Caribbean - Central America Weather

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
404 PM AST Tue Mar 6 2018

.SYNOPSIS...Large area of low pressure continued to move eastward
into the north central Atlantic, as a high pressure ridge builds
across the southwest Atlantic and north of the region. This will
induce a light northerly wind flow through Wednesday becoming east
to southeast by the end of the work week. A mid to upper level ridge
will establish across the region by the end of the week.

&&

.SHORT TERM...Tonight through Friday...
The strong low pressure that brought very large swell to Puerto Rico
and the U.S. Virgin Islands will begin to move northeast out of the
west central Atlantic tonight. High pressure will then spread
southwest off the southeastern coastal Atlantic waters of the United
States to connect with high pressure extending west southwest from
25 north 26 west toward the northeast Caribbean sea. This will bring
easterly surface flow by Wednesday to the local area. As the center
of the high pressure shifts east to make room for yet another
vigorous low to move up the coast of the United States Wednesday and
Thursday, flow will become more east southeast. Although the
strongest center of the vigorous low pressure will be offshore in
the western Atlantic, only limited swell is expected from this
center, since most of the winds are not aligned to direct swell this
way.

The next weather maker for the local area consists of a moisture
plume now stretching out of Venezuela to Guadeloupe. There, it is
producing a deck of low clouds and ceilings around 4500 feet. Radar
shows only very limited shower activity over the Windward islands at
this time. That moisture plume is forecast by the GFS to broaden
and advance into the local area Wednesday and Thursday. Precipitable
water values are forecast to rise from 1.15 inches at 06/12Z to 1.68
inches by 08/18Z. During this time the Lifted Index will rise from
plus 6 at 06/06Z to minus 6 on 08/18Z and 09/18Z. This is an
impressive change in stability that will also be accompanied by the
complete erasure of the capping inversion over us now. Currently
upper level support seems to be quite weak Thursday and Friday, with
the best divergence aloft at 08/18Z in an axis which runs through
the Mona channel and northeast into our local Atlantic waters,
moving further northwest by 09/00Z. However this represents a trend
toward some strengthening of the divergence aloft, so cannot
discount the possibility of thunderstorms developing especially over
northwest Puerto Rico Thursday in the plume of moisture. The core
of that plume crosses Puerto Rico after sunset on Wednesday so will
not be strongest at the time of maximum heating Thursday. Therefore,
at this time, showers should yield only 1 to 2 inches of rainfall
over NW PR, but will monitor the development of this situation.
Moisture will begin to abate after it peaks around 08/18Z, and
Fridays moisture will not be as deep. Convection may still
initiate, but best showers are expected on Thursday.

.LONG TERM...Saturday through Wednesday...An upper level ridge
will build across the Northeast Caribbean. As a result, overall
dry weather conditions are so far forecast for this period. A
cold front is forecast to approach the local region, inducing a
southerly flow and gradual increase in moisture across the region
by the middle of next week.

&&

.AVIATION...VFR conds to prevail. Sfc winds dominated by land/sea
breeze effects next 24 hours with flow shifting from north to east
during that period. Few if any -SHRA--top of the moist layer is
FL100. Aft 07/06Z sct/bkn040 lyr to spread NW across TKPK/TNCM, but
MVFR not expected. Mtns ocnly topped with shallow clouds. Winds alf
westerly abv FL050. Winds abv 50 knots btwn FL240-490. Max winds 74
knots at FL430.

&&

.MARINE...Coastal flood warnings and High surf warnings continue
along the north facing coastlines and near Cabo Rojo as 10 to 14
foot seas with periods of 14 to 15 seconds were still creating
breaking waves between of 17 to 20 feet. As the threshold for warnings
is 18 foot breaking waves, the warnings has been extended for the afternoon
package through Wednesday morning as the offshore buoys continued to
suggest the arrival of additional dangerous seas and swell action.
Please refer to the latest Coastal Waters Forecast,(CWFSJU),Coastal
Hazard Message (CFWSJU) , and Marine Weather Message (MWWSJU), issued
by the National Weather Service WFO San Juan PR.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 71 82 73 87 / 20 20 20 50
STT 69 83 74 84 / 10 30 30 50

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
440 AM AST Wed Mar 7 2018

.SYNOPSIS...Today most of the region will transition from an
cooler airmass to a more humid one. A ridge of high pressure to
the east of the island will bring a plume of moisture out of the
deep tropics across Puerto Rico and the U.S. Virgin Islands today
through Thursday. The aforementioned ridge will cause winds to
veer to the east to southeast on Thursday and Friday thus
triggering scattered showers. Friday, the GFS and EURO model move
the moisture plume to the northwest of the Islands and allows
drier air to filter back across the area with the weekend looking
great with an occasional isolated shower.

&&

.SHORT TERM...Today through Saturday...Clear skies prevailed across
Puerto Rico and the U.S. Virgin Islands overnight. No shower
activity was observed over land areas. Local remain under the
influence of a mid to upper level ridge. This feature is maintaining
very dry and stable conditions across the region. However, for this
afternoon, the remnants of an old frontal boundary will move across
the region. As a result, an increase in cloudiness with showers is
expected to affect the local islands. This feature will exit the
local region by Thursday. For Friday, very dry weather conditions
are expected to prevail, with scattered showers affecting mainly the
northern half of Puerto Rico as winds shift southerly. These winds
will promote higher than normal temperature along the north coast of
Puerto Rico Friday and Saturday.

.LONG TERM...Saturday through Thursday...The long term period
will be fairly quiet due to an upper level ridge that will hold
across the Caribbean waters. As a result drier weather conditions
will prevail across the islands but can`t rule out an occasional
shower due to the trade winds. Next Thursday a cold front will
move into the Atlantic waters and move close to the area by Friday
this should cause showers across the northern areas of Puerto
Rico.

&&

.AVIATION...VFR conditions will continue to prevail across all TAF
sites through at least 07/16Z. Increasing cloudiness with showers
can be expected after 07/16Z affecting TJBQ and TJMZ. Low level
winds will be mainly east northeast at 10 to 15 kts.

&&

.MARINE...The concern is still the marine conditions. Buoys to
the north of San Juan are showing seas ranging from 8 to 12 feet
with a wave period of 13 sec as a result the Coastal flood
warning was extend until later this evening but if conditions
improve later today it could be discontinue. Expect hazardous
seas, extremely high surf and life threatening rip currents
through at least Thursday, but marine conditions should improving
slowly thereafter. Civilians are are advised to avoid beaches
exposed to the Atlantic Ocean and local passages during this
dangerous swell event

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 82 74 87 74 / 30 20 50 50
STT 76 75 78 76 / 30 30 50 50

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
532 PM AST Wed Mar 7 2018

.SYNOPSIS...A ridge of high pressure will continue to build north and east of
the region through Thursday. This will gradually lift a plume of
moisture out of the deep tropics across the forecast area. Meanwhile
a polar trough and subtropical jet will lift east northeast across
the western Atlantic. The surface ridge will induce an east to southeast
wind flow on Thursday and Friday. This expected pattern will increase
moisture convergence and instability aloft across the area and therefore
increase the chance for afternoon convection particularly across the
northwest quadrant of PR. Drier conditions are again expected by late
Friday and into the weekend with only isolated to scattered showers
expected mainly in the early morning and afternoon hours.

&&

.SHORT TERM...Tonight through Saturday...
The strong low pressure that brought very large swell to Puerto Rico
and the U.S. Virgin Islands will move into the northeast Atlantic
out of the west central Atlantic tonight. High pressure north of the
area will consolidate northeast of the area on Thursday. This will
bring easterly surface flow overnight and southeast flow Thursday
and Friday. The complex of low pressure that exited the east coast
of the United States this morning will remain in the western Atlantic
near Newfoundland beyond Saturday, but Puerto Rico and the U.S. Virgin
Islands will remain shielded from its effects by another high pressure
out of Florida. The swell generated by this system will be strong but
winds will not be aligned in such a way that major swell will reach
the local islands. It will play some role in prolonging the current
high surf, high swell episode.

