Caribbean - Central America Weather

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
551 AM AST Fri Feb 21 2020

.SYNOPSIS...

Mostly fair weather conditions prevail through much of the day
today across the local islands, though isolated to scattered
showers are expected in the afternoon over western and interior
Puerto Rico. Hazy skies will also persist over the area today.
Shower activity is expected to remain relatively limited as we
enter the weekend, picking up Sunday into Monday with the approach of
a frontal boundary.

&&

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

Hazy skies will continue today across the region and mostly fair
weather conditions are expected to prevail with isolated to locally
scattered afternoon shower development over portions of central and
western Puerto Rico. Drier air will continue to limit shower
development across the islands through Saturday. Low level moisture
starts to increase somewhat on Sunday, as an upper level trough and
associated frontal boundary at the surface across the western
Atlantic moves further into the central Atlantic. This pattern will
induce a prefrontal trough late in the weekend across the region and
turn winds more from the south/southeast. Therefore, expect shower
activity to gradually increase across the islands on Sunday.
However, no significant rainfall amounts are anticipated at this
moment. A long period northerly swell will increase seas and the
risk of rip currents across the north facing beaches of the islands
on Sunday.

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

On Monday morning, a decaying cold front will be draped across the
northwestern parts of the region. This will bring continuing
increased moisture to the area, with precipitable water levels near
or above seasonal normals - the 0Z run of the GFS shows levels
around 1.2 to 1.8 inches. Meanwhile, the remnants of an old frontal
boundary will approach the region from the east, embedded in the
trade winds, contributing to low-level moisture convergence across
the area. Furthermore, weak troughing at the mid-levels will allow
for a greater vertical extent of this moisture, to around 500 hPa,
though instability aloft will likely not be sufficient to sustain
convective activity. These factors will allow for increased shower
activity, with the potential for locally heavy rainfall, though
flooding does not appear to be a major concern at this time.

On Tuesday, a slow, gradual drying trend will begin. The mid-level
trough will also pull away from the area, increasing stability
aloft. As such, decreasing shower activity is expected, a trend that
will continue through the end of the week. Moisture is likely to
remain near seasonal normal levels Tuesday into Wednesday, and
showers continue to be likely, both passing showers during the
morning and overnight, affecting windward parts of the local
islands, and afternoon showers due to local effects and diurnal
heating. The drying becomes more pronounced during the second half
of the week and into the weekend, and the inhibited shower activity
is likely to lead to generally stable conditions over the local
islands. There will, however, likely be sufficient moisture in the
low levels to support some, likely isolated, shower activity,
especially during the afternoon caused by sea breeze convergence and
daytime heating.

&&

.AVIATION...

Mainly VFR conditions are expected to prevail across all
terminals during the next 24 hours. Brief MVFR cigs possible from
16z-21z at TJMZ/TJBQ due to SHRA. East winds at 10-15 knots with
higher gusts and sea breeze variations expected after 14z.

&&

.MARINE...

Winds are subsiding somewhat, though there remains moderate easterly
trade winds across the regional waters. And, with the slowing
winds, seas are also subsiding. Wave heights to around 6 feet are
likely for portions of the local waters, including offshore waters
and local passages; seas to 7 feet are still expected into this
afternoon in the offshore Atlantic waters. Conditions will
continue to improve into Saturday. However, another northerly
swell is expected to arrive in the local waters early on Sunday,
at which point seas are expected to once again turn hazardous. For
beachgoers, there remains a moderate risk of rip currents across
most of the local beaches in the north and southeast of Puerto
Rico, as well as St. Croix, St. Thomas, Vieques, and Culebra;
there is otherwise a generally low risk of rip currents elsewhere.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 85 73 87 73 / 10 0 10 10
STT 83 71 82 71 / 20 20 20 20

&&

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
523 AM AST Sat Feb 22 2020

.SYNOPSIS...
Generally fair weather continues today. Though there remains the
potential for showers due to local effects and diurnal heating,
showers are not expected to be widespread, and little rainfall
accumulation is expected. Under the influence of an approaching
frontal boundary, shower activity is expected to increase
tomorrow, lasting into the first part of the workweek.

&&

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

Drier air aloft and moisture capped below 800mb will continue to
promote mostly fair weather conditions across the region today. A
light southerly steering wind flow will prevail and this may carry a
few showers over the Caribbean waters across portions of southern PR
during the morning hours. Under the southerly winds, above normal
daytime temperatures are expected across coastal areas and the
northern sections of Puerto Rico. Any shower development today will
be induced by the sea breeze convergence over central and along the
northern slopes of Puerto Rico. However, minor to moderate rainfall
amounts are expected due to the limited available low level
moisture and stable conditions aloft.

Moisture will pick up gradually on Sunday and Monday as an upper
level trough and associated frontal boundary at the surface
approaches from the western Atlantic. The southerly winds will
continue on Sunday and diurnally induced afternoon showers will once
again be focused across portions of the interior and west/northwest
PR. On Monday, winds are to turn from the northeast and increase
behind the frontal boundary as a broad surface high pressure builds
over the western Atlantic. This will promote an advective pattern,
with cloudiness and showers lingering over PR and across the
northern U.S. Virgin Islands through at least Monday night.

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

On Tuesday morning, the frontal boundary will still be draped over
the area, as will its associated moisture. Aloft, however, the mid-
and upper-level troughs are expected to have begun to pull away from
the region. As this occurs, increasingly stable conditions are
expected aloft, leading to decreasing vertical extent of the
moisture over the area. There will, however, be sufficient moisture
and instability to help sustain the passing showers and develop the
afternoon showers caused by local effects and diurnal heating. A
slow, gradual drying trend is expected for midweek into the end of
the week; the bulk of the moisture will generally be trapped in the
lower levels from midweek onward, and is currently forecast to be at
or below seasonal normals. With the drying trend, the weather
pattern will become less active, with the number and areal extent of
showers decreasing. There will still be some patches of moisture
carried into the region, embedded in the trade winds, and there is
the potential for isolated to locally scattered showers. During the
day on Saturday, another trough is expected to begin to approach the
region from the northwest. Increasing moisture is expected late
Saturday through the rest of the weekend, and therfore increasing
shower activity is likely.

&&

.AVIATION...

Mainly VFR conditions are expected to prevail across all
terminals during the next 24 hours. Southerly winds up to 10 knots
are expected, with sea breeze variations along the northern coast of
Puerto Rico after 15z.

&&

.MARINE...

Relatively tranquil marine conditions continue this morning, with
seas less than 5 feet likely across the local waters. Late tonight,
seas will begin to build with an arriving swell. Sunday morning will
see a return of hazardous conditions to the local waters, starting
with the offshore Atlantic waters, then spreading to nearshore
waters and passages. Small craft advisories have been issued for
the local Atlantic waters starting on Sunday. The effects of this
swell are forecast to last through at least the first half of the
week in our regional waters. For beachgoers, there remains a low
to moderate risk of rip currents across the local beaches.
However, this risk will increase with the arrival of the swell,
and there will be a high risk of rip currents for north- facing
beaches of Puerto Rico on Sunday morning.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 73 86 74 / 10 10 30 50
STT 83 75 82 74 / 10 10 20 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
552 AM AST Sun Feb 23 2020

.SYNOPSIS...

With the approach of a cold front from the northwest, showers are
increasing and will continue to do so today. This increased shower
activity will last into midweek, followed by a drying trend for
the latter part of the week.

&&

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

Showers and have increased ahead of an approaching front across the
Atlantic waters and the southwestern coastal waters of Puerto Rico.
This activity should remain mainly over the waters during the
morning hours, however, as light southwesterly steering winds are
prevailing some of these showers could move over the southwest and
western municipalities of PR. As the day progresses, this surge of
moisture in combination with a northerly sea breeze along the north
coast of PR, will aid in the development of afternoon showers over
the interior and northern half of PR as well as over the San Juan
metro area.

The cold front is forecast to move over local Atlantic waters and
slowly meander across the region, with the bulk of moisture sinking
across the northern sections of PR and the northern USVI through
Monday evening. Periods of prolonged moderate to heavy showers will
lead to urban and small stream flooding across PR and the northern
USVI during this period. A broad surface high pressure building over
the western Atlantic will promote north-northeast trades on Monday
and Tuesday. This will continue to promote an advective weather
pattern across portions of the USVI and northeastern sections of PR
through at least Tuesday.

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

On Wednesday, there will remain lingering moisture over the area,
with some additional patches of moisture being carried in, embedded
in the trade winds. On the whole, though, the trend is towards drier
conditions. Aloft, a mid-level ridge will park itself over the
region, bringing increasing stability, and will stay in place into
the weekend. As such, most of the moisture will generally be trapped
in the lower levels. Through the end of the week, increasing dryness
is expected, with the driest days being Saturday and Sunday. There
will likely remain sufficient moisture to sustain some isolated
passing showers during the overnight and morning hours each day, as
well as some isolated to scattered afternoon showers caused by local
effects and diurnal heating.

During the weekend, a cold front will begin to slowly approach the
area from the northwest. This system will bring increasing moisture
to the area, likely starting by early Monday morning. Additionally,
the mid-level ridge will start to pull away from the region on
Saturday into Sunday, leading to decreasing stability aloft. And on
Monday, an upper-level trough is forecast to be to the west of the
area, which would suggest divergence aloft and increasing
instability. These factors will contribute to increasing shower
activity for Monday. Scattered showers are likely to be seen across
the majority of the local islands. The wind flow is currently
forecast to be generally out of the north at that time, which would
suggest that the peak shower activity would be in southern Puerto
Rico. Presently, thunderstorms do not look likely, despite the
increased instability; 500 hPa temperatures are expected to remain
around -6C to -5C, and models are also suggesting a high-shear
environment.

&&

.AVIATION...

