Prognostic Meteorological Discussion
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FXCA20 KWBC 091935
PMDCA

TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
234 PM EST FRI DEC 09 2016

TROPICAL DISCUSSION FROM DEC 09/12 UTC: BROAD MID/UPPER LEVEL
TROUGH DOMINATES THE FLOW ACROSS NORTH AMERICA. THROUGH THIS
EVENING IT PULLS ACROSS THE EASTERN USA TO THE WESTERN
ATLANTIC...WHERE IT IS EXPECTED TO GRADUALLY DAMPEN AS IT LIFTS
OVER THE SUBTROPICAL RIDGE TO THE EAST AND SOUTH. AT LOW
LEVELS...THE ASSOCIATED FRONT MOVES TO THE NORTHWEST/CENTRAL
BAHAMAS-WESTERN CUBA INTO THE GULF OF MEXICO JUST NORTH OF THE
YUCATAN...TO VERACRUZ. IN A TIGHT GRADIENT...FRONTAL NORTHERLIES
OF 35-45KT ARE TO ENVELOP THE WESTERN GULF OF MEXICO THROUGH
SATURDAY MORNