Puerto Rico Weather

Area Forecast Discussion
National Weather Service San Juan PR
551 AM AST Wed Oct 26 2016

.SYNOPSIS...Upper trough will continue to exit the region Today
as ridge builds from the central Caribbean and holds through the
end of the week. Another short wave trof is forecast to move aloft
from the western Atlantic by early next week. At lower levels,
frontal boundary to the north of the area and troughiness will
continue to keep a moist environment for the next couple of days.
An easterly wave will move mainly south of the area through
Thursday. Surface high across the western Atlantic will maintain
an east to northeast wind flow through the end of the work week.
East to southeast winds return during the weekend.


&&

.DISCUSSION...Scattered showers on a northeasterly wind were
observed across the coastal Atlantic waters with a few reaching
coastal areas and the northern U.S. Virgin Islands. However,
mostly clear skies with a few clouds prevailed across the rest of
the forecast area. For the rest of the morning hours, showers are
expected to increase across the northern half of the island.
Enough moisture will lead to another round of showers and
thunderstorm development over the mountains and to the
west/southwest of them during the afternoon hours. A similar
weather pattern is expected each day with easterly wave/steering
east winds favoring convection over the western side of the island
during the afternoons. During the weekend as winds turn more from
the southeast, afternoon convection should focus across the
northwest quadrant of the island.

Moisture content with normal to above normal PWAT will continue
for the next several days even as ridge builds aloft. There seems
to be a slight drop of moisture content during the weekend but
showers and isolated thunderstorms are still expected. The
easterly wave is currently producing scattered showers and
thunderstorm activity to the east of Guadeloupe. This wave is
forecast to move east to the south of the area and aid to the
development of showers and thunderstorms across the offshore
Caribbean waters and increase the available low level moisture
through Thursday. For early next week, another short wave trof
will move from the western Atlantic weakening the ridge and
bringing more unstable conditions.

&&

.AVIATION...VFR conds expected at most of the terminals durg the
forecast period. However, NE trade winds will push SCT SHRA near
TJBQ, TJSJ and TIST thru at least 14Z. As a result...Brief MVFR in
passing SHRA are possible at times. SHRA/TSRA fcst to develop ovr
and downwind of the Cordillera Central of PR. MVFR and mountain
obscurations possible in and around TJMZ/TJPS between 26/17Z-21Z.
NE winds of 10-15 kt will prevail below FL100.


&&

.MARINE...Seas will continue 3-5 feet overall across most of the
waters...increasing to 6 feet by Thursday across the offshore
Atlantic waters. East to northeast winds will continue between
5-15 knots. Turning east to southeast during the weekend. There is
a moderate risk of rip currents across the Atlantic exposed
beaches of the islands.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 78 88 79 / 50 30 30 40
STT 89 79 88 78 / 50 30 30 40

Area Forecast Discussion

National Weather Service San Juan PR

503 AM AST Fri Oct 28 2016



.SYNOPSIS...High pressure ridge will build overhead through

Sunday. Ridge is to then erode on Monday and Tuesday of next week

as a short wave trough is forecast to move across the western

Atlantic and become amplified across the local area by Wednesday

and the remainder of the next work week. Moisture trailing a tropical

wave now crossing the Dominican Republic will continue to exit the

region this morning. Meanwhile a weak ridge will spread across the

region as the surface high over the north central Atlantic sinks

farther southwards into the central Atlantic. This will induce a

light east to southeast trade wind flow across the area. A weak

easterly perturbation east of the northern Leewards will continue

westwards and bring another patch of low level moisture to the

region by Saturday morning.



&&



.DISCUSSION...Passing trade wind showers will continue to affect

the coastal waters and windward sections of the islands during

the early morning hours. For the remainder of the day and into

the upcoming weekend, expect a seasonal weather pattern as the

tropical wave and associated trailing moisture will exit the region

later this morning. However, diurnal effects and local sea breeze

convergence will give way to showers and isolated thunderstorms

across parts of the islands during the afternoon hours. Over Puerto

Rico activity should be focused over the North central and northwest

sections of the island including parts of the San Juan metro area.

Mostly isolated afternoon showers can be expected in and around the

U.S Virgin Islands.



Localized urban and small stream flooding will again remain possible

particularly over parts of Puerto Rico today and during the upcoming

weekend due to already saturated soils and the expected slow moving

afternoon convection.



