Puerto Rico Weather

Area Forecast Discussion

National Weather Service San Juan PR

502 AM AST Thu Apr 13 2017



.SYNOPSIS...Low pressure to the north of the local area will

slowly drift southwest and in the process it will cause an

increase in moisture across the local area. It will also keep

light winds which will cause the afternoon showers and

thunderstorms that develop over PR persisting over any one area

before they dissipate. Soils are saturated and loose over much of

PR and any rain that does fall will quickly turn into runoff.

Showers and thunderstorms are expected today. A flash flood watch

has been issued for PR, which is in effect from 8 AM AST today to

6 PM AST Friday.



&&



.SHORT TERM...The available moisture will combine with the overall

instability and upper air ventilation to cause another round of

showers and thunderstorms across the local area, in particular

across the central and northern sections of PR. This is due to

upper level divergence and a SFC low just north to the local area

which is causing a convergence zone over PR along with fairly

light winds. This means that any and all showers and thunderstorms

that develop this afternoon will likely affect any one place for

some time before dissipating, then due to the light winds, other

showers and thunderstorms could develop nearby, affecting the

adjacent municipalities. So a pattern of persistent showers and

thunderstorms over a generalized area is expected today. The

local soils are saturated and loose in some areas. This will cause

for quick runoff when the showers affect those areas and mud

slides are possible in areas of steep terrain. The high resolution

guidance is persistent in having a good amount of precipitation

over many parts of the northern half of PR with some models

favoring some areas over others but generally the consensus is for

northern PR to have good shower activity today. For that reason a

Flash Flood Watch was issued for today and Friday. Now Friday

doesn`t look quite as rainy as today but it does look like showers

and thunderstorms will once again affect portions of PR and

depending just on how much rain it falls today we could observe

some flash flooding once again on Friday as it may not take as

much rain to have flooding due to yet more areas with saturated

and loose soils.



.LONG TERM...Saturday through Friday.

Significant moisture and instability is expected to persist on

Saturday and Sunday, which could cause the development of

persistent showers and thunderstorms across different sectors in

our forecast area. The latest guidance does show a boundary of

deeper moisture and higher instability which may affect south and

eastern PR as well as the local waters and the USVI. This means

that the activity may not be limited to locally induced showers

and thunderstorms but instead the upper levels will combine with

the surface convergence and available moisture to cause the

development of some of these showers and thunderstorms, while the

local effects of PR may enhance some of the thunderstorm activity.

At this time it looks like Saturday may be a bit of a lull in the

shower and thunderstorm activity but by no means looks like a dry

day, while Sunday looks to have a much more widespread shower

coverage and some areas over PR maybe observing locally heavy

rainfall. After Sunday things look a bit quieter with mainly

locally induced showers due to the still deep moisture over the

area.



&&



.AVIATION...WDLY SCT SHRA ovr coastal waters and en route btw

islands during entire prd with prevailing VFR at local TAF sites.

Mtn Top obscr due to passing SHRA and low CIG mainly over the E

interior section of PR and low cig til 13/14z. Fm 13/16Z-13/22z

+SHRA/psbl TSRA will dvlp over interior sections of PR and spread

north and eastward causing TEMPO MVFR/psbl IFR at

TJBQ/TJSJ/TJMZ/TJNR. SFC wnds SE-S 5-10 kts and veering with

height bcm SW-W abv FL110 and max wnd nr 85 kt btw FL350-410.





&&



.MARINE...Seas will be generally 5 feet or less across the local

offshore Atlantic waters and up to 4 feet elsewhere today. The

coastal winds are expected to be gentle and up to 10 knots with

the exception of near showers and thunderstorms that may develop

today. Moderate risk of rip currents from the northwest to the

northeast beaches of PR.



&&



.PRELIMINARY POINT TEMPS/POPS...

