AM AST Wed Jun 27 2018

.SYNOPSIS...Hazy skies due to Saharan dust will continue through
at least Thursday. This will limit shower development over the
islands. A tropical wave is forecast to move mainly south of the
region on Friday. Dry mid level air returns during the weekend.
Another tropical wave with better moisture is forecast to move
across the region on Monday.


&&

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

Once again, clear skies prevailed across Puerto Rico and the U.S.
Virgin Islands overnight. Very light showers were detected by the
Doppler radar across the Atlantic waters. No shower activity was
observed over land areas. Local area remains under a very dry air
mass which will continue to dominate the local area through at least
Thursday. Surface high pressure will continue to dominate the region
through Thursday.

By Friday, an upper level trough is expected to did southwest
weakening the high pressure. As a result, atmospheric conditions
will destabilize creating better chances for shower and thunderstorm
development by the end of the work week. A tropical wave is expected
to pass mainly south of the region Friday. As a result, an increase
in low level moisture in combination with the aformentioned upper
level trough will increase the chances for showers and thunderstorms
on Friday afternoon. This wave will move quickly westward and by
Friday night is expected to move away from the area. Behind the
wave, very dry air is expected to encompass the region.

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

Drier air aloft and Saharan dust will continue on Sunday ahead of
a tropical wave, that will move between late Sunday night through
Monday across the region. Showers and thunderstorms are expected
to develop over the interior and western sections of Puerto Rico.
The potential for urban and small stream flooding will increase on
Monday afternoon. Other than the wave passage on Monday, it will
dry out once again during the rest of the long term period. Mostly
fair weather conditions will prevail across all the local islands.
Temperatures will range in the upper 80s to low 90s each day
across the lower elevations and across the USVI. A surface high
pressure builds across the Atlantic Basin and will promote
moderate to locally fresh trades by midweek.

&&

.AVIATION...Mainly VFR conditions are expected to prevail during the
next 24 hours. Hazy conditions will continue today across all
terminals. However, no restriction to visibilities is expected. Sea
breeze variations and gusty winds at the surface expected after
27/14z.


&&

.MARINE...Seas will range between 3-5 feet. Easterly winds will
prevail between 5-15 knots. A moderate risk of rip currents
continue for the north and southeastern beaches of the islands.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 77 89 79 / 20 10 20 10
STT 88 79 88 81 / 20 10 20 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
431 AM AST Thu Jun 28 2018

.SYNOPSIS...Upper level low will linger close to the area through
Saturday. At the surface, a tropical wave will approach the
region Friday. Next tropical wave will approach the region Monday
into Tuesday next week.


&&

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

Upper level low over Hispaniola will provide good divergence aloft
today and on Friday. At lower levels, a tropical wave will enter the
eastern Caribbean tonight and pass mainly south of the region
through early Friday. This will cause a surge on low level moisture
and in combination with favorable upper levels it will aid in the
development of afternoon thunderstorms over the west coast of PR and
across the offshore Caribbean waters. An upper level ridge and drier
air follows quickly through Saturday, with precipitable water
reaching a minimum of almost 1 inch by Saturday evening. Therefore,
showers, if any, should be confined to west PR in diurnally induced
activity. Elsewhere, fair weather conditions are expected to
prevail.

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

Upper level ridge will build across the northeast Caribbean at the
beginning of next week. Very dry weather conditions are expected
to prevail on Sunday, before low level moisture increases
significantly by Monday and Tuesday next week as a tropical wave
make its way to the local region. Latest computer guidance
indicated the bulk of moisture from this wave will affect the
local region late Monday. Therefore, an increase in shower and
thunderstorm activity is expected. Dry weather conditions with
limited shower development will return to the region on Wednesday
after the passage of the wave.

&&

.AVIATION...Mainly VFR conditions are expected to prevail across all
terminals during the next 24 hours. However, tempo MVFR expected at
TJMZ/TJBQ between 16z-22z due to SHRA developing over western PR.
East winds will continue between 10-15 kt and sea breeze variations
are expected after 13z.