For the long term...as previously mentioned the ridge aloft is forecast

to erode early next week as a short wave trough becomes amplified and

sink southwards into the Central and eastern Caribbean basin. Consequently

the surface trough will deepen and a low is expected to develop just

north of the region by mid-week. This overall pattern will result in

deep tropical moisture convergence and upper level instability across

the forecast area beginning on Tuesday and continuing through the

remainder of the week. As usual will continue to monitor and see how

this forecast pattern unfolds over the next few days. Regardless, local

soil will remain nearly saturated in most areas across the interior

sections of Puerto Rico. Any additional heavy rainfall over the next

few days may lead to minor urban and small stream flooding as well

as mudslides in areas of steep terrain.



&&



.AVIATION...Mostly VFR conditions expected through 28/16Z across the

local flying area. However, VCSH expected across TISX, TIST, TNCM

and TKPK until 28/14Z. Winds will be mainly light and variable

across PR and USVI terminals until 28/13Z but are expected to

increase after that. Afternoon convection across PR could cause at

least VCTS for TJSJ, TJMZ, and TJBQ after 28/16Z and mtn obscurations

over most of PR.



&&



.MARINE...A slowly subsiding northerly swell of 4-6 ft at 10 sec

will continue to affect the local Atlantic Waters and Caribbean

Passage today through Saturday, followed by gradually improving

conditions on Sunday and into next week. Seas are expected to remain

below advisory levels through the forecast period. However...Small

craft operators should exercise caution today and through early

Saturday due to seas up to 6 feet across the local Atlantic

waters and the Mona passage .



&&



.PRELIMINARY POINT TEMPS/POPS...

SJU 90 78 89 77 / 30 40 40 30

STT 88 79 87 79 / 30 40 40 30

Area Forecast Discussion...CORRECTED

National Weather Service San Juan PR

524 AM AST Mon Oct 31 2016



.SYNOPSIS...A ridge aloft will erode rapidly today as a broad

trough amplifies across the western Atlantic and into the central

Caribbean. A developing surface low north of the local islands

will continue to promote light to gentle low levels southerly

winds through late Tuesday night. Showers and thunderstorms will

continue to prevail across the forecast area each day with the

wettest/unstable period expected Tuesday and Wednesday. Due to

saturated soils, flooding potential will continue to increase

across the forecast area through at least midweek.



&&



.DISCUSSION...Numerous showers and isolated to scattered

thunderstorms affected many sectors of Puerto Rico Sunday

afternoon and evening. This activity caused many areas to

observe urban and small stream flooding, especially across

eastern interior through western sections of PR. Several flood

advisories were issued. The combination of the already saturated

soils and the excessive rainfall also caused several major rivers

to go above their respective flood stages, some of which are

expected to remain under a flood warning until early Monday

morning.



The upper level ridge across the region is expected to erode

rapidly today as a broad trough amplifies across the western

Atlantic and into the central Caribbean. Atmospheric conditions

across the region will become even more conductive for widespread

convection across the forecast area today and through at least

Wednesday. This evolving weather pattern combined with plenty of

moisture and a developing surface low north just north of the area

which is promoting light low level winds across the region will

result in numerous showers and isolated to scattered thunderstorms

across the local islands. Due to saturated soils across most of

the region, a high potential of flooding as well as mudslides in

areas of steep terrain are expected to continue until at least

midweek. At this time, the wettest/unstable period is between

Tuesday and Wednesday with widespread activity across land areas.



Shower and Thunderstorm activity is expected to decrease late in

the evenings, overnights and early in the mornings, but the runoff

from the afternoons rainfall will maintain some of the local

rivers at high levels all the period.



&&



.AVIATION...Flow has become southwesterly below FL330. VFR conds

will prevail at all TAF sites thru 31/16z with VCSH, very brief

MVFR CIGS may occur at TNCM and TKPK. Aft 31/15Z, +TSRA will

develop over interior PR and spread towards the coasts with brief

MVFR psbl at TJPS, TJBQ, TJMZ. Mtn obscurations aft 31/16z. Winds

10 kt or less below FL160 with little change through 01/00z.

Southerly wind across the leewards and brief MVFR will continue to

be psbl through 01/02z in SHRA due to CIGS.