VFR conditions expected across most of the terminals
through the forecast period. SHRA expected across interior and
northeastern PR through 22z, this may cause tempo MVFR at TJSJ. MVFR
conditions are possible tonight and through late in the forecast
period across the northern PR terminals and TIST due to an
approaching cold front. Winds will continue light with a S/SW
component.

&&

.MARINE...

A northerly swell is starting to increase seas in the local waters
this morning. Seas are forecast to start to become hazardous today
into tomorrow in the Atlantic waters and local passages. Hazardous
marine conditions are forecast to last into midweek, though model
guidance is starting to back off on its expectations near the end of
the event during midweek. For the early part of the week, guidance
has remained generally consistent. For the beachgoers, there is a
high risk of rip currents at north-facing beaches of Puerto Rico,
Culebra, and St. Thomas today, as well as southwestern beaches of
Puerto Rico. Elsewhere, the risk of rip currents is low to
moderate.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 88 75 80 73 / 50 80 80 50
STT 82 71 82 73 / 20 60 60 50

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
457 AM AST Mon Feb 24 2020

.SYNOPSIS...

A weak frontal boundary across the Atlantic waters is causing
showers across the local waters. The frontal boundary will
continue to produce showers across the local waters today; this
activity will then spread inland during the afternoon. High
pressure will move over the region by mid-week and hold through
Sunday. The high pressure will cause relatively tranquil weather,
however an isolated showers can`t be ruled out during the
afternoon. Sunday, another frontal boundary is expected to move
close to the area, and bring an end to the relatively tranquil
weather for Puerto Rio and the U.S. Virgin Islands.

&&

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

A frontal boundary is providing plenty of moisture across the
islands. This front will linger and dissipate over the region
through the short term. Although there is high uncertainty about
where is going to be observed the rain activity, the available
moisture will result in cloudy skies and rainy conditions across
many parts of the islands. However, this activity should remain
mainly over the waters, and from the northwest to northeast portions
of Puerto Rico and the northern U.S. Virgin Islands. Shower activity
will spread across the interior and southern sections by mid-morning
into the afternoon hours. The less potential to observe rain
activity is in St Croix. Therefore, we are forecasting fair weather
for them. As the day progresses, the available moisture in
combination with surface convergence and mountain effects, will aid
in the development of afternoon showers over the interior, west and
northern half of PR. Under light steering winds periods of prolonged
moderate to locally heavy rains will lead to urban and small stream
flooding across portions of the islands.

As the aforementioned frontal boundary dissipate, a surface high
pressure which is forecast to move eastward into the Central
Atlantic Ocean will promote an advective pattern by Wednesday.
Therefore, winds will return from the east and the typical trade
wind showers.

&&

.LONG TERM...Thursday through Tuesday...

Relatively stable weather is prog to prevail through most of the
long-term period as a result of ridging at the surface and aloft.
As the ridges hold across the area, they will also transport a
drier air across Puerto Rico and the U.S. Virgin Islands, and
increase the trade wind cap through Saturday Afternoon. However,
moisture confined between 1000 to 700 MB, local, and diurnal
effects could produce a few showers during the afternoon. Showers
that do develop will be short-lived and produce light rainfall
amounts.

Saturday will be a transition day as a frontal boundary across the
western Atlantic begins to weaken the surface and mid-level
ridge, which will allow moisture to slide underneath the ridges.
The moisture increase will aid in the development of showers
during the early morning across eastern and northern Puerto Rico,
and the U.S. Virgin Islands. Then showers across the western and
interior during the afternoon. Sunday, a short-wave, and jet-steak
are forecast to round the best of the trough mentioned above. As
a result, the frontal boundary will continue to move south and
near the local waters late Sunday night into Monday morning.

The GFS shows the frontal boundary draped over Puerto Rico by Monday
afternoon, and lingering through Tuesday morning. Additionally,
the GFS shows precipitable water values ranging from 1.5 to 2.0
inches Monday through early Tuesday morning. The moisture
increase, low-level convergence, adequate instability, and
northerly wind flow will aid in the development of scattered to
numerous showers Monday through Tuesday morning.

By Tuesday afternoon, current guidance shows the frontal boundary south
of Puerto Rico, and precipitable water values decreasing
throughout the day. Nevertheless, lingering moisture will combine
with local and diurnal effects to induce scattered to isolated
showers during the afternoon. At this time, thunderstorm
development looks bleak due to warm 500 MB temperatures and
limited upper-level divergence over Puerto Rico and the U.S.
Virgin Islands. However, a few isolated thunderstorms may develop
across the Atlantic, and Caribbean waters were current guidance
has the highest upper-level divergence.

&&

.AVIATION...

SHRA/-SHRA will affect the terminals of N/W-PR/St Thomas
as a frontal boundary stall near the region. Therefore, expects
ceilings btwn FL030-FL070 at JBQ/JMZ/JSJ/IST through much of the
fcst period. SHRA will slowly move into the interior and S-PR after
24/15z, impacting JPS. ISX/NCM/KPK can expect tranquil weather
conditions. Winds will continue light and VRB, increasing around 10
knots with a NE component and sea breeze variations after 24/13z.
S/SW component.

&&

.MARINE...

A northerly swell and winds up to 20 kts will cause hazardous
seas through the middle of the week. There is a small craft
advisory in effect for the Atlantic waters, Mona Passage, Anegada
Passage and the northern near-shore waters of Puerto Rico.
Additionally, there is a high risk of rip currents for the
northern, eastern and western beaches of Puerto Rico. Also, there
is a high risk of rip currents for Saint Thomas, Saint John and
the beaches of Culebra. Winds will be from the northeast to east-
northeast ranging from 10 to 20 kts.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 82 73 82 73 / 70 40 60 50
STT 83 73 83 74 / 10 50 50 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
504 AM AST Tue Feb 25 2020

.SYNOPSIS...

A dissipating front and its associated moisture will continue to
cause scattered to numerous showers over Puerto Rico today. Soils
are saturated from previous days rainfall, and any additional
rainfall could cause flooding. Conditions are forecast to improve
tomorrow with drier weather forecast to prevail Thursday and
through the weekend. Early next week a frontal boundary is
forecast to move over the local area late Sunday night into early
Monday. This feature will bring an end to the relatively drier
weather for Puerto Rico and the U.S. Virgin Islands.

&&

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

A dissipating frontal boundary providing plenty of moisture will
result in showery conditions throughout the day. Cloudy skies will
persist today, though St Croix can expect periods of sunshine with
partly cloudy skies. The northern Virgin Isles as well as north,
east and southeast Puerto Rico can expect cloudy skies with frequent
showers especially through the morning hours. Shower activity will
spread across the interior and western sections of Puerto Rico by
mid-morning into the afternoon hours. Once again, St Croix will have
fair weather conditions with pleasant temperatures, while the rest
of the islands will observe rainy conditions. The northeast corner
of Puerto Rico and the northern U.S. Virgin Islands seems to be more
susceptible to receive the best rainfall amounts. However, the
western and interior sections will observe decent rainfall
accumulations during the afternoon and evening hours.

As the aforementioned frontal boundary dissipate, a surface high
pressure which is forecast to move eastward into the Central
Atlantic Ocean will promote an advective pattern by Wednesday and
Thursday. Also, a ridge pattern aloft will build to limit vertical
development. Therefore, a drying trend is forecast after mid-week.

&&

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

Current guidance continues to support relatively stable weather
for Puerto Rico and the U.S. Virgin Islands through Sunday afternoon;
as a result of ridging at the surface and aloft. The ridges will
usher in a relatively drier air over the region, and promote a
strong inversion in the mid-levels of the atmosphere. Analysis of
the cross-sections and TJSJ Skew-T shows moisture trapped between
1000 to 700 MB, through the entire long-term period. Nevertheless,
local and diurnal effects will yield a few isolated showers
during the afternoon. Still, due to the inversion, drier air and
limited moisture will cause showers that do develop to be short-
lived.

During the weekend, the next feature forecast to affect the
local weather is a frontal boundary, which is forecast to move
into the western Atlantic waters on Thursday. The frontal boundary
will continue to sink southward over the next several days due to
several jet- streaks and a short-wave trough, resulting in the
weakening of the surface and mid-level ridge. As the ridges
retreat a slight uptick in low-level moisture is forecast, the GFS
shows moisture going from 0.75 on Thursday, to 1.0 inches through
the weekend. The front and its associated moisture are forecast
to reach the local waters and northwestern areas of Puerto Rico
early Monday, and continue to spread across the remainder of the
island and U.S. Virgin Island the rest of the day. The GFS shows
precipitable water peaking to 1.7 inches Monday afternoon.

Additionally, the GFS cross-sections depict the best upward
motions over the area on Monday and Tuesday, albeit restricted to
the 1000 to 700 MB. Nevertheless, the moisture increase, low-level
convergence, adequate instability, and northerly wind flow will
aid in the development of scattered to numerous showers Monday
through Tuesday morning.

Late Tuesday morning, the GFS shows the frontal boundary south
of Puerto Rico, and precipitable water values decreasing
throughout the day. However, lingering moisture will combine with
local and diurnal effects to induce scattered to isolated showers
during the afternoon.

The GFS and ECMWF show 500 MB heights warming late Monday through Tuesday,
ranging from -6.0 to -3.5 degrees Celsius on Tuesday. Also, the
models above continue to put the best upper-level divergence over
the Atlantic and Caribbean waters. Therefore, due to the above
conditions, thunderstorms were not introduced to the long-term
grids.

Wednesday, the frontal boundary and its associated moisture are
forecast to push through Puerto Rico, into the Caribbean waters as
the mid-level ridge tries to establish itself over the region
again.

&&

.AVIATION...