The next weather maker for the local area consists of a moisture
plume now stretching out of Venezuela and spreading across the
entire eastern Caribbean the Leeward and Windward Islands. Convection
has been very limited with this plume. And Guadeloupe radar shows
only a few streaks of minor showers moving west across the windward
Islands. Some mid level clouds at 9 kft have been detected. Precipitable
water values are forecast to rise from the 1.10 inches seen at 07/12Z
to 1.82 inches by 09/00Z. During this time the Lifted Index will
rise from plus 7 at 07/12Z to minus 6 on 09/12Z and 09/18Z. This
is an impressive change in stability that will also be accompanied
by the complete erasure of the capping inversion over us now. Currently
upper level support seems to be quite weak until Thursday afternoon.
At that time the GFS wants to paint a bulls eye of divergence
over northwestern Puerto Rico. For this reason isolated thunderstorms
are still expected over northwest Puerto Rico Thursday. However,
the main axis of divergence continues to be northwest of the area
and this will play a role in keeping convection over northwest
Puerto Rico limited on Thursday and Friday. Moisture will also be
almost completely gone by 09/06Z from layers at and above 700 mb,
so we will return to limited shower activity Friday and Saturday,
although moisture will be more abundant than today.

.LONG TERM...Sunday through Friday...Most of the long term period
will be fairly quiet due to a mid to upper level ridge which is
forecast to hold across the northeastern Caribbean. As a result
drier weather conditions will prevail across the region, but still
will not rule out the possibility of isolated to scattered early
morning and afternoon showers over portions of the islands each
day. By next Thursday a cold front is so far forecast to move into
the western Atlantic and approach the region by Friday. This should
again increase the chance for additional shower development across
the region.

&&

.AVIATION...VFR conditions will continue to prevail across all TAF
sites through at least 08/18Z. Increasing cloudiness with isolated
showers expected after 08/18Z affecting TJBQ and TJMZ. Mtn obscurations.
Low level winds will be mainly east northeast at 10 to 15 kts bcmg
east 6 to 12 kt aft 07/21Z with land/sea breeze influences. Maximum
winds WSW 70 kt btwn FL400-450. A plume of moisture moving into
the area will increase clds aft 08/08z. Ltd MVFR psbl btwn 08/00-06Z
TKPK and btwn 08/03-09Z TNCM otherwise VFR thru 08/16Z.

&&

.MARINE...Buoy 41053 continued to report seas 12-14 feet with a 14
second period. This will still yield breaking waves of 16 to 20 feet.
Therefore will continue with the High Surf and Coastal flood Warnings
for northern coasts on all but all but Vieques and Saint Croix at least
into the evening hours. Although the warnings are out until 10 PM AST,
we will be looking to see if they can be downgraded to advisory status
during the evening, but currently models have maintained hazardous marine
conditions through the end of the week.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 73 87 71 88 / 10 30 30 40
STT 73 84 75 78 / 10 20 20 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
447 AM AST Thu Mar 8 2018

.SYNOPSIS...A mid to upper level ridge will spread a plume of
tropical moisture northwest across Puerto Rico and the U.S.
Virgin Islands later today. GOES 16 satellite image shows the
moisture to the southeast of Puerto Rico and moving east
northeast. At the surface winds are out of the east at 5 to 10 kts
but later today the winds will veer to the east to southeast
which will allow moisture to converge over the islands. The
combination of low level tropical moisture and daytime heating
will create enough instability for afternoon convection across the
northern Puerto Rico today and early Friday.

Friday, the moisture will begin to decrease with drier conditions
prevailing this weekend through early next week with a possibility
for scattered showers due to the trade winds.

&&

.SHORT TERM...Today through Saturday...Clear skies prevailed across
Puerto Rico and the U.S. Virgin Islands overnight. No shower
activity was observed over land areas. Local area remain under the
influence of a mid to upper level ridge. Mid level cloudiness will
continue to stream across the local islands the rest of today.
Latest satellite images depicted an area of cloudiness with some
showers across the Caribbean Sea. This area is expected to move
toward the north and is expected to encompass the region later
today. At this time, this feature looks diffuse on satellite
images. However, the combination of it with daytime heating and
orographic effects, will aid in the development of showers and
possible thunderstorms this afternoon across the western interior
and northwest sections of Puerto Rico. Elsewhere, partly cloudy
skies are expected with little shower activity.

For Friday and Saturday, a very dry air mass is expected to dominate
the local area. As a result, chances for shower development will be
minimal both days. A mid level ridge will build across the area,
producing stable atmospheric conditions for the first part of the
weekend.

.LONG TERM...Sunday through Friday...Fair weather conditions will
prevail this weekend through early next week due to a mid to upper
level ridge of high pressure. This ridge will cause drying in the
low, mid and upper levels of the atmosphere thus shower activity
will be limited.

Currently global models shows a cold front moving into the
Atlantic waters on Sunday and approaching the local area late
Friday or early Saturday. If this front holds together and
approaches the islands rain chances will increase Friday into the
weekend but we have several days to see if this comes to
fruition.

&&

.AVIATION...VFR conditions will continue to prevail across all TAF
sites through at least 08/16Z. Increasing cloudiness with showers
can be expected after 08/16Z affecting TJBQ and TJMZ. Low level
winds will be mainly east northeast at 10 to 15 kts.

&&

.MARINE...This morning a gradual decrease in seas but local buoys
are showing waves heights ranging from 10 to 11 feet with wave
periods of 10 to 12 seconds. This will cause breaking waves of 15
to 20 feet as result a Coastal Flood and High Surf advisory are in
effect until this afternoon.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 85 76 88 76 / 30 30 40 20
STT 78 78 78 78 / 20 20 40 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
500 AM AST Fri Mar 9 2018

.SYNOPSIS...Building ridge will favor a drying trend and fair
weather conditions over the region through next week. At the
surface, a high pressure system will build across the western
Atlantic, resulting in east to east southeast winds across the
region next couple of days.

&&

.SHORT TERM...Today through Sunday... Clear to partly cloudy skies
prevailed across Puerto Rico and the U.S. Virgin Islands overnight
and early this morning. No shower activity was observed over land
areas. Local area will remain under the influence of a mid to upper
level ridge. Mid level cloudiness will continue to stream across the
local islands the rest of today. For this afternoon, the limited
available moisture across the region in combination with daytime
heating and orographic effects, will aid in the development of
showers and possible a couple of thunderstorms across the western
interior and northwest sections of Puerto Rico. Elsewhere, partly
cloudy skies are expected with little shower activity. Low level
winds will continue from the southeast at 10 to 15 mph. This wind
flow will induce warmer than normal temperatures across the northern
coastal municipalities of Puerto Rico. For Saturday and Sunday a mid
level ridge will build across the area, producing stable atmospheric
conditions and resulting in a very dry air mass across the local
islands. As a result, chances for shower development will be
minimal both days.

.LONG TERM...A mid to upper level ridge will take control of the
weather locally from Sunday through most of next week. Local area
is forecast to remain under a persistent southeast wind flow,
which will result in warmer than normal temperatures mainly along
the northern slopes of Puerto Rico early next week. Very dry
weather conditions are forecast to prevail during the long term.

&&

.AVIATION...Mostly VFR conditions will continue to prevail across
the local flying area through at least 09/16Z. Increasing cloudiness
with showers can be expected after 09/16Z affecting mostly TJBQ and
TJMZ. Low level winds will be mainly east southeast at 10 to 15
kts.

&&

.MARINE...Local buoy continue showing subsiding seas across the
local waters. Seas between 6 to 8 feet are expected to continue
today while subsiding. Coastal flood is no longer expected. As a
result, coastal flood advisory was allowed to expire. High surf
conditions will prevail through tomorrow.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 88 75 88 75 / 10 10 20 20
STT 84 75 84 75 / 20 20 20 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
326 PM AST Fri Mar 9 2018

.SYNOPSIS...Surface high will continue northeast of the region
through next week. Deep southerly wind flow will prevail across
the region, keeping overall warm conditions through the long term
period. Isolated to scattered shower development due to diurnal
effects are expected each afternoon across the northwestern
portions of Puerto Rico. Drier conditions are expected elsewhere
across the islands.