&&



.MARINE...Local buoys are reporting seas mainly in the 2-4 ft

range in the northern waters and around 1-2 ft across the

nearshore southern waters. Seas are expected to be up to 5 feet

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

Atlantic facing coasts of the local islands.



&&



.HYDROLOGY...Moisture transport and instability across the

region will continue to increase today and at least through

Wednesday due to the combination of an upper trough and an elongated

surface trough. Additionally, an area of low pressure is forecast

to develop north of the region. Models have been consistent in

maintaining high moisture content across the region with the best

chance for increased showers and thunderstorm activity expected

Tuesday through Wednesday. There is a high probability that areas

in the west and along the northern half of Puerto Rico will

continue to receive excessive rainfall which will lead to flooding

of local rivers...streams...urban and low-lying areas. In addition

mud slides are also expected in areas of steep terrain.



Residents in the flood prone areas are urged to take precautionary

measures which would include preparing plans to move or protect

pets...livestock...equipment and personal belongings. These plans

should be put in place if the National Weather Service issues a

Flash Flood Watch or Flash Flood Warnings.



&&



.PRELIMINARY POINT TEMPS/POPS...

SJU 89 76 86 76 / 80 30 60 60

STT 86 77 86 76 / 40 30 60 60

Area Forecast Discussion

National Weather Service San Juan PR

546 AM AST Thu Nov 3 2016



.SYNOPSIS...Moist flow will continue to bring showers over the

local area from the northeast today. Winds will shift direction

and become more southerly beginning Friday. Showers will increase

over the weekend and into early next week. Southerly flow is

expected to hold showers mostly over the north half of the island.



At upper levels...Short wave ripples will keep troughiness over

the local area through Saturday. Southwesterly flow will begin as

another long wave digs weakly into the Caribbean on Sunday. This

long wave will lift to the northeast by mid week next week, but

weak cyclonicity will remain over the area afterward.



At mid levels...Troughing will continue over the area until a

second long wave trough drops into the western Caribbean to bring

more southwesterly flow loaded with moisture. The moisture will

abate after the trough moves east of the area on Wednesday.



At lower levels...A trough associated with low pressure well

northeast of the Leeward Islands will drift back north west and

over the local area on Friday bringing more moisture to the area.

It will return from the west under the influence of a mid-latitude

low moving out into the Atlantic for a third pass. For most of

next week a boundary just northwest of the area will keep clouds

and scattered showers in the forecast driven by high pressure over

the Western Atlantic.



&&



.DISCUSSION...Showers in the northeast flow passed over the U.S.

Virgin Islands and most of the northeastern two thirds of Puerto

Rico. Amounts ranged from a few hundredths to half an inch where

rain fell. The proximity of the trough and another weak pulse of

moisture will keep much of the northeastern two thirds of Puerto

Rico wet through this afternoon. Dynamics are weak and moisture is

still not very deep (the transition from wet to dry goes from

10-15 kft) so only expect a few isolated thunderstorms over Puerto

Rico and only a meager chance anywhere else. The trough at low

levels will drift back over the area on Friday bringing an

increase in moisture. This trend will continue through Monday when

the trough returns after toughing Hispaniola. Flow is expected to

turn southerly by Friday and with an increase in warmth and

instability. This will cause more showers during the afternoon on

the north side of the Cordillera Central through Tuesday.

Northeast low level flow returns late next week. Although the

chances of rain will remain higher than normal, rain amounts are

not expected to be extreme.





&&



.AVIATION...Sct to Numerous SHRA expected across the local area on a

NE wind flow...at about 10KT...will affect TJBQ/TJSJ and the

USVI/Leeward terminals through 03/16Z. After 03/16Z, SHRA through

the local area with possible TSRA will affect the vicinity of the

local terminals. However, there should be enough SHRA/TSRA activity

to cause brief MVFR conditions at TJSJ, TIST, TIST, TNCM, and TKPK

terminals and mtn obscurations.



&&



.MARINE...Since the original low pressure that moved south from

north of Puerto Rico into the Caribbean has become more of an open

trough, winds have weakened and marine conditions will slowly

improve. High moisture content will mean showers and thunderstorms

will continue for much of the next 7 day over the local waters,

but seas will likely remain below small craft advisory conditions

during that time. Later strong lows forming in the Atlantic will

be able to send swell toward the area that may bring seas back to

7 feet. Winds will shift to a more southerly direction Friday and

into the weekend. High Rip current risk on the north coast will

remain today, be spotty tonight and should be gone by Friday

afternoon.



