Puerto Rico Weather

Area Forecast Discussion

National Weather Service San Juan PR

530 AM AST Sun Nov 13 2016



.SYNOPSIS...Trade wind showers during the morning hours across

E PR/USVI followed by locally induced afternoon showers and

thunderstorms across W PR and downwind of the USVI will continue

to prevail through Tuesday. A stable weather pattern is expected

to prevail across the forecast area Wednesday through Friday under

strengthening ridge aloft. A surface boundary will reach the local

islands the upcoming weekend.



&&



.DISCUSSION...A mid to upper level ridge will hold across the

forecast area during the next several days. However, at least

through Tuesday, this feature is not strong enough to suppress

shower/thunder development. A significant strengthening is expected

by the end of the week, and therefore could delay the onset of

afternoon showers and thunderstorms or even suppress it. As a

result through Tuesday, continue to expect passing showers across

eastern Puerto Rico and the U.S. Virgin Islands in the morning and

late evening hours, followed by locally induced showers and

thunderstorms across western sections of Puerto Rico under

easterly winds and a relatively moist airmass. In fact,

precipitable water values are expected to remain near or slightly

above the normal values through midweek. As the aforementioned

ridge aloft strengthens, available moisture is expected to erode.

This will result in more stable weather conditions across the

local islands Wed-Fri. Showers and thunderstorms are expected to

increase across the forecast area the upcoming weekend as a

surface boundary reaches the local islands.



Based on NHC, A broad area of low pressure is expected to gradually

form over the southwestern Caribbean Sea during the next few

days. Environmental conditions are forecast to be conducive for

slow development of this system, and a tropical depression could

form later this week while the low drifts northward or northeastward.



&&



.AVIATION...VFR conditions to prevail at least through 13/13z

across the local terminals with VCSH due to ISOLD/SCT SHRA.

SHRA/TSRA developing across PR after 13/16Z to affect the vcnty of

TJSJ, TJPS, TJMZ, and TJBQ. TJMZ may observe TEMPO MVFR conds. Low

level east winds should continue at around 5 kts through 13/13Z,

increasing to 10-15 kts after 13/13Z with sea breeze variations

developing.



&&



.MARINE...Pulses of a moderate NNW swell will reach the local

Atlantic waters through today. This will keep seas 3-5 feet the

rest of the weekend. Then...seas will subside to 2-4 feet on

Monday. Tranquil marine conditions will prevail the rest of the

work week.



&&



.PRELIMINARY POINT TEMPS/POPS...

SJU 88 78 87 78 / 30 40 40 40

STT 88 78 86 78 / 20 40 40 40



&&

Area Forecast Discussion

National Weather Service San Juan PR

408 AM AST Tue Nov 15 2016



.SYNOPSIS...Another round of locally induced showers and

thunderstorms are expected this afternoon across central and

western PR with possible isolated thunderstorms across portions of

the San Juan metropolitan area as well.



Weak tropical wave near 59W is expected to reach the Lesser

Antilles today but the bulk of the moisture associated should stay

South of the local area until late Thursday where the available

moisture is expected to increase over the local islands. Overall

pattern is expected to keep easterly winds through this week until

Saturday into Sunday when a frontal boundary approaches the area

but stays to our north. High pressure in the upper levels is

dominating and will continue through the workweek.



&&



.DISCUSSION...Scattered showers will continue to be expected

through the morning and late evening hours, mainly affecting the

local waters, USVI and eastern PR, but not leaving significant

amounts of rainfall. However, the available moisture and diurnal

heating will once again combine with the local effects and

prevailing wind flow to cause the development of showers and

thunderstorms in the afternoon across central and western PR with

some showers and thunderstorms also possibly affecting portions of

the San Juan metro. The soils are very saturated and any

significant showers will quickly become runoff, likely causing at

least some urban and small stream flooding. However, river

flooding is also very possible with the heaviest showers.



There is so much available moisture that afternoon convection is

likely every afternoon mainly across the central and western

sections of PR. This means that little relief is seen in terms of

drying up the soils across these sectors. The pattern should

remain fairly constant until maybe this weekend when a frontal

boundary approaches the local islands from the north. At this time

it looks like the boundary will stay just to our north but the

long range models indicate that it will get close enough to

disrupt the wind pattern and cause a shift to NE winds across the

westernmost sections of our forecast area as well as bring

cloudiness to the local area, possibly causing moderate rain and

thunderstorms due to advection and not locally induced convection.

This setup may also cause a decrease in daytime maximum

temperatures a few degrees.



&&



.AVIATION...VFR conditions will continue to prevail at all TAF sites

through 15/13z with VCSH possible at JSJ/IST/ISX. SHRA/TSRA

developing across PR after 15/16Z and this may result in MVFR conds

and mountain obscurations in and around TJPS/TJMZ through 15/22z.

Light and VRB winds through 15/13Z...becoming easterly at around

10 knots with sea breeze variations thereafter.



&&



.MARINE...Fairly tranquil seas at least until the end of the work

week, with a northerly swell expected to arrive to the local

Atlantic waters by early next week. There is a moderate risk of

rip currents across the Atlantic facing coasts of Puerto Rico,

Culebra, and Saint Thomas.



&&



.PRELIMINARY POINT TEMPS/POPS...

SJU 87 78 88 78 / 20 40 40 40

STT 87 78 87 78 / 20 40 40 40

Area Forecast Discussion

National Weather Service San Juan PR

549 AM AST Thu Nov 17 2016



.SYNOPSIS...Mid-upper level ridge will prevail over the Northeast

Caribbean Region through the end of the week. Surface trough is

moving across the forecast area today...promoting a moist and

unstable pattern across Puerto Rico and the U.S. Virgin Islands.

Then...a frontal boundary will stall over the local islands during

the weekend. The shearline/trough associated with the frontal boundary

will prolong the unsettled pattern through early next week.



&&



.DISCUSSION...Satellite derived precipitable water analysis indicated

abundant moisture over the Eastern Caribbean associated with the

aforementioned surface trough. Southeasterly flow will promote

moisture transport over the forecast area today. As a result...

showers and isolated thunderstorms will likely affect the south

and east portions of PR and the U.S. Virgin Islands during the

morning hours. Then...local island effects will combine with deep

tropical moisture to induce the development of showers and thunderstorms

across the Central Interior, West and Northwest PR. A similar pattern

is forecast for Friday.



Over the weekend, a frontal boundary will approach the local

islands from the north-northwest. The boundary and its associated

moisture is forecast to stall over the Puerto Rico between Sunday

and Monday. The shearline/trough over the local area will enhance

the moisture convergence across the local islands...resulting

in organized convection over Puerto Rico and the adjacentislands.

This unstable pattern is forecast to persist across the area

through Tuesday. Conditions will gradually improve by midweek next

week as drier and more stable air mass will move over the region.



&&



.AVIATION...VFR conditions will continue to prevail across all

terminals through at least the late morning hours. VCSH possible

across the USVI/Southeastern PR area. SHRA/TSRA developing across

the interior and western PR btwn 17/17-22Z will impact mainly the

flying area of TJMZ/TJBQ with tempo MVFR conds and mtn top obscd.

Also, isolated TSRA is possible between el Yunque and TJSJ. Low

level winds will continue east-southeast at 8-15 knots with sea

breeze variations aft 17/13z across the north/northwestern terminals

of PR.



&&



.MARINE...Tranquil marine conditions will prevail across the local

waters through Friday. Then, a short-period northerly swell will

gradually increase the seas during the weekend and early next

week.



&&



.PRELIMINARY POINT TEMPS/POPS...

SJU 88 77 87 77 / 40 30 40 40

STT 86 77 87 77 / 40 40 40 50



&&

Area Forecast Discussion

National Weather Service San Juan PR

557 AM AST Sat Nov 19 2016



.SYNOPSIS...Broad upper ridge will continue for the next several

days meandering over the eastern Caribbean Sea as polar troughs

press against it through early next week. Meanwhile at lower

levels, a cold front and prefrontal trough will meander

between Hispanola and the local Atlantic waters for the next

couple of days providing abundant moisture across the area.

This will result in periods of showers and thunderstorms over

already saturated soils across mainland PR, keeping a high threat

of flooding along major rivers and tributaries and mudslides

across areas of steep terrain.



&&



.DISCUSSION...Scattered to locally numerous showers affected the

northeastern portions of PR during the overnight hours as a line

of showers developed just off the northern coastal waters of PR.

This activity left around 3 inches of rain across portions of

Rio Grande. For the rest of the morning hours, under an easterly

light steering wind flow additional showers with heavy rainfall

are possible across the north/eastern portions of PR. For the rest

of the day, cloud cover is not expected as yesterday and daytime

heating will aid to the development of showers and thunderstorms

across the interior/western portions of PR.



The prefrontal boundary is expected to meander across the Mona

Passage and western PR through early next week. Precipitablewater

will remain very high across the forecast area and as trough

pattern holds through the short term period...shower and

thunderstorm activity across the local waters and mainland PR

will likely continue for the next several days. Therefore, the

flash flood watch has been extended through this afternoon and

could likely continue through the rest of the weekend as the rain

threat remains high.



&&



.AVIATION...VFR conds with some VCSH will prevail across the TAF

sites during the morning hours. SHRA/ISOLD TSRA will affect the

coastal waters, the north and east of PR and the USVI thru 16Z.

Brief MVFR/IFR conditions possible with passing SHRA/TSRA at TJMZ

and TJPS between 17Z-22Z. Mtn top obscr expected across the

interior sections of PR. Sfc wnd fm E 10-15 kts.



&&



.MARINE...Seas will continue at 5 feet or less Today. A northerly

swell around 7 feet will enter the Atlantic waters and Passages

late Sunday and continue through at least Monday. This will

result in hazardous seas and dangerous rip currents along the

Atlantic coastline of Puerto Rico, Culebra and St. Thomas. Winds

will continue from the east at 10-15 kts increasing 15-20 kts from

the northeast across the Atlantic waters by Sunday.



&&



.PRELIMINARY POINT TEMPS/POPS...

SJU 86 76 84 76 / 60 40 60 50

STT 87 78 86 77 / 60 40 40 50

Area Forecast Discussion

National Weather Service San Juan PR

521 AM AST Tue Nov 22 2016



.SYNOPSIS...Polar trough continued eastward across the western Atlantic

and north of the region, as high pressure ridge continued to settle

in across the forecast area. This is inducing a westerly wind flow

aloft. However A mid level short wave trough and associated vort

max is expected to sweep across the region today and this should

help destabilize the mid to upper levels particularly during the

late morning and afternoon hours. This trough will be quickly

followed by mid level ridging later in the evening and through the

end of the work week. The frontal boundary/shear line continued

across western Puerto Rico and the Mona Passage today. This will

maintain a moist low level environment across the region with

precipitable water values still ranging around two inches or so.

This frontal boundary will continue to meander across the region

while slowly dissipating and sinking south of the region, as

surface high pressure ridge will build across the west Atlantic

and north of the region Wednesday through the end of the week.

This in turn will gradually induce prevailing east to northeast

winds along with a tightening of the local pressure gradient and

increasing the northeasterly trade winds.



&&



.DISCUSSION...

Expected sufficient breaks in cloud cover and mid to upper level

instability to support afternoon late morning and convection in

some areas across the islands today. The dominant low level

moisture convergence across the region and prevailing light to

moderate easterlies should focus most of the activity across the

interior and west sections of Puerto Rico today. Persistent moisture

entrainment in some areas may lead to some localized heavy rainfall

which in turn will quickly lead to urban and small stream flooding

in isolated areas as soil remain completely saturated across Puerto

Rico. Lesser activity is expected across the U.S Virgin Islands

however isolated to scattered showers will remain likely in isolated

areas and brief periods of moderate to locally heavy rainfall will

also remain possible. Lesser low level moisture transport and

pooling is expected across the region during the latter part of

the week, as the aforementioned frontal boundary and associated

moisture field will gradually diminish.



&&





.AVIATION...VFR conds expected across the local terminals through

22/14Z. SHRA is present across the local flying area but generally

not affecting the local terminals but VCSH is very possible. Winds

overnight should be mainly light and variable. SHRA/TSRA expected

across PR after 22/16Z, VCTS likely for TJBQ/TJMZ and possible at

the sites, while VCTS is possible for TJSJ and TJPS. Sct SHRA

expected to TIST/TISX so VCSH is on TAF. Winds becoming easterly at

about 10KT after 22/13Z.



&&



.MARINE... Overall seas will continue to fluctuate between 6 to 7

feet over the offshore Atlantic waters during the next 6-12 hrs

or so due to a subsiding northerly swell. however,seas will then

increase to near 7 feet once again during the latter part of the

week as the local surface pressure gradient tightens and the

northeasterly trades increase. Therefore, small craft advisories

will remain in effect for the offshore Atlantic waters due to the

slowly subsiding swell action and increasing choppy seas. Small

craft should exercise caution elsewhere.



&&



.PRELIMINARY POINT TEMPS/POPS...

SJU 85 76 84 76 / 40 30 30 20

STT 85 77 86 77 / 50 30 30 20

Area Forecast Discussion

National Weather Service San Juan PR

443 AM AST Thu Nov 24 2016



.SYNOPSIS...An upper level ridge will continue to erode the

boundary remnants and strengthens the trade wind across the

region during the next few days. Surface high pressure across the

Western Atlantic will promote moderate to fresh east to northeast

trades across the forecast area and will also aid to push the

available moisture toward the Caribbean waters. An upper level

trough is expected to reach the region by Monday.



&&



.DISCUSSION...Doppler radar detected isolated to scattered showers

across the surrounding coastal waters with few of them moving

inland over eastern and northern sections of Puerto Rico

overnight. This activity will continue this morning, but they are

expected to be brief as they are moving relatively quickly. Also,

because of how quickly they are moving, the showers may go a bit

further inland than we normally see for early morning showers, so

some of the showers could briefly make it to central PR, but

rainfall accumulations are expected to be minimal.



A relatively quiet weather conditions are expected this afternoon in

comparison with the past several days. An upper level ridge

building over the area will continue to erode the moisture

associated with the frontal boundary remnants across the local

islands. A surface high pressure across the Western Atlantic will

induce an increase in the trade winds across the northeast

Caribbean and will also aid to push the available moisture

southward across the Caribbean waters. However, isolated to

scattered showers are possible today through the local area with

some more significant showers over southwest Puerto Rico during

the afternoon hours.



No significant weather feature is expected to affect the region

as the local weather will continue to gradually improve over the

next several days. An upper level trough is expected to approach

to the region by Monday next week, slightly increasing the

chances of showers.



&&



.AVIATION...VFR at all terminals and en route btw islands...except

for passing SHRA in dominant l/lvl NE wind flow til 24/12z. Prds of

-SHRA ovr nrn half and E PR as well as coastal waters surrounding

USVI. Brief MVFR in -SHRA and Mtn top obscr psbl ovr E PR vcty of El

Yunque Pico Del Este due to low clds and passing SHRA til 24/12z.

VCSH at TJSJ/TJBQ/TJNR and TNCM/TKPK in Nrn leeward islands... SHRA

at TJMZ/TJPS. Fm 24/16z-24/22z...Isold-Sct SHRA likely ovr interior

PR with Sct-Bkn cld lyrs. Sfc wnds fm E-NE winds 10-15 kts ocnl

higher gust up to 25 knots psbl durg aftn...bcmg 5-10 kts aft

23/23z.