&&

.SHORT TERM...Tonight through Monday...
High pressure is now 1250 miles east northeast of San Juan and will
build northeast during the period. Meanwhile another high pressure
will move east toward the area from northern Florida. The complex of
low pressure that exited the east coast of the United States
Wednesday morning is now building over the eastern coast of
Newfoundland. A second low will exit the United States late Sunday.
Puerto Rico and the U.S. Virgin Islands will remain shielded from
the effects of both of these lows by the ridge to our north. The
swell generated by the back edge of the last system will be strong
but winds will not be aligned in such a way that major swell will
reach the local islands until late next week. These lows, however,
will play some role in prolonging the surf and swell in the Atlantic
Friday through Sunday.

Moisture over the area has faded slightly and this trend will
continue through Sunday Night. On Sunday moisture will be similar to
today at 1.43 inches but will plummet, according to the GFS, to
around 0.9 inches on Monday (12/18Z). Still expecting a few
thunderstorms to develop and dissipate quickly over northwest Puerto
Rico today, but conditions will be somewhat less favorable over the
weekend and shower activity has generally been weak anyway. There is
a chance of showers on Saturday and Sunday, but showers will be few--
if any--on Monday. Temperatures which are running several degrees
above normal due to southeasterly flow will continue in the upper
80s or around 90 owing to the abundant sunshine weak moisture, even
after the southerly flow becomes more easterly at the surface Monday.

.LONG TERM...Tuesday through Saturday...
Mid to upper level ridge will dominate the local weather
conditions through at least Saturday. Drying trend will continue
through this period with fair weather conditions prevailing across
the islands. However, shallow moisture and diurnal effects could
lead to afternoon shower development over the northwestern
portions of PR each day. Broad surface high pressure northeast of
the region will keep a moderate southerly wind flow. Therefore,
temperatures are expected to continue above normal values, with
highs reaching the high 80s and low 90s each day, especially
across the lower elevations. At the end of the forecast period,
the GFS and the ECMWF have different solutions for a polar trough
and associated front at the surface. The GFS has it stalling to
the north of the area during the weekend and the ECMWF is more
aggressive pushing the front across the region between Friday and
Saturday.


&&

.AVIATION...VFR conditions prevail area-wide at the moment. Areas of
MVFR due to CIGS and SHRA/TSRA in NW PR psbl aft 09/18Z until
09/21Z. Areas of mtn obscurations til 10/00Z. Sfc flow SE 5 to 15 kt
but with moderate sea/land breeze influences. Max winds W 50-70 kt
btwn FL310-470 highest at FL360.


&&

.MARINE...Northeast swell continues to subside and seas are
expected to range generally between 4-7 feet during the weekend.
Therefore, due to seas of 7 feet, small craft advisories continue
in effect across the Atlantic waters and local passages. East to
southeast winds will prevail between 10-15 knots and locally
higher at times. Long period fading NE swell will continue to
result in rough surf conditions and strong rip currents across the
Atlantic beaches of the islands during the weekend. The southern
beaches of PR will experience a moderate to high risk of rip
currents due to above normal breaking waves generated by the
southerly trades.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 75 88 74 87 / 20 20 20 20
STT 75 84 75 84 / 10 20 20 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
517 AM AST Sat Mar 10 2018

.SYNOPSIS...Surface high pressure ridge north and east of the region
will dominate the local weather conditions through the rest of the
weekend and into early next week. A low level southerly wind flow will
prevail across the region, keeping overall warm and dry conditions
across the islands. Isolated to scattered shower development due to
local and diurnal effects are expected each afternoon mainly across
the northwestern Puerto Rico. Mostly sunny skies are expected elsewhere
across the islands.

&&

.SHORT TERM...Today through Monday...Clear to partly cloudy skies
prevailed across Puerto Rico and the U.S. Virgin Islands overnight
and early this morning. No significant shower activity was observed
over land areas and surrounding waters as local area remains under
the influence of a mid to upper level ridge. Moisture over the area
will continue to diminish and this trend is expected to continue
through at least Monday. A surface high pressure across the central
Atlantic east northeast of Puerto Rico will build northeast while
another high pressure will move east toward the area from northern
Florida.

Mid level cloudiness will continue to stream across the local
islands from the southwest. For this afternoon, the limited moisture
across the region in combination with daytime heating and orographic
effects, will aid in the development of some shower activity across
western interior and northwest sections of Puerto Rico. Elsewhere,
clear to partly cloudy skies are expected with little shower
activity. Low level winds will continue from the east to east
southeast at 10 to 20 mph. This wind flow will induce warmer
temperatures mainly across the northern coastal municipalities of
Puerto Rico. For Sunday and Monday the mid to upper level ridge
will remain across the area, producing stable atmospheric conditions
and resulting in a dry air mass across the local islands. As a result,
chances for shower development will be minimal both days.

.LONG TERM...Tuesday through Sunday...
Although a short wave trough is forecast to move across the western
Atlantic during the latter part of the period, the mid to upper level
ridge is expected to hold in place and dominate the local weather
conditions. Therefore, a drying trend will continue with overall
fair weather and mostly sunny skies expected to prevail. However,
shallow moisture and diurnal effects may lead to afternoon shower
development over parts of the northwestern portions of PR each
day. Broad surface high pressure north and east of the region will
maintain a moderate south to southeast wind flow. Therefore,
temperatures are expected to continue slightly above normal
values, with highs reaching the high 80s each day, especially
along the north coastal sections. As previously mentioned,
previously, model guidance continued to suggest the approach of a
cold front during the latter part of the period. So far it is
still expected to stall and remain mainly northwest of the region
Friday through Sunday.

&&

.AVIATION...Mostly VFR conditions will continue to prevail across
the local flying area through at least 10/16Z. Increasing cloudiness
with some shower activity can be expected after 10/16Z affecting
mostly TJBQ and TJMZ. Low level winds will be mainly east to east
southeast at 10 to 15 kts.

&&

.MARINE...Hazardous seas will continue through the weekend with seas
ranging between 4 to 7 feet. There is a moderate to high risk of rip
current for most of the local beaches. Please refer to the latest
Marine weather Message (MWWSJU), Coastal Hazard Message (CFWSJU)
and Coastal Waters Forecast (CWFSJU) issued by the National Weather
Service WFO San Juan PR.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 73 87 73 / 20 20 20 20
STT 84 75 84 73 / 20 20 20 20

&&

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
525 PM AST Sat Mar 10 2018

.SYNOPSIS...Surface high will continue northeast of the region
through next week. Deep southerly wind flow will prevail across
the region, keeping overall warm conditions through the long term
period. Isolated shower development due to diurnal effects are
expected each afternoon across the northwestern portions of Puerto
Rico. Drier conditions are expected elsewhere across the region.


&&

.SHORT TERM...Today through Monday...
Mostly sunny to partly cloudy skies were observed across the
islands today. A few low level clouds developed over the mountain
ranges and from streamers off the smaller islands but no rainfall
was detected over land areas. Highs today were in the mid to high
80s across the islands. Surface high pressure will continue to
build east northeast of the region across the Atlantic during the
next few days. This will keep an east to southeast moderate to
locally fresh trade wind flow through the next couple of days.
Building ridge aloft will keep a drying trend and fair weather
conditions through the short term. Best moisture will be limited
below 850 mb and this moisture content combined with diurnal
effects could lead to afternoon isolated showers over the NW
portions of PR and streamers developing off the island with
mostly light rain showers over the coastal waters.


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

...FROM PREVIOUS DISCUSSION...

Although a short wave trough is forecast to move across the western
Atlantic during the latter part of the period, the mid to upper level
ridge is expected to hold in place and dominate the local weather
conditions. Therefore, a drying trend will continue with overall
fair weather and mostly sunny skies expected to prevail. However,
shallow moisture and diurnal effects may lead to afternoon shower
development over parts of the northwestern portions of PR each
day. Broad surface high pressure north and east of the region will
maintain a moderate south to southeast wind flow. Therefore,
temperatures are expected to continue slightly above normal
values, with highs reaching the high 80s each day, especially
along the north coastal sections. As previously mentioned,
previously, model guidance continued to suggest the approach of a
cold front during the latter part of the period. So far it is
still expected to stall and remain mainly northwest of the region
Friday through Sunday.


&&

.AVIATION...VFR conds are expected to prevail at all TAF sites
through the forecast cycle. -SHRA/SHRA still possible in and around
JBQ through 10/23z. ESE winds at 10-15 knots with sea breeze
variations becoming light and variable overnight.

&&

.MARINE...Fading NE swell and wind driven seas will keep hazardous
marine conditions through the rest of the weekend. Seas will
range between 6 to 8 feet across the offshore Atlantic waters and
the Mona Passage through at least late Sunday night. Elsewhere,
choppy seas between 5 to 7 feet are expected to prevail. Small
craft advisories are in effect through Monday night across most of
the regional waters. East to southeast winds will prevail between
15-20 kts through next week. A high risk of rip currents continues
mainly for the northern and eastern beaches of the islands.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 75 87 73 88 / 20 20 10 10
STT 74 84 73 83 / 20 20 10 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
427 AM AST Sun Mar 11 2018

.SYNOPSIS... Surface high pressure ridge will extend over the region
through the middle of next week to maintain a light to moderate east
southeast wind flow. Mid to upper level ridge will also hold across
the region through most of the upcoming week. As a result an
overall dry and stable airmass with mostly fair weather skies and
slightly warmer temperatures is expected to prevail for the next
several days.

&&

.SHORT TERM...Today through Tuesday...
Clear to partly cloudy skies prevailed across the local islands
overnight and early this morning. No significant shower activity was
observed over land areas and surrounding waters as local area remains
under the influence of a building mid to upper level ridge. This ridge
will result in stable atmospheric conditions and generally dry air
mass across the local islands. This trend is expected to continue
through at least Tuesday. However, during the afternoons, the limited
available moisture across the region in combination with daytime heating
and orographic effects, will aid in the development of some shower
activity across western interior and northwest sections of Puerto Rico.
Elsewhere, Mostly sunny to partly cloudy skies are expected to continue
with little shower activity.

Surface high pressure will continue to build east northeast of the region
across the Atlantic waters during the next few days. This will keep
an east to southeast moderate to locally fresh trade wind flow through
the next couple of days. This wind flow will induce warmer temperatures
mainly across the northern coastal areas of Puerto Rico.

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

The combination of the mid to upper level ridge and fairly strong
surface high pressure ridging across the region is expected to hold
and dominate the local weather conditions. Therefore, an overall drying
trend and stable airmass will continue to support a fair weather pattern
with mostly sunny skies across the islands. However, occasional patches
of shallow moisture advection along with local and diurnal effects may
lead to brief afternoon shower development mainly over parts of the
central and northwestern portions of PR each day. The broad surface
high pressure north and east of the region will maintain a moderate
east to southeast wind flow through the end of the week. Therefore,
temperatures are expected to continue slightly above normal values,
with highs reaching the high 80s to near 90 degree each day, especially
along the north coastal sections. Surface winds are expected to gradually
become more east to northeast by Sunday of the following weekend, as
short wave trough and associated cold front is forecast to move across
the western Atlantic during the latter part of the period. Model guidance
continued to suggest that the cold front is expected to stall and remain
mainly northwest of the region through Sunday and therefore should have
no direct effect on the forecast area at this time.

&&

.AVIATION...Mostly VFR conditions are expected to prevail across
the local flying area through the forecast period. -SHRA/SHRA still
possible in and around TJBQ after 11/17z. Latest TJSJ sounding
indicated an ESE wind flow up to 30 knots, from the surface to
around 12k feet, becoming light and variable between 12-26K feet and
then stronger from the west above 26k feet.

&&

.MARINE...Hazardous marine conditions will continue through Sunday
with seas ranging from 5 to 8 feet across the Atlantic waters and
the Mona Passage. Elsewhere, choppy wind driven seas between 5 to
7 feet are expected to prevail. Small craft advisories are in effect
through at least Monday night across most of the regional waters.
East to southeast winds will prevail between 15-20 kts through early
next week. A high risk of rip currents continues mainly for the northern
and eastern beaches of the islands except for Vieques where there is
a moderate risk.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 73 89 73 / 10 10 10 10
STT 85 75 84 76 / 20 10 20 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
506 PM AST Sun Mar 11 2018

.SYNOPSIS...Surface high pressure will continue to build and
spread across the central and eastern Atlantic. This will maintain
a southeasterly wind flow across the region through next week.
At the upper levels, a ridge will also continue to build and
promote a drying trend and fair weather conditions for the next
several days. Normal to above normal temperatures are expected to
prevail through the work week.


&&

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

Mostly sunny to partly cloudy skies were observed today across
the islands. Breezy east to southeast winds prevailed across the
region with gusts around 25 mph. No significant change is expected
through the short term period as building ridge aloft continues to
promote a drying trend across the region. However, the limited low
level moisture combined with diurnal effects should result mainly
in partly cloudy skies with a brief shower or two over isolated
areas of northwestern Puerto Rico and light streamers developing
off the smaller islands.

.LONG TERM...from previous discussion...Wednesday through Monday...

The combination of the mid to upper level ridge and fairly strong
surface high pressure ridging across the region is expected to hold
and dominate the local weather conditions. Therefore, an overall drying
trend and stable airmass will continue to support a fair weather pattern
with mostly sunny skies across the islands. However, occasional patches
of shallow moisture advection along with local and diurnal effects may
lead to brief afternoon shower development mainly over parts of the
central and northwestern portions of PR each day. The broad surface
high pressure north and east of the region will maintain a moderate
east to southeast wind flow through the end of the week. Therefore,
temperatures are expected to continue slightly above normal values,
with highs reaching the high 80s to near 90 degree each day, especially
along the north coastal sections. Surface winds are expected to gradually
become more east to northeast by Sunday of the following weekend, as
short wave trough and associated cold front is forecast to move across
the western Atlantic during the latter part of the period. Model guidance
continued to suggest that the cold front is expected to stall and remain
mainly northwest of the region through Sunday and therefore should have
no direct effect on the forecast area at this time.


&&

.AVIATION...VFR conds are expected to prevail at all TAF sites
through the forecast cycle. -SHRA/SHRA still possible in and around
JBQ through 11/23z. ESE winds at 10-15 knots with sea breeze
variations becoming light and variable overnight.


&&

.MARINE...Coastal buoys were indicating seas around 4 feet at 13
seconds through the day. Small crafts advisories were cancelled
for the coastal waters as model guidance is currently over
estimating the seas in the near shore waters. However, small
crafts should continue to exercise caution across these waters due
to seas up to 6 feet and/or winds up to 20 knots. A small craft
advisory continues in effect for the offshore waters and the Mona
Passage due to 7 ft seas through at least Monday.

East to southeast winds will continue to prevail between 10-20 kts
with higher gusts at times across all regional waters under
influence of a surface high northeast of the region.

A moderate to high risk of rip currents will continue across the
islands. Please refer to the latest surf zone forecast (SRFSJU)
and coastal hazard message (CFWSJU) for detailed information.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 75 87 75 88 / 0 0 0 10
STT 74 83 75 84 / 10 0 20 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
345 AM AST Mon Mar 12 2018

.SYNOPSIS...Surface high pressure will continue to build and
spread across the central and eastern Atlantic. This will maintain
a southeasterly wind flow across the region through next week.
At the upper levels, a ridge will also continue to build and
promote a drying trend and fair weather conditions for the next
several days. Normal to above normal temperatures are expected to
prevail through the work week.