SJU 85 75 87 75 / 80 50 30 40

STT 83 74 84 75 / 40 40 40 40

Area Forecast Discussion

National Weather Service San Juan PR

524 AM AST Sun Apr 16 2017



.SHORT TERM...A rich plume of moisture has been moving north over

Hispaniola and turning toward the east over the local area around

a ridge at 700 mb that extends from the Windward Islands to

Hispaniola. Yesterday most of the moisture from this flow stayed

over our local Caribbean waters and just south of there. Today it

is forecast to move over Puerto Rico. The center of a jet of west

winds at 22 degrees north latitude has been moving east and is

currently located northeast of the Leeward Islands. Although

convergence aloft was over the area yesterday at 15/18Z, today

good divergence aloft is expected in the right entrance of the jet

over the local area. This should bring better dynamics to the

area and enhance the local rainfall mainly over the interior of

Puerto Rico. Areas of moisture at mid levels can already be seen

in the latest GOES-IR clean channel moving into Puerto Rico out of

the southwest. Although this moisture may impede initial convection

as it shields the island from early heating, when convection does

fire off later this afternoon we should have ample moisture to keep

it going. The models did not end convection over the area during

the evening hours this evening, but rather kept some showers active

right through Monday. Expect most showers in the interior to end

before midnight though. With lower level winds increasing as high

pressure sags south in the western Atlantic onshore winds should

keep showers off the northern coast as flow from the north is not

particularly moist, but there is still a slight chance of one hundredth

of an inch.



Moisture fades insignificantly on Monday and Tuesday, and upper level

dynamics, that were not so favorable in previous runs, now appear to

increase and may cause another several rounds of heavy showers and

isolated thunderstorms. These will fight the approach of the mid

and upper level ridge to the west and the dry air that is encroaching

from the northeast and north, but the driest air remains northeast

of the forecast area as it is pulled into the low that will cut off

in the central Atlantic today. Therefore we will see better than usual

precipitation both of those days.





.LONG TERM...Weather conditions are forecast to significantly improve

across the region by Wednesday, as a surface high pressure ridge

will continue to spread eastward into the central Atlantic inducing

a dominant northeast wind flow. This expected pattern will tighten

the local pressure gradient consequently increase the east to northeast

low level winds. In addition, with the building and spreading of the

mid to upper level ridge just west of the region, expect increasing

subsidence aloft and a much drier airmass to filter in across the region.

Although the overall moisture transport will continue to decrease by

Wednesday and during the latter part of the upcoming work week, still

expect the moderate trade winds to advect occasional patches of shallow

low level moisture across the region from time to time. This will

be sufficient to combine with local and diurnal effect to produce

early morning showers and afternoon convection mainly over parts

of the interior and west to southwest sections of Puerto Rico.

Meanwhile, the remainder of the islands should experience partly

cloudy to mostly sunny skies with only brief early morning passing

showers followed by isolated areas of streamer like afternoon shower

activity mainly downwind of the islands each day.



&&



.AVIATION...Currently VFR. The GFS forecasts the best moisture of

next 7 days today with enhanced upper air dynamics begg aft 16/12z.

Therefore, aft 16/16Z expect areas of SHRA/isold TSRA with MVFR-LIFR

and hir trrn obscured to dvlp ovr much of interior PR. Brief pds of

MVFR are psbl at TJMZ, TNCM, TKPK otherwise VFR will prevail at TAF

sites. Some VCSH TJSJ, TJMZ, TJPS and in USVI and Leeward Islands

psbl. LLVL flow NNE-ENE but sea breezes dvlp aft 15/14Z arnd 10 to

15 kt. Max winds W up to 80 kt FL350-400 diminishing during the day

at the lower altitude.



&&



.MARINE...Mariners can expect increasing easterly winds of 10 to 15

knots and seas increasing up to 7 feet across the regional waters

today. Winds and seas are expected to continue to increase through

at least Wednesday. Therefore small craft advisories will be in effect

for the Atlantic Waters and portions of the local passages. Please refer

to the latest Coastal Waters Forecast and Marine Weather Message issued

by the WFO National Weather Service San Juan PR for the latest update

and information.



For the beach goers, the risk of rip current will increase to high

along the Atlantic Coastline of Puerto Rico and Culebra today, and

to moderate along most of the U.S. Virgin Islands.



&&



.PRELIMINARY POINT TEMPS/POPS...