SHRA/-SHRA will continue to affect the N, E and SE
portions of PR and the northern USVI through the morning hours. The
frontal boundary will continue to result in BKN conds and sometimes
OVC btwn FL030-FL070 at JSJ/IST. A TEMPO for MVFR conditions is in
place for TIST until 25/12z. SHRA will slowly move into the interior
and W-PR after 25/15z, impacting JPS/JMZ. Winds will continue from
the NE at around 10 kt, increasing up to 15 kt and gusty after
25/13z.

&&

.MARINE...

Hazardous marine conditions will continue across most of the
local and offshore waters through early Thursday. As a result of a
northerly swell and east to northeast winds up to 20 kts; small
craft advisories are in effect for the Atlantic waters and most
of the local waters except for the Caribbean and the southern
near- shore waters of Puerto Rico. A High Surf Advisory is effect
through 10 AM AST today, due to breaking waves of 10-12 ft. A risk
of rip currents for all the local beaches except for the
southwestern and southern beaches of Puerto Rico. Winds will be
from the east to northeast at 10 to 20 kts.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 82 73 85 74 / 60 30 30 20
STT 83 74 84 74 / 60 30 10 10

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
453 AM AST Wed Feb 26 2020

.SYNOPSIS...

Marine conditions are forecast to improve throughout the day
across the local waters. Residual moisture from the remnant
frontal boundary will produce scattered to numerous showers across
eastern and western areas of Puerto Rico today. This could lead
to flooding in areas that received rain over the past several
days. Weather conditions are forecast to improve by the end of the
week as a surface and mid-level ridge builds over the area. Late
Sunday into early Monday morning a frontal boundary is forecast
to move into the area from the northwest, this will end the
relatively quiet weather for Puerto Rico and the U.S. Virgin
Islands.

&&

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

Moisture associated with the remnants of a frontal boundary will
fuel today`s rain activity. Periods of persistent moderate rains
will produce ponding of water in roads and low lying areas. This
activity is expected to mainly across the north, east and southeast
portion of Puerto Rico during the morning, spreading into the
interior and western sections by the afternoon and evening. We
encourage the communities in the shelters of southwest-PR to
exercise caution with this activity. On the other hand, the U.S.
Virgin Islands can expect pleasant temperatures improving weather
conditions today. However, quick passing showers cannot be ruled out
at times.

The showery weather will continue through at least tonight as a
drier and cooler air mass will be pushed by a migratory surface high
pressure across the Atlantic Ocean Thursday and Friday.

&&

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

The GFS shows minor changes in the long-term period; otherwise, no
significant changes are forecast at this time. First, the GFS 25/18Z and 26/00Z
guidance has more moisture over Puerto Rico and the U.S. Virgin Islands during
the weekend ahead of the sinking trough. Secondly, the timing of the front
moving across Puerto Rico is now Monday afternoon instead of late Sunday night
and early Monday morning.

What`s has stayed consistent is the ridging at the surface, and mid-levels will
promote a strong inversion, which will limit shower development on Friday and
early Sunday. However, showers are forecast to develop as a result of local and
diurnal effects. The GFS TJSJ cross-section and Skew-T, shows moisture trapped
between 1000 to 600 MB Sunday through late Tuesday night.

The frontal boundary and its associated moisture are prog to entered the local waters
and northwestern Puerto Rico on Monday. Therefore, expect an increase in clouds, rain,
and low-level moisture. The 25/00Z GFS shows precipitable water values increasing from
1.25 inches during the weekend to 1.63 inches early Monday, and peaking at 1.7 early
Tuesday morning.

The precipitable water peaks coincide with the GFS cross-section for Puerto Rico, which
depicts the best upward motion on Monday and Tuesday. The upward motion is a result of
low-level convergence of winds and moisture over land, also meager upper-level forcing
over the region. Nevertheless, the above conditions will lead to the development of
scattered to numerous showers on Monday and Tuesday.

The GFS and ECMWF continue to show 500 MB heights warming late Monday through Tuesday,
ranging from -5.0 to -3.5 degrees Celsius.

Wednesday, the frontal boundary and its associated moisture are forecast to push near
the southern coast of Puerto Rico. Still expect rainy conditions for Puerto Rico and
adjacent Islands on Wednesday. Thursday, a mid-level ridge will nose in from the west,
the ridging at the surface and mid-level should bring a reprieve to the moderate to
heavy rainfall.

&&

.AVIATION...

SHRA/-SHRA will continue to affect the N, E and SE
portions of PR through the morning hours. USVI terminals can expect
improving conditions. SHRA will result in BKN ceilings at FL016 over
NCM/KPK through at least 26/12z. SHRA will slowly move into the
interior and W-PR after 26/15z, impacting JPS/JMZ. Winds will
continue from the NE at around 10 kt, increasing up to 15 kt and
gusty after 26/13z.

&&

.MARINE...

A subsiding northerly swell will continue to cause hazardous seas
across the local waters today. However, the swell and winds are
forecast to diminish throughout today. There is a small craft
advisory for the Atlantic waters, Mona Passage and the near- shore
waters of Puerto Rico. Also, there is a high risk of rip currents
for the northern, eastern, western beaches of Puerto Rico; and
the beaches of the USVI, Culebra and Saint thomas and Saint John.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 83 72 83 72 / 60 20 0 10
STT 84 72 84 73 / 40 10 10 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
410 AM AST Fri Feb 28 2020

.SYNOPSIS...

A fair weather pattern will dominate local weather through at
least early Sunday morning. However, patches of moisture embedded
in the trades will reach the islands at time. Unstable weather
conditions are forecasted for the first part of next week as a
cold front moves closer and linger over the islands.

&&

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

No change in the short-term forecast as ridging and a drier air mass
will create relatively fair weather conditions through early Sunday.
However, patches of moisture embedded in the easterly trade winds
will induce isolated to scattered showers across Puerto Rico and the
U.S. Virgin Islands during the mornings, and the western areas
during afternoons. In any event, the meager moisture and ridging
will limit the vertical development of showers and make them short-
lived.

The frontal boundary currently over the western Atlantic will
continue to meander south over the next several days before reaching
the forecast area Sunday afternoon into early Monday morning. The
polar trough will continue to weaken the mid-level ridge during the
weekend. As the ridge weaken and move off to the northeast surface
winds will turn in a southerly direction. The southerly wind flow
will slowly increase low-level moisture and destabilize the
atmosphere. Sunday, low-level convergence ahead of the frontal
boundary will result in an increase in cloud cover as well as rain
chances on Sunday.

.LONG TERM...

A polar trough moving near the islands will replace the ridge
aloft that prevailed through last week. At the surface, a cold
front forecasted to stall until dissipates over the islands will
induce a surface trough and will bring plenty of moisture through
much of the week. Both GFS and ECMWF are suggesting shower
conditions and pleasant temperatures through the first half of
next week. Global models have been consistent in suggesting an
unstable and moist weather pattern during the medium-range
forecast. Therefore, confidence in them has increased today.

Surface high pressure behind the front will move into the central
Atlantic Wednesday and Thursday. Furthermore, an upper-level
ridge is forecast to build over the Northeast Caribbean. GFS is
now indicating additional moisture being push over the islands
through at least Friday. Although moisture is forecast to slowly
erodes, showery weather looks possible through the second part of
the work-week too. At this time, there is a lot of uncertainty
in this scenario. Moisture will erodes ahead of a cold front,
suggested near the region by the weekend.

&&

.AVIATION...

VFR will continue to prevail through 29/03Z. A few
iso/sct shra across PR E terminals and USVI through 28/15Z. Then
iso/sct shra developing near terminal TJBQ, TJMZ and northwestern PR
by 28/18Z with SHRA dissipating by 29/01z. Sfc wnds fm E btw 5-15
kts.

&&

.MARINE...

A northeasterly swell will continue to move across the Atlantic
Water and Caribbean Passages through at least Sunday. Then,
another northerly swell is forecasted early next week. Surface
high pressure, moving across the Atlantic Ocean, is forecasted to
bring fresh to locally strong easterlies inducing hazardous seas
Monday through the next work-week,

Mariners can expect east to northeast winds around 15 knots and
seas at 4 to 6 feet across the Atlantic waters and between 2 and
5 feet across the Caribbean Waters.

Beachgoers, a moderate risk of rip currents will continue for most
of the northern beaches of the islands through the weekend.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 84 74 86 73 / 20 50 30 40
STT 84 73 84 72 / 30 50 30 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
535 AM AST Sat Feb 29 2020

.SYNOPSIS...

Limited shower activity is expected for much of the weekend as dry
conditions in combination with a ridge aloft are expected to
prevail through Sunday. A cold front is expected to affect the
region by the end of the weekend and thus providing unstable
weather conditions through midweek. A drying trend is expected for
the rest of the forecast period. Winds and seas will increase due
to a a northerly swell that will push into the Atlantic waters
and Mona Passage on Sunday.

&&

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

Mostly fair weather is expected today across the local area with
drier than normal moisture. A ridge aloft will also help keep a
stable atmosphere. That said, the limited moisture may combine with
the local effects to cause some shower development across the W/NW
sections of PR this afternoon, some of the showers could be moderate
to heavy for brief periods. The available moisture will gradually
increase into Sunday, with also a broad upper trough moving in from
the west, which is expected to help in the development of showers
across Puerto Rico and around the USVI on Sunday. Add to that the
fact that a cold front is moving in and will keep higher than normal
moisture into Tuesday. At this time the mid level temps are not
expected to be cold enough for significant thunderstorm development
on Sunday since the forecast soundings indicate 500 mb temps of -5
to -6C temps, which is actually higher than normal. However, shower
activity is expected to increase with the increase in moisture and
as the upper trough approaches for Sunday and Monday. There is some
disagreement among the hi-res guidance though, some are a lot more
bullish than others in their solutions, but we decided to go with
the GFS for the global model and the WRF for the higher resolution
model, which put good amounts of rain for the south and east
sections of PR and around the USVI on Sunday, then more generalized
scattered showers across the local area on Monday. The winds are
expected to be relatively light today and Sunday, but stronger winds
start moving in late Sunday into Monday as the cold front starts to
get very lose to the local islands.