&&

.SHORT TERM...Today through Wednesday...
Mostly clear to partly cloudy skies will prevail until the early
morning hours. Only a few very light showers are expected mainly
over the coastal waters. No significant precipitation is forecast
over land areas as a mid to upper level high pressure ridge will
continue to hold across the region to maintain a fairly strong
trade wind cap inversion. This will continue to limit moisture
pooling across the region and will result in and overall dry and
stable weather pattern through the entire period. Recent satellite
analysis product and latest model guidance both suggest the
layered precipitable water expected to be an inch or less. That
said, expect mostly sunny and fair weather skies to prevail except
for a few isolated showers of short duration which may develop
mainly the northwest sections of PR during the afternoons.
Otherwise pleasant daytime weather conditions and slightly warmer
temperatures can be expected under a prevailing southeasterly wind
flow. This dominant wind flow should maintain daytime high
temperatures along the north coastal areas of PR slightly above
normal in the high 80`s to near 90 degrees. Over the U.S. Virgin
Islands mostly sunny skies is forecast for the next several days
with little of no significant rainfall expected.

.LONG TERM...Thursday through Tuesday...
Strong surface high pressure will hold across the central
Atlantic, northeast of the region through early in the weekend
when a second surface high pressure system moves over the
southwestern Atlantic. An upper lever ridge is also expected to
hold over the region until late in the weekend. These features
will continue to dominate the local weather pattern across the
forecast area through at least Sunday, resulting in an overall
drying trend and stable airmass. Therefore a fair weather pattern
with mostly clear skies and limited shower activity is expected to
continue across the islands. Only occasional patches of shallow
moisture embedded in the trades in combination with local and
diurnal effects may produce brief afternoon shower activity
mainly over parts of the central and northwestern portions of PR
each day. The broad surface high pressure northeast of the region
will maintain a moderate to fresh east to southeast wind flow
through at least Saturday. Therefore, temperatures are expected to
continue slightly above normal values, with highs reaching the
high 80s to near 90 degree each day, especially along the north
coastal sections. Surface winds are expected to gradually become
more east to northeast by Sunday as the second surface high
pressure moves across the southwest Atlantic. This surface high
pressure will push a frontal boundary across the western Atlantic
during the latter part of the forecast period. Model guidance
continued to suggest that the cold front is expected to remain
mainly to north and northwest of the region through Sunday.
However, the nearness of this system will result in an increase
in moisture across the local islands early next week.

&&

.AVIATION...VFR conds will prevail at all terminals and local flying
area durg entire prd. FEW -SHRA en route btw local islands...SCT-
BKN cld lyrs nr FL022...FL035...mostly SKC ABV. ESE winds at 10-20
knots blo FL150 BCMG fm W and incr w/h ABV...Max wnd 70-75 kts nr
FL350. Sfc wnd E-SE less than 10 kts. No sig operational wx
impacts attm.

&&

.MARINE...Seas up to 7 feet and winds up to 20 knots are expected
to continue across most of the local waters today. A small craft
advisory continues in effect for the Atlantic and Caribbean
offshore waters and for the Mona Passage due to 7 ft seas through
at least early Tuesday. East to southeast winds will continue to
prevail between 10-20 kts with higher gusts at times across all
regional waters under influence of a surface high northeast of the
region.

A moderate to high risk of rip currents will continue across the
islands. Please refer to the latest surf zone forecast (SRFSJU)
and coastal hazard message (CFWSJU) for detailed information.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 75 88 74 / 0 0 10 10
STT 83 75 84 74 / 10 20 20 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
420 AM AST Tue Mar 13 2018

.SYNOPSIS...Surface high pressure will continue to build across
the central Atlantic. This will maintain a southeasterly wind
flow across the region through the end of the week. An upper level
ridge will also continue to build and promote a drying trend and
fair weather conditions for the next several days. Normal to above
normal temperatures are expected to prevail through the work
week. A polar trough and associated surface front are forecast to
approach the region late during the weekend and early next week.

&&

.SHORT TERM...Today through Thursday...
High pressure at the surface will continue across the east central
sub-tropical Atlantic and will maintain southeast flow across the
area through Thursday morning of 10 to 20 knots in the lower layers.
Flow turns more easterly on Thursday when ridging pushes out of
Florida and connects with the high in the east central Atlantic.
Since this flow generally taps air with relatively low moisture the
only moisture plumes that can be initiated are those from local
convection in northwest Puerto Rico and a few streamers off the
Leeward islands. These will be limited to the warmest afternoon
hours, but may continue over the downstream waters during the
evening. Precipitable water during the period remains less than 1.1.
inches and reaches a nadir at 0.87 inches late on Thursday according
to the GFS. With winds out of the southeast, this means that the
south coast will generally have a little higher relative humidity
than usual and that the north coast will be warmer than normal where
some areas close to the ocean may reach 90 degrees. Thickness values
trend very slightly lower during the period. Although the GFS showed
a spike of warmth on Thursday, this may be an anomaly.

At upper levels, high pressure over Venezuela will move northeast
over their local waters and strengthen slightly. This will keep a
west southwest jet fragment over or just northwest of the local
area. Upper levels have very little divergent motion over the local
area during the period and are not particularly favorable to the
convection that could form over the northwest portion of Puerto
Rico, but the capping strongly present over the area yesterday
(Monday) will erode today and be nearly insignificant on Thursday,
creating a somewhat more favorable environment for showers absent
better moisture.

.LONG TERM...Friday through Wednesday...
Strong surface high pressure will hold across the central
Atlantic, well northeast of the region through the upcoming
weekend. An upper lever ridge is also expected to hold over the
region until early next week. These features will continue to
dominate the local weather pattern across the forecast area
through, resulting in an overall drying trend and stable airmass
across the local islands and surrounding waters. Therefore, a
fair weather pattern with mostly clear skies and limited shower
activity is expected to continue across the islands until late in
the weekend. However, patches of shallow low level moisture
embedded in the trades in combination with local and diurnal
effects may produce brief afternoon shower activity mainly over
parts of the central and northwestern portions of PR each day. The
broad surface high pressure will also continue to maintain a
moderate to fresh east to southeast wind flow through at least
Saturday. Therefore, temperatures are expected to continue
slightly above normal values, with highs reaching the high 80s to
near 90 degree each day, especially along the north coastal
sections.

A low pressure system will move across the Canadian Maritime
Provinces by Friday. Model guidance suggests that the associated
cold front is expected to stall to the north and west of the
region during the weekend. However, by early next week, the
remnants of the frontal boundary will move across the region,
resulting in an increase in moisture across the local islands.

&&

.AVIATION...VFR conditions to prevail at all TAF sites. Isold SHRA
and mtn obscurations psbl NW PR btwn 13/17-21Z. Some MVFR CIGS SE PR
13/14-18Z. Expect sfc winds SE 5 to 10 kt plus sea breeze influences
aft 13/14Z. Max winds WSW 50-68 kt btwn FL310-460 highest at
FL360.

&&

.MARINE...Seas will continue in the range of 4 to 6 feet today
and tonight, but are expected to increase to 5 to 7 feet across
the Atlantic waters on Wednesday. Winds will continue from the
southeast at 15-20 knots across most of the regional waters. A
moderate risk of rip currents is expected today across most of
the northern and southern beaches of the islands.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 89 74 89 73 / 0 10 10 10
STT 84 76 84 74 / 10 10 10 10

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
414 AM AST Wed Mar 14 2018

.SYNOPSIS...Fair weather will continue with high pressure keeping
southeast flow over the area through Friday. Moisture will
increase over the weekend when scattered showers will appear.

&&

.SHORT TERM...Today through Friday...
The weather in the short term period will be tranquil due to
ridging at the surface and aloft. As a result, drier conditions
will continue for Puerto Rico and the U.S. Virgin Islands with
southerly winds of 5 to 10 mph. As for rainfall, model guidance
has been persistent on drier air remaining at the surface and
upper level of the atmosphere. The 14/00Z Skew-T had a
precipitable water value of 0.87 which is 2 standard deviations
below climatology. This trend has persisted since last weekend.
Drier air extends from the surface up to 200 mb. Data also points
to 200, 1000-500, 1000-500 mb heights being in the 50 to 75
percentile above climatology which tells us that the surface, mid
and upper level ridges are quite strong and that temperatures will
remain slightly above normal. These ridges created a trade wind
cap across the region that has suppressed cloud development for
showers.