SJU 85 75 85 74 / 20 30 40 40

STT 85 75 85 75 / 20 20 20 20

Area Forecast Discussion...CORRECTED

National Weather Service San Juan PR

523 AM AST Tue Apr 18 2017



.SYNOPSIS...Residual moisture and favorable upper level dynamics

will contribute to another round of showers and isolated

thunderstorms that will likely lead to local flooding and rapid

rises on area rivers in Puerto Rico. The remnant of a frontal boundary will

shift south today through Friday then gradually return to the area

with another plume of moisture from South America that will last

into mid-week next week. Moisture increasing over the weekend

will be accompanied widespread shower activities which may lead to

flooding that could extend through the first half of next week.



&&



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

The Flash Flood Watch for Puerto Rico and the the U.S. Virgin

Islands has been extended through this afternoon. For today, the

lingering moisture across the region is expected to combine with

daytime heating and local effects to produce another round of

showers and thunderstorms across the region. A slight shift to an

ENE wind is expected today, which will cause the convection to

develop across the interior and the southwest quadrant of PR this

afternoon. Due to saturated soils from previous rainfall across

most of Puerto Rico, urban and small stream flooding and river

flooding are possible again this afternoon. Drying should spread

across the area later tonight from the northeast.



Drier weather conditions are expected to encompass the region

Wednesday and Thursday as a high pressure system builds across the

region and precipitable waters values decrease to near 1.5

inches. However, some afternoon showers and thunderstorms are

expected both Wednesday and Thursday afternoon as lingering

moisture combines with diurnal heating and local effects that

could lead to very localized urban and small stream flooding.





.LONG TERM...Friday through Thursday...

The boundary that has plagued Puerto Rico and the U.S. Vrigin

Islands with record rainfall in some areas will move into the

central Caribbean. The upper level ridge that will be found over

the central Caribbean Wednesday will diminish in intensity and

move over the local area Friday. The passage of the ridge followed

immediately by a moderately strong jet segment over the local

outer Atlantic waters of up to 90 knots will again set in motion a

trend toward wetter weather. By Saturday local urban and small

stream flooding will return and by next week the plume of moisture

out of South America will likely be sufficient to generate more

widespread flooding.



&&



.AVIATION...Mostly VFR conditions expected across the local flying

area through 18/16Z. After 18/13Z the winds will increase to about

15-20 kt with occasional higher gusts as high as 30 kt. SHRA and

isolated TSRA expected across interior and western PR after 18/17Z

causing VCSH/VCTS across TJBQ and TEMPO SHRA/TSRA across TJMZ

with VCSH expected across the rest of the TAF sites. Hir trrn

will be obscured. Weather conditions are expected to improve after

19/00Z, leaving Partly cloudy skies with ISOLD/SCT SHRA across

the local flying area. Maximum winds will decrease from WSW at 85

knots around FL440.



&&



.MARINE...Seas have proven to be higher than model forecast with

the outer buoy showing 10 to 12 feet and the inner buoy near San

Juan showing 6.5 to 8.0 feet. Maximum wave height recorded at the

San Juan buoy was over 15 feet overnight. A high risk of rip

currents exist for almost all beaches with northern exposures. A

high surf advisory is also in effect. Mariners will find seas

growing up to 10 feet in the local Atlantic outer waters with some

action extending into the passages. Winds will increase today to

15 to 20 knots making the Caribbean rough as well. Conditions are

expected to begin improving by later today with more tranquil

condtions by Thursday. Weaker, but still significant northeast

swell, will return to the area Saturday evening.



&&



.PRELIMINARY POINT TEMPS/POPS...

SJU 84 76 86 76 / 40 10 20 20

STT 86 76 86 73 / 40 10 10 20

Area Forecast Discussion

National Weather Service San Juan PR

453 AM AST Sat Apr 22 2017



.SYNOPSIS...An upper level ridge over the region will begin to

erode rapidly Saturday and Sunday as an upper level trough and an

associated surface low move across the southwest Atlantic late in

the weekend and early next week. In addition, a subtropical jet

will holds aloft through the weekend. A surface high pressure

north of Hispaniola will drift eastward into the Central Atlantic

through early next week.



&&



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

Surface high pressure north of the area will continue to move

into the Central Atlantic and promote a moderate to locally fresh

trade wind flow across the forecast area. Trade wind cap will

limit diurnally induced afternoon showers to the western sections

of Puerto Rico today. Isolated thunderstorms are possible as short

wave trof moves aloft later this afternoon.



