Puerto Rico Weather

Area Forecast Discussion

National Weather Service San Juan PR

536 AM AST Sat Jan 28 2017



.SYNOPSIS...Mid level ridge will continue over the area through

the rest of the weekend as it moves over the Central Atlantic

through early next week. TUTT is forecast to move northeast of

the area by Monday. Surface high pressure will continue to build

across the Central Atlantic and into the Eastern Atlantic by mid

week next week as polar trof and associated frontal boundary moves

over the Western Atlantic. This will result in an east to

southeasterly trade wind flow for the next several days.





&&



.DISCUSSION...Mostly clear skies and limited shower activity was

observed during the overnight hours across the forecast area.

Showers were increasing late in the morning hours across the

offshore Atlantic waters to the northwest of the forecast area.

Temperatures were in the high 50s to low 60s across the higher

elevations and in the low 70s across the coastal areas of Puerto

Rico. In the U.S. Virgin Islands, overnight temps were in the low

70s. Winds were light and variable over land areas. However,

steering winds carrying the showers over the waters were from the

E-ESE around 10 knots.



For the rest of the morning hours mostly sunny skies are expected.

Later in the afternoon, a few clouds and light showers are

expected to develop from streamers off the USVI and over portions

of the north/northwest sections of PR. Trade wind showers are

expected to return during the overnight hours. Similar conditions

are expected on Sunday. By early next week, moisture is forecast

to increase over the area, as ridge aloft and surface high

pressure shifts further east across the Atlantic waters and a

weak TUTT establishes to the northeast of the forecast area.

Steering southeasterly winds will prevail through at least Tuesday.

However, at the moment this only favors a slight increase in

diurnal shower development over the interior and northwestern

sections of PR. Also, trade wind showers over the waters are

expected to move from time to time over portions of the islands

through much of next week.





&&



.AVIATION...VFR conds at all terminals during the forecast period.

Some clouds and scattered showers will move into the flying area

from the east after 18Z. In addition, sea breezes across western

PR this afternoon will help in the development of SHRA near TJMZ

and TJBQ between 18Z-22Z. East to southeast winds of 10-15 kt will

prevail below FL150.





&&



.MARINE...Northerly swell is fading away. Latest buoy readings as

of 5 AM are indicating seas under 4 feet across the coastal waters

of the islands. There is a moderate risk of rip currents across

much of the Atlantic beaches of the islands and the southern coast

of St. Croix. Seas are expected to range between 3-5 feet across

the offshore waters and 2-4 feet across the near shore waters

today. As winds increase between 15-20 knots from the east-

southeast tonight into Sunday...seas are expected to increase

between 4-6 feet across much of the regional waters and small

craft operators should exercise caution for the next few days.



&&



.PRELIMINARY POINT TEMPS/POPS...

SJU 87 74 87 74 / 30 20 20 10

STT 84 74 84 74 / 30 20 20 20

Area Forecast Discussion

National Weather Service San Juan PR

456 AM AST Mon Jan 30 2017



.SYNOPSIS...Surface high pressure across the central Atlantic

will shift eastward today as a weak cold front will move across

the western Atlantic. This will help create weak troughiness across

the region and also diminish the local trade winds through Tuesday.

The high pressure ridge will again reestablish north of the area

during the latter parts of the week. Broad mid to upper level high

pressure will also remain in place across the central Atlantic to

maintain an overall dry and subsident pattern aloft for the next

several days.



&&



.DISCUSSION...Winds were calm to light and variable across the

islands overnight, but are expected to become more southeasterly

during the rest of the day except for local sea breeze variations

in some areas. A fairly dry airmass will remain in place across

the region, however the prevailing easterly trades will bring a

small surge of low to mid level moisture across the region by later

this afternoon and during the early evening. This moisture transport

along with diurnal and local effects will lead to some brief showers

across portions of the islands. No significant rainfall accumulations

is anticipated across the region. The prevailing southeast to south

low level wind flow will bring warmer temperatures across the northern

half of PR. Therefore expect afternoon high temperatures to be slightly

warmer than normal in some areas. However the expected increase in

afternoon cloudiness may limit the daytime heating.



For the long term ...winds will again become more easterly and slightly

increase by Wednesday as the surface high will reestablish and spread

north of the region. This will again result in the continued transport

of shallow low to mid leve moisture fragment across the regional waters

and portions of the islands from time to time. For the most part expect

mostly fair weather conditions to prevail for the next several days

with no significant weather feature in sight.



&&



.AVIATION...VCSH are possible across the Leewards, USVI TAF and TJSJ

sites until 30/16Z. Mostly VFR conditions expected across the rest

of the local flying area during the morning hours. After 30/18Z VCSH

are expected over TJMZ and TJBQ, but no significant impact on

operations expected. Winds ESE 15-20KT with occasional gusts and sea

breeze variations.



&&



.MARINE...Seas were up to 5 feet are offshore and less than 4 feet

over the near shore waters. Expect little change today and Tuesday

with easterly winds between 10 to 15 knots. By midweek...winds and

seas are so far forecast to increase to up to 7 feet as the local

pressure gradient tightens and a northerly swell is forecast to arrive

across the local Atlantic waters. By then small craft advisories may

be required for portions of the local waters.



&&





THE SAN JUAN AREA/PR CLIMATE NORMALS FOR TODAY



NORMAL RECORD YEAR

MAXIMUM TEMPERATURE (F) 83 89 1998

MINIMUM TEMPERATURE (F) 72 63 1965





SUNRISE AND SUNSET FOR SAN JUAN PR:



JANUARY 30 2017.......SUNRISE 658 AM AST SUNSET 617 PM AST



JANUARY 31 2017.......SUNRISE 658 AM AST SUNSET 618 PM AST



&&



.PRELIMINARY POINT TEMPS/POPS...

SJU 86 74 87 74 / 30 10 20 20

STT 82 73 84 74 / 30 20 20 20

Area Forecast Discussion

National Weather Service San Juan PR

452 AM AST Wed Feb 1 2017



.SYNOPSIS...

A mid level ridge will continue to build across the region today.

This feature will limit the vertical development of showers

across the local islands for the next couple of days. An upper

level trough to the east northeast of the local islands is

expected to lift northeastward while filling today. A surface high

pressure across the central Atlantic will continue to transport

patches of cloudiness and showers across the region for the next

several days.



&&



.DISCUSSION...

Doppler weather radar detected isolated to scattered showers

moving mainly westward from the surrounding waters across the U.S.

Virgin Islands, Vieques, Culebra as well as across the eastern

sections of Puerto Rico. The easterly trade winds associated with

a surface high pressure over the central Atlantic will continue

to transport patches of low level cloudiness and showers across

the local islands for the next several days. The available low

level moisture in combination with diurnal and local effect are

expected to induce some afternoon convection across western and

interior sections of Puerto Rico. However, not widespread or

significant precipitation is expected.



A mid level ridge over the region will inhibit the vertical

development of the showers and therefore thunderstorms

development are not expected at this moment. An upper level trough

to the east of the region is expected to lift northeast while

filling today and tonight. A weak frontal boundary north of the

region will provide some instability to aid in the development of

Showers across western and interior Puerto Rico this afternoon.





For the next several days an overall fair weather

pattern is expected across the region with some interruptions of

cloudiness and brief showers across the windward sections of the

local islands overnights and early in the mornings followed by

some convection during the afternoons over western and interior

sections of Puerto Rico.



&&



.AVIATION...

ISO-SCT SHRA expected through 01/12Z across the local flying area

will likely cause VCSH across most of the local terminals except

TJMZ and TJPS. SHRA becoming more ISOLD after 01/12Z but still

brief VCSH are possible. Winds will increase slightly after 01/12Z

to 10-15 KT but continued easterly with sea breeze variations.

SCT SHRA expected across western PR after 01/16Z possibly causing

VCSH at TJMZ and TJBQ.



&&



.MARINE...

Winds of 10 to 15 knots increasing to 15-20 knots tonight and

seas increasing up to 7 today mostly across the Atlantic waters are

expected across the local waters...due to the arrival of a

northerly swell. Therefore, a small craft advisory is in effect.

There is a high risk of rip current for the Atlantic beaches of

Puerto Rico.



&&



.PRELIMINARY POINT TEMPS/POPS...

SJU 86 74 84 74 / 20 20 40 20

STT 85 73 84 74 / 20 30 40 20

Area Forecast Discussion

National Weather Service San Juan PR

713 AM AST Fri Feb 3 2017



.SYNOPSIS...The ridge pattern is flattening aloft. Trade wind

showers at times and seasonable temperatures will continue to

prevail across the U.S. Virgin Islands and Puerto Rico during the

next seven days.



&&



.DISCUSSION....Instability increased somewhat across the islands

as the ridge pattern flattens. Trade winds pushed showers mainly

across the regional waters overnight into early this morning.

Some of these showers moved across the windward sections of PR and

the USVI. Shower activity in the form of streamers are expected

downwind from the U.S. Virgin Islands and across east Puerto Rico.

In addition, locally induced afternoon showers are expected across

west Puerto Rico.



Under this evolving pattern, surge of moisture embedded in the

trades will continue to increase across the local islands through

at least tomorrow. This will result in frequent passing showers

across the USVI and the eastern half of PR each day. By Sunday a

drier air mass will result in a mixture of clouds and sunshine

with little shower activity.



Trade winds will continue to enhance moisture advection across

the eastern Caribbean while weakening. A ridge pattern will build

across the forecast area and hold much of the next work week. At

lower levels, migratory surface highs across the Atlantic Ocean

will continue to promote moderate easterly winds during the next

several days.



&&



.AVIATION...

VFR for much of the fcst prd at all terminals. Quick passing

-SHRA/shra possible ovr local waters and en route btw islands.

SCT-BKN cld lyrs nr FL025...FL050..FL080...few tops nr FL120. VCSH

fcst to develop ovr the interior and west sections of PR aft

03/16z, impacting mainly TJMZ where brief MVFR psbl in SHRA. L/lvl

wnds E-ESE 10-20 kts from e blo FL250. SFC wnd lgt/vrb to calm

bcmg fm E-SE..10-15 kts w/ocnl higher gusts aft 03/14z.



&&



.MARINE...Seas up to 6 feet and east winds at 10 to 15 knots are expected

to continue across most of the regional waters as the northerly

swell continued to fade and moderate easterly trade winds prevailed.

Small crafts should continue to exercise caution. There is a

moderate risk of rip currents for the majority of the north and

east facing beaches of Puerto Rico and the U.S. Virgin Islands.



&&



.PRELIMINARY POINT TEMPS/POPS...

SJU 86 74 84 74 / 10 30 30 40

STT 84 75 84 74 / 20 30 30 30

Area Forecast Discussion

National Weather Service San Juan PR

543 AM AST Sun Feb 5 2017



.SYNOPSIS...Trade wind showers will continue as areas of moisture

pass through Puerto Rico and the U.S. Virgin Islands.



At upper levels...Westerly flow continues. A sub equatorial jet

will into the area from the southwest late this week as a long

wave trough moves into the western Atlantic over the following

weekend. It will be joined by the sub tropical jet Saturday or

Sunday.



At mid levels...High pressure extending over the area from the

east northeast will become focused over the sub- tropical

Atlantic to our east northeast and a weak trough will move into the

area by late in the week. Weak troughs can be seen just south of

the local islands near 600 mb. Mid levels will see bubbles of

moisture pass through mostly dry air.



At lower levels...High pressure is moving east in the mid

latitudes and will settle in the north central Atlantic Monday. A

second high will move into the western Atlantic on Monday and

reinforce the first high beginning mid week. A low developing on a

front north of the area late next week will form a trough over

the area Friday or Saturday with a pre frontal trough over the

area and the cold front approaching. Models are not clear if the

front will actually pass through the area.



&&



.DISCUSSION...Showers continued over the north coastal

municipalities--mainly west of Canovanas--through much of the

night and some of this activity remains off the northwest coast of

Puerto Rico as of 05/09Z. This activity has been shallow and

entirely under 20 kft, but persistent, and many hours of showers

caused flooding in Hatillo. The trough at 600 mb south of the

islands may have helped with favorable conditions for shallow

convection. This trough will persist through Tuesday.



Winds are shifting a little more to the east northeast today so

the best convection is expected to form closer to the Cordillera

Central this afternoon. Although there is to be a break in the

moisture later this afternoon and evening, it may not come early

enough to prevent heavy, though shallow, showers across southwest

and west Puerto Rico with the possibility of urban and small

stream flooding. Because of the break in moisture and the more

northeasterly orientation of the winds rain is not expected to

persist so long tonight. Another patch of moisture will move

through the area on Monday with good chances for rain. Then winds

will begin to respond to the pre-frontal trough that will form

late in the week with the aid of some upper level jets and rain

chances will continue, but southeast flow will then favor the

northwest corner of Puerto Rico. This band is expected to persist

into early next week with clouds and showers that will also

depress temperatures several degrees.



Limited showers are expected during the upcoming week

for the U.S. Virgin Islands, but measurable rain cannot be ruled

out.



&&



.AVIATION...ISOLD to SCT SHRA across the local area will cause VCSH

across the local terminals through 05/14Z except for TJMZ with E to

ENE winds between 5-10KT. After 05/14Z the local winds will increase

slightly to 10-15KT from the E to ENE with sea breeze variations.

Developing SHRA in the afternoon will cause VCSH at TJSJ, TJPS, and

particularly TJMZ where the SHRA may affect the station and cause

brief MVFR conds.



&&



.MARINE...Seas will respond to higher than usual winds and some

areas in the outer Atlantic will see 7 foot seas. Later on Monday

a rising northerly swell will cause sea heights to continue at or

above 7 feet possibly through the week and into early next week--

mainly in the northern and subsequently the northeastern corner of

the forecast area. Some parts of the Mona passage will be affected

as well. Currently it is expected that the risk of rip currents

will increase from moderate to high Monday afternoon.



&&



.PRELIMINARY POINT TEMPS/POPS...

SJU 85 75 86 74 / 30 40 40 30

STT 85 74 84 74 / 40 30 30 30

Area Forecast Discussion

National Weather Service San Juan PR

559 AM AST Tue Feb 7 2017



.SYNOPSIS...Broad surface high pressure will continue across the

Central Atlantic promoting a moderate to fresh trade wind flow

across the islands. A polar trof and associated front will enter

the Western Atlantic on Wednesday and move north of the area by

late in the work week. In the short term, weak short wave trofs

will continue to promote moisture advection across the islands.

Mid level ridge will build from the east and a surface

perturbation will also move from the east on Thursday enhancing

the available low level moisture and weakening the cap inversion.



&&



.DISCUSSION...Trade wind showers continued across the local waters

with a some moving at times across the USVI and eastern portions

of Puerto Rico. The Doppler radar estimated less than a quarter of

an inch of rain with the heaviest showers over eastern PR. For the

rest of the day, trade wind shower pattern will continue and

diurnally induced scattered to numerous showers can be expected in

the afternoon across portions of western/northwestern PR. Similar

conditions are expected on Wednesday, but showers should be

isolated to scattered during the afternoon. Trade winds will

increase today as surface high north of the area moves and builds

across the Central Atlantic.



Later on Thursday, a surface perturbation will increase once again

the chances of showers across the islands through the late evening

hours. A polar trof and associated frontal boundary are forecast

at the moment to remain north of the area by Friday and linger

through the weekend. Meanwhile a strong surface high pressure

will build behind the front bring patches of the remnants of the

front and moisture advection on a northeasterly wind flow by early

next week.



&&



.AVIATION...Mostly VFR conds will prevail across the area thru the

fcst pd. However, -SHRA in trade wind SHRA could affect the

Leeward/USVI and TJSJ terminals through 07/16z. Brief MVFR cigs and

mtn obscurations are likely near TJBQ/TJMZ btwn 07/18-21Z due to

afternoon SHRA over the mtn ranges and downstream from central and

wrn PR. Llvl winds from the E-ESE will increase to 15-20 kts aft

07/13Z with higher gusts and sea breeze variations expected aft

07/14z. Maximum winds 285/55 kt at FL410.



&&



.MARINE...Seas up to 8 feet and east winds up to 21 knots are

expected today. Small craft advisories are in effect for all the

near shore waters the islands, except the southern and western

coastal waters of Puerto Rico. There is a high risk of rip

currents along the Atlantic beaches of the islands.



&&



.PRELIMINARY POINT TEMPS/POPS...

SJU 85 74 86 75 / 40 20 20 10

STT 84 75 83 74 / 30 10 20 10