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

The cold front is forecast to start dissipating and moving away
from our region by Tuesday. This will induce a surface trough and
will bring plenty of moisture through much of the week. Model
guidance is suggesting shower conditions through the first half of
next week. Global models continue being consistent in suggesting
an unstable and moist weather pattern during the medium-range
forecast.

Surface high pressure behind the front will move into the central
Atlantic Wednesday and Thursday. Furthermore, an upper-level
ridge is forecast to build over the Northeast Caribbean. Additional
moisture is expected over the islands through at least Friday.
Although moisture is forecast to slowly erode, showery weather
looks possible through the second part of the work-week. However,
there still high uncertainty present in this scenario. Latest
model guidance indicates moisture will erode ahead of a cold
front, suggested near the region by the weekend.


&&

.AVIATION...

VFR conds will prevail through today. Isol/Sct SHRA
expected across TJBQ and TJMZ after 29/18Z into the evening hours.
Relatively light winds are expected today at around 10kts from the
east with sea breeze variations developing after 29/13Z. VCSH
possible across the local terminals after 01/00Z as moisture
increases and SHRA becomes SCT across the local area.

&&


.MARINE...

Gentle to moderate southeasterly winds will prevail across the local
waters, as a cold front approaches the region. Seas less than 5 feet
are expected for most of the weekend. On Sunday night, a cold front
will push into the area from the northwest, bringing increased shower
activity. Winds and seas will also increase with the arrival of the
front as well as a northerly swell that will push into the local
waters around the same time.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 82 72 81 71 / 20 30 30 30
STT 79 77 78 76 / 20 30 60 60

&&

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
520 AM AST Sun Mar 1 2020

.SYNOPSIS...

A cold front will provide unstable weather conditions today
through early in the week. Another cold front will reach the area
promoting an increase in moisture and better dynamics to generate
widespread shower activity across the islands and local waters
during the weekend. The arrival of a northerly swell will cause
hazardous seas through midweek.


&&


.SHORT TERM...Tonight through Monday...

Isolated to scattered showers are expected this morning across the
local islands. The available moisture will gradually increase today,
with also a broad upper trough moving in from the west, which is
expected to help in the development of showers across Puerto Rico
and around the USVI this afternoon. The hi-res models favor areas
along the interior, southern slopes into eastern Puerto Rico and
parts of the San Juan metro as the areas with the best chance for
significant rainfall. In these areas urban and small stream flooding
could occur. The fact that a cold front to our northwest is moving
in and will keep the higher than normal moisture into Tuesday. This
will keep numerous shower activity across portions of the local
forecast area at least through Monday. For Tuesday, the stronger
easterly winds return, which will cause western PR to have the
higher chance of rain in the afternoon when combined with the local
effects. The mid level temps are not expected to be cold enough for
significant thunderstorm development over the next few days since
the forecast soundings indicate 500 mb temps of -5 to
-6C, which is actually higher than normal. There is some
disagreement among the hi-res guidance, some are a lot more
bullish than others in their solutions, which was also seen
yesterday, but we decided to go with a combination of the WRF and
NMM models in order to split the difference between the
aggressive WRF and the more moderate NMM, while the location of
the shower activity is similar over land areas they do differ on
the rainfall over the local waters and around the USVI.


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

As the cold front gradually dissipates an moves away from the area,
leftover moisture will continue to promote showery conditions
through mid-week. A surface low will promote a more southeasterly
flow and with that, a return of the low-level moisture associated
with what will then be the remnants of the cold front by
Wednesday and Thursday. Therefore, shallow moisture will be able
to combine with local and diurnal effects to generate showers
mainly in the afternoons. Slightly drier air will begin to
gradually filter in on Friday. However, model guidance continues
suggesting a showery conditions and a shift in wind direction more
to the north.

During the weekend, another cold front will begin to slowly
approach the area from the northwest. This system will bring
increasing moisture to the area, likely starting by early Sunday
morning. Additionally, the mid-level ridge will start to pull away from the
region on Saturday into Sunday, leading to decreasing stability
aloft.

&&

.AVIATION...

VFR conds will prevail through 01/16Z. SHRA/+SHRA
expected thereafter, causing VCSH at TJMZ, TJPS, and TJSJ. TEMPO
MVFR conds are possible. Relatively light winds expected today at
around 10kts from the east with sea breeze variations developing
after 01/13Z. However, TJBQ will have slightly stronger winds from
the NE. TJPS, TJMZ, and TJBQ could observe CIGS at around FL060-070,
but lower CIGS are possible after 01/16Z as SHRA develops. TJSJ
could have CIGS at around FL040-060 after 01/18Z.

&&

.MARINE...

Winds and seas will increase with the arrival of a frontal boundary
and a northerly swell that that will sink southwards and spread
across the Atlantic waters and Mona Passage Sunday through Monday.
For the beachgoers, a high risk of rip currents is in effect for
the north central beaches of Puerto Rico through Monday afternoon.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 83 72 82 73 / 30 40 50 30
STT 84 73 82 73 / 50 60 40 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
514 AM AST Mon Mar 2 2020

.SYNOPSIS...Surface high pressure north of the local islands will
cause east to northeast winds today, turning mainly easterly on
Tuesday.Winds will remain mainly easterly until late in the week
when another, and much stronger SFC high pressure moves north of
the local area. Winds are expected to turn SE around Saturday,
then increase and turn NE on Sunday into the following Monday.
A cold front is expected to move in today, bringing an increase
in moisture, clouds and shower activity over the local area. The
moisture will linger through Tuesday and early Wednesday, which
will contribute to scattered to locally numerous shower activity
over the local area. Fair weather is expected for the latter part
of the workweek.

&&

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

Cloudiness and shower activity will increase across the region
through today as the front interacts with a broad upper level
trough. Periods of moderate to locally heavy rainfall could cause
urban and small stream flooding, across portions of Puerto Rico
and the northern U.S. Virgin Islands in the afternoon hours. For
Tuesday,and Wednesday leftover moisture will promote showery
conditions over the local area in the morning and nighttime
hours, but in the afternoon hours, the moisture will combine with
local and diurnal effects to promote shower development across
western Puerto Rico. Models suggest some increase in winds as a
surface high pressure moves east as it travels to the north of the
local islands.

.LONG TERM...Thursday through Tuesday...

Generally fair weather with a drier than normal air mass is
expected over the local area from Thursday through late Friday.
The upper levels will have either a ridge over the local area or
zonal wind flow in the upper levels are to be expected. At the
surface, east or ESE winds are expected as SFC high pressure
across the central Atlantic dominates the local wind flow on
Thursday and Friday. However, a SFC low across the western
Atlantic will shift the local winds to a ESE direction while the
winds weaken. A frontal boundary associated with said low pressure
will move in and over the local area on Sunday and Monday as it
is pushed by a surface high pressure moving into the western
Atlantic. This may cause a significant increase in moisture and
wind speed. The long range models have been consistent in showing
a significant increase in wind speed late on Sunday into Monday.
At the same time there may be a broad upper trough moving through
the local area which, according to the forecast soundings, could
produce an upper level jet of as much as 100 knots over the local
area. Because of this, the models are bullish on the rainfall late
on Sunday and the following Monday, and thus thunderstorms were
included in the forecast. Although the models have been consistent
for the past couple of days, this is way too far in the forecast
period to have a high confidence.

&&

.AVIATION...Expect increase in cloud cld cover and shower
activity across flying area due to approaching frontal boundary
coming from the northwest. SCT-BKN cld lyrs nr FL025...FL050 and
OVC cld lyrs nr FL080. Scattered to numerous SHRA ovr Atl waters
and btw islands til 02/22Z. SFC wnds fm ENE AT 5-15 kts with ocnly
hir gust with the heaviest rains at least til 02/22Z.


&&

.MARINE...The northerly swell is expected to invade the local
waters today, albeit a bit later than previously anticipated. The
latest model guidance is in agreement that the local seas will
gradually increase today and become hazardous. Therefore the small
craft advisory for the local waters continue in effect. As of this
writing the buoy just NW of PR is reporting seas up to a bit over
5 feet, but gradually increasing. The San Juan buoy is reporting
seas of just under 4 feet, but also is showing indications that
seas are increasing. The current forecast has seas increasing up
to 7 to 8 feet across the offshore Atlantic waters and 5 to 7 feet
across the nearshore waters. For tonight, when the peak of the
wave heights are expected, seas could increase up to 10 feet. Seas
are expected to gradually subside on Tuesday, and by Wednesday
morning the local seas are expected to be below 7 feet. The local
winds are expected to be between 10 and 20 knots across most of
the local waters, but seas up to 25 knots could be observed
across the offshore Atlantic waters.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 82 73 83 74 / 50 40 20 30
STT 83 72 83 73 / 30 30 20 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
500 AM AST Tue Mar 3 2020

.SYNOPSIS...Easterly winds will prevail over the next few days as
a surface high pressure moves across the Atlantic. Broad upper
trough will continue to move east as it amplifies northeast of the
local islands. Lingering moisture will cause isolated to scattered
showers across the local area, and also will combine with the
local effects to develop showers across portions of central and
western Puerto Rico today. Drier air expected to move in by
Wednesday, and therefore less shower activity is expected for the
second half of the workweek.


&&

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

The lingering moisture will combine with diurnal and local
effects to support the development of scattered to locally
numerous showers this afternoon across the interior and western
sections of Puerto Rico. Latest model guidance continues
suggesting that the frontal boundary will dissipate by this
evening. Slightly drier air will filter into the area to limit
shower activity by Wednesday. Rainfall accumulations are not
expected to be significant, but due to previous rainfall activity,
some ponding of water could be possible, mainly across urban and
poor drainage areas. Trade winds are expected to increase as a
developing surface high pressure moves eastward across the
western Atlantic Wednesday and Thursday. A more stable weather
pattern is expected by Thursday. Thus, generally fair weather
conditions are expected to prevail.