Later on Sunday through Monday, precipitable water content increases

across the forecast area as surface ridge northeast of the area

weakens due to deep polar trof deepening across the Western Atlantic

into the local area and an area of low pressure at the surface moves

across the south-southeast coast of USA and a moist southerly wind

flow pulls tropical moisture over the area. This will result in

periods of scattered to numerous showers and thunderstorms across

the waters and islands. The flood threat will increase across

mainland PR, specially on Monday. Also, periods of heavy rainfall

will result in mudslides in areas of steep terrain.



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

An upper level trough and an associated surface low is expected

to develop across the western Atlantic early in the upcoming week.

This will result in a significant increase in moisture across the

northeast Caribbean. In fact, PWAT values will increase up to

2.20 inches early in the upcoming week and until at least early

Wednesday. A surface high pressure is expected to drift

northeast toward the central Atlantic early during the upcoming

week. As this happens, the local winds will shift from the

southeast. This change in wind direction will bring a moist and

very unstable tropical moisture across the region from the

southeast Caribbean. This moisture will continue to result in a

significant increase in shower and thunderstorm activity across

the region until at least early Wednesday. With the ground across

Puerto Rico still saturated from previous days rainfall, urban

and small stream flooding and possible river flooding is likely to

Monday Afternoon and Tuesday. Weather conditions will slowly

improve on Thursday as the local winds shift eastward. Due to

expected southeast wind flow, warmer than normal temperatures are

expected especially along the northern coastal municipalities of

Puerto Rico Tuesday and Wednesday.



&&



.AVIATION...Mainly VFR conditions are expected to prevail across all

terminals. However diurnally induced afternoon SHRA/TSRA across

western PR can result in MVFR conds at TJMZ and affect briefly the

flying area of TJBQ. Low level winds ENE at 10-15 knots with

higher winds in sea breeze variations after 14z.



&&



.MARINE...Seas up to 6 feet are expected across the Atlantic

waters and the local passages today. Marine conditions will begin

to deteriorate rapidly this evening as a north to northeast swell

invades the local waters and passages. Small craft advisories will

begin in effect this evening for some of the coastal waters and

a high risk of rip currents is expected today for the northwest to

northeast beaches of Puerto Rico and Culebra.



&&



.PRELIMINARY POINT TEMPS/POPS...

SJU 84 74 85 74 / 10 10 20 30

STT 85 73 84 75 / 20 10 10 50



&&

Area Forecast Discussion

National Weather Service San Juan PR

504 AM AST Mon Apr 24 2017



.SYNOPSIS...Moist and unstable conditions will keep the potential

for showers and a few thunderstorms high through at least Tuesday.

Conditions will gradually improve by midweek as mid level ridge

builds over the Central Caribbean.



&&



.SHORT TERM...Today through Wednesday...Surface low pressure across

the southwestern Atlantic and a surface high pressure northeast of

the area are promoting low level wind convergence and favoring a

moist southeasterly wind flow across the region. Precipitable water

is expected to remain above 2 inches across much of the forecast

area. Deep trof aloft is forecast to move from the west through

Wednesday. Providing good divergence aloft to enhance the

development of thunderstorm with periods of heavy rainfall.



For today, shower activity should continue to increase across the

USVI`s and the southeastern/interior sections of PR through the rest

of the morning hours. Hi-res models continue to suggest best shower

activity and possible isolated thunderstorm development over the

eastern half of PR into the USVI`s later this afternoon into the

evening hours. As trof aloft moves near the region on Tuesday,

organized convection and higher rainfall amounts are expected on

Tuesday afternoon, mainly over and to the north of the Cordillera

Central as well as across the USVI`s. On Wednesday, the base of the

trof should move to the northeast of the forecast area as ridge

builds from the west. However, sufficient moisture will linger

across the islands to aid the development of diurnally induced

afternoon showers over the islands.



Residents across the islands should continue to monitor the progress

of the weather conditions as periods of frequent rainfall can result

in urban and small stream flooding as well as localized flash

flooding.



