Caribbean - Central America Weather

[cycloneye]

December 16 Jamaica forecast:

Code: Select all

Significant Feature: Surface trough over the central Caribbean.

Morning: Mainly fair.

Afternoon: Partly cloudy over northern parishes, mainly fair elsewhere.

Tonight: Fair.

Winds: Will reach in excess of 15 knots (18 mph)

Temperatures: High: 31C (88F)     Low: 24C (75F)

 

Location
 Sunrise
 Sunset
 
Kingston
 6:31 a.m.
 5:35 p.m.
 
Montego Bay
 6:36 a.m.
 5:40 p.m.
 
Negril
 6:37 a.m.
 5:41 p.m.
 



[cycloneye]

Good morning. The weather will continue to be good for the NE Caribbean in the next few days.

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
538 AM AST SUN DEC 16 2012

.SYNOPSIS...SURFACE HIGH PRESSURE ACROSS THE WESTERN ATLANTIC WILL
MAINTAIN RELATIVELY DRY CONDITIONS ACROSS THE REGION. PATCHES OF
LOW LEVEL MOISTURE WILL MOVE ACROSS THE AREA FROM TIME TO TIME.
UPPER LEVEL RIDGE WILL BUILD OVER THE NORTHEAST CARIBBEAN NEXT
FEW DAYS.

&&

.DISCUSSION...PATCHES OF LOW LEVEL MOISTURE HAVE BEEN AFFECTING
PUERTO RICO OVERNIGHT AND EARLY THIS MORNING. SCATTERED SHOWERS
HAVE BEEN AFFECTING THE NORTHERN HALF OF PUERTO RICO MOST OF THE
NIGHT...WITH THE HEAVIEST ACTIVITY CONCENTRATED OVER THE NORTHEAST
SECTION OF PUERTO RICO. CONDITIONS WILL IMPROVE SOMEWHAT THIS
AFTERNOON...AS STABLE ATMOSPHERIC CONDITIONS CONTINUE OVER THE
REGION. PRECIPITABLE WATER VALUES REMAINS NEAR 1.2 INCHES...WITH THETAE
VALUES AT 700MB REMAINING AT OR BELOW 320K. ALSO...SATELITE IMAGES
SHOWS A SLOT OF DRY AIR EAST OF THE U.S. VIRGIN ISLANDS...AND THIS
DRY AIR WILL ENCOMPASS THE REGION NEXT 12 TO 24 HOURS.
THEREFORE...ONLY ISOLATED TO SCATTERED SHOWERS ARE EXPECTED OVER
THE NORTH AND NORTHEAST SECTIONS OF PUERTO RICO EACH DAY. AN UPPER
LEVEL RIDGE IS EXPECTED TO BUILD ACROSS THE NORTHEAST CARIBBEAN
NEXT WEEK...WHICH WILL MAINTAIN VERY DRY CONDITIONS WITH LITTLE
SHOWER ACTIVITY ACROSS THE REGION. IN THE NEAR FUTURE...NO
SIGNIFICANT WEATHER FEATURES ARE FORECAST TO AFFECT THE REGION.

&&

.AVIATION...BRIEF PERIODS OF MVFR CONDITIONS CAN BE EXPECTED OVER
TJSJ AND TIST THROUGH AT LEAST 16/16Z. ELSEWHERE VFR CONDITIONS
ARE EXPECTED. WINDS WILL CONTINUE MAINLY NORTHEAST AT 10 TO 15 KTS
WITH HIGHER GUSTS.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 83 72 83 72 / 50 20 20 20
STT 84 72 85 73 / 30 10 10 30

[cycloneye]

Good weather will prevail in the Eastern Caribbean for the next few days.


AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
303 PM AST SUN DEC 16 2012

.SYNOPSIS...SURFACE HIGH PRESSURE ACROSS THE WEST AND SOUTHWESTERN
ATLANTIC WILL HELP MAINTAIN LIGHT TO MODERATE EASTERLY TRADE WINDS
ACROSS THE REGION. UNDER THIS GENERAL FLOW...PATCHES OF LOW LEVEL
MOISTURE FROM OLD FRONTAL BOUNDARIES WAS BEING TRANSPORTED SOUTHWEST
ACROSS THE AREA FROM TIME TO TIME. A MID TO UPPER LEVEL TROUGH NOW
MOVING ACROSS THE REGION WILL GRADUALLY LIFT EAST NORTHEAST WHILE
FILLING OVER THE NEXT DAY OR SO. UPPER LEVEL RIDGE TO THE WEST WILL
BUILD FURTHER EASTWARD ACROSS THE NORTHEAST CARIBBEAN DURING THE NEXT
FEW DAYS. THEREFORE...INCREASING SUBSIDENCE AND OVERALL DRY AND STABLE
AIR ALOFT WILL DOMINATE THE LOCAL WEATHER CONDITIONS. THE LIGHT TO MODERATE
EAST NORTHEAST TRADE WINDS WILL PREVAIL THROUGH AT LEAST MID WEEK FOLLOWED
BY A GRADUAL INCREASE IN EASTERLY WIND FLOW DURING THE LATTER PART OF
THE WORK WEEK...AS THE STRONG SURFACE RIDGE SHIFTS EASTWARDS AND BUILDS
NORTH OF THE AREA.

&&

.DISCUSSION...PATCHES OF LOW LEVEL TRADE WIND MOISTURE AND FEW
EMBEDDED SHOWERS WILL CONTINUE TO AFFECT THE REGION FROM TIME TO
TIME...ESPECIALLY DURING THE LATE EVENING AND EARLY MORNING HOURS.
DURING THE DAYTIME...EXPECT DIMINISHING CLOUDINESS AND SHOWER ACTIVITY
OVER THE ISLANDS. THE GENERAL WIND FLOW WILL CONTINUE TO HELP STEER
AND DEVELOP SOME CLOUDINESS AND ISOLATED SHOWERS DURING THE AFTERNOON
HOURS...MAINLY ACROSS PARTS OF THE INTERIOR AND SOUTHWEST SECTIONS
OF PUERTO RICO. THE SHOWER ACTIVITY WILL HOWEVER BE OF SHORT DURATION
WITH NO SIGNIFICANT RAINFALL EXPECTED FOR THE NEXT SEVERAL DAYS.
LATEST MODEL GUIDANCE ALL SUGGEST A GRADUAL DECREASE IN PWAT VALUES
TO NEAR 1.2 INCHES OR SO AS WELL AS CONTINUED DECREASING THETA-E
VALUES. THEREFORE EXPECT THIS WEATHER REGIME FOR THE NEXT SEVERAL
DAYS...WITH ISOLATED TO SCATTERED EARLY MORNING PASSING SHOWERS
MAINLY OVER THE NORTH AND NORTHEAST SECTIONS OF PUERTO RICO EACH
DAY...FOLLOWED BY ISOLATED AFTERNOON SHOWERS ACROSS PARTS OF THE
ISLANDS.

&&

.AVIATION...MAINLY VFR CONDITIONS ARE EXPECTED ACROSS THE LOCAL
TERMINALS. ISOLD SHRA MAY BRIEFLY AFFECT TJSJ...TIST...AND TISX.
SCATTERED SHOWERS ARE FORECAST IN AND AROUND TJPS AND TJMZ UNTIL
17/00Z...THEREFORE VCSH IS EXPECTED AND POSSIBLE BRIEF MOMENTS WITH
MVFR CONDITIONS DUE TO TEMPO LOWER CEILINGS AND REDUCED VISIBILITIES
WITH THE SHRA. MOUNTAIN OBSCURATIONS WILL ALSO OCCUR AS CLOUDINESS
CONTINUES TO INCREASE. SURFACE TO FL020 WINDS EXPECTED TO BE FROM
THE ENE TO NE WITH SEA BREEZE VARIATIONS AT 5-10 KNOTS.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 71 82 71 82 / 20 20 20 20
STT 73 85 73 85 / 10 10 30 30

[Macrocane]

The Central American Cold Surges Thread has been updated with the first event of December, it produced a freezing of -5°C (23°F) in Quetzaltenango, Guatemala, it was the coldest temperature in Central America since December 2010. In El Salvador a minimum temperature of 4.2°C (39.6°F), the coldest in the country since January 2011. More info here: http://www.storm2k.org/phpbb2/viewtopic.php?f=22&t=106879&p=2292802#p2292802

[cycloneye]

Good morning. No change to the pattern of good weather for the Eastern Caribbean.

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
408 AM AST MON DEC 17 2012

.SYNOPSIS...A SURFACE HIGH PRESSURE AREA ACROSS THE WEST AND SOUTHWEST
ATLANTIC...WILL CONTINUE TO MOVE EAST AND INTO THE CENTRAL ATLANTIC
TONIGHT AND TUESDAY.