&&

.MARINE...Seas between 3 to 5 feet and winds up to 20 knots are
expected. Small Craft should exercise caution due to winds across
the Atlantic waters.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 89 78 89 78 / 10 10 10 10
STT 88 79 89 78 / 20 40 40 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
504 AM AST Fri Jun 29 2018

.SYNOPSIS...Surface high pressure across the north central
Atlantic will continue promoting easterly winds across the local
area for the next few days. Tropical wave to pass south of the
local islands today, causing an increase in moisture and slightly
increasing the shower activity today. Another tropical wave
expected on Monday which may cause a more significant increase in
shower ans thunderstorm activity across the local islands.

&&

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

A tropical wave is forecast to move south of the local area, but
will quickly move away from the region overnight. An increase in
shower and thunderstorm probabilities can be expected today, mostly
focused across the interior and western portions of PR, where
showers and isolated thunderstorms are expected. With the proximity
of drier air and Saharan dust trailing behind it, weather
conditions are expected to improve overnight.

During the rest of the weekend, drier air and hazy skies due to an
increase in Saharan dust particles is expected over the region.
Overall weather conditions will be dry with the exception of some
shower development mostly across the western portions of PR in the
afternoons.

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

Tropical wave is expected to pass over the local islands on
Monday, bringing an increase in moisture and possibly causing
showers and thunderstorms across the local area. The latest WRF
model suggests some of upper level divergence across the local
area on Monday, which would only help in the development of
showers and thunderstorm. Having said that, Saharan dust may be
present in the area as well, but this upper level support may be
enough to cause showers and thunderstorms across the local area on
Monday. After Monday, the local weather dries up for most of the
workweek. Drier than normal air and stable conditions are forecast
by the long range models. So isolated to scattered brief showers
are to be expected for the rest of the workweek.


&&

.AVIATION...Expect hazy skies today, but VIS remaining P6SM. Fair
WX expected in the morning. Brief MVFR conds at JMZ/JBQ 29/16Z to
29/22Z in SHRA/TSRA, elsewhere VCSH possible. MNT obscurations
across the interior with a mixture of clouds and HZ. ESE at 10-15
kts with possible gusts up to 25 kts. A tropical wave is forecast
to move south of the area later today, however, significant
weather impacts are not expected.


&&

.MARINE...Seas up to 5 feet expected today with winds between 10
and 20 knots. Small craft operators are urged to exercise caution
across some of the local waters. There is a moderate risk of rip
currents across many of the local beaches.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 88 78 89 78 / 30 20 30 20
STT 88 79 90 78 / 30 20 20 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
416 AM AST Sat Jun 30 2018

.SYNOPSIS...Surface high pressure across the north central
Atlantic will continue to promote easterly winds through the
weekend. A surface low develops just north of the local area by
Monday at the same time that a tropical wave moves through the
local area. A series of upper level lows will be present to the
west, north and northeast of the local islands through early in
the upcoming week. However, a weak upper ridge may be over the
local islands on Monday. Saharan dust will continue over the area
for the next several days. Monday is the day with the highest
chance of showers and thunderstorms over the local islands, but
the global models have backed off a bit in the amounts of rain and
the coverage area compared to previous runs.

&&

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

Today and Sunday, the Saharan air layer will remain across the
region through the remainder of the weekend with hazy skies and
fair weather is expected to prevail. Scattered showers are
possible mainly across the western portions of Puerto Rico during
the afternoon hours but, currently the likelihood is slim. Showers
that form during the weekend will be brief due to the lack of low
level moisture and dry low to mid layers of the atmosphere. This
will cause showers to have little to no vertical development.
Relative humidity values at 1000 to 850mb and 500 to 250mb will
be above 50 percent today but these values will decrease to less
than 40 percent on Sunday.

Monday, a tropical wave moves across the Caribbean waters,
increasing low level moisture across the region. An upper level low
will remain to the north of the area and may help support upper
level divergence across the forecast area, but the models are not
quite as bullish in the latest run. The upper level divergence
would aid in the development of showers and thunderstorms across
the forecast area on Monday.

.LONG TERM...Tuesday through Monday...