.LONG TERM...Thursday through Tuesday...Overall moisture content

will decrease through Saturday as a mid-upper level ridge will

develop over the Western and Central Caribbean. Easterly winds

will return to the local area on Thursday as a strong high pressure

builds over the Central Atlantic. Weather conditions will remain

fairly stable from Thursday through the weekend as subsidence and

drier air aloft will limit the shower coverage across the local

region.



An upper level trough/TUTT will amplify over the Tropical Atlantic...

northeast of the region by early next week. As the TUTT retrogress

across the Northeast Caribbean Islands...weather conditions will

become unstable between Tuesday and Wednesday next week.



&&



.AVIATION...BKN-OVC cigs between FL040-FL090 will continue

across the forecast area with mtn top obscd across mainland PR.

Brief MVFR at times possible across much of the terminals today as

cloudiness and TSRA/SHRA increases over the waters and between the

Leeward/USVI/Eastern PR terminals during the afternoon/evening

hours. Southeast winds below FL050 will continue at 10-22

knots...westerlies abv and increasing w/height.



&&



.MARINE...Prevailing winds will shift to the south-southeast over

the next few days as a surface low moves over the Western Atlantic.

A decaying northerly swell of 5-7 feet will subside through tonight.

Hazardous marine conditions will continue across the Offshore Waters

and Caribbean Passages through late tonight. A high risk of rip

currents remains in effect for the Atlantic Beaches of Puerto Rico

and Culebra.



&&



.PRELIMINARY POINT TEMPS/POPS...

SJU 88 76 89 76 / 40 40 50 50

STT 85 77 84 76 / 60 60 60 60

Area Forecast Discussion

National Weather Service San Juan PR

518 AM AST Wed Apr 26 2017



.Synopsis...Ridge at the surface across the Atlantic will continue

for the next several days. Southeast winds continue through

Thursday, becoming east-northeast through next week. Upper ridge

builds west of the area and across the Central Caribbean. TUTT

develops northeast of the area during the weekend and persist

through early next week.



&&





.Short Term...Wednesday through Friday...



Mostly cloudy skies prevailed overnight and early this morning

across the local islands. Showers were observed across the regional

waters as well as over coastal municipalities of Puerto Rico.

Rainfall accumulations associated with these showers were between

one and three inches. Temperatures were in the upper 70s to low 80s

at the lower elevations.



Although the upper level trough across the Central Atlantic and into

the northeast Caribbean will continue to shift east and away from the

forecast area today, another trough aloft, a TUTT, is expected to

establish north of the area by Friday. At lower levels, a moist

southeasterly wind flow will continue to prevail today, becoming

more easterly Thursday and into the upcoming weekend as a surface

high across the north central Atlantic relocates across the central

Atlantic. Latest guidance continues to suggest a decrease in

precipitable water during the next two days or so, but remaining

above the normal range.



As a result, continue to expect passing showers across the coastal

areas of Puerto Rico as well as USVI during the morning hours with

shower and thunder activity increasing across the forecast area in

the afternoon. These showers and thunderstorms are expected mainly

across the northwest quadrant of the island as well as portions of

the San Juan Metro Area. With the heaviest showers, urban flooding

likely. A similar pattern should prevail Thursday and Friday,

although morning showers will be focused across E PR and USVI.



.Long Term...Saturday through Thursday...



TUTT pattern to the northeast is expected to provide instability

across the area to aid the development of showers and possible

isolated thunderstorms during Saturday afternoon across the

interior and western portions of PR. PWAT content erodes quickly

on Sunday and best moisture content remains below 800 mb through

the end of the forecast period. This in response to trade wind cap

as ridge pattern dominates the Western Atlantic. Therefore, best

chances for showers are during the weekend across the islands.

During the week, limited shower activity is expected across the

region...with brief periods of trade wind showers across the

USVI`s and the north and eastern portions of PR at times and

localized afternoon shallow convection over west/southwest PR.





&&



.AVIATION...VFR conds expected to prevail this morning at the

Leeward and USVI terminals with SHRA possible in and around JSJ.

SHRA/TSRA development expected aft 26/16z to result in brief periods

of MVFR conds in and around JBQ/JMZ and possibly JSJ through 26/22z.