&&

.DISCUSSION...AN AREA OF LOW LEVEL MOISTURE CONTINUED TO MOVE
ACROSS THE LOCAL REGION THROUGH THE OVERNIGHT HOURS. THESE SHOWERS
ARE FORECASTED TO CONTINUE TO AFFECT OUR AREA THROUGH AT LEAST MID
MORNING. AN AREA OF DRIER AIR MASS WILL MOVE OVER THE REGION
LIMITING THE SHOWER COVERAGE ACROSS THE LOCAL FORECAST AREA THIS
AFTERNOON.

THIS WEATHER PATTERN WILL CONTINUE FOR THE NEXT SEVERAL DAYS AS
PATCHES OF LOW LEVEL TRADE WIND MOISTURE WILL GENERATE SHOWERS
MAINLY ACROSS THE EAST AND NORTHEAST PORTIONS OF PUERTO RICO
DURING THE OVERNIGHT HOURS.


&&

.AVIATION...MAINLY VFR CONDITIONS WILL PREVAIL ACROSS ALL TAF SITES
THROUGH AT LEAST 17/22Z. VCSH CAN BE EXPECTED OVER TIST..TISX...TJSJ...AND
TJBQ. SURFACE WINDS WILL CONTINUE MAINLY NORTHEAST AT 10 TO 15 KTS
WITH HIGHER GUSTS.


&&

.MARINE...A NORTHEASTERLY SWELL WILL CONTINUE TO AFFECT THE ATLANTIC
WATERS...THESE SWELL EVENT WILL PEAK EARLY TODAY AND THEN SLOWLY
SUBSIDE THROUGH WEDNESDAY. A MORE SIGNIFICANT SWELL EVET IS FORECAST
TO REACH OUR LOCAL ATLANTIC WATERS ON FRIDAY. MARINERS AND BEACHGOERS
SHOULD MONITOR THE DEVELOPMENT OF THIS SWELL EVENT AS IT COULD GENERATE
SMALL CRAFT ADVISORIES AND HIGH SURF ADVISORIES FOR OUR LOCAL WATERS
AND LOCAL COASTS FOR THE INCOMING WEEKEND.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 82 71 82 71 / 30 40 40 40
STT 85 73 85 73 / 30 10 10 10

[cycloneye]

Here is the December 17 Jamaica forecast:

Code: Select all

 
A high pressure ridge across the western Atlantic and a surface trough across the central Caribbean will result in partly cloudy conditions with isolated showers mainly over northern parishes.


Significant Feature: Surface trough over the central Caribbean.

Morning: Partly cloudy.

Afternoon: Expect isolated showers mainly over northern parishes.

Tonight: Fair.

Winds: Will reach in excess of 15 knots (18 mph)

Temperatures: High: 31C (88F)     Low: 24C (75F)

 

Location
 Sunrise
 Sunset
 
Kingston
 6:32 a.m.
 5:35 p.m.
 
Montego Bay
 6:37 a.m.
 5:40 p.m.
 
Negril
 6:38 a.m.
 5:41 p.m.
 

 


[cycloneye]

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
247 PM AST MON DEC 17 2012

.SYNOPSIS...MID TO UPPER LEVEL TROUGH NOW NORTH NORTHEAST OF THE
LOCAL REGION...WILL CONTINUE TO FILL AND LIFT FURTHER NORTHEAST
AS A BROAD UPPER RIDGE BUILDS ACROSS THE AREA FROM THE WEST. THE
RIDGE ALOFT WILL GRADUALLY MOVE ACROSS THE AREA AND REMAIN IN PLACE
THROUGH AT LEAST THE LATTER PART OF THE WORK WEEK WHILE SLOWLY ERODING.
THIS WILL REINFORCE THE PRESENT UPPER LEVEL SUBSIDENCE CAP AND THUS
LIMIT CONVECTIVE DEVELOPMENT FOR THE NEXT FEW DAYS. LATEST SATELLITE
IMAGERY AND MODEL GUIDANCE CONTINUED TO SUGGEST GRADUAL DRYING TREND
THE REST OF TODAY AND FOR THE NEXT FEW DAYS ALTHOUGH SMALL POCKETS
OF TRADE WIND MOISTURE WILL CONTINUE TO PROPAGATE ACROSS THE NORTHEAST
CARIBBEAN FROM TIME TO TIME.

&&

.DISCUSSION...UNDER THE PREVAILING EAST NORTHEAST TRADE WINDS...
PATCHES OF LOW LEVEL TRADE WIND MOISTURE WITH A FEW EMBEDDED SHOWERS
WILL CONTINUE TO AFFECT PARTS OF THE ISLANDS AND SURROUNDING WATERS...
ESPECIALLY DURING THE LATE EVENING AND EARLY MORNING HOURS. AFTERNOON
SHOWERS AND SOME CLOUDINESS WILL BE LATER FOCUSED MAINLY ACROSS PARTS
OF THE CENTRAL INTERIOR AND WEST SECTIONS OF PUERTO RICO. THE LIMITED
SHOWER ACTIVITY WILL BE OF SHORT DURATION AND MOSTLY OF LIGHT INTENSITY.

FOR THE LONG TERM...LATEST MODEL GUIDANCE SUGGEST A COLD FRONT TO
SWEEP ACROSS THE WEST ATLANTIC BY MID WEEK...WITH A FRONTAL BOUNDARY/SHEAR
LINE TO SET UP JUST NORTH OF THE AREA. IT WILL LATER SINK SOUTHWARDS
TOWARDS THE LOCAL REGION BY THE END FOR THE WORK WEEK...AS STRONG SURFACE
HIGH PRESSURE WILL QUICKLY BUILD BEHIND IT AS SUGGESTED BY THE GFS MODEL
GUIDANCE. THIS SURGE OF FRONTAL MOISTURE SHOULD BRIEFLY INCREASE PWAT
VALUES ONCE AGAIN AND THUS INCREASE THE CHANCE FOR MORE ENHANCED SHOWER
ACTIVITY ACROSS THE REGION AT LEAST THURSDAY AND FRIDAY. A GRADUAL
DRYING WILL ONCE AGAIN BEGIN OVER THE UPCOMING WEEKEND AS A MODERATE
COOL NORTHERLY WILL PREVAIL. IN ADDITION...BY THURSDAY THE LOW LEVEL
WINDS ARE EXPECTED TO INCREASE AS THE LOCAL SURFACE PRESSURE GRADIENT
TIGHTENS ACROSS THE REGION WITH THE BUILDING HIGH PRESSURE AND INCREASING
NORTHERLY WINDS. SO FAR HOWEVER... STILL NO SIGNIFICANT WEATHER FEATURE
IS EXPECTED TO MOVE ACROSS THE REGION FOR THE NEXT SEVERAL DAYS.

&&

.AVIATION...AN AREA OF MOISTURE IS MOVING THROUGH THE SRN LEEWARD
ISLANDS AND WILL PASS THRU THE CARIBBEAN...BRUSHING TIST LATER
TONIGHT. PERIODS OF MVFR CONDS ARE POSSIBLE AT TKPK THRU 17/21Z AND
TIST BTWN 18/03-09Z. ELSEWHERE EXPECT VFR THRU 18/22Z. LLVL WINDS NE
TO E 5 TO 15 KT UP THRU 10 KFT. WINDS BTWN 20-34 KFT NLY 25-35 KT.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 72 83 71 83 / 20 20 30 30
STT 73 85 74 86 / 20 20 20 20

[cycloneye]

Good morning. The good weather pattern will continue to prevail in the NE Caribbean for the next few days.

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
354 AM AST TUE DEC 18 2012

.SYNOPSIS...MID TO UPPER LEVEL TROUGH NOW NORTH NORTHEAST OF THE
LOCAL REGION...WILL CONTINUE TO FILL AND LIFT FURTHER EAST NORTHEAST
AS A BROAD UPPER RIDGE BUILDS ACROSS THE AREA FROM THE WEST. THIS
WILL REINFORCE THE PRESENT UPPER LEVEL SUBSIDENCE CAP AND THUS
LIMIT CONVECTIVE DEVELOPMENT FOR THE NEXT FEW DAYS.

&&

.DISCUSSION...PATCHES OF LOW LEVEL MOISTURE EMBEDDED ON THE
PREVAILING EAST NORTHEAST TRADE WINDS...WILL CONTINUE TO MOVE
ACROSS THE LOCAL REGION. THEREFORE EXPECT ISOLATED TO LOCALLY
SCATTERED SHOWERS TO AFFECT THE NORTHEAST PORTIONS OF PUERTO RICO
THROUGH THE OVERNIGHT HOURS. IN THE SAME WAY EXPECT AFTERNOON
SHOWERS TO DEVELOP ALONG THE CORDILLERA CENTRAL AND WESTERN
PORTIONS OF PUERTO RICO DURING THE AFTERNOON HOURS. THE LIMITED
SHOWER ACTIVITY WILL BE OF SHORT DURATION AND MOSTLY OF LIGHT
INTENSITY.