&&



.PRELIMINARY POINT TEMPS/POPS...

SJU 87 77 87 77 / 80 40 40 60

STT 88 77 86 79 / 70 70 50 60

Area Forecast Discussion

National Weather Service San Juan PR

501 AM AST Sat Nov 5 2016



.SYNOPSIS...Moist southeasterly flow on the east side of a surface

trough and upper level short waves in a weak trough over the area will

keep weather unstable and generally showery with isolated to

scattered thunderstorms through Tuesday. Shower activity will

decrease after mid-week.



At upper levels...Several short waves will pass through a long

wave trough pattern north of the area before the last trough

crosses through Wednesday. Then high pressure will dominate the

local area and the Caribbean Sea into mid-November.



At mid levels...Moisture in the mid levels will increase through

Monday, with only moderate moisture thereafter through 14 Nov. A

trough over the Bahama Islands today will pass north of the area

Sunday night when a strong low drops south into the western

Atlantic across from Delaware. Then high pressure will build from

the western tropical Atlantic over the Caribbean sea and persist

through at least the next 8 days.



At lower levels...An inverted trough will persist west of the area

until it crosses Puerto Rico and the U.S. Virgin Islands again on

Tuesday. A weak trough rebuilds late next week and good moisture

persists through the entire period, reaching a minimum on Thursday

morning.



&&



.DISCUSSION...Southeast flow brought showers and thunderstorms

over the U.S. Virgin Islands and the southeastern two thirds of

Puerto Rico overnight. Amounts of 1 to 3 inches fell over the area

causing several rivers, including the Guayanes, Cerrillos and the

Rio Grande de Arecibo to rise above flood stage. Showers

dissipated by 2 AM AST. More showers and thunderstorms are

expected to develop over the area, possibly as early as mid-

morning this morning and persist beyond sunset. These showers

could cause urban and small stream flooding again today,

especially if some of the thunderstorms reform persistently over

the same areas. Moisture will increase through Monday with much

the same pattern in southeasterly flow. Mid level moisture will

diminish after Tuesday and shower and thunderstorm activity will

diminish, but not disappear. Models also indicate that the best

moisture may form east of Puerto Rico over the U.S. Virgin Islands

today, but only have moderate confidence considering spatial

performance of the models last several days.



&&



.Hydrology...The level of water in Lago Dos Bocas has fallen 5

feet in about 6 hours. Most of this water should reach the ocean

through the down stream stretches during the next 10 to 15 hours.

A flood warning continues on the Rio Grande de Arecibo in

anticipation of rapidly rising waters later this morning.



&&



.AVIATION...Mainly VFR conditions will prevail across most TAF sites

through at least 05/15z. However, VCSH/VCTS can be expected across

TJSJ and TJBQ through 05/017z. Brief periods of MVFR conditions can

be expected across TNCM and TKPK through at least 05/16z. Low level

winds will continue mainly southeast at 10 to 15 kts with higher

gusts in SHRA/TSRA. Mountain obscurations are expected. Winds

aloft, will become more southwesterly during the day today up

through FL180 at 10 to 15 knots.



&&



.MARINE...Seas are expected to continue to diminish. Thunderstorms

that develop later today may cause seas to roughen in their

vicinity. Small craft advisories are not expected until Wednesday

night, when lows from several days before send swell into the

local area. Nevertheless showers and thunderstorms will be

scattered across the area with heavy visibility-limiting rains and

gusty winds through Tuesday.



&&



.PRELIMINARY POINT TEMPS/POPS...

SJU 89 76 89 76 / 30 30 80 60

STT 86 79 87 77 / 60 40 40 70

Area Forecast Discussion

National Weather Service San Juan PR

600 AM AST Mon Nov 7 2016



.SYNOPSIS...Upper level trough continued across the Western

Atlantic with the base of the trough now just north of the region.

Surface high pressure centered over the central Atlantic and a

trough extending across Hispaniola and the Mona passage, will

maintain a light to moderate but moist southeast wind flow across

the region. Winds are forecast to gradually become more east to

northeast through Tuesday, as a high pressure ridge will build

across the southwestern Atlantic then north of the forecast area

during the latter part of the upcoming week.