After the tropical wave expected to have already passed by early
Tuesday, the local weather is expected to be relatively benign
with mostly fair weather conditions. A few showers here and there
are possible in the morning hours across eastern PR and the USVI in
the overnight and morning hours then some showers could develop
across western PR in the afternoon hours due to local effects, but
eastern PR and the USVI are expected to remain with mainly fair
weather in the afternoon hours. Drier than normal moisture is
expected for most of the week with Saharan Dust likely remaining
present, causing haze. Therefore this upcoming week, at this time
it looks like it will be dominated by Saharan dust and mostly fair
weather conditions with a slight chance of showers, western PR has
a slightly higher chance of showers as they could develop due to
local effects. Very long range models is suggesting a tropical
wave towards the end of the forecast period on Sunday and Monday.

&&

.AVIATION...VFR conds will continue to prevail through the 30/18Z
TAF period. ESE winds around 15 knots with higher gusts are
possible. SCT to ISOLD SHRA possible across TJBQ and TJMZ by
30/18Z. Although hazy skies will prevail, visibilities expected to
remain P6SM.


&&

.MARINE...Choppy seas up to 5-6 feet across the local waters
expected today with a gradual improvement through the weekend into
Monday. Moderate risk of rip currents are expected today across
most of our local beaches.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 89 78 89 78 / 10 10 20 50
STT 90 79 88 79 / 10 20 20 50

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
401 AM AST Sun Jul 1 2018

.SYNOPSIS...Saharan dust continues to be present across the local
area and will prevail at least for the next several days, some
days causing more haze than others. Moderate easterly winds will
prevail for the next several days as a surface high pressure
across the north central Atlantic dominates the local wind flow.
Tropical wave expected to pass to the south of the local area on
Monday, bringing a brief increase in moisture and shower activity.
Otherwise, mainly fair weather with some haze due to Saharan dust
is expected for most of the forecast period.

&&

.SHORT TERM...Today through Tuesday..

A dry hazy air mass will remain across the region today, as a result
shower activity will be limited over the region. If showers do
develop today they will be brief due to the lack of low level
moisture in the low to mid layers of the atmosphere remaining fairly
dry. This will inhibit the vertical development of showers, therefore
,expect a fair weather day across the area with hazy skies.

Monday a tropical wave is expected to move into the Caribbean waters
later tonight into Monday morning. Several things have changed since
the last update model guidance have decreased the precipitable water
value for Puerto Rico. The GFS showed a value of 1.5 inches
yesterday now it shows a value of 1.30 inches at 18Z on Monday. The
models now keep the wave well to the south of Puerto Rico on Monday
with the saharan dust still over the region it will absorb some of
the waves moisture needed to sustain showers over the area.

Analysis of the Skew T shows LI value of -5 which means there is
marginal instability across the area this also coincides with the
analysis of the 250 mb heights derived by the GFS. Analysis of the
250 mb GFS shows two upper level lows one to the west over Cuba and
the other well to the north of Puerto Rico, as a result, the area
lacks the upper level forcing needed for large instability.
Therefore showers are expected to be locally and diurnally induced
across the area with the highest instability being over western
portions of Puerto Rico during the afternoon on Monday.

Tuesday the tropical wave moves out of the area and Saharan dust
once again spreads across the region creating hazy skies.

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

The latter part of the workweek will be dominated by drier than
normal moisture and with some Saharan dust. Rather uneventful
weather pattern in which mainly fair weather is to be expected.
Isolated and brief showers are possible, leaving minimal
accumulations, but the dry and stable atmosphere with Saharan dust
will not allow for much rainfall this coming week. Winds will
prevail from the east and the daytime maximum temps are expected
to be in the upper 80s to low 90s across the lower elevations,
which is typical for this time of year. In the very long term, the
GFS model is suggesting another tropical wave moving quickly across
the local islands on the following Monday.

&&

.AVIATION...VFR conds will continue with ISO SHRA possible mainly
across terminals TJBQ and TJMZ by 01/18Z. Easterly winds around 10
to 15 knots with some sea breeze variations . Although hazy skies
will continue, visibilities are expected to remain above 6SM.


&&

.MARINE...Slightly choppy seas up to 5 feet expected today across
the local waters expected today and Monday. Moderate risk of rip
currents are expected today across the beaches of northern PR and
some beaches in southeastern PR, northern Culebra, Eastern Vieques
and eastern Saint Croix.