MODELS CONTINUED TO SUGGEST A COLD FRONT TO MOVE SOUTHEAST ACROSS
THE WEST ATLANTIC BY MID WEEK...WITH A FRONTAL BOUNDARY/SHEAR LINE
TO SET UP JUST NORTH OF THE AREA ON THURSDAY. INCREASING FRAGMENTAL
SHOWERS ASSOCIATED TO THIS SHEAR LINE WILL AFFECT THE LOCAL REGION
MAINLY ON THURSDAY NIGHT. T

NO SIGNIFICANT WEATHER FEATURE IS EXPECTED TO MOVE ACROSS THE
REGION FOR THE NEXT SEVERAL DAYS.

&&

.AVIATION...BRIEF MOMENTS OF MVFR CONDITIONS POSSIBLE FOR TISX
EARLY THIS MORNING AS A MINOR WAVE SPREADS MOISTURE OVER THE
AREA...CAUSING LOCALLY SCT SHRA. FOR THE REST OF THE AREA...VFR
CONDITIONS ARE EXPECTED FOR THE NEXT 24 HOURS. AFTER 18/12Z...WIND
TO BECOME MAINLY EASTERLY AT AROUND 10 KNOTS ACROSS THE LOCAL
TERMINALS WITH SEA BREEZE VARIATIONS DEVELOPING AFTER 18/14Z.

&&

.MARINE...ALTHOUGH MOST OF THE ENERGY WILL MOVE EAST OF PUERTO
RICO...A NORTHERLY SWELL EVENT IS FORECAST TO REACH OUR LOCAL
ATLANTIC WATERS ON FRIDAY. MARINERS AND BEACH GOERS SHOULD MONITOR
THE DEVELOPMENT OF THIS SWELL EVENT AS IT COULD GENERATE SMALL
CRAFT ADVISORIES AND HIGH SURF ADVISORIES FOR OUR LOCAL WATERS AND
LOCAL COASTS FOR THE INCOMING WEEKEND.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 83 71 83 73 / 20 20 20 30
STT 85 74 86 74 / 20 20 20 40

[cycloneye]

December 18 Jamaica forecast:

Code: Select all

A high pressure ridge across the western Atlantic and a surface trough across the central Caribbean will result in partly cloudy conditions with isolated showers mainly over northern parishes.

Significant Feature: Surface trough over the central Caribbean.

Morning: Mainly fair.

Afternoon: Partly cloudy with isolated showers mainly over northern parishes.

Tonight: Fair.

Winds: Will reach in excess of 15 knots (18 mph)

Temperatures: High: 31C (88F)     Low: 24C (75F)

 

Location
 Sunrise
 Sunset
 
Kingston
 6:32 a.m.
 5:36 p.m.
 
Montego Bay
 6:37 a.m.
 5:41 p.m.
 
Negril
 6:38 a.m.
 5:42 p.m.
 



[cycloneye]

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
358 PM AST TUE DEC 18 2012

.SYNOPSIS...AT UPPER LEVELS...SEVERAL WEAK RIDGES OVER THE AREA
WILL GIVE WAY TO A BROAD TROUGH ON MONDAY ASSOCIATED WITH A DEEP
LOW OVER NOVA SCOTIA AT THAT TIME. HIGH PRESSURE WILL RETURN TO
THE CARIBBEAN AFTER CHRISTMAS.

AT MID LEVELS...THE HIGH PRESSURE THAT STRETCHES FROM THE YUCATAN
PENINSULA TO JUST NORTH OF PUERTO RICO WILL BE REPLACED BY A
STRONG TROUGH OVER THE MID LATITUDES OVER THE WEEKEND.
HIGH PRESSURE RETURNS TO THE NORTHWEST CARIBBEAN AND SPREADS ITS
INFLUENCE OVER ALL THE CARIBBEAN BY WEDNESDAY OF NEXT WEEK.

AT LOWER LEVELS...HIGH PRESSURE CONTINUES TENUOUSLY ACROSS THE
WATERS JUST NORTH OF 20 DEGREES NORTH LATITUDE WHILE SEVERAL
STRONG LOW PRESSURES MOVE ACROSS THE NORTHEASTERN UNITED STATES
AND WEAKEN THEM. AFTER CHRISTMAS HIGH PRESSURE WILL DOMINATE THE
WESTERN ATLANTIC INTO THE FOLLOWING WEEKEND.

&&

.DISCUSSION... A WEAK WAVE IS SLOWLY PUSHING SOUTH OF SAINT CROIX
SPREADING LIGHT TO MODERATE SHOWERS ACROSS THE NEARBY CARIBBEAN
WATERS. ABOUT 15 HUNDREDTHS OF AN INCH FELL AT FREDERIKSTED AND A
FEW LIGHT SHOWERS WERE NOTED OVER THE SOUTHEAST COAST OF PUERTO
RICO. SOME OF THIS MOISTURE WILL BE CARRIED INTO PUERTO RICO
OVERNIGHT BUT EASTERLY FLOW WILL RESULT IN MOSTLY DRY
CONDITIONS...THEREFORE POPS DO NOT EXCEED 30 PERCENT. DRIER AIR
ALSO FOLLOWS THE WAVE AND WILL BRING SUNNIER CONDITIONS
TOMORROW...AT LEAST DURING THE DAY. MOISTURE INCREASES UNSTEADILY
BEGINNING WEDNESDAY NIGHT AND LIGHT SHOWERS WILL LIKELY INCREASE IN
COVERAGE WEDNESDAY NIGHT THROUGH MONDAY.

MOST OF OUR USUAL GFS...NAM MODELS DID NOT COME IN TODAY AT 12Z
DUE TO SOME AS YET UNDISCOVERED TECHNICAL PROBLEMS...BUT WEB BASED
RESOURCES SUGGEST THE PATTERN OF LIGHT SHOWERS AND OCCASIONAL
SUNNY DAYS WILL CONTINUE THROUGH THE NEXT 10 DAYS.

&&

.AVIATION...SHORT WAVE VORTEX CONTINUES TO MOVE WESTWARD...BRINGING
ISOLATED TO SCATTERED SHOWERS ACROSS THE LOCAL AREA ESPECIALLY IN
AND AROUND TISX. PERIODS OF MVFR CONDITIONS EXPECTED AT TISX AS A
RESULT...ELSEWHERE MOSTLY VFR. SURFACE WINDS WILL CONTINUE MAINLY
EAST AT 10 TO 15 KTS WITH SEA BREEZE VARIATIONS. LATE NIGHT
MOUNTAIN OBSCURATIONS ARE LIKELY IN PR AND THE USVI.

&&

.MARINE...STRONG LOW PRESSURES IN THE ATLANTIC WILL SEND HIGHER
SWELL TOWARD THE AREA. SEAS INCREASE OVER THE WEEKEND. SOME
BREAKING WAVES COULD REACH 11 TO 13 FEET SINCE ALTHOUGH SEAS WILL
ONLY BE 6 OR 7 FEET PERIODS MAY BE AS HIGH AS 15 SECONDS IN NORTH SWELL.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 83 73 84 72 / 20 20 20 30
STT 85 74 85 74 / 30 20 20 40

[Macrocane]

A strong cold-wind surge is expected by Thursday night, it will probably cause the strongest winds of the season so far:

GAP WINDS...
LOOKING AHEAD...A COLD FRONT WILL SHIFT RAPIDLY ACROSS THE
GULF OF MEXICO ON THU. WINDS BEHIND THIS FRONT WILL FUNNEL
THROUGH THE CHIVELA PASS INTO THE GULF OF TEHUANTEPEC WHICH WILL
LEAD TO A STRONG GAP WIND EVENT. NORTHERLY WINDS WILL START TO
FUNNEL INTO THE GULF OF TEHUANTEPEC BY THU EVENING...WITH STRONG
GALE...AND POSSIBLY STORM CONDITIONS...BY FRI MORNING. AT THIS
TIME...THE GFS GLOBAL MODEL SUGGESTS WINDS OF 40-50 KT. SEAS ARE
EXPECTED TO BUILD IN EXCESS OF 15-19 FT. THE FNMOC ENSEMBLE
FORECAST SYSTEM ALSO DISPLAYS A HIGH PROBABILITY OF GALE FORCE
WINDS BETWEEN FRI MORNING AND SAT MORNING.

WINDS WILL ALSO INCREASE ACROSS THE GULF OF PAPAGAYO BY FRI.
EXPECT NE TO E WINDS OF 20-25 KT AND SEAS OF 8-10 FT IN AND
DOWNSTREAM OF THE GULF TO ABOUT 92W BY SAT MORNING.