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

Generally fair weather with a drier than normal air mass is
expected over the local area from Friday into Sunday, with a cold
front bringing an increase in moisture late Sunday into Monday,
but drier air will follow the front for Tuesday into Wednesday.
However, there may be a patch of moisture briefly affecting the
islands on Saturday afternoon. In the upper levels, northwest flow
will prevail on Thursday, until a weak ridge passes on Friday,
then a broad upper trough is forecast to move through the local
area late Saturday into Monday, which, according to the forecast
soundings, could produce an upper level jet of almost 100 knots
over the local area. At the surface, low pressure entering the
western Atlantic and a surface high pressure northeast of the
local area will bring east or east southeast winds on Thursday and
Friday. Winds will weaken on Saturday as the aforementioned low
pressure moves northeast across the western Atlantic, causing the
local pressure gradient to relax a little. A frontal boundary
associated with this low pressure will move in and over the local
area on Sunday and Monday, pushed by a surface high pressure
moving into the western Atlantic. This may cause a significant
increase in moisture and wind speed. The long range models have
been consistent in showing a significant increase in wind speed
late on Sunday into Monday. Because of all this, particularly the
increase in moisture and the strong upper level jet, the models
are bullish on the rainfall late on Sunday and the following
Monday, and thus thunderstorms were included in the forecast.
Although the models continue to be consistent, like they have
been for the past couple of days, this is too far ahead in the
forecast period to have a high confidence.


&&

.AVIATION...SHRA and cloud cover are gradually dissipating as cold
front exists the area. Expect mainly VFR conditions for all
terminals. However, SHRA across western PR PR could bring brief
MVFR conditions for TJMZ between 03/18Z and 03/22Z. SFC wnds from
the east AT 5-15 kts with occasional gusts with the heaviest
rains.


&&

.MARINE...Seas continue to be hazardous across the local waters.
Although the latest nearshore buoy observations indicate seas of
slightly over 6 feet, buoy 41043 to the north of the local area is
still observing wave heights of around 9 feet, and the swell
direction is from the north-northwest. For that reason the small
craft advisories continue in effect, as seas are forecast to
reach 9 feet today across the offshore Atlantic waters and up to 7
or 8 feet across the nearshore Atlantic waters, waters surrounding
the northern USVI, and the local passages. There is also a high
risk of rip currents today from the northwest to northeast coasts
of Puerto Rico, Culebra island, and northwest Saint Thomas.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 82 72 85 74 / 40 40 40 40
STT 84 73 84 74 / 30 20 20 20

&

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
510 AM AST Wed Mar 4 2020

.SYNOPSIS...
Surface high pressure ridge over the north central Atlantic will
slowly lift northeastward today through Thursday as a cold front
will enter and move across the west and northwest Atlantic. This
will result in a moderate easterly wind flow across the region.
A mid to upper level ridge will build eastwards across the region
from the western Caribbean and increase the trade wind cap
inversion, while eroding low level moisture advection and
therefore support stable conditions aloft during the next few
days.

&&

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

A drying trend is expected over the local area as a drier than
normal air mass approaches from the east. An upper level ridge will
support stability aloft, providing mainly fair weather conditions
through the end of the forecast period. However, satellite imagery
indicates there is still remaining patches of low-level moisture
that will aid in development of afternoon convection over interior
and western portions of PR. Increasing winds are anticipated for
Thursday and Friday, associated with a surface ridge pushing
southward towards the area. For Friday, models are suggesting the
arrival of a broad upper-level trough that will flatten the
existing ridge and will then bring an increase in moisture and
instability aloft. Therefore, periods of passing showers are expected
during the morning hours followed by afternoon convection across
interior and western portions of the islands.

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

Generally fair weather conditions will persist over the local
area from at least through Saturday into early Sunday, with a cold
front still forecast to bring an increase in moisture and
instability across the region late Sunday through Monday.
Thereafter, a gradual drying trend is again expected by late
Tuesday through Thursday.

There may however be occasional patches of moisture, briefly
affecting the islands and local waters, early Saturday and during
the afternoon hours. In the upper levels, the approach of the
broad polar trough will begin to erode the ridge aloft move
through the local area Sunday through Monday. By then, an area of
low pressure entering the western Atlantic, and the surface high
pressure northeast of the area will induce a low level surface
trough across the region. This will result in better moisture
convergence across the forecast areas as well as the instability
aloft. A frontal boundary associated with the aforementioned low
pressure will sink southwards across the region Sunday through
Monday, as high pressure will again build and spread across the
western Atlantic. This overall pattern may cause a significant
increase in moisture and instability, followed by increasing winds
during the early part of the week.

Recent model guidance remain consistent in showing a fairly moist
pattern during the early part of the period along with a
significant increase in low level wind speeds by Monday. In
addition, cold air advection suggested in the 500 millibar level
would also suggest and favor good potential for increase rainfall
rates with the possibility of isolated thunderstorm activity
especially Sunday through Monday or early Tuesday. For the rest of
the period, expect a gradual improvement in the overall weather
condition based on the latest model guidance.

&&

.AVIATION...Drier air is approaching the area. Therefore, VFR conds
will prevail during the 24 hour period across all terminals. Sfc
winds ENE 10-15 kt with higher gusts til 04/22Z. VCSH across TJMZ
and TJBQ around 03/18Z due to afternoon convection.

&&

.MARINE...Hazardous marine conditions will persist mainly across
the Atlantic waters and Mona Passage into the early morning hours,
but will gradually improve throughout the day, as a northerly
swell will continue to fade. Small Craft Advisories are therefore
in effect for these waters until 8 AM AST. Small craft operators
should exercise caution elsewhere during the rest of today.
Mariners can expect seas between 5 to 8 feet and winds between 15
to 20 knots offshore and 10 to 15 knots near shore. Please refer
to the latest Coastal Waters Forecast (CWFSJU)and Marine Weather
Message (MWWSJU) issued by WFO San Juan PR.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 85 73 85 73 / 20 20 20 30
STT 85 74 84 73 / 10 10 20 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
519 AM AST Thu Mar 5 2020

.SYNOPSIS...A generally fair weather pattern is expected to prevail
through Saturday. Wetter conditions and organized convection are
then expected Sunday onwards as a frontal boundary associated with
a mid to upper level trough sinks southwards across the region.

&&

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

During the rest of the early morning hours, a patch of trade wind
moisture will bring brief showers and clouds across the local waters
and coastal areas of the islands from time to time. However, no
significant rainfall accumulations are anticipated as mostly light
to moderate shower activity is expected. Elsewhere and for the rest
of the day, mostly fair weather and sunny skies will prevail. The
exception will be over parts of the interior and west sections of
Puerto rico where a few locally and diurnally induced showers may
develop, as well as mainly on the west-end or downstream of the
USVI.

An overall drying trend is expected during most of the period as the
mid to upper level high pressure ridge is to build and hold in place
through Friday or early Saturday. This will therefore limit
convective development. However, patches of trade wind moisture will
continue to move across the region resulting in periods of quick
passing showers especially during the evening and overnight hours.
This will be followed by locally and diurnally afternoon shower
activity mainly in isolated areas over central and west sections of
Puerto Rico. Mostly fair weather skies should prevail in and around
the adjacent islands as well as the USVI.

On another note, resent aerosol model guidance continued to
suggest a fairly low concentration of Saharan dust to move across
portions of the region later today and through at least Friday or
early Saturday. This may cause some slightly hazy conditions, but
so far it should not be a significant problem for the Aviation
community.

By Saturday, expect a gradually erosion of the mid to upper level
ridge in response to a polar trough moving across the western
Atlantic and approaching the region. This in turn will decay the
trade wind cap and favor a better chance for some afternoon shower
development over portions of the islands. However, with relatively
dry air and the presence of the low concentration of Saharan dust
across the region, rainfall accumulation is still not expected to be
significant and should be limited to the interior and west to
northwest sections of Puerto Rico and some of the adjacent islands,
where some streamer like shower activity will remain possible.

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

A wetter pattern and organized convection are expected early
next week as a frontal boundary associated with a mid to upper
level trough sinks southwards across the region. Although the bulk
of moisture as well as instability are expected Mon-Tue, the
chance for shower activity will begin to increase on Sunday as the
prefrontal trough establishes over the area.

Recent model guidance remains consistent (GFS and ECMWF),
therefore numerous showers and T-storms were included in the
forecast package during late Monday into Tuesday when moisture
and favorable upper level dynamics are expected to peak. Precipitable
water values are expected to range between 1.50 and 1.75 inches
by Monday afternoon. Breezy conditions are expected as well Monday
and Tuesday.

Available moisture is expected to decrease somewhat on Wednesday,
but this will be short lived. Moisture advection will prevail once
again on Thursday as trofiness aloft returns to the forecast
area. As a result, another round of showers and isolated thunderstorms
is possible across the forecast area.

Overall, there is an increasing potential for shower and thunderstorms
activity as well as urban and small stream flooding next week.

&&

.AVIATION...VFR conds will prevail durg prd. Isold SHRA en route btw
islands and the surrounding waters. Brief MVFR w/SHRA...SCT-BKN lyrs
nr FL025...FL040...FL080 and MTN top obscr psbl ovr E PR til 05/12Z.
Sfc winds lgt/vrb to calm, bcmg fm E 15-20 kts and ocnly hir gusts
with sea breeze variation aft 05/14z. L/lvl wnds fm E-SE 15-20 kts
Blo FL150 bcmg fm N and incr w/ ht abv.

&&

.MARINE...Choppy marine conditions are expected to prevail across
the Atlantic waters and the Mona Passage throughout the day
today under a subsiding northerly swell. Nevertheless, seas will
remain below the Small Craft Advisory criteria.

Hazardous marine conditions and dangerous rip currents are then
expected to prevail early next week as a frontal boundary
approaches the local waters increasing winds and seas as well as
the potential for shower activity.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 85 73 85 73 / 30 30 30 40
STT 84 74 84 74 / 20 20 20 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
455 AM AST Fri Mar 6 2020

.SYNOPSIS...Fair weather is expected to prevail across the forecast
area through Saturday. The chance for shower and thunderstorm
activity is expected to increase Sunday onwards as a surface front
reaches the local islands.

&&

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

Patches of low level moisture with embedded showers carried by the
prevailing trades, will continue to affect the coastal waters and
portions of the east coastal sections of some of the islands into
the early morning hours. Thereafter mostly sunny skies and fair
weather expected for most areas. However, pockets of available
moisture will aid in the development of some afternoon showers,
mainly over portions of the interior and west to northwest sections
of Puerto Rico. Fewer afternoon shower activity is forecast for the
remainder of the islands including the USVI, but mostly sunny skies
and fair but hazy weather conditions should prevail during he rest
of the day. No widespread shower activity or significantly high
rainfall amounts are anticipated for today.

By Saturday, the mid to upper level ridge will begin to erode as a
polar trough sweep across the west Atlantic and approaches the
region. This will gradually decrease the stability aloft along with
the trade wind inversion. In addition, the development of a weakly
induced prefrontal trough will bring a quick surge of early morning
moisture to the region. This will therefore favor better potential
for early morning and afternoon shower development. Even so,
significant and widespread rainfall is no expected at this time.

A moist and unstable wetter pattern with more organized convection
is still forecast by late Sunday into early next week, as a frontal
boundary and associated mid to upper level trough will sink
southwards across the region. Although the bulk of moisture as well
as instability are expected late Sunday through Monday, the chance
for shower activity will begin to increase on early Sunday as the
prefrontal trough establishes over the area. By then urban and small
stream flooding will be possible.

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

Long term forecast still on track with unsettled weather conditions
expected early the next week as a surface front associated with
a mid to upper level trough sinks southwards over the local area.
The GFS and ECMWF continue to suggest bulk of moisture as well as
instability across the local islands Monday and Tuesday with
precipitable water values reaching 1.80 inches by Tuesday
afternoon. In addition to plenty of moisture and favorable upper
level dynamics, this front will bring breezy conditions with
northeast winds near 25 knots on Monday. Although the available
moisture is expected to decrease somewhat on Wednesday, this will
be short-lived. Moisture advection is expected once again on
Thursday as trofiness aloft returns to the forecast area. As a
result, another round of organized convection is possible. An
overall drying trend is then expected by the end of the week into
the next weekend.

In response to this evolving pattern, expect unstable weather
conditions Monday and Tuesday with periods of showers and isolated
thunderstorms particularly over the northern and eastern sections
of Puerto Rico as well as the US Virgin Islands. Although fast-
moving showers and thunderstorms are expected, the potential for
urban and small stream flooding will increase. At this time, the
highest chance for showers and thunderstorms is Monday night into
early Tuesday morning.

&&

.AVIATION...VFR conds will prevail at all terminals and across the
flying area. Aftn SHRA may result in brief MVFR conds in and around
TJBQ/TJMZ with SCT-BKN lyrs nr FL028...FL050 til 06/22Z. VCSH at
TJSJ/TIST/TISX/TKPK/TNCM til 06/14z. Sfc wnds calm to Lgt/Vrb bcmg
fm E btw 10-15 knots and higher gusts with sea breeze variations. No
sig operational wx impacts durg prd.

&&

.MARINE...Choppy marine conditions are expected to prevail across
the Mona Passage throughout the day today. Nevertheless, seas will
remain below the Small Craft Advisory criteria through Saturday.
Hazardous marine conditions and dangerous rip currents are then
expected to prevail Sunday onwards as a frontal boundary approaches
the local waters increasing winds and seas as well as the
potential for shower activity.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 85 73 86 73 / 50 40 40 60
STT 85 73 84 73 / 50 40 40 60

&&

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
532 AM AST Sat Mar 7 2020

.SYNOPSIS....Overall fair weather conditions is expected to prevail
across the region through early Sunday. Increasing instability
aloft and good moisture advection is forecast by late Sunday through
early next week, with high potential for convective development
and thunderstorm activity across the forecast area. This unfolding
pattern is due to the approaching upper level polar trough along
with arrival of the associated surface frontal boundary and shear
line moisture. A increasingly wet weather pattern is therefore expected
by Sunday into early next week.

&&

.SHORT TERM...Saturday through Monday...

Mostly clear to partly cloudy skies prevailed across the local
islands during the overnight hours. Trade wind showers were observed
across the local waters with a few of them affecting eastern Puerto
Rico and the outlying islands. Rainfall totals, however, were
minimal. The overnight low temperatures ranged from the low to mid
70s across the lower elevations and in the mid to upper 60s across
the higher elevations. Winds were light and variable.

Trade wind showers will continue to prevail across the forecast area
today. These showers will be focused mainly across the coastal areas
of eastern Puerto Rico as well as over the outlying islands. Locally
induced afternoon showers are expected as well over central Puerto
Rico as the result of daytime heating and local effects.

The weather scenario will quickly change Sunday onwards as a polar
trough with its associated surface front sinks southward into the
northeast Caribbean. Increasing moisture is expected on Sunday, with
the development of a pre-frontal trough, as a surface front
approaches the local islands from the northwest. Model guidance
suggests bulk of moisture as well as increased upper level
divergence late Monday into early Tuesday. Precipitable water values
are expected to peak at around 1.80 inches by Monday afternoon. In
addition to moisture and favorable upper level dynamics, breezy
conditions with winds near 25 knots are expected as well.

In response to this evolving pattern, the chance for showers and
thunderstorms will increase on Sunday. These showers and
thunderstorms will be focused over the northern and eastern coastal
areas of Puerto Rico, the US Virgin Islands and the southwest tip of
Puerto Rico. Breezy. Numerous showers with thunderstorms are then
expected on Monday. Breezy to windy. Although fast-moving showers
and thunderstorms are expected early the next work week, there is an
increasing potential for urban and small stream flooding.

.LONG TERM...TUESDAY THROUGH SUNDAY...

Unsettled weather conditions expected to continue through at least
the middle of next week, due to a combination of lingering frontal
boundary, shearline moisture,the proximity of the broad polar
trough, and a short wave trough forecast to move through the
region Wednesday through Thursday. Overall a moist advective
pattern is forecast with increasing moderate to strong northeast
trade winds expected through at least Wednesday, as a surface high
will build and spread eastward across the western Atlantic.

As the frontal boundary and associated polar trough sinks southwards
across the area, the increasing low level moisture convergence/pooling
and instability aloft will support high potential for enhanced
convection during the early part of the period. Recent model guidance
continued to initialize well and is persistent in suggesting a wet
weather pattern for much of the work week. The secondary short wave
trough is also progged to move across the region Wednesday through
Thursday to maintain unstable conditions aloft.

An overall drying trend is expected by Friday into the weekend due
to increasing stability aloft as a high pressure ridge will build
from the west and strengthen the trade wind cap inversion, and
consequently erode the low level moisture advection and
convergence across the region.

To sum it all up, expect unstable weather conditions through mid
week with periods of showers and isolated thunderstorms particularly
over the northern half and eastern sections of Puerto Rico as
well as the U.S. Virgin Islands. Although fast- moving showers and
isolated thunderstorms are expected, the potential for enhanced
convection will increase the chance for urban and small stream
flooding at least until Thursday. At This time, the best chance
for enhanced convection with isolated thunderstorm activity is
Tuesday through Thursday.

&&

.AVIATION...VFR conditions will continue to prevail at all TAF sites
with VCSH possible in and around the Leeward and USVI terminals as
well as JSJ. Aft 07/16z showers are expected to develop over central
Puerto Rico and this may result in VCSH at JMZ/JBQ through 07/22z.
ESE at around 10 kt with higher gusts and sea breeze variations are
expected after 07/13z.

&&

.MARINE...Mariners should expect seas up to 5 feet and winds at
around 15 knots throughout the day. However, deteriorating seas,
hazardous marine conditions and dangerous rip currents are
expected to prevail Sunday into early the next week as the frontal
boundary approaches the local waters with increasing winds and
seas.

A northerly swell will also move across the Atlantic Waters on
Sunday, in association with the frontal system approaching the
area. Therefore, hazardous marine conditions and rough and
confused seas can be expected from Sunday through early next
week. Small craft advisories will go into effect by Sunday
afternoon. Therefore, mariners should closely monitor the marine
forecast products and updates.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 86 74 82 74 / 20 60 70 70
STT 84 72 82 73 / 50 60 70 70

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
418 AM AST Sun Mar 8 2020

.SYNOPSIS...
Expect increasing instability aloft and moisture advection across
the area later today through at least Tuesday. This will support
good potential for convective development and possibly isolated
thunderstorm activity across portions of the forecast area. This
unfolding pattern is due to a broad polar trough moving eastward
across the west and central Atlantic along with the arrival of an
induced surface trough, a frontal boundary and moisture associated
with a shear line which will cross the region during that time. The
light easterly winds today, will quickly become more northeasterly
later tonight through Tuesday and significantly increase, as a
high pressure ridge will build north of the region, resulting in
the tightening of the local pressure gradient.

&&

.SHORT TERM...Sunday through Tuesday...

Variably cloudy skies prevailed across the local islands during the
overnight hours. Passing showers were observed across the local waters
with a few of them affecting eastern and southern Puerto Rico. Rainfall
totals, however, were minimal. The overnight low temperatures ranged
from the low to mid 70s across the lower elevations under light and
variable winds.