&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 89 79 90 78 / 10 20 40 20
STT 89 79 89 79 / 10 20 20 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
420 AM AST Mon Jul 2 2018

.SYNOPSIS...
Hazy and dry conditions will continue to prevail across the
region over the next several days. A surface ridge of high
pressure to the northeast of Puerto Rico will continue to promote
moderate to fresh easterly winds of 10 to 15 mph over the area. A
tropical wave in the Caribbean sea will remain south of Puerto
Rico today, but some moisture from the wave could cause isolated
showers during the afternoon today. A stable air mass will create
fair weather conditions through Sunday. Due to drier conditions
fire weather may become a concern for most of the area of Puerto
Rico due to easterly winds continuing to dry out fuels. The next
chance for rain will be next Monday as another tropical wave is
forecasted to move into the Caribbean and across Puerto Rico.

&&

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

Tropical wave will approach the local area today, causing an
increase in the local moisture. The latest satellite imagery are
rather unremarkable with respect to the convection associated with
this tropical wave. The satellite derived precipitable water imagery
indicates that there is in fact much deeper moisture to the south
and southeast of the local islands associated with the tropical
wave, but the latest guidance suggests that the best moisture will
stay to our south and only a slight increase in moisture will occur
over the local islands today. There is also the Saharan dust which
continues to affect the local islands and is expected to continue
affecting us for the next several days. In addition, there is simply
not too much upper level dynamics to help in the development of
thunderstorms over the local islands. There are 3 upper level lows
to the west, north, and northeast of the islands, but right over us
there is a weak ridge, which should work towards inhibiting the
convection. Therefore, for today we expect only a slight increase in
shower activity during the day with some locally induced showers and
isolated thunderstorms across western PR in the afternoon hours. The
different Hi-Res models are in some agreement as location of
rainfall in concerned but not in amounts. The WRF model is quite a
bit more bullish with the amounts of rain and also coverage, but the
other models have a smaller coverage area, less amounts and also
shorter duration. Given the amount of uncertainty that the weak
ridge aloft combined with the Saharan dust but the increase in
moisture brought by the tropical wave, we have decided to split the
difference in the model guidance and hence out forecast of scattered
showers and isolated thunderstorms across portions of western PR,
mainly locally induced in areas of sea breeze convergence. At times,
thunderstorm development with Saharan dust can cause strong storms
with intense lightning, and although possible in isolated areas, the
weak ridge aloft should inhibit the development of very strong
thunderstorms. Not to mention that the forecast soundings show a
great deal of dry air in the mid levels as well as weak signals from
other parameters. So given all the information available, we are
more inclined to expect modest amounts of rain across western PR
that may cause ponding of water on poor drainage areas, especially
if an isolated thunderstorm were to develop.

Once the tropical wave passes we expect fair weather and hazy skies
for Tuesday and Wednesday with little to no rainfall to speak of.
The max temperatures will be in the low 90s today, Tuesday and
perhaps into Wednesday across the lower elevations. Winds will
prevail from the east for the next several days.

&&

.LONG TERM...Thursday through Tuesday...
The end of the work week into the weekend will be influenced by
dry air and Saharan dust which will create a stable atmosphere
across the region. Therefore, hazy skies and brief isolated
showers are possible mainly during the afternoon hours across
portions of the western interior with very light accumulations. If drier
than normal conditions persist fire weather will become a
concern, as a result of easterly winds continuing to dry out
fuels and the lack of precipitation over the area.

Early next week both the GFS and EURO depicts a strong tropical
wave moving through the Caribbean waters and reaching the local
area on Monday. There`s plenty of time to watch what evolves
because the same models depicted healthy waves moving across
Puerto Rico the last couple of weeks, but as a result of the dry
air and Saharan dust, the tropical waves moisture diminishes
before reaching Puerto Rico.


&&

AVIATION...VFR conds to continue with brief -SHRA possible across
the local terminals for the next 24 hours. However, between 02/17Z
and 02/22Z there may be SHRA/TSRA development across western PR that
could cause VCTS at TJMZ and TJBQ. Otherwise mainly fair weather is
expected with brief periods of -SHRA. Saharan dust will continue
causing haze across the area but visibilities are expected to remain
P6SM.