The cold front that moved off the continental U.S. Monday will
continue to push southeast until it comes within 325 miles of Puerto
Rico when it will slow considerably. At this distance it will have
no effect on Puerto Rico and the U.S. Virgin Islands weather. So, we
expect continual warmth and fair weather through the Friday.

.LONG TERM...Saturday through Wednesday
High pressure at the surface will continue east northeast of the
area. A cold front approaches the area, but the local area will
see only the presence of the shearline at the tail of the front
when it moves into the area Saturday night and Sunday. This
additional moisture and some transitory divergence aloft will
generate some showers over the weekend and into early next week.
Mainly over Puerto Rico with isolated showers possible over the
northern U.S. Virgin Islands. A trough passage aloft Sunday night
and surface high pressure retreating to the east Monday and
Tuesday will allow moisture to diminish again through the end of
the period.

&&

.AVIATION...VFR conds will continue to prevail. Sfc Winds will
be from the SE at 10 to 15 kts then turn west at 23 kft to 45 kft.
Winds will range from 10 to 70 kts. Maximum wind at FL410.


&&

.MARINE...Northeast swell will fade during the day and northwest
swell will increase late this afternoon and overnight. Seas will
then continue to increase through late Thursday afternoon and
evening. Small craft advisories will be hoisted beginning this
afternoon and continuing until Thursday night in the Atlantic
waters and passages. Rip current risk will become high today in
Puerto Rico and for all northern coastlines by tomorrow morning.
High surf may also be possible along the northern shores of Puerto
Rico late Thursday.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 88 75 87 75 / 0 10 10 0
STT 83 75 83 74 / 0 0 10 10

&&

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
444 PM AST Wed Mar 14 2018

.SYNOPSIS...
A high pressure centered over the Central Atlantic will induce a
southeasterly wind flow across the local islands. No shower
activity is expected the rest of tonight through Thursday morning.
An upper level trough will swing north of the island, weakening
somewhat the upper level ridge by Thursday afternoon. Shower
activity will develop over the western interior and northwest
sections of Puerto Rico Thursday afternoon. Fair weather
conditions will return by Friday.

&&

.SHORT TERM...Tonight through Friday...
Another warm and rain free day prevailed especially across the
northern sections of mainland Puerto Rico. Where the maximum
temperatures reported at the Luis Munoz Marin Airport reached 88
degrees Fahrenheit. The U.S. Virgin Islands have sunny skies with
no rain but maximum temperatures were in the mid 80s. Fair
weather conditions with no shower activity is expected tonight
through at least Thursday morning across the local islands.

As an upper level trough interact with the upper level ridge local
instability is expected to increase somewhat by Thursday
Afternoon especially along the northwest quadrant of Puerto Rico.
Model guidance are indicating a slight increase in the available
moisture across this quadrant. Under a southeast wind flow, the
available moisture combined with diurnal effects will lead to
afternoon shower over isolated areas of northwest PR. Elsewhere,
mostly sunny to partly cloudy skies with southeast winds will
continue to result in warmer than normal temperatures mainly along
the coastal areas.

A dry air mass and a strong trade wind cap will limit shower
activity across Puerto Rico and the U.S. Virgin Islands on Friday.

LONG TERM...Saturday through Wednesday...
High pressure at the surface will continue east northeast of the
area. A cold front approaches the area, but the local area will
see only the presence of the shearline at the tail of the front
when it moves into the area Saturday night and Sunday. This
additional moisture and some transitory divergence aloft will
generate some showers over the weekend and into early next week.
Mainly over Puerto Rico with isolated showers possible over the
northern U.S. Virgin Islands. A trough passage aloft Sunday night
and surface high pressure retreating to the east Monday and
Tuesday will allow moisture to diminish again through the end of
the period.

&&

.AVIATION...
VFR conditions will continue to prevail for the next 24
hours across all terminals. Low level winds will prevail from the
ESE at 10-22 kts. However, light and variable winds are expected
overnight at the surface.

&&

.MARINE...
41043 began to register the northerly swell, which is expected
later tonight across the regional waters. At this time, the
northwest swell detected had a wave height around 7.5 feet at 13
seconds. As the swell reach the region, marine and coastal
conditions especially along the Mona Passage and Atlantic Waters
are expected to deteriorate. A small craft advisory is in effect
for these waters. The winds will continue from the east to east
southeast at 10 to 15 knots.

The swell is expected to create breaking waves higher than 10
feet and life threatening rip currents along the north facing
beaches of the Atlantic Coastline of Puerto Rico. As a result, a
High Surf Advisory is in effect between Thursday morning and
Friday Morning. The risk of rip currents is expected high for the
north facing beaches of the U.S. Virgin Islands, Culebra, Vieques
and from the northwest to northeast Puerto Rico.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 75 87 75 87 / 0 0 20 20
STT 74 83 74 83 / 0 0 20 20

&&

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
449 AM AST Thu Mar 15 2018

.SYNOPSIS...While a cold front eases toward the area, high
pressure east northeast of us is driving southeast flow with
limited moisture across the area. Moisture slowly increases after
Friday, as the cold front stalls northeast of the general area.
The associated moisture is also aided by convergence at lower
levels and will boost rain chances. This moistening trend is
expected to continue through the following week.

&&

.SHORT TERM...Today through Saturday...
Earlier this morning showers moved inland across portions of
Ponce and Vicinity, southeast, and northeast Puerto Rico with
light rainfall amounts. The TSJU 00Z sounding still shows drier
air at the surface to 200 mb but the precipitable water value
today is 1.16 inches. This is higher than yesterday`s value of
0.81 inches, showing that some low level moisture has come back,
but with respect to climatological norms it is only in the 25th
percentile--well below normal. Similar to the previous day`s
southeasterly flow, winds of 5 to 15 mph will bring with warmer
conditions to the north coasts of Puerto Rico. Temperatures will
be near the mid to upper 80s across Puerto Rico and the U.S.
Virgin Islands.

Now, there are big differences between current model guidance
compared to yesterday. For instance, the current 00Z models have
precipitation grater than 40 percent across portions of northwest,
western interior, north central Puerto Rico. The eastern portions
of Puerto Rico the models shows a 20 percent chance of
precipitation. Yesterday most models depicted precipitation
values of less than 15 percent area wide.

To account for these differences, precipitation was increased
slightly, and analysis of water vapor, the skew-T sounding and
night time infrared imagery shows some moisture across the region.
But at this time, current thinking is that it`s not enough to
warrant pops greater than 30 percent. Expectations are similar for
Friday.

Saturday, moisture increases rapidly ahead of a decaying shear line
which could spark a few showers across the northern portions of
Puerto Rico.

.LONG TERM...Sunday through Friday...
Northwest flow at 700 mb brings slightly cooler and drier air into
the area as a shear line entering the area bulges across the
local islands ahead of adjoining segments. Surface flow, however,
remains southeast during the period. This will bring showers to
eastern Puerto Rico first and then western Puerto Rico during the
afternoon. This moisture moves into the southeastern portion of
our marine area and beyond. A cold front will sweep through
Florida early next week and slowly approach the area during the
week. At the same time moisture that just passed through the area
Sunday and Monday will return. The proximity of the front later
next week is expected to enhance rain chances and amounts then.

&&

.AVIATION...VFR conditions to prevail at all TAF sites. Isold SHRA
and mtn obscurations psbl over SW and SE PR through 15/12Z.
Expect sfc winds SE 5 to 10 kt plus sea breeze influences aft
15/14Z. Max winds W 50-60 kt btwn FL305-435 highest at FL435.