The chance for shower activity will continue to increase today as a
pre-frontal trough prevails across the forecast area. Therefore, expect
passing showers across southeast Puerto Rico and the US Virgin Islands
early in the morning. As the prevailing wind flow shifts more east
northeast, passing showers will be then focused over north and east
Puerto Rico as well as the outlying islands in the afternoon and
evening hours. Under increasing moisture, locally induced afternoon
showers are expected across southwest Puerto Rico as well.

Still expect bulk of moisture and increased upper level divergence
associated with an approaching surface front and its upper level
trough Monday into early Tuesday. The precipitable water values are
expected to peak at around 1.80 inches by Monday afternoon. In
addition to plenty of moisture and favorable upper level dynamics,
breezy conditions with winds near 25 knots are expected early the
next work week. As a result, still expect frequent showers with
thunderstorms Monday into early Tuesday particularly over the local
waters, eastern Puerto Rico and the US Virgin islands. Although fast-
moving showers and thunderstorms are expected through the forecast
period, there is an increasing potential for urban and small stream
flooding.

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

A short wave trough is forecast to become amplified and move through
the region Wednesday through early Friday. Surface winds will become
more east to southeast through Friday and into the weekend as the
Atlantic high pressure ridge shifts farther eastward into the central
and northeast Atlantic. The prevailing moderate easterly winds will
continue to advect patches of moisture from the decayed frontal boundary
across the region from time to time. This available moisture and the
instability aloft will continue to support enhanced early morning and
afternoon convection across portions of the islands and regional waters
until Friday. This scenario will favor periods of moderate to locally
rainfall across the regional waters especially overnight and during
The early morning hours, followed by isolated to scattered afternoon
convection each day at least until Friday.

Improving conditions is so far forecast by Saturday and through
the weekend into Monday, as a high pressure ridge is forecast to
build and spread eastward across the forecast area. This in turn
will gradually strengthening the trade wind cap inversion resulting
in erosion of low level moisture advection and convergence. Therefore
a more seasonal weather pattern can be expected for the weekend with
limited shower activity in and around the islands during the overnight
and afternoon hours.

&&

.AVIATION...Brief periods of MVFR conditions in SHRA will remain
possible at IST/JSJ/JBQ throughout the day today. VCSH are expected
in and around JPS/JMZ aft 08/16z. VFR conditions will continue to
prevail at the Leeward terminals. The chance for shower and thunder
activity will increase across the flying area overnight into Monday
morning as a surface front reaches the northeast Caribbean. Winds
increasing at around 15 knots after 08/12Z from the east.

&&

.MARINE...Seas are expected to remain at 5 feet or less for the rest
of the morning hours. However conditions will quickly deteriorate
and become hazardous later this afternoon; and is then expected
to remain rough and hazardous through at least Tuesday. This is
due to the arrival of a northerly swell along with the rapidly
increasing northeasterly tradewinds, following a frontal boundary
forecast to sink southwards across the regional waters. Increased
potential for enhanced shower activity and possibly isolated
thunderstorms is also expected later today and continuing through
Monday. Please refer to the latest Coastal Waters Forecast (CWFSJU)
and Marine Weather Message (MWWSJU) issued by the National Weather
Service WFO San Juan PR.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 83 74 80 72 / 60 70 70 70
STT 82 73 82 72 / 60 70 70 70

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
508 AM AST Mon Mar 9 2020

.SYNOPSIS...
Hazardous marine conditions are expected to continue across the
area through the next several days, along with strong winds. A
cold front will continue to bring showers today. Pockets of
moisture will continue to filter into the region from time to time
through the rest of the workweek.

&&

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

At upper levels, a strong trough over Cuba will move over and north
of the local area on Tuesday. A second trough will move into the
central Caribbean and Cuba area late in the period to keep flow
strong and generally from the southwest.

At mid levels a ridge of high pressure will continue over the
tropical Atlantic. A low pressure over the Bahama island just
southeast of Florida will move east to be found about 600 miles
north of Puerto Rico late Tuesday evening.

A cold front was seen stretched across the Dominican Republic and
extending to the east northeast, however the evening sounding
suggested that it was also over San Juan at about 850 mb. Multiple
boundaries appear to be present in the area. Northeast flow is now
and will continue to prevail through this morning, but by afternoon
will be seen to be switching to the east. Moisture along and ahead
of the front will continue over and north of Puerto Rico, somewhat
north of the northern U.S. Virgin Islands. The best moisture with
this front is expected to peak over the area at 09/18Z today. A very
dry slot at 850 mb will then move into the area tonight to displace
the showers toward the northwest. There may even be some sun in
Puerto Rico and the northern U.S. Virgin Islands by daybreak
Tuesday, but pockets of moisture follow quickly and showers are
expected to return on Tuesday in southeasterly flow. Flow returns to
the east on Tuesday night and showers are mainly expected in eastern
Puerto Rico and the northern U.S. Virgin Islands, but will taper off
during the day Wednesday to favor central and western Puerto Rico by
afternoon.

Through all of this the frontal band appears to remain north of the
area or no further south than Puerto Rico, and hence Saint Croix
will generally enjoy partly sunny skies and maximum temperatures in
the low to mid 80s Monday through Wednesday.

Surface winds are fresh along and behind the cold front with 15 to 25
knots over northern Puerto Rico and the Atlantic to the north with
gusts up to 35 knots or 40 mph. These winds will remain strong
through the day and begin to taper off later tonight as winds gain a
southerly component. Warmer temperatures should return to
northern Puerto Rico Tuesday and Wednesday with these winds.

.LONG TERM...Thursday through Tuesday...
The remnants of the cold front will continue to bring patches of
clouds and showers on Thursday and Friday. As the surface high
pressure system moves to the east, across the eastern Atlantic,
winds are expected to shift from the east to east-southeast.
Therefore, areas of eastern and southeastern Puerto Rico, as well as
the U.S. Virgin Islands should receive showers, especially during
the nighttime and in the early morning hours. In the afternoon, as
is usual with this weather pattern, showers should develop across
the northwestern quadrant of Puerto Rico due to a combination of the
available moisture and local effects. In addition, a trough in the
mid to upper levels will provide some instability across the region,
which could favor isolated thunderstorms with the strongest
activity on Thursday.

For Saturday, the latest guidance suggest drier air filtering in at
the mid-levels as the winds shift more from the northeast. However,
at the surface, enough moisture at the lower levels should, once
again, bring fragmented groups of clouds across the area. By Sunday
and into the beginning of the workweek, a ridge in the mid and upper
levels will build over the region with a drier air mass also
taking place over the area, limiting shower activity across the
islands.



&&

.AVIATION...A cold front stretches east northeast from the Dominican
Republic and will remain north of the area. Moisture ahead of the
front will keep skies mostly cloudy north of TIST and TKPK with CIGS
btwn 030-060. Periods of MVFR CIGS are expected over PR north of the
Cordillera Central with HIR TRRN obscured. Sfc winds 10-25 kt with
gusts to 35 kt psbl mainly alg the N coast of PR. Max winds SW 80-90
kt btwn FL350-440. Tstms psbl ovr central/wrn PR aft 09/16Z.


&&

.MARINE...
Seas will continue to deteriorate today due to a combination of a
northerly swell, the proximity of a cold front and an increase in
winds. In fact the San Juan buoy is already reporting seas up to
10 feet and wind gusts up to 35 knots. On the other hand, Buoy
41043, northeast of Puerto Rico is showing seas up to 14 feet and
wind gusts also near 35 knots. These strong winds and hazardous
seas are expected to continue through the next several days. Small
craft advisories are in effect for all of the local waters. Please
refer to the latest Marine Weather Message (MWWSJU) and Coastal
Hazard Message (CFWSJU) for the latest updates.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 78 73 85 72 / 90 90 70 70
STT 79 73 84 74 / 80 80 40 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
506 AM AST Tue Mar 10 2020

.SYNOPSIS...
A cold front north of the region is expected to remain north of
the islands. Under a southeasterly wind flow, drier conditions are
anticipated by today. However, hazardous marine conditions
continue to affect most of the local waters, and seas will stay
deteriorated through much of the workweek.

&&

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

At upper levels, a ridge continues over the tropical Atlantic. A
sharp trough is over the Windward Passage. As it moves eastward it
is preceded by an unusually strong southwest jet of up to 100 knots.
The trough will retreat to the northeast, but the jet will linger
through the period, weakening somewhat after tomorrow.

At mid levels a ridge of high pressure will continue over the
tropical Atlantic. A low pressure north of Haiti and the Bahama
Islands will move east northeast to become north of Saint Thomas by
early Wednesday morning. Although the trough passes, a second trough
begins to form north of and over Haiti on Thursday to hold the flow
at mid levels mostly westerly.

A cold front and its associated moisture is over the local Atlantic
waters this morning and is being displaced to the northwest by a
surge of southeasterly flow induced by a weak low to the north that
is expected to manifest today. Satellite images also see a precursor
of the lower level low in the jet passing near its point of
formation. This will keep the area drier than yesterday, but
moisture, that was never that far away, will return in a limited way
on Wednesday as flow around the western side of the low brings
moisture back into the local forecast area. The GFS shows an extreme
moisture minimum of around one inch of precipitable water by 11/00Z
followed by a return of moderate moisture around 1.5 inches by
12/14Z Wednesday morning. Moisture increases again Thursday
afternoon and showers will return to eastern Puerto Rico later that
night.

.LONG TERM...Friday through Wednesday...
For the end of the workweek, the main feature at the mid and upper
levels is a trough located to the northeast of the Caribbean. The
latest guidance suggest that the islands will not be under the area
of best divergence, hence the support for shower activity will be
limited. At the lower levels, however, available moisture associated
with an old frontal boundary should bring some showers across the
area. Due to a surface high pressure over the eastern Atlantic, the
wind flow will be out of the northeast, and therefore, morning
activity will be favored over the eastern and northern half of
Puerto Rico, with afternoon showers developing across the
southwestern quadrant of the area.