OF NOTE...THE MONTHLY DISTRIBUTION OF TEHUANTEPEC EVENTS SHOWS
THAT THE LARGEST NUMBER OF GALE-FORCE EVENTS OCCURS IN DECEMBER.
STORM-FORCE EVENTS OCCUR MOST OFTEN IN JANUARY. THE 2006-2007
COLD SEASON HAS THE MOST STORM-FORCE EVENTS WITH A TOTAL OF 13.

[cycloneye]

Good morning. A change to a more wet pattern will begin on Friday and last thru the weekend.


AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
527 AM AST WED DEC 19 2012

.SYNOPSIS...A MID TO UPPER LEVEL RIDGE WILL CONTINUE ACROSS THE
LOCAL AREA THROUGH AT LEAST THURSDAY NIGHT...BEFORE AN UPPER LEVEL
TROUGH PASSES ACROSS OR JUST NORTH OF THE FA FRIDAY AND FRIDAY
NIGHT. A DEEPER LAYERED TROUGH WILL THEN APPROACH THE LOCAL REGION
FOR SATURDAY AND SUNDAY.

&&

.DISCUSSION...THROUGH THURSDAY...LITTLE OVERALL CHANGE TO THE
SAME GENERAL PATTERN OF THE PAST SEVERAL DAYS...AS BANDS AND
PATCHES OF MOISTURE WILL MOVE ACROSS THE LOCAL AREA FROM TIME TO
TIME...RESULTING IN INTERVALS OF CLOUDINESS AND ISOLATED TO
SCATTERED PASSING SHOWERS ACROSS THE LOCAL ISLANDS. OUTSIDE OF
THESE CLOUD AND SHOWER BANDS...GENERALLY FAIR WEATHER SHOULD
PREVAIL. THEN...FOR THURSDAY NIGHT AND FRIDAY THROUGH SATURDAY AND
SUNDAY...FALLING MID TO UPPER LEVEL HEIGHTS...POOLING MOISTURE
LOCALLY AND POSSIBLY AN APPROACHING FRONTAL BOUNDARY OR SURFACE
TROUGH...SHOULD YIELD AN OVERALL INCREASE IN CLOUDINESS AND
SHOWERS ACROSS THE FA.

&&

.AVIATION...VFR CONDITIONS EXPECTED THROUGH THE FORECAST PERIOD.
SURFACE WINDS WILL CONTINUE MAINLY EAST AT 10 TO 15 KTS WITH SEA
BREEZE VARIATIONS.

&&

.MARINE...GENERALLY EXPECT WINDS OF 20 KNOTS OR LESS ACROSS THE
REGIONAL WATERS THROUGH AT LEAST FRIDAY. SEAS SHOULD GENERALLY BE
5 FEET OR LESS IN LONG PERIOD NORTH NORTHEAST SWELLS THROUGH
THURSDAY...BEFORE SLOWLY BUILDING THURSDAY NIGHT AND ESPECIALLY
FRIDAY ACROSS THE LOCAL ATLANTIC WATERS AND THE CARIBBEAN
PASSAGES...AS A NEW PULSE OF NORTH SWELLS BEGINS TO AFFECT THESE
WATERS.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 84 73 83 73 / 20 30 30 40
STT 85 74 85 74 / 20 40 40 30

[cycloneye]

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
227 PM AST WED DEC 19 2012

.SYNOPSIS...AT UPPER LEVELS...A WEAK RIDGE WILL MOVE THROUGH ON THURSDAY
FOLLOWED BY A WEAK SHORT WAVE TROUGH FRIDAY NIGHT. THEN OVER THE
WEEKEND A STRONG AND DEEP LONG WAVE TROUGH WILL PASS FROM WEST TO
EAST OVER THE ATLANTIC WATERS NORTH OF THE AREA BUT WILL ENHANCE THE
WEST SOUTHWEST FLOW OVER US TO AS MUCH AS 65 KNOTS ON SUNDAY
MORNING. HIGH PRESSURE WILL GRADUALLY BUILD BACK INTO THE EASTERN
CARIBBEAN BY THURSDAY.

AT MID LEVELS...VERY DRY AIR WILL PREVAIL OVER THE LOCAL AREA
EXCEPT FOR A WEAK BRUSH WITH MOISTURE ON SUNDAY. HIGH PRESSURE OVER
THE AREA GIVES WAY TO A STRONG TROUGH ASSOCIATED WITH A LOW
PRESSURE OVER THE NORTHERN TIP OF MAINE. HIGH PRESSURE GRADUALLY
RETURNS TO THE CARIBBEAN NEXT WEEK.

AT LOWER LEVELS...EAST NORTHEAST FLOW WILL CONTINUE AT LOWER LEVELS
UNTIL EARLY NEXT WEEK. MOISTURE WILL DECREASE TUESDAY.

&&

.DISCUSSION...
SHALLOW MOISTURE IN EAST NORTHEAST FLOW HAS GENERATED SHOWERS
ALONG THE NORTHEAST COAST OF PUERTO RICO WITH AMOUNTS EXCEEDING
ONE INCH IN A FEW AREAS INCLUDING THE LUIS MUNOZ MARIN AIRPORT.
PATCHY MOISTURE CONTINUES IN EAST NORTHEAST FLOW INTO THE
WEEKEND...BUT HIGH PRESSURE WILL MOVE NORTH OF THE AREA ON FRIDAY
AND CONSTRICT THE AIR OVER THE AREA FLOWING FROM THE TROPICAL
ATLANTIC AND BRING AN INCREASE IN SHOWER ACTIVITY...ESPECIALLY ON
THE WINDWARD SLOPES OF ALL THE ISLANDS. SHOWERS INCREASE WITH
MOISTURE. MOISTURE INCREASES ON THURSDAY NIGHT...DIVES ON SATURDAY
NIGHT BUT SURGES SEVERAL TIMES MORE TO A 7-DAY HIGH ON WEDNESDAY
OF NEXT WEEK. HENCE MUST EXPECT SHOWERS...EVEN THOUGH SCATTERED
AND NOT CONTINUOUS IN NATURE...ON THE NORTHWEST HALF OF PUERTO
RICO AND IN THE U.S. VIRGIN ISLANDS SATURDAY THROUGH WEDNESDAY AND
LIKELY BEYOND.

&&

.AVIATION...MAINLY VFR CONDITIONS EXPECTED ACROSS THE LOCAL FLYING
AREA THROUGH THE FORECAST PERIOD WITH ONLY BRIEF PASSING SHOWERS
BRIEFLY AFFECTING THE LOCAL TERMINALS. TJSJ 19/12Z SOUNDING
INDICATED AN EAST NORTHEAST WIND FLOW UP TO 15 KNOTS ALL THE WAY
FROM THE SURFACE TO AROUND 25K FEET...BECOMING WESTERLY AND A LITTLE
STRONGER ALOFT.

&&

.MARINE...NORTH NORTHEAST SWELL WILL INCREASE ABRUPTLY SATURDAY
AFTERNOON AND EVENING AND MAY REQUIRE A HIGH SURF ADVISORY BY
SATURDAY AFTERNOON WHEN PERIODS REACH 14-15 SECONDS AND HEIGHTS
INCREASE TO 9-10 FEET AT THE OUTER BUOY AND INSIDE THE ATLANTIC
WATERS OF THE FORECAST AREA. SMALL CRAFT ADVISORIES WILL BEGIN ON
FRIDAY...MAINLY IN THE ATLANTIC AND PASSAGES.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 70 81 72 81 / 30 30 40 40
STT 73 84 74 84 / 40 40 30 30

[Macrocane]

TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS HYDROMETEOROLOGICAL PREDICTION CENTER COLLEGE PARK MD
207 PM EST WED DEC 19 2012

DISCUSSION FROM DEC 19/00UTC: MID/UPPER RIDGE CENTERS JUST NORTH
OF PUERTO RICO AND EXTENDS WESTWARD ACROSS MOST OF THE GREATER
ANTILLES INTO SOUTHERN MEXICO. THIS RIDGE CONTINUES PRODUCING A
STRONG SUBSIDENCE CAP THAT WILL CONTINUE LIMITING VERTICAL
DEVELOPMENT OF CONVECTION THROUGH THE CYCLE.