Southeasterly winds at 10 to 15 knots with sea breeze variations,

becoming light and variable overnight.





&&



.MARINE...Coastal buoys across the islands are indicating seas

between 2-4 feet and east-southeast winds at 5-10 knots. Higher

gusts were observed with showers and thunderstorms across the

Atlantic waters and the southwestern coastal waters of Puerto

Rico. Seas should continue between 3-5 feet and east to

southeasterly winds up to 15 knots. Moderate risk of rip currents

continue for the northern and southern coasts of the islands.





&&



.PRELIMINARY POINT TEMPS/POPS...

SJU 90 77 87 76 / 30 30 30 30

STT 86 76 86 76 / 40 30 30 30

Area Forecast Discussion...CORRECTED

National Weather Service San Juan PR

531 AM AST Fri Apr 28 2017



.SYNOPSIS...There is a chance of showers and thunderstorms each

day under developing TUTT and plenty of low level moisture. A more

seasonable weather pattern will prevail by the end of next week.



&&



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



A surge of moisture moved across the islands overnight resulting in

scattered to numerous showers across the local waters, the U.S.

Virgin Islands and east and south Puerto Rico. In general, the skies

over Puerto Rico and the U.S. Virgin Islands were partly to mostly

cloudy. Moist and unstable weather conditions are expected to

prevail today enhancing showers across the windward sections of

the islands during the morning hours. However, little or no shower

activity is forecast for the west half portion of Puerto Rico.

Shower activity is expected to increase in intensity and coverage

during the afternoon, with the strongest activity over the

interior and west portion of Puerto Rico. In addition, the local

effects will result in shower activity streaming downwind from the

U.S. Virgin Islands and moving into the eastern sections of

Puerto Rico. Thunderstorm activity is expected mainly along the

Cordillera Central.



Model guidance indicated an unstable weather pattern for the

upcoming weekend. Low level convergence with precipitable water

values around two inches are forecast for Saturday. These will

combined with a TUTT Low, which is forecast to swing by the islands

through the weekend. Showers and thunderstorms are expected each day

across the islands and surrounding waters. The activity will be

focused over the coastal waters and the windward sections overnight

and early in the morning. Then, thunderstorms can be expected

mainly over the western and interior portion of Puerto Rico during

the afternoon hours through Sunday. Urban and small stream

flooding can be expected especially today and Saturday afternoon.



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



TUTT will hold across the forecast area through midweek next week.

As this feature weakens Wednesday and into early Thursday, a mid to

upper level ridge is expected to build across the forecast area from

the west. The ridge aloft is then expected to hold through at least

the weekend. At lower levels, a high pressure across the central

Atlantic will move eastward Wed-Thu, promoting moisture advection

from the southeast Friday through Saturday under the prevailing east

southeast wind flow.



Therefore, early next week still expect periods of showers and

thunderstorms across E PR and USVI during the evening and early

morning hours followed by shower and thunder development across

west PR in the late morning and afternoon hours. As the ridge

builds and moisture erodes Thu-Fri, a more seasonable weather

pattern is expected. However, under the aforementioned moist

southeasterly wind flow, the shower coverage may increase Sat-Sun.



&&



.AVIATION...-SHRA/SHRA will continue mainly across TISX/TIST/TJPS/

TJSJ/TNCM during the morning hours. Then, mount obsc with

SHRA/TSRA are expected over the interior and west section of PR.

This will result in VCTS across the terminals in PR, and possibly

MVFR or IFR conds btwn 28/17Z-23Z at TJMZ/TJBQ/TJSJ. Sfc winds

from the east at 5 to 10 knots til 28/12z. Increasing easterly

winds at 10 to 20 with higher gusts



&&



.MARINE...Moderate to locally fresh trade winds will continue to

prevail during the next several days, as a strong surface high

pressure across the central Atlantic will maintain a fairly tight

local pressure gradient. Short period wind driven seas are still

expected to increase across the offshore waters and passages

today and during the weekend. A moderate risk of rip currents

expected across much of the local beaches.



&&



.PRELIMINARY POINT TEMPS/POPS...

SJU 86 76 83 76 / 50 50 50 50

STT 86 75 83 75 / 40 50 50 50