&&



.DISCUSSION...Showers with thunderstorms were seen across the

local waters this overnight. Some of these showers affected the

south and southeast sections of Puerto Rico and Saint Croix in the

Virgin Islands. A moist and unstable air mass will continue to

prevail across the local islands under the influence of an upper

level trough and a very moist southeasterly wind flow.



For today and tomorrow, no changes in this weather pattern is

expected as the upper level trough continues over the local area

and maintains favorable conditions for shower and thunderstorm

development. It is not until Wednesday, a drier trend is expected

as an upper level ridge develops across the area.



&&



.AVIATION...Brief SHRA are possible across TIST/TISX/TNCM/TKPK

during the morning. SHRA/TSRA are expected during the afternoon

mainly over mainland PR. Some of this SHRA can produce brief MVFR or

even IFR conditions between 07/16-22z at TJSJ/TJMZ/TJPS/TJBQ. Across

the rest of the local flying area only VCSH are expected. Winds will

continue very light but mostly from the south, increasing at around

10 knots with higher gusts after 07/13Z.



&&



.MARINE...Seas up to 4 feet and winds up to 10 knots are expected.

Moderate risk of rip current along some north facing beaches of

Puerto Rico.





&&



.PRELIMINARY POINT TEMPS/POPS...

SJU 87 77 86 77 / 40 40 40 20

STT 87 77 86 77 / 50 40 30 20

Area Forecast Discussion

National Weather Service San Juan PR

606 AM AST Thu Nov 10 2016



.SYNOPSIS...

A mid-upper level ridge is expected to build across Eastern

Caribbean today into Friday. An upper level trough is forecast to

move across Western Atlantic and off to the North of the islands

Friday through Saturday. At lower levels, A surface trough will

move across the region this afternoon into early Friday,

increasing cloud cover and the potential for shower and

thunderstorm activity. A frontal boundary will move eastward

across the Atlantic Ocean and will lingered to the north of the

region during the weekend. Plenty of tropical moisture will pool

over the region during the next few days.



&&



.DISCUSSION...

Limited shower activity was observed over Mainland Puerto Rico

and the U.S. Virgin Islands overnight. Most of the showers were

detected across the surrounding waters, and a few of them affected

the windward areas from time to time. In general, calm weather

conditions with pleasant temperatures prevailed overnight and

early this morning across the U.S. Virgin Islands and Puerto Rico.



A surface low will continue its way into the region this morning,

passing mostly south of the local islands this afternoon into

early Friday. As this feature moves near the region, an overall

moist environment will persist for the next couple of days.

This moisture combined with local and diurnal effect will lead to

afternoon convection mainly along and to the west of the

Cordillera Central and downwind from the Islands of Vieques,

Culebra and the U.S. Virgin Islands. In addition, due to the

previous rainfall events the soils are already saturated, and any

persistent heavy rainfall will lead to Urban and Small stream

flooding across parts of the island, as well as quick rises in

water level along rivers and streams.



Although, atmospheric conditions does not represent the best

dynamic for enhance convection, plenty of tropical moisture will

combined each day with the local and diurnal heating to produce

afternoon convection across the islands.



&&



.AVIATION...

SHRA/TSRA are expected to increase late in the morning into the

afternoon over western interior and northwestern PR. As a result,

brief MVFR or even IFR conditions between 10/16-22z at TJMZ and

TJBQ with mountain obscurations can be expected. Across the rest

of the local flying area VCSH are expected. Winds will continue

mostly from the east, increasing at around 10 to 15 knots with

higher gusts and sea breeze variations after 10/13Z.



&&



.MARINE...

Seas up to 10 feet will continue across the Atlantic waters and

Anegada Passage, as a long period northerly swells will continue

to affect the regional waters today. Therefore, mariners can

expect hazardous seas, life threatening rip currents and rough

surf across these waters and along the Atlantic coastline of the

islands through at least this evening. Additional information is

provided in the local marine products produced by your Weather

Forecast Office-San Juan.



&&



.PRELIMINARY POINT TEMPS/POPS...

SJU 88 77 88 78 / 30 20 20 20

STT 87 78 87 78 / 30 20 20 20