TO THE SOUTH...RETROGRESSING TROUGH ACROSS THE CENTRAL CARIBBEAN
IS INTERACTING WITH LOW-LEVEL TROUGH EMBEDDED IN THE EASTERLIES.
UPPER TROUGH IS TO MEANDER ACROSS THE SOUTHERN/CENTRAL CARIBBEAN
WHILE LOW-LEVEL TROUGH PROGRESSES WESTWARD INTO CENTRAL AMERICA.
THE LATTER WILL MOVE INTO A REGION OF UPPER COLD AIR ADVECTION AND
DECENT VENTILATION...BETWEEN UPPER TROUGH AND RIDGE TO ITS WEST.
THIS WILL PRODUCE A ROUND OF HEAVY RAINS IN EASTERN CENTRAL
AMERICA IN INTERACTION WITH ENHANCED CONVECTIVE INSTABILITY AND
INCREASING BOUNDARY LAYER MOISTURE. ON DAY 02 EXPECTING
ACCUMULATIONS TO REACH 15-20MM/DAY AND MAXIMA OF 30-60MM ACROSS
EASTERN COSTA RICA/SOUTHEASTERN NICARAGUA/NORTHWESTERN PANAMA.
LOW-LEVEL CONVERGENCE WILL BE ENHANCED EVEN MORE BY ARRIVING
SHEAR-LINE (SEE BELOW) TO PRODUCE SIMILAR ACCUMULATIONS INCREASING
TO 15-30MM/DAY AND ISOLATED MAXIMA OF 40-80MM.

UPPER TROUGH ACROSS THE CENTRAL ATLANTIC WILL CONTINUE MOVING
EASTWARD. ASSOCIATED SURFACE FRONT WILL MOVE ACROSS THE NORTHERN
BAHAMAS BY 24 HRS TO START FRONTOLIZING AFTERWARDS...WHILE DRIER
AIRMASS REMAINS JUST TO THE NORTHEAST OF THE BAHAMAS. RAPIDLY
MOVING PRE-FRONTAL SHEAR LINE WILL EXTEND ACROSS THE LEEWARD/ST
CROIX INTO THE SOUTH CENTRAL CARIBBEAN BY 24 HRS...AND ACROSS THE
WINDWARD ISLES INTO NORTHEAST VENEZUELA BY 48 HRS...TO THEN START
TO WEAKEN AS BEST CONVERGENCE AFFECTS THE ABC. ENHANCED LOW-LEVEL
CONVERGENCE WILL INTERACT WITH VENTILATION IN THE PERIPHERY OF
SUB-EQUATORIAL RIDGE. THIS WILL LEAD TO ACCUMULATIONS ACROSS THE
SOUTHERN WINDWARDS/NORTHEAST VENEZUELA OF 10-15MM/DAY AND MAXIMA
OF 20-30MM BY 36-60 HRS DECREASING AFTERWARDS.

LOW-LEVEL TROUGH IN THE EASTERLIES WILL PROGRESS WESTWARD ACROSS
THE BASIN. THIS WILL INCREASE ACCUMULATIONS ACROSS NORTHERN
VENEZUELA/EXTREME NORTHERN COLOMBIA/ABC. EXPECTING ACCUMULATIONS
OF 00-05MM/DAY AND MAXIMA OF 10MM GRADUALLY INCREASING TO
10-15MM/DAY AND MAXIMA OF 20-30MM. ACROSS PUERTO RICO...EXPECTING
HEAVIEST BETWEEN 48 AND 72 HRS WITH ACCUMULATIONS OF 05-10MM/DAY
AND ISOLATED MAXIMA OF 15-20MM. ACROSS THE DOMINICAN
REPUBLIC...EXPECTING ENHANCEMENT UNDER INTERACTION WITH OROGRAPHY
AND ARRIVING UPPER TROUGH FROM THE NORTHWEST. THIS WILL LEAD TO
SHOWERS AND A FEW THUNDERSTORMS PRODUCING 10-15MM/DAY AND MAXIMA
OF 20-40MM IN EASTER TIER.

NEXT POLAR TROUGH WILL EXTEND ACROSS CENTRAL USA BY 36 HRS...EAST
COAST 60 HRS. AT LOW LEVELS...THIS WILL INDUCE A PROGRESSIVE FRONT
THAT WILL EXTEND ACROSS TEXAS INTO COAHUILA MEXICO BY 24-30
HRS...TO NORTHERN TAMAULIPAS BY 36 HRS. A 30-40KT JET WILL THEN
DRIVE THE BOUNDARY SOUTHWARD ACROSS NORTHERN FLORIDA-GULF OF
VERACRUZ BY 48 HRS...SOUTHERN FLORIDA-NORTHERN
YUCATAN-CHIAPAS/SOUTHERN VERACRUZ BY 60 HRS...CENTRAL
BAHAMAS-CENTRAL CUBA-QUINTANA ROO BY 72 HRS...SOUTHEASTERN
BAHAMAS-SOUTHERN CUBA-BELIZE-NORTHERN GUATEMALA BY 84 HRS. A
STRONG 45-60KT TEHUANTEPECER WILL DEVELOP BY 48 THROUGH 60 HRS TO
THEN START GRADUALLY WEAKENING. A PRE-FRONTAL SHEAR LINE WILL
DEVELOP BY 42-48 HRS. BY 48 HRS THE SHEAR LINE WILL EXTEND ACROSS
THE YUCATAN PENINSULA INTO CHIAPAS...BY 60 HRS ACROSS THE CAYMAN
ISLANDS INTO NORTHEASTERN HONDURAS...BY 72 HRS ACROSS THE
SOUTHEASTERN BAHAMAS INTO JAMAICA AND THEN EASTERN NICARAGUA.
FRONT WILL PRODUCE STRONG OROGRAPHIC FORCING AND LOW-LEVEL
INSTABILITY ONCE PROGRESSING INTO SOUTHERN MEXICO AND THEN THE
GULF OF HONDURAS. THIS WILL LEAD TO ACCUMULATIONS INCREASING TO
25-50MM/DAY AND MAXIMA OF 75-150MM ACROSS CHIAPAS/TABASCO/NORTHERN
GUATEMALA BY 60-84 HRS. ACROSS THE GULF OF HONDURAS...EXPECTING AN
INCREASE TO 15-30MM/DAY AND MAXIMA OF 40-80MM. ACROSS THE BAHAMAS
AND CUBA...PRE-FRONTAL CONVERGENCE AND LOW-LEVEL INSTABILITY WILL
PRODUCE FREQUENT BRIEF SHOWERS WITH ACCUMULATIONS OF 00-05MM/DAY
AND ISOLATED MAXIMA OF 10MM. SHEAR-LINE WILL INTERACT WITH TROUGH
ACROSS EASTERN CENTRAL AMERICA TO ENHANCE ACCUMULATIONS BY LATE
CYCLE.

ACROSS THE EASTERN PACIFIC...ITCZ DEEP CONVECTION IS WEAKER THAN
USUAL. STRONG NORTHERLIES ACROSS THE PANAMA ITHSMUS BY MID-LATE
CYCLE WILL DRIVE THE CONVERGENCE ZONE SOUTHWARD INTO THE SOUTHERN
CHOCO. IN THE MEANTIME...MOST ACTIVE CONVECTION ACROSS COLOMBIA
WILL CONCENTRATE ACROSS THE CHOCO AND EJE CAFETERO...SLOWLY
MIGRATING NORTHWARD THROUGH THE CYCLE AS TROUGH PATTERN ACROSS
NORTH-CENTRAL CARIBBEAN PERSISTS.

[cycloneye]

Good morning.


AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
530 AM AST THU DEC 20 2012

.SYNOPSIS...A MID TO UPPER LEVEL RIDGE WILL CONTINUE ACROSS THE
LOCAL AREA THROUGH TONIGHT OR EARLY FRIDAY...BEFORE AN UPPER
LEVEL TROUGH PASSES ACROSS OR JUST NORTH OF THE FA LATER FRIDAY
AND FRIDAY NIGHT. A DEEPER LAYERED TROUGH WILL APPROACH THE LOCAL
REGION SATURDAY AND THEN AFFECT THE LOCAL ISLANDS SUNDAY THROUGH
AT LEAST MONDAY.

&&

.DISCUSSION...THROUGH TODAY AND EARLY TONIGHT...EXPECT LITTLE
OVERALL CHANGE TO THE PATTERN OF THE PAST SEVERAL DAYS...AS BANDS
AND PATCHES OF MOISTURE CONTINUE TO MOVE ACROSS THE LOCAL AREA
FROM TIME TO TIME...RESULTING IN INTERVALS OF CLOUDINESS AND
PASSING SHOWERS ACROSS THE LOCAL ISLANDS. AT THIS TIME...SATELLITE
AND WSR-88D DATA ARE SHOWING YET ANOTHER BLOSSOMING AREA OF
CLOUDINESS AND SHOWERS OVER THE EASTERN PARTS OF THE FA AND EXPECT
THIS TO EXPAND/MOVE WEST THROUGH THIS MORNING...PRODUCING ANOTHER
RATHER UNSETTLED AND DAMP MORNING...WITH A GOOD DEAL OF
CLOUDINESS...SHOWERS OF VARYING INTENSITY...OCCASIONALLY REDUCED
VISIBILITIES AND WET ROADS WITH LOCAL PONDING OF WATER. MORNING
COMMUTERS ARE URGED TO SLOW DOWN AND ALLOW A LITTLE EXTRA TIME TO
REACH THEIR DESTINATIONS. OUTSIDE OF THESE CLOUD AND SHOWER
AREAS...GENERALLY FAIR WEATHER SHOULD PREVAIL.

THEN...FOR LATER TONIGHT AND FRIDAY THROUGH SATURDAY...FALLING
MID TO UPPER LEVEL HEIGHTS...POOLING MOISTURE LOCALLY FROM GOOD
LOW LEVEL CONVERGENCE AND POSSIBLY AN APPROACHING FRONTAL
BOUNDARY OR SURFACE TROUGH...SHOULD YIELD AN OVERALL INCREASE IN
CLOUDINESS AND SHOWERS ACROSS THE FA. IN FACT...AT THIS POINT...
FRIDAY AND FRIDAY NIGHT INTO AT LEAST THE FIRST PART OF
SATURDAY...LOOK TO BE QUITE UNSETTLED WITH LOTS OF CLOUDINESS AND
A GOOD CHANCE OF SHOWERS...ESPECIALLY ALONG AND NORTH OF THE
CORDILLERA CENTRAL. WEATHER AND POPS MAY NEED TO BE INCREASED
FURTHER WITH LATER FORECASTS. DESPITE AFOREMENTIONED MID TO UPPER
LEVEL TROUGHINESS...SUNDAY MAY TURN OUT A BIT DRIER THAN THE TODAY
THROUGH SATURDAY TIME FRAME...BUT IT LOOKS MORE SHOWERY AGAIN FOR
MONDAY.

&&

.AVIATION...VFR CONDITIONS EXPECTED ACROSS THE LOCAL TAF SITES
THROUGH THE FORECAST PERIOD. ISOLD TO SCT SHRA WILL AFFECT THE
FLYING AREA TODAY...ESPECIALLY THE NORTH AND EAST SECTIONS OF PR
AND USVI BTWN 20/10Z AND 20/15Z. LLVL NORTHEAST WIND FLOW WILL
PREVAIL AT 10 TO 20 KNOTS.

&&

.MARINE...GENERALLY EXPECT WINDS OF 21 KNOTS OR LESS ACROSS THE
REGIONAL WATERS THROUGH AT LEAST SATURDAY. SEAS SHOULD GENERALLY
BE 6 FEET OR LESS IN LONG PERIOD NORTH NORTHEAST SWELLS THROUGH
TONIGHT...BEFORE SLOWLY BUILDING FRIDAY THROUGH SATURDAY AND
SUNDAY ACROSS THE LOCAL ATLANTIC WATERS AND THE CARIBBEAN
PASSAGES...AS A NEW PULSE OF NORTH SWELLS INVADES THESE WATERS.
SMALL CRAFT ADVISORIES MAY BE NEEDED FOR AMZ710 AS EARLY AS LATE
FRIDAY AFTERNOON...WITH CONDITIONS EXPANDING TO OTHER WATERS
THEREAFTER. ADDITIONALLY...THESE BUILDING NORTH SWELLS WILL
PRODUCE INCREASINGLY LARGE BREAKING WAVES AND RIP CURRENTS...
RESULTING IN DANGEROUS SURF CONDITIONS. THUS...HIGH SURF
ADVISORIES WILL PROBABLY BE REQUIRED AS WELL. FOR TODAY...SMALL
BOAT OPERATORS SHOULD EXERCISE CAUTION ACROSS PARTS OF THE LOCAL
COASTAL WATERS.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 81 74 81 73 / 40 40 40 40
STT 84 76 84 76 / 20 20 20 20

[cycloneye]

December 20 Jamaica forecast:

Code: Select all

Significant Feature: Surface trough over the central Caribbean.

Morning: Mainly fair.

Afternoon: Partly cloudy with isolated showers mainly over northern parishes.

Tonight: Fair.

Winds: Will reach in excess of 15 knots (18 mph)

Temperatures: High: 31C (88F)     Low: 24C (75F)

 

Location
 Sunrise
 Sunset
 
Kingston
 6:33 a.m.
 5:37 p.m.
 
Montego Bay
 6:38 a.m.
 5:42 p.m.
 
Negril
 6:39 a.m.
 5:43 p.m.
 


[cycloneye]

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
316 PM AST THU DEC 20 2012

.SYNOPSIS...AT UPPER LEVELS...A WEAK UPPER LEVEL TROUGH WILL PASS
THROUGH THE AREA FRIDAY NIGHT WITH A SMALL JET-LET. THEN AFTER A
BRIEF RIDGE PASSAGE A STRONGER AND LARGER LONG WAVE TROUGH WILL
BRUSH THE LOCAL AREA WITH WINDS PEAKING AT 70 KNOTS FROM THE
SOUTHWEST 23/18Z, TROUGHINESS WILL GIVE WAY TO ANOTHER RIDGE BY
MID WEEK.

AT MID LEVELS...HIGH PRESSURE WILL MOVE EAST INTO THE TROPICAL
ATLANTIC AHEAD OF A TROUGH HANGING DOWN FROM A STRONG LOW CROSSING
THROUGH THE NEW ENGLAND STATES. AFTER TROUGH PASSAGE SUNDAY OR
MONDAY...HIGH PRESSURE RETURNS TO THE CARIBBEAN BY MID WEEK. ONLY
LIMITED MOISTURE IS PRESENT AT MID LEVELS ON SUNDAY AND SUNDAY
NIGHT...OTHERWISE MID LEVELS ARE ALMOST COMPLETELY DRY.

AT LOWER LEVELS...FLOW AT LOWER LEVELS WILL SLOWLY SHIFT TO THE
EAST SOUTHEAST OVER THE WEEKEND AS HIGH PRESSURE TO THE NORTH
SLOWLY MIGRATES EAST INTO THE CENTRAL ATLANTIC. BANDS OF SHALLOW
MOISTURE WILL TRAVERSE THE AREA DURING THIS TIME. A SECOND FRONT
WILL APPROACH THE AREA SATURDAY AND SUNDAY ...BUT WILL NOT REACH
THE LOCAL AREA LEAVING US UNDER MODIFIED TROPICAL AIR.

&&

.DISCUSSION...SHOWERS WERE MUCH FEWER TODAY THAN YESTERDAY AS A
SHEARLINE APPROACHES THE LOCAL AREA. A PATCH OF MOISTURE THAT IS
VISIBLE IN THE SATELLITE IMAGERY TO THE NORTHEAST AND IN THE MIMIC
PRODUCT IS EXPECTED TO ARRIVE TONIGHT AND BRING MORE LIGHT TO
MODERATE SHOWERS TO THE NORTHEAST AND EAST PARTS OF PUERTO RICO
AND THE NORTHER U.S. VIRGIN ISLANDS. THE LATEST MODEL RUN FROM
22/06Z SHOWS A BAND OF MOISTURE CONSOLIDATING IN AN E-W POSITION
AND THEN STALLING OVER THE AREA THURSDAY THROUGH SATURDAY. THIS
WILL INCREASE SHOWERS OVER THE ISLANDS. MOISTURE PEAKS NEAR 1.7
INCHES OF PRECIPITABLE WATER SATURDAY NIGHT AND THEN GRADUALLY
DIMINISHES FROM 1.3 TO 1 INCH BY TUESDAY NIGHT. AFTER WHICH
MOISTURE INCREASES AGAIN. THIS IS A WINTER TIME PATTERN HOWEVER
AND SIGNIFICANT INFLUXES OF MOISTURE FOR HEAVY RAINFALL EVENTS ARE
NOT FORESEEN. IN FACT THE GFS SHOWS STRONG CONVERGENT FLOW SUNDAY
AFTERNOON AT UPPER LEVELS THAT WOULD INHIBIT CONVECTION IF MID
LEVEL MOISTURE WERE SUPPORTIVE...WHICH IT IS NOT. THEREFORE
SHOWERS REMAIN SHALLOW THOUGH SOMEWHAT MORE PERSISTENT THAN MOST
WERE HOPING FOR OVER THE WINDWARD SLOPES AND COASTS OF PUERTO RICO
AND MUCH OF THE NORTHERN U.S. VIRGIN ISLANDS.


&&

.AVIATION...
MOSTLY VFR CONDITIONS ARE EXPECTED ACROSS ALL OF THE LOCAL
FLYING AREA UNTIL AT LEAST 21/04Z. MOISTURE WILL INCREASE AFTER
21/04...RESULTING IN BRIEF PERIODS OF MVFR CONDITIONS ACROSS THE
LOCAL TERMINALS. TJSJ 20/12Z SOUNDING INDICATED AN EAST NORTHEAST
WIND FLOW UP TO 20 KNOTS ALL THE WAY FROM THE SURFACE TO 25K
FEET...THEN GRADUALLY BECOMING WESTWARD AND A LITTLE STRONGER
ALOFT.