&&

.MARINE...
Seas 3 to 5 feet with easterly winds of 10 to 20 kts. Therefore,
small craft should exercise cautions. A moderate risk of rip
currents for the northwestern and north central beaches of Puerto
Rico and the northeastern beaches of St. Croix.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 90 78 89 79 / 20 20 20 20
STT 89 79 89 80 / 30 30 20 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
432 AM AST Tue Jul 3 2018

.SYNOPSIS...
Fair weather conditions and saharan dust will reign over the
region through Saturday, then a tropical wave is forecasted to
move into the local waters late Saturday. As a result, an
increase in low level moisture and rain chances through Monday
across the region, then the wave moves away from the area early
Tuesday with drier air moving in from the east. Wednesday another
tropical wave is forecasted to shift in from the east and increase
rain chances across the U.S. Virgin Islands and Puerto Rico.

&&

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

Drier than normal airmass has returned to the local area with
Saharan dust, therefore hazy skies will continue to be observed
today and through the next several days. The GFS model is
indicating that the precipitable water values will dip down around
1.25 inches today, making it about 2 standard deviations drier than
normal. Therefore the forecast for today is for fair weather with
only a slight chance of brief showers, producing minimal rainfall
accumulations if any. A brief patch of moisture moved in on
Wednesday, which will still be below normal moisture but the slight
increase in moisture may cause scattered showers to develop across
western PR on Wednesday afternoon when combined with the local
effects, isolated showers expected elsewhere. The same story is for
Thursday with slightly higher moisture expected in the afternoon,
which could help in the development of showers across western PR,
but limited if any shower activity expected elsewhere.

Maximum temperatures today are expected to be in the low 90s across
the lower elevations with apparent temps in the 97-102 range. The
max temps on Wednesday and Thursday may be a degree or two cooler
than today because of the slightly higher moisture, but the apparent
temps may be similar because of the slightly higher relative
humidity.

Bottom line is that an overall fair weather pattern expected today
with a slightly higher chance of some rain on Wednesday and Thursday
in the afternoon hours across western PR, with isolated light
showers elsewhere across the local islands.

&&

.LONG TERM...Friday through Wednesday...
Dry Saharan air will create a stable airmass with hazy skies
Friday and Saturday. Therefore, fair weather is expected across
Puerto Rico and the U.S. Virgin Islands. During the afternoon
streamers and isolated showers are possible, but any showers that
do develop will be short-lived due to the lack of instability.

A slight change from yesterday`s guidance shows the axis of the
tropical wave reaching the forecast area early Sunday morning
instead of late Sunday early Monday, either way an increase in
low level moisture and rain chances are expected Sunday through
Monday. A drier airmass arrives across the region on Tuesday, but
another tropical wave is forecasted to move over the area on
Wednesday with another round of showers and thunderstorms.

&&

.AVIATION...VFR conds expected for the next 24 hours. East winds at
around 15 knots with occasional gusts and sea breeze variations
expected after 03/13Z.Saharan dust will cause haze today
but visibilities are expected to remain above 6SM.

&&

.MARINE...
Seas up to 6 feet across the Mona Passage and Caribbean waters
today, therefore a small craft operator are urged to exercise
caution. Elsewhere, seas up to 5 and east winds up to 20 kts are
expected across all waterways.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 90 79 88 80 / 10 20 20 20
STT 89 79 89 78 / 10 20 20 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
507 AM AST Wed Jul 4 2018

.SYNOPSIS...Saharan dust and fair weather is expected to prevail
for most of the upcoming days. Weak tropical wave will pass to our
south, causing a slight increase in moisture. Locally induced
scattered showers across western PR are possible each afternoon.
Tropical wave could approach the local islands early on Monday,
causing an increase in shower and thunderstorm activity.

&&

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

Fair weather with hazy skies due to Saharan dust will continue
through Thursday creating a stable airmass. The recent sounding
shows two inversion one at 900 mb and the other at 600 mb. The
inversions at 900 mb will erode away this afternoon due to the
environmental temperature exceeding the convective temperature, but
the inversion at 600 mb will remain due to the lack of upper level
and low level forcing needed to break the cap. As a result, of the
drier Saharan air, very low instability and the lack of low to
mid level moisture any showers that develop today through Thursday
will be short-lived. An indication of how dry the atmospheric
conditions are SJU-GFS model depicts precipitable water values
remaining two standard deviations drier than normal. As a result
of the drier conditions persisting fuels continue to dry out
across the southern coastal plains due to the lack of rainfall, as
a result fire danger will tilt from moderate to elevated.