As the trough moves to the east, an upper level ridge will begin to
build late on Saturday over the western Caribbean, while high
pressure also strengthen at the mid- and lower levels. This should
result in a mainly fair weather pattern across the region, although
showers carried by the trade winds will continue to affect the
islands from time to time. This high pressure system will also
tighten the gradient, resulting in moderate to strong winds through
the weekend and into early next week.


&&

.AVIATION...A cold front stretches across the outer Atlantic waters.
TSTMs have retreated to north of 20 north along the front. Some
light rain SHRA persist over the area--mainly in NE PR. VFR will
prevail at local TAF sites as drier air moves in from the SE. SHRA
are expected to dvlp ovr interior and wrn PR aft 10/15Z and cont byd
10/22Z with brief MVFR conds. Sfc winds are easterly and over and
near land are less than 10 knots. Sfc winds will increase to 5-15 kt
by 10/15Z with sea breeze influences. Max winds SW 80-100 knots btwn
FL300-460, strongest at FL400.


&&

.MARINE...
Hazardous marine conditions continue across most of the local
waters due to strong winds, a northerly swell and a frontal
boundary over the Atlantic waters. Seas up to 14 feet,
occasionally up to 18 feet are expected to continue today. In the
Caribbean waters, seas up to 10 feet, occasionally up to 11 feet
can be expected. Small craft advisories remain in effect for
these areas. Please refer to the latest Marine Weather Message
(MWWSJU) and Coastal Hazard Message (CFWSJU) for the latest
updates.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 84 71 84 71 / 40 40 30 40
STT 84 74 84 75 / 20 30 20 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
514 AM AST Wed Mar 11 2020

.SYNOPSIS...
As a cold front slowly weakens north of the area, moisture
lingers providing scattered showers. Weak troughiness is found
west of the area through Thursday but pressure lowers northeast of
the area on Friday and continues through next Wednesday which
results in enhanced northeasterly flow with continued shallow
showers.

&&

.SHORT TERM...Today through Friday...
A mid to upper level trough located just to the west of the
region will provide instability across the area through the short-
term forecast period. At the lower levels, the remnants of a cold
front will continue to supply moisture to the islands. In fact,
the forecast soundings are showing precipitable water values near
1.4 to 1.7 for today. Taking all these factors into
consideration, showers are expected to develop across the area,
with the heaviest activity occurring along the interior and
northwestern Puerto Rico during the afternoon hours. Additional
activity will also be possible over the San Juan metro area. Urban
and small stream flooding cannot be ruled out with this activity.
By Thursday, even though the mid to upper level trough remains in
place, at 700 mb, a ridge will begin to develop west of the area.
Precipitable water values are also expect to drop to near 1.3-1.4
inches due to drier air filtering at this level. Nonetheless,
showers could still develop across the area, although with a
lesser degree of coverage and intensity. By Friday, the mid and
upper level trough axis is expected to be closer to the islands.
Temperatures at 500 mb are also expected to cool to about -10 to
-9 degree Celsius. Once again, this should result in shower
activity, with possible isolated thunderstorms developing, mainly
over the interior and western Puerto Rico during the afternoon
hours.

.LONG TERM...Saturday through Wednesday...
The upper level trough finally pulls through the area early
Saturday morning and flow becomes northwesterly. This continues
until a weak trough begins to form northwest of the area. This
trough will pull through next Wednesday, but a third trough forms
upstream immediately afterward.

A trough will be found at low and mid levels that cuts across the
Leeward Islands and scarcely moves through the end of the period.
A closed low will also be seen northeast of the Leeward Islands
Saturday through Monday. This brings in a prevailing
northeasterly flow that carries shallow moisture and drier patches
of air repeatedly across the forecast area. This will result in
persistent showers over the windward side of Puerto Rico during
the overnight and early morning hours, followed by some shower
activity over southwest Puerto Rico and along the Cordillera
Central during the afternoons. Culebra and Vieques and the US.
Virgin Islands will be less affected but will still have some
scattered showers through the period. Because mid level
temperatures rise through Monday, the atmosphere will not support
thunderstorms during the period.

&&

.AVIATION...Mainly VFR conditions are expected to prevail across all
terminals. VCSH are expected to affect TJSJ/TISX and TNCM/TKPK at
least until 11/12Z. These showers could briefly result in MVFR
conditions across these terminals. ESE winds at 10 to 15 knots are
expected for today. Maximum winds SW 80-95 kt btwn FL345-460.
Strongest at FL400.

&&

.MARINE...Winds have already begun to diminish and are forecast to
remain less than 20 knots during the next several days. Seas are
gradually diminishing, but were still running at 12 feet at the
outer buoy 41043 and 9 feet at the inner buoy 41053. Hazardous
seas of more than 6 feet are likely to continue through the period
in the outer Atlantic waters but all other areas should see seas
less than 7 feet by Thursday evening.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 84 71 86 74 / 30 40 20 30
STT 84 75 84 74 / 30 30 30 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
505 AM AST Thu Mar 12 2020

.SYNOPSIS...High pressure continues over the Atlantic waters and a
weakening front to the north continues to be a source of clouds
and scattered showers. On Friday low pressure will develop at
lower levels to the northeast of the area and will cause flow to
become northeasterly here. This will send patches of moisture
across the area through much of next week, with night and early
morning showers in the northeast portion of Puerto Rico and
afternoon showers in the south and southwest when sufficient
moisture exists. The islands to the east will generally see
seasonal temperatures and isolated showers.

&&

.SHORT TERM...Thursday through Saturday...
A mid to upper level trough will continue to hold over the
eastern Caribbean through the end of the workweek. On Thursday,
however, dry air is expected to filter in at the mid-levels. In
fact, the latest estimates from GOES- 16 Total Precipitable Water
satellite product shows an area of precipitable water as low as
1.0 to 1.1 inches just to the southeast of the forecast area,
while the guidance are suggesting values of about 1.2 to 1.3
inches. This will translate to a reduction in rain activity
across the area, although a few showers carried by the trade winds
could still move over portions of eastern Puerto Rico and the
U.S. Virgin Islands, especially in the morning hours. However, in
the afternoon, due to local effects, showers should develop over
the northwestern quadrant of Puerto Rico. Additionally,
temperatures at 500 mb are expected to be at around -10 degree
Celsius and since the trough will provide some instability aloft,
isolated thunderstorms cannot be ruled out.

Moving into Friday, moisture increase at the mid-levels once again,
with precipitable water values climbing back to 1.6 inches. Also,
with the axis of the trough at the mid to upper levels closer to
the area, conditions will become more favorable for enhance shower
activity over the area and isolated thunderstorms. The heaviest
activity is expected across the interior and western Puerto Rico
during the afternoon hours, but additional activity will also be
possible over eastern Puerto Rico, including the San Juan metro
area. Urban and small stream flooding will be possible as well.

On Saturday, the upper level trough will begin to move toward the
east, while at the surface and the induced trough at lower levels will
shift the winds from the northeast, with drier air anticipated.
However, small patches of moisture may bring passing showers over
the islands.

.LONG TERM...Sunday through Thursday...
The upper level trough that has been hanging around for several
days will pass through on Saturday and a second weaker trough
will move through on Tuesday. Although the flow aloft will turn
to the northwest after the trough passage on Saturday it will
quickly become westerly late Sunday and continue through Thursday.

The lingering trough aloft will be instrumental in the continuing
development of an area of low pressure to the northeast of the
area at low and mid levels. This low will also have a northeast
southwest oriented trough that will pass just to the southeast of
the area that will cause mid and lower level flow to become
northeasterly and remain so for the rest of the period.

Air to our northeast is cooler and the lower levels will have
patches of moisture that will drive showers across the area for
much of the period. The NBM and the GFS are at extreme odds with
each other as to the probabilities of precipitation during this
period with the NBM forecasting 70-90 percent chances of rain and
the GFS dipping even into the single digits. Drier air will
certainly enter into the forecast area at 700 mb and cause shower
activity to diminish in quantity and intensity, but low level
moisture should not completely disappear and fragments of moisture
are expected to break off of the showers around the low pressure
to the northeast and ride across the forecast area. Expect these
fragments to result in minor but persistent passing showers--
mainly over Puerto Rico. Moisture from the fragments will also
cause shower activity in the south and southwest around the
Cordillera Central to occur if moisture patches coincide with
afternoon heating. On Thursday 500 mb temperatures may again
return to minus 9 degrees, but moisture will be limited,
nevertheless an isolated thunderstorm cannot be ruled out then.

&&

.AVIATION...VFR conditions are expected to prevail through 12/16Z
across all terminals. After that, VCSH and VCTS could cause brief
reductions in VIS to MVFR conditions across TJMZ/TJBQ,
respectively, until 12/22Z. Winds at FL050 will be out of the ESE
at 10 to 16 knots. Maximum winds WSW 75-85 knots btwn FL330-470, .
diminishing after 12/15Z.

&&

.MARINE...Seas have now been mainly driven by winds. These winds
are now tapering off. The outer buoy was running 20 to 22 knots
earlier this morning, but is now generally below 20 knots. Seas
there have come down a foot from the 12 feet they were earlier. At
the inner buoy winds are considerably lower and seas have just
dropped below 7 feet. Models have been fairly consistent in
bringing all seas in the local forecast area to below 7 feet by 2
AM AST tomorrow, (Friday). A new set of northeasterly swell will
enter the area Saturday night, but seas will scarcely rise above
7 feet early next week.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 85 74 84 75 / 40 50 40 40
STT 84 74 83 73 / 20 30 30 40

&&