&&

.MARINE...LONG PERIOD SWELL WILL INCREASE BEGINNING TONIGHT IN THE
ATLANTIC WATERS AND CARIBBEAN PASSAGES. SWELL WILL BECOME AS HIGH
AS TEN FEET AND A HIGH SURF ADVISORY IS LIKELY FROM FRIDAY NIGHT
OR SATURDAY MORNING IMMEDIATELY FOLLOWING THE SMALL CRAFT
ADVISORIES FOR THE SAME AREAS.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 74 83 73 82 / 40 40 30 30
STT 74 84 72 84 / 20 20 10 20

[Macrocane]

Here comes the front...very windy conditions expected for southern Mexico and Central America starting tonight:

GAP WINDS...
STRONG HIGH PRES BEHIND A FAST-MOVING COLD FRONT MOVING OFF THE
TEXAS COAST INTO THE GULF OF MEXICO WILL INDUCE A SUDDEN INCREASE
IN GAP WINDS THROUGH CHIVELA PASS INTO THE GULF OF TEHUANTEPEC
WITHIN THE NEXT 12-15 HOURS. WINDS WILL SUDDENLY AND DANGEROUSLY
SURGE FROM NEAR CALM CONDITIONS AHEAD OF THE COLD FRONT TO GALE
FORCE CONDITIONS WITHIN MINUTES...THEN CONTINUE TO BUILD TO STORM
FORCE TONIGHT. SEAS WILL RAPIDLY BUILD IN EXCESS OF 15-20 FT IN
BY FRI MORNING. GFS MODEL GUIDANCE INDICATES STORM FORCE WINDS
WILL PERSIST TONIGHT THROUGH EARLY SAT...WITH GALE CONDITIONS
CONTINUING THROUGH SUN MORNING. WIND-DRIVEN SEAS WILL FAN OUTWARD
FROM THE SOURCE REGION AS N-NE SWELL EXTENDING DOWNWIND FROM THE
GULF OF TEHUANTEPEC TO 110W...MERGING WITH NW SWELL FROM THE COLD
FRONT MENTIONED EARLIER.

WINDS ACROSS THE GULF OF PAPAGAYO CONTINUE TO PULSE TO 20 KT AT
NIGHT INTO EARLY MORNING HOURS FROM NOCTURNAL DRAINAGE FLOW. AS
THE TRADE WIND FLOW INCREASES ACROSS THE SW CARIBBEAN BY FRI...
EXPECT NE TO E WINDS OF 20-30 KT AND SEAS BUILDING TO NEAR 12 FT
IN AND DOWNSTREAM OF THE GULF OF PAPAGAYO BY SAT AFTERNOON.

[Macrocane]

DISCUSSION FROM DEC 20/00UTC: MID/UPPER RIDGE CENTERS ACROSS MOST
OF THE GREATER ANTILLES AND INTO THE WESTERN ATLANTIC. THE RIDGE
WILL PUSH EASTWARD THROUGH THE CYCLE AS TROUGH DEEPENS TO ITS
WEST. THIS RIDGE HAS LEAD TO STRONG SUBSIDENCE INVERSION ACROSS
THE GREATER ANTILLES/BAHAMAS THAT WILL DOMINATE DURING MOST OF THE
CYCLE. THIS WILL LIMIT VERTICAL DEVELOPMENT...LIMITING RAINFALL
EVENTS FOR THE MOST PART TO PERSISTENT SHALLOW
CONVECTION/OROGRAPHIC INTERACTIONS.

UPPER TROUGH EXITING ACROSS THE CENTRAL ATLANTIC WILL CONTINUE
SUSTAINING A SURFACE FRONT. THE FRONT WILL HOWEVER REMAIN WELL TO
THE NORTHEAST OF THE FORECAST DOMAIN...BRUSHING THE EASTERN
BAHAMAS WITH LIGHT ACCUMULATIONS IN SHALLOW CONVECTION THROUGH DAY
01. PRE-FRONTAL SHEAR LINE WILL HOWEVER PERSIST EXTENDING ACROSS
THE WINDWARD ISLES INTO NORTHEAST VENEZUELA BY 24 HRS...TO THEN
START LOSING DEFINITION WHILE EXTENDING ACROSS THE WINDWARD INTO
THE SOUTHERN CARIBBEAN ISLES. THIS WILL BE A FOCUS OF LOW-LEVEL
CONVERGENCE LEADING TO ACCUMULATIONS OF 05-10MM/DAY AND ISOLATED
MAXIMA OF 15-20MM ACROSS THE WINDWARDS AND NORTHEAST VENEZUELA
THROUGH 36 HRS. BY 36-60 HRS...MAXIMA WILL INCREASE TO 15-25
ACROSS THE WINDWARD/NORTHEAST VENEZUELA/COASTAL GUYANA. BY
60-84HRS...IN INTERACTION WITH ITCZ...IT WILL PRODUCE 10-15MM/DAY
AND MAXIMA OF 20-40MM ACROSS THE NORTHERN GUIANAS.

NEXT UPPER TROUGH ARRIVING IN THE BASIN WILL EXTEND ACROSS THE
MISSISSIPPI VALLEY BY 24 HRS. BY 48 HRS...IT WILL ENTER IN PHASE
WITH A RETROGRESSING TUTT ACROSS THE CARIBBEAN...AND WILL EXTEND
FROM THE EAST COAST OF THE USA ACROSS WESTERN CUBA INTO COSTA
RICA. BY 72 HRS...THE UPPER TROUGH WILL THEN EXTEND FROM JUST WEST
OF BERMUDA TO THE CENTRAL BAHAMAS AND COSTA RICA. THIS TROUGH WILL
GRADUALLY ENHANCE UPPER DIVERGENCE TO ITS SOUTHEAST...ESPECIALLY
BY LATE CYCLE. THIS WILL ENHANCE CONVECTION ACROSS AND TO THE
NORTHEAST OF HISPANIOLA ON DAY 03. IN THE MEANTIME...TROUGH
SUSTAINS A PROGRESSIVE SURFACE FRONT...PUSHED BY A 30-40KT
NORTHERRLY LOW-LEVEL JET. THE FRONT WILL EXTEND ACROSS NORTHERN
FLORIDA-GULF OF VERACRUZ BY 24 HRS. BY 48 HRS IT WILL EXTEND
ACROSS CENTRAL BAHAMAS-CENTRAL CUBA-QUINTANA ROO-CHIAPAS. BY 72
HRS THE FRONT WILL EXTEND ACROSS SOUTHEASTERN CUBA-JAMAICA-GULF OF
HONDURAS-CENTRAL GUATEMALA. POLAR RIDGE ENTERING THE GULF OF
MEXICO WILL INDUCE A STRONG 45-60KT TEHUANTEPECER BY 24 THROUGH 36
HRS. THE JET WILL SLOWLY WEAKEN AFTERWARDS. ACROSS THE BAHAMAS AND
CUBA...FRONTAL CONVERGENCE AND THEN ENHANCED POST-FRONTAL
LOW-LEVEL CONVECTIVE INSTABILITY WILL PRODUCE FREQUENT BRIEF
SHOWERS WITH ACCUMULATIONS OF 00-05MM/DAY AND ISOLATED MAXIMA OF
10MM. BY 60-84 HRS...SLIGHT ENHANCEMENT IN INTERACTION WITH UPPER
TROUGH WILL PRODUCE 05-10MM/DAY AND MAXIMA OF 15MM ACROSS EASTERN
CUBA.

A PRE-FRONTAL SHEAR LINE WILL ALSO DEVELOP TODAY...IN ASSOCIATION
WITH FRONT AND UPPER TROUGH. BY 24 HRS...THE SHEAR LINE WILL
EXTEND ACROSS THE YUCATAN PENINSULA INTO CHIAPAS. BY 48 HRS ACROSS
THE SOUTHEASTERN BAHAMAS-JAMAICA AND THEN INTO COSTA RICA/SOUTHERN
NICARAGUA. BY 72 HRS IT WILL EXTEND ACROSS PUERTO RICO-CENTRAL
CARIBBEAN INTO SOUTHEASTERN COSTA RICA/BOCAS DEL TORO IN PANAMA.
THE SHEAR LINE WILL ENHANCE LOW-LEVEL CONVERGENCE AND LOCALLY
HEAVY RAINFALL...ESPECIALLY IN AREAS WHERE OROGRAPHIC INTERACTION
BECOMES A FACTOR. SOUTHERN VERACRUZ/CHIAPAS/TABASCO/NORTHERN
GUATEMALA IS ONE OF THEM...WHERE EXPECTING ACCUMULATIONS OF
25-50MM/DAY AND MAXIMA OF 75-150MM BY 36-60 HRS. THE GULF OF
HONDURAS IS OTHER REGION OF CONCERN...WHERE EXPECTING
ACCUMULATIONS OF 15-20MM/DAY AND MAXIMA OF 40-80MM BY 36-84
HRS...WITH LOCALLY LARGER AMOUNTS. ANOTHER REGION OF CONCERN IS
THE NORTHEASTERN DOMINICAN REPUBLIC. THERE...SHEAR LINE WILL
INTERACT WITH OROGRAPHY/UPPER TROUGH/LOW-LEVEL TROUGH TO THE SOUTH
(SEE BELOW) PRODUCING FREQUENT SHALLOW CONVECTION AND A FEW
THUNDERSTORMS. EXPECTING ACCUMULATIONS PEAKING AT 15-20MM/DAY AND
MAXIMA OF 25-60MM BY 60-84 HRS.