The Saharan dust is expected to slightly decrease across the
region on Friday which should allow more showers to develop
across the local area.

Temperatures will be in the upper 80s to lower 90s in lower
elevations, and the upper lower to middle 80s in higher elevations.
Winds will prevail out of the east at 10 to 15 mph with higher gusts
possible.

.LONG TERM...Saturday through Thursday...

Saharan dust will continue affecting the local islands as far as
the local guidance can reach with possibly a brief break early on
Monday, only to return again late Monday into Tuesday and for
several days after that, so the persistent Saharan dust is
expected to continue. As far as the local weather, mainly fair
weather with only isolated to scattered brief showers due to local
effects every day from Saturday through Thursday, EXCEPT Monday.
The latest GFS and ECMWF models both have the current Invest 95L
approaching the local area as a tropical wave late Sunday into
Monday, which could cause a significant increase in shower and
thunderstorm activity over the local area if the models were to
verify. It pays to know that there is a great deal of uncertainty
with how exactly this tropical wave will evolve and how close it
could get to the local islands, so the confidence is low. We will
continue to monitor the latest information on Invest 95L but at
this time it looks like the Invest 95L will weaken considerably
just east of the Leeward islands and get close to our local
islands late Sunday into Monday.

&&

.AVIATION...VFR conds to continue with an isolated SHRA in and
around JMZ after 04/18z. Easterly winds around 15 knots with
higher gusts and sea breeze variations. Although hazy skies will
continue, visibilities are expected to remain above 6 SM.


&&

.MARINE...Small craft operators are urged to exercise caution due
to winds up to 20 knots and seas up to 6 feet today and tonight,
improving on Thursday. Moderate risk of rip currents across most
of the beaches in PR, Vieques, Culebra, and Saint Croix.
However,the beaches along western PR and western St. Croix as
well as most beaches in St. Thomas and St. John have a low risk.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 89 79 89 79 / 10 20 20 30
STT 89 78 89 78 / 20 30 30 20

[msbee]

hi Luis
How are you?
what do you think about 95L? everyone on St Maarten getting nervous about it, of course

[NotSparta]

hi Luis
How are you?
what do you think about 95L? everyone on St Maarten getting nervous about it, of course

Developed or not, TUTT should shear it enough to just be a rainmaker for the islands

[cycloneye]

hi Luis
How are you?
what do you think about 95L? everyone on St Maarten getting nervous about it, of course

Hi Barbara. As my friend said it will not be a storm when it arrives on late Sunday to the Leewards,only plenty of rain with some gusts.

[cycloneye]

From NWS San Juan discussion:

Saharan dust will continue affecting the local islands as far as
the local guidance can reach with possibly a brief break early on
Monday, only to return again late Monday into Tuesday and for
several days after that, so the persistent Saharan dust is
expected to continue. As far as the local weather, mainly fair
weather with only isolated to scattered brief showers due to local
effects every day from Saturday through Thursday, EXCEPT Monday.
The latest GFS and ECMWF models both have the current Invest 95L
approaching the local area as a tropical wave late Sunday into
Monday, which could cause a significant increase in shower and
thunderstorm activity over the local area if the models were to
verify. It pays to know that there is a great deal of uncertainty
with how exactly this tropical wave will evolve and how close it
could get to the local islands, so the confidence is low. We will
continue to monitor the latest information on Invest 95L but at
this time it looks like the Invest 95L will weaken considerably
just east of the Leeward islands and get close to our local
islands late Sunday into Monday.

[cycloneye]

Satellite imagery indicates that shower activity associated with a
small area of low pressure and a tropical wave located several
hundred miles west-southwest of the Cabo Verde Islands has become
better organized during the past few hours. Some additional
development of this system is possible, and a tropical depression
could form during the next day or two while it moves westward to
west-northwestward at 15 to 20 mph over the tropical Atlantic
Ocean. By the weekend, upper-level winds are expected to become less
conducive for development when the system approaches the Lesser
Antilles.
* Formation chance through 48 hours...medium...50 percent.
* Formation chance through 5 days...medium...50 percent.