&&

.MARINE...Northwest swell brought 7 to 8 foot seas with 12 to 14
second periods to the outer buoy overnight, and up to 6 foot seas
at the inner bouy (41053). These are expected to peak around 12Z
Friday. It has brought small craft advisories, a high risk of rip
currents and even some high surf to the Atlantic waters and exposed
northern coasts. See the Surf Zone Forecast and the Coastal
Hazard Message for more details. This is expected to be the last
major swell event for the next 7 to 10 days.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 75 87 74 / 10 20 20 20
STT 83 74 83 74 / 0 20 20 10

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
531 AM AST Fri Mar 16 2018

.SYNOPSIS...The shearline just northwest of the area will move
through over the weekend to bring increase moisture and showers
followed by some drying early in the week. Patches of moisture
will move across the area later in the week until a second
stronger front approaches next weekend.

&&

.SHORT TERM...Today through Sunday...
Today a weak frontal boundary will stall to the northwest of
Puerto Rico and cause easterly winds over the islands. This front
will remain north of the area before phasing into a weak shear
line. GFS has precipitable water reaching it`s lowest point at
16/06Z but, it increases throughout the rest of today before
peaking on Sunday. CIMSS total precipitable water (MIMIC) map
shows a surge of moisture working in from the east. This, combined
with the subtropical jet influence should create showers across
the northwest and northeast Puerto Rico. As for yesterdays
rainfall a weak theta-e ridge moved over Puerto Rico and created
enough instability which triggered showers across portions of
northwest and northeast Puerto Rico. The atmosphere across the
region is still recovering from the dip in precipitable water so
showers today should be somewhat lighter than Thursday.

Saturday, low level moisture surges back across the region ahead of
a dissipating shearline and strong subtropical jet this combined
with daytime heat should cause showers across interior, to the north
and west of the Cordillera Central and downwind from the U.S. Virgin
Islands each day. Moisture will continue to rise somewhat on
Sunday and showers will affect more of the island during the night
and early morning. Better rainfall is also expected on Sunday in
the northwest.

.LONG TERM...Monday through Saturday...
High pressure will begin to build over the northeast Atlantic and
spread over the Caribbean as it shifts a little southwest during
the week next week. After a weak low pressure shifts offshore
from the United States into the western Atlantic Sunday, another
more vigorous low will slip offshore on Tuesday and move along
the coast away from the area. This will keep surface flow somewhat
moist and east to southeast. A cold front/shearline will approach
the area but should not affect the local islands until Saturday
if the models are handling the trough well, but bubbles of
moisture begin to form ahead of the shearline in weakening surface
flow that will increase shower activity next weekend.

&&

.AVIATION...VFR conditions to prevail at all TAF sites. Isold SHRA
are possible by 16/12Z over SW and SE Puerto Rico. SHRA possible
in and around JBQ through 15/22z. Mtn obscurations. ESE winds 10
to 12 knots becoming light and variable overnight. Max winds W
50-60 kt btwn FL306-424 highest at FL435.

&&

.MARINE...models drop the seas somewhat abruptly, but seas are
coming down. Have left a small craft advisory in the Mona channel
where 7 foot seas linger through at least 8 AM AST, since the
model is slightly underestimating seas. Small craft advisory
conditions will not return this week or next.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 75 87 74 / 20 20 20 40
STT 83 72 85 75 / 20 20 20 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
449 AM AST Sat Mar 17 2018

.SYNOPSIS...Drier weather will prevail over the next several days
with a possibility for an isolated shower across northwest Puerto
Rico today and Sunday. The next weather maker will be a cold
front that will move off the east coast of the United states on
Wednesday with the front nearing the islands next Saturday.

&&

SHORT TERM...Today through Monday...
Weak high pressure at the surface rests just north of the Bahamas
and will drift to north of the local area at 25 north. Clouds from a
shearline drape across Hispaniola and stretch northeast into the
cold front about 375 miles north of San Juan. This cloudy area
should remain just northwest of the forecast area through 18/03Z and
then blow through to the Caribbean waters on northwest flow at 700
mb. by Sunday night. Yesterday no stations reported rainfall except
Maricao with 0.03 inches. Our forecast area remains under this same
relatively dry air mass--due to the proximity of the front. Also
the 17/00z relative humidity was over forecasted over the area by
the GFS. Therefore, based on model performance yesterday which
had areas of very high POPs during the afternoon over northwest
Puerto Rico, (Hi-RES models) and a general area of higher POPs
(GFS) over central Puerto Rico, and model output today, which
continues to develop very high POPs over the western coast (HI-
RES) and nearly 100 percent POPs just east of the center of Puerto
Rico (GFS) am greatly limiting expectations to around 30 percent.
(Tool rounding may show a different field than forecast.) Do
consider that weak moisture increases could lead to more shower
development today than yesterday, but it should be limited due to
dry mid layers.

This consideration will play into the forecast for Sunday also,
except that the model is bringing the clouds associated with the
shearline through and moisture is forecast to be higher. Also the
presence of an upper level jet entrance just north of the area
should enhance shower activity over the area. Current indications
suggest that the front may not break through the area as modeled so
have scaled back the precipitation forecast somewhat while allowing
the area affected to expand. As the surface flow turns more easterly
from Sunday to Monday we will see a more typical distribution of
precipitation should moisture move through as expected. Hence on
Sunday night and Monday morning scattered showers are expected on
the eastern slopes of Puerto Rico with isolated showers in the U.S.
Virgin Islands, followed by some convection over the inland portion
of western Puerto Rico in the afternoon with little shower activity
in the U.S. Virgin Islands.

.LONG TERM...Tuesday through Sunday...A surface and mid level
ridge of high pressure will create quiet conditions during the
beginning of the long term period.

Wednesday, a cold front will move off the east coast of the
United States and will continue to move south into the Atlantic
waters. Ahead of the front east southeast winds will pull moist
air over Puerto Rico and the U.S. Virgin Islands with scattered
showers across northwest, central and southwestern portion of
Puerto Rico through Friday.

Saturday, the front will be to the northwest of Puerto but with
southerly moist flow combining with orographic lift will create
showers across the offshore waters.

Sunday, a diffuse front moves over Puerto Rico bringing moisture
across portions of northwest and northern Puerto Rico during the
afternoon this moisture will continue to spread east across
northeast Puerto Rico and the U.S. Virgin Islands.

&&

.AVIATION...VFR conds are expected to prevail through 18/12Z. Some
SHRA are psbl in NW PR with mvfr conds and mtn obscurations from
17/17Z thru 17/22Z, but TAF sites may only be brushed by this if
affected. Sfc winds will be southeast 6-12 kt, sea breezes will
dominate aft 17/14Z. Winds alf W 60-80 kt btwn FL310-510 winds incrg
thru 18/12Z. Maximum winds FL410.


&&

.MARINE...Seas will range from 4 to 6 feet across the Atlantic waters and Mona
passage, and between 3 and 5 feet elsewhere. A high risk rip
currents risk is in effect for the northern beaches of Puerto RIco
until Sunday.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 89 74 87 74 / 10 10 20 20
STT 85 74 85 73 / 10 10 10 20

&&

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
449 AM AST Sat Mar 17 2018

.SYNOPSIS...Drier weather will prevail over the next several days
with a possibility for an isolated shower across northwest Puerto
Rico today and Sunday. The next weather maker will be a cold
front that will move off the east coast of the United states on
Wednesday with the front nearing the islands next Saturday.

&&

SHORT TERM...Today through Monday...
Weak high pressure at the surface rests just north of the Bahamas
and will drift to north of the local area at 25 north. Clouds from a
shearline drape across Hispaniola and stretch northeast into the
cold front about 375 miles north of San Juan. This cloudy area
should remain just northwest of the forecast area through 18/03Z and
then blow through to the Caribbean waters on northwest flow at 700
mb. by Sunday night. Yesterday no stations reported rainfall except
Maricao with 0.03 inches. Our forecast area remains under this same
relatively dry air mass--due to the proximity of the front. Also
the 17/00z relative humidity was over forecasted over the area by
the GFS. Therefore, based on model performance yesterday which
had areas of very high POPs during the afternoon over northwest
Puerto Rico, (Hi-RES models) and a general area of higher POPs
(GFS) over central Puerto Rico, and model output today, which
continues to develop very high POPs over the western coast (HI-
RES) and nearly 100 percent POPs just east of the center of Puerto
Rico (GFS) am greatly limiting expectations to around 30 percent.
(Tool rounding may show a different field than forecast.) Do
consider that weak moisture increases could lead to more shower
development today than yesterday, but it should be limited due to
dry mid layers.