ANOTHER SYSTEM OF IMPORTANCE IS A WEAK LOW-LEVEL TROUGH IN THE
EASTERLIES CROSSING THE CARIBBEAN. BY 48 HRS WILL START TO
INTERACT WITH UPPER TROUGH TO ITS NORTHWEST AND AMPLIFY. IT WILL
THEN EXTEND ACROSS THE DOMINICAN REPUBLIC INTO ZULIA IN VENEZUELA.
IT WILL START WEAKENING AFTERWARDS. THIS TROUGH IS ACCOMPANIED BY
ENHANCED PRECIPITABLE WATER. THIS WILL ENHANCE ACCUMULATIONS
ACROSS NORTHERN VENEZUELA/ABC AND NORTHERN COLOMBIA. ACROSS
EXTREME NORTHERN VENEZUELA/ABC...EXPECTING HEAVIEST BY 36-60 HRS
WITH ACCUMULATIONS OF 10-15MM/DAY AND MAXIMA OF 20-35MM. ACROSS
NORTHERN COLOMBIA EXPECTING MOST WIDESPREAD BY 60-84
HRS...REACHING 05-10MM/DAY AND MAXIMA OF 15-25MM. ACROSS
SANTANDERES...EXPECT ALSO AN INCREASE BY 60-84 HRS TO 10-15MM/DAY
AND MAXIMA OF 20-30MM.

ANOTHER LOW-LEVEL TROUGH ACROSS THE SOUTHWESTERN CARIBBEAN IS
ENHANCING CONVECTION ACROSS EASTERN CENTRAL AMERICA/SAN ANDRES
NUEVA PROVIDENCIA. THIS TROUGH IS INTERACTING WITH A REGION OF
UPPER COLD AIR ADVECTION AND DECENT VENTILATION. THIS WILL SUSTAIN
ACCUMULATIONS OF 15-20MM/DAY AND ISOLATED MAXIMA OF 30-60MM ACROSS
EASTERN COSTA RICA/NICARAGUA/WESTERN PANAMA/SAN ANDRES AND NUEVA
PROVIDENCIA THROUGH 36 HRS. LOW-LEVEL CONVERGENCE WILL BE ENHANCED
BY ARRIVING SHEAR-LINE (SEE ABOVE) AFTERWARDS. YET...EXPECTING
SIMILAR AMOUNTS.

ACROSS THE EASTERN PACIFIC...ITCZ DEEP CONVECTION IS WEAKER THAN
USUAL. STRONG NORTHERLIES ACROSS THE PANAMA ITHMUS BY MID-LATE
CYCLE WILL DRIVE THE CONVERGENCE ZONE SOUTHWARD INTO THE SOUTHERN
CHOCO. IN THE MEANTIME...MOST ACTIVE CONVECTION ACROSS COLOMBIA
WILL CONCENTRATE ACROSS THE CHOCO AND EJE CAFETERO/WESTERN
COLOMBIA WITH ACCUMULATIONS OF 10-15MM/DAY AND ISOLATED MAXIMA OF
20-30MM. AN INCREASE IS EXPECTED ACROSS THE LLANOS/AMAZONIA INTO
SOUTHERN VENEZUELA BY 60-84 HRS...WHEN EXPECTING 10-15MM/DAY AND
MAXIMA OF 20-40MM.

[cycloneye]

Good morning. A variable weekend is expected with some scattered showers but also with plenty of sunshine.

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
614 AM AST FRI DEC 21 2012

.SYNOPSIS...A MID LEVEL RIDGE WILL CONTINUE ACROSS THE LOCAL AREA
THROUGH TONIGHT OR EARLY SATURDAY...AS AN UPPER LEVEL TROUGH
PASSES ACROSS OR JUST NORTH OF THE FA LATE TODAY AND TONIGHT. A
DEEPER LAYERED TROUGH WILL APPROACH THE LOCAL REGION SATURDAY AND
SATURDAY NIGHT AND THEN AFFECT THE LOCAL ISLANDS SUNDAY THROUGH AT
LEAST MONDAY OR MONDAY NIGHT BEFORE LIFTING NORTHEAST.

&&

.DISCUSSION...FOR TODAY AND TONIGHT THROUGH AT LEAST THE FIRST
PART OF...IF NOT ALL OF SATURDAY...EXPECT MOISTURE ASSOCIATED
WITH THE TAIL END OF AN OLD FRONTAL BOUNDARY TO LINGER ACROSS THE
LOCAL AREA. THIS MOISTURE WILL BE ENHANCED BY DECENT LOW LEVEL
CONVERGENCE AND LOCAL EFFECTS AND ALTHOUGH IT WILL NOT BE CLOUDY
AND SHOWERY ALL THE TIME...EXPECT A GOOD DEAL OF CLOUDINESS WITH
SCATTERED PASSING SHOWERS OF VARYING INTENSITY...OCCASIONALLY
REDUCED VISIBILITIES AND WET ROADS WITH LOCAL PONDING OF WATER.
COMMUTERS ARE ONCE AGAIN URGED TO SLOW DOWN AND ALLOW A LITTLE
EXTRA TIME TO REACH THEIR DESTINATIONS.

THEN...FOR SUNDAY AND MONDAY AND PROBABLY TUESDAY ALSO...DESPITE
AFOREMENTIONED MID TO UPPER LEVEL TROUGHINESS...AN OVERALL DRIER
PATTERN IS INDICATED BUT CERTAINLY WILL NOT BE COMPLETELY DRY OR
CLOUD FREE...AS A TYPICAL WINTER PATTERN OF PASSING BANDS AND
PATCHES OF MOISTURE WITH EMBEDDED SHOWERS WILL PREVAIL.

&&

.AVIATION...VFR CONDITIONS ARE EXPECTED TO PREVAIL ACROSS MOST OF
THE LOCAL TAF SITES THROUGH THE FORECAST PERIOD. SCT SHRA WILL
AFFECT THE FLYING AREA TODAY. SHWRS WILL CLUSTER MAINLY ACROSS THE
EAST AND NORTH SECTIONS OF PR AND USVI. AS A RESULT...BRIEF MVFR
CONDS MAY OCCUR IN PASSING SHRA ACROSS TJSJ...TIST AND TISX. LLVL
WIND FLOW WILL CONTINUE FM THE EAST-NORTHEAST AT 10 TO 20 KNOTS.

&&

.MARINE...GENERALLY EXPECT WINDS OF 20 KNOTS OR LESS ACROSS THE
REGIONAL WATERS THROUGH AT LEAST SUNDAY. LARGE...LONG PERIOD NORTH
SWELLS WILL BEGIN TO AFFECT THE ATLANTIC COASTAL WATERS LATE THIS
AFTERNOON AND EARLY TONIGHT AND THEN THE CARIBBEAN PASSAGES LATE
TONIGHT AND SATURDAY...WITH THESE SWELLS THEN LINGERING ACROSS
THE WATERS THROUGH AT LEAST SUNDAY AND MONDAY. THESE SWELLS WILL
RESULT IN INCREASINGLY ROUGH AND HAZARDOUS MARINE CONDITIONS.
SMALL BOAT OPERATORS SHOULD EXERCISE CAUTION ACROSS MOST OF THE
LOCAL COASTAL WATERS TODAY AND A SMALL CRAFT ADVISORY GOES INTO
EFFECT FOR THE LOCAL ATLANTIC OFF SHORE WATERS (AMZ710) AT 3 PM
AST THIS AFTERNOON.

ADDITIONALLY...THESE BUILDING NORTH SWELLS WILL PRODUCE
INCREASINGLY LARGE BREAKING WAVES AND RIP CURRENTS...RESULTING IN
DANGEROUS SURF CONDITIONS. THUS...HIGH SURF ADVISORIES WILL LIKELY
BE REQUIRED FOR THE NORTHWEST THROUGH NORTHEAST COASTS OF MANY OF
THE LOCAL ISLANDS LATER TODAY.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 83 73 82 72 / 40 40 40 0
STT 84 72 84 72 / 30 20 20 0