[msbee]

thank you for the updates, Luis
Barbara

[cycloneye]

Shower activity associated with a small area of low pressure and a
tropical wave located about 1000 miles west-southwest of the
Cabo Verde Islands continues to become better organized. A tropical
depression is likely to form during the next day or two while the
system moves westward to west-northwestward at 15 to 20 mph over the
tropical Atlantic Ocean. By the weekend, however, upper-level winds
are expected to become less conducive for development when the
system approaches the Lesser Antilles.
* Formation chance through 48 hours...high...70 percent.
* Formation chance through 5 days...high...70 percent.

[Gustywind]

hi Luis
How are you?
what do you think about 95L? everyone on St Maarten getting nervous about it, of course

Hi Barbara. As my friend said it will not be a storm when it arrives on late Sunday to the Leewards,only plenty of rain with some gusts.

Hi Barbara glad to see you here. Yes, let's hope that 95L will bring a lot of water but not enough to put us in trouble Let's wait and see.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
453 AM AST Thu Jul 5 2018

.SYNOPSIS...
Saharan dust is still established across the area, but on Friday
showers should help to lower the concentrations. The Saharan dust
is expected to once again increase on Saturday. Sunday a surge of
moisture will move in from the east ahead of invest 95L so
showers are expected to increase across the U.S. Virgin Islands
during the morning, then across Puerto Rico during the afternoon.
Monday invest 95L will transverse the area with scattered to
numerous showers with isolated thunderstorms, then the wave
clears the region on Tuesday with fair weather returning to the
region through Friday.

&&

.Short Term...Today through Saturday...

Saharan dust along with low relative humidity in the mid to upper
levels of the atmosphere will continue to dominate the local
weather today. Locally induced showers can be expected over the
western and western interior PR in the afternoon but due to the
lack of moisture along the mid levels and little instability,
showers are expected to be short lived. On Friday, Saharan dust
concentration is expected to decrease and a patch of low level
moisture along with the proximity of an upper level low will then
create a better platform for shower development over the local
islands. On Saturday, drier air will move into the area resulting
in mostly fair weather conditions once again.

Temperatures will be in the upper 80s to lower 90s in lower
elevations, and the upper lower to middle 80s in higher elevations.
Winds will prevail out of the east at 10 to 15 mph with higher
gusts. Also, because drier conditions continue and very little
rainfall has occured, fire danger will moderate today.

&&

.LONG TERM...Sunday through Friday...
There`s a lot of uncertainty in the long-term period due to
invest 95L in the eastern Atlantic, but what is certain is the
increasing rain chances for Puerto Rico and the U.S. Virgin
Islands on Sunday and Monday. Sunday moisture ahead of 95L will
reach the forecast area, as a result, rain will move into the U.S.
Virgin Islands during the morning and continue to spread east
across Puerto Rico during the afternoon.

The current GFS and ECMWF models both have invest 95L approaching
the local area as a tropical wave on Monday, this could cause an
increase in showers and thunderstorms over the region if this
comes to fruition. We will continue to monitor the situation as
invest 95L continues to move across the eastern Atlantic.
Remember the National Hurricane center is the official source for
all information concerning invest 95L. The moisture from the
tropical wave is forecasted to move out of the area on Tuesday,
then dry air and saharan dust works in from the east. A fair
weather pattern is expected to prevail starting Wednesday and last
through Friday.

&&

.AVIATION...VFR conds are expected to prevail. Hazy skies will
continue, but, visibilities will remain VFR cat. SHRA can be
expected in and around of TJMZ/TJBQ from 04/17-04/22Z. Winds will
continue from the east at around 10 kts increasing 15 to 20 kts with
higher gusts after 05/13Z.

&&

.MARINE...
Seas up to 6 feet and winds up to 15 kts with possible gusts up to
20 through Saturday. Small craft operators are urged to exercise
caution. Moderate risk of rip currents across most of the beaches
in PR, Vieques, Culebra, and Saint Croix.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 89 79 89 79 / 10 10 20 30
STT 89 78 89 78 / 20 10 10 20