&&



.MARINE...Small craft advisories continue in effect. Seas are

expected to increase up to 7 feet today and continuing for the

next few days. The local nearshore buoy 41053 is reporting seas of

about 6 feet while the buoy in Rincon is reporting seas of 6.5

feet. High risk of rip currents for the Atlantic beaches of

Puerto Rico, Culebra and Saint Thomas until remains in effect

until Thursday afternoon.



&&



.PRELIMINARY POINT TEMPS/POPS...

SJU 86 77 85 75 / 20 20 20 20

STT 87 77 87 76 / 30 20 20 20

Area Forecast Discussion

National Weather Service San Juan PR

455 AM AST Sat Nov 26 2016



.SYNOPSIS...A band of moisture and a passing trough will cause

moisture levels and showers to increase through Sunday night.

Drying and more northerly flow at all levels will bring much drier

weather beginning Tuesday although a few small showers will be

possible on the windward coasts. Conditions will become breezy

Tuesday and Wednesday.



At upper levels...A weak ripple will pass through today in the

westerly flow, then a short wave trough will pass mainly north of

the area on Monday. Afterward, high pressure will build over the

central Caribbean and continue through the weekend.



At mid levels...High pressure over the western Caribbean will

retreat farther west as a short-wave trough passes through the

area on Monday. High pressure then builds northeast into the

Bahama Islands mid-week and continues through the following

Sunday. Mid levels will moisten briefly today through Monday, but

then they will dry into mid-week and continue very dry through the

weekend.



At lower levels...Low pressure will continue in the southern

Caribbean Sea and another low will deepen in the western Atlantic

west of Maryland to pull lower pressure across the local area

Sunday night and Monday. High pressure will build across the

western Atlantic mid-week and increase the local gradients across

the area bringing and increase in winds. Winds will abate by the

weekend.



&&



.DISCUSSION...A few intense, but small and fast-moving showers

came onshore in Puerto Rico and the northern U.S. Virgin Islands.

In San Juan they left 0.12 inches as of 4 AM AST, which was just

enough to bring the total rainfall for the month there to 16.00

inches. This is now the wettest November on record since 1899 when

records began. The previous record was 15.96 inches in 1976. It

is also the fourth wettest month on record. Charlotte Amalie

observed 0.06 inches overnight.



The MIMIC product showed moisture increasing to our northeast and

this band was about to enter the forecast area this morning. This

will mean some additional shower coverage for Puerto Rico and the

U.S. Virgin Islands. Amounts are expected to be light. Moisture

will continue steady through Sunday and then increase again

slightly on Sunday night and possibly Monday when the best

showers of the week are expected. Rapid drying will follow with

shower activity reaching a minimum as the week progresses. The

strong drying of the mid-levels will not allow deep convection

during this time, however some shallow passing showers will still

be possible along the windward coasts. Winds become more northerly

on Tuesday, but will slowly veer back to the east Saturday.



&&



.AVIATION...VFR conds are expected across all terminals for the

next 24 hrs. Trade wind SHRA will cause VCSH and brief -SHRA at

times. SHRA expected to develop over central and western PR

between 26/16-22Z, possibly impacting the TJMZ terminal and the

vicinity of TJPS, TJBQ and TJSJ. SFC winds are expected to

continue light and variable over PR through 26/13Z while the USVI

and Leewards should observe E to ENE winds at around 5-10 knots.

After 26/14Z winds will be more easterly at 10-15 kts with sea

breeze variations.



&&



.MARINE...Seas in the around the local islands are expected to

continue subsiding. Seas at San Juan inner buoy and the Rincon

buoy had subsided below 6 feet in the last hour and will slowly

subside until Monday morning. The increased winds Tuesday and

Wednesday are now expected to bring small craft advisories for

seas of 7 feet or higher to both the Atlantic and the Caribbean.



&&



.PRELIMINARY POINT TEMPS/POPS...

SJU 86 77 86 74 / 40 30 50 60

STT 86 76 85 74 / 30 30 30 60