This consideration will play into the forecast for Sunday also,
except that the model is bringing the clouds associated with the
shearline through and moisture is forecast to be higher. Also the
presence of an upper level jet entrance just north of the area
should enhance shower activity over the area. Current indications
suggest that the front may not break through the area as modeled so
have scaled back the precipitation forecast somewhat while allowing
the area affected to expand. As the surface flow turns more easterly
from Sunday to Monday we will see a more typical distribution of
precipitation should moisture move through as expected. Hence on
Sunday night and Monday morning scattered showers are expected on
the eastern slopes of Puerto Rico with isolated showers in the U.S.
Virgin Islands, followed by some convection over the inland portion
of western Puerto Rico in the afternoon with little shower activity
in the U.S. Virgin Islands.

.LONG TERM...Tuesday through Sunday...A surface and mid level
ridge of high pressure will create quiet conditions during the
beginning of the long term period.

Wednesday, a cold front will move off the east coast of the
United States and will continue to move south into the Atlantic
waters. Ahead of the front east southeast winds will pull moist
air over Puerto Rico and the U.S. Virgin Islands with scattered
showers across northwest, central and southwestern portion of
Puerto Rico through Friday.

Saturday, the front will be to the northwest of Puerto but with
southerly moist flow combining with orographic lift will create
showers across the offshore waters.

Sunday, a diffuse front moves over Puerto Rico bringing moisture
across portions of northwest and northern Puerto Rico during the
afternoon this moisture will continue to spread east across
northeast Puerto Rico and the U.S. Virgin Islands.

&&

.AVIATION...VFR conds are expected to prevail through 18/12Z. Some
SHRA are psbl in NW PR with mvfr conds and mtn obscurations from
17/17Z thru 17/22Z, but TAF sites may only be brushed by this if
affected. Sfc winds will be southeast 6-12 kt, sea breezes will
dominate aft 17/14Z. Winds alf W 60-80 kt btwn FL310-510 winds incrg
thru 18/12Z. Maximum winds FL410.


&&

.MARINE...Seas will range from 4 to 6 feet across the Atlantic waters and Mona
passage, and between 3 and 5 feet elsewhere. A high risk rip
currents risk is in effect for the northern beaches of Puerto RIco
until Sunday.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 89 74 87 74 / 10 10 20 20
STT 85 74 85 73 / 10 10 10 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
355 PM AST Sun Mar 18 2018

.SYNOPSIS....Fair weather is expected to prevail much of the
upcoming workweek with afternoon showers developing each day
over the Cordillera Central and west sections of Puerto Rico.
A frontal boundary will move close to the local isles Friday
into the weekend.

&&

.SHORT TERM...Tonight thru Tuesday...

Heights will continue to fall through at least tomorrow with
precipitable water values remaining near the normal range which
is 1.35 inches. On Tuesday, ridge pattern aloft will build across
the local isles and hold through midweek. At lower levels, winds
are expected to be light and variable overnight, becoming more
east southeast Monday and Tuesday.

Under the aforementioned pattern expect a few passing showers
across the northern and eastern sections of Puerto Rico as well
as the USVI each day. Afternoon showers are also expected to
develop over the Cordillera Central and west areas of the island
both days. However, the intensity and areal coverage of showers
should decrease on Tuesday under building ridge.

.LONG TERM...Wed thru Mon.../issued 515 AM AST Sun Mar 18 2018/

Wednesday, the surface and mid to upper level ridge starts to
weaken ahead of a cold front moving off the east coast of the
United states. Southerly winds will carry warm moist air over the
region giving a possibility for showers during the afternoon
Wednesday through early Friday.

Friday, a col will form to the northeast of Puerto Rico with a
weak shear line forming over the western half of Puerto Rico with
showers and possible thunderstorms.

Saturday-Monday, A prevailing east northeast wind flow combined
with low level moisture will keep the islands in a unsettled
pattern with isolated showers mainly during the morning and
afternoon.

&&

.AVIATION...Mainly VFR conditions will prevail across all terminals
during the next 24 hours. However, +SHRA over the interior sections
of PR could result in tempo MVFR conds at TJMZ/TJBQ/TJSJ through at
least 23z. Light winds with a southerly component will continue
through the evening hours...light and variable during the
overnight.

&&

.MARINE...Tranquil marine conditions will continue to prevail
across the local waters during the next few days with seas below
the Small Craft criteria.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 86 74 85 74 / 30 20 20 20
STT 83 72 84 74 / 20 20 30 30

[cycloneye]

Area Forecast Discussion...CORRECTED
National Weather Service San Juan PR
442 AM AST Mon Mar 19 2018

.SYNOPSIS...A weak shear line remains to the northeast of Puerto
Rico as a result showers with isolated thunder will be
possible today. A ridge will build across the local area on
Tuesday, which will promote fair weather conditions with an
occasional shower until early Thursday. Late Thursday will be a
transition day for most of the region due to an approaching cold
front that will create unsettled weather through the weekend.

&&

SHORT TERM...Today through Wednesday...
A ridge near the Bahamas and the remnants of a shear line to the
north of the islands will linger around through at least Tuesday.
Under this pattern, patches of moisture will move across the islands
from time to time. Light southerly winds will aid in sea breeze
formation today. This combined with diurnal heating and the presence
of a jet segment aloft will result in scattered to locally numerous
afternoon showers across the Cordillera Central, north and west
Puerto Rico. Shower formation in the form of streamers is possible
downwind from the U.S. Virgin Islands by mid morning into the
afternoon hours.

As a ridge pattern builds, moisture will erodes and shower activity
is expected to be limited Tuesday and Wednesday. But, shower
activity will remain possible across the USVI and eastern sections
of PR during the night time diminishing during the morning hours.
Sea breezes and diurnal heating would be the driver mechanisms
for afternoon convection each day. By Wednesday, easterly winds at
10 to 15 mph are expected to return as a high pressures across
the Western Atlantic tighten the local pressure gradient.

.LONG TERM...Thursday through Tuesday...
Thursday, A vertical stacked ridge will promote fair weather
earlier on Thursday but, the ridging will begin to weak late in
the day due to an approaching cold front. East southeast winds
will carry warm moist tropical air over the islands late in the
day, as result isolated to numerous showers will be possible
across the northern coast of Puerto Rico during the evening.

Friday, a col will form to the northeast of Puerto Rico as a cold
front continues to make its way closer to Puerto Rico with showers
and east northeast winds.

Saturday-Monday, Currently model guidance is showing a frontal
passage on late Sunday or early Monday. A prevailing east
northeast wind flow, upper level instability combined with low
level moisture will keep the islands in an unsettled pattern with
showers mainly during the morning and afternoon.

Tuesday, Winds will remain out of the east northeast with patches
of low level moisture moving across the islands as the surface
and mid level ridge tries to reestablish itself over the local
area.

&&

.AVIATION...VFR conds are expected to prevail through 19/17Z. SHRA
are posible in NW and north central PR between 19/17-23z with brief
MVFR conds and mtn obsc. VCTS were included at TJBQ and TJMZ, where
is possible to form. Passing shower are expected at TJPS/TISX aft
19/23Z. Sfc winds will be calm to light and vrb becoming from the SE
at 10 kt and with sea breeze variations aft 19/14Z.

&&

.MARINE...Seas 3 to 5 feet with an east to southeast winds 5 - 10
kts. Seas will remain around 3 to 5 feet across all local waters
ways through Wednesday. There`s a High Rip Currents risk for
northern beaches of Puerto Rico until Wednesday.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 86 75 86 75 / 20 20 20 20
STT 84 73 84 75 / 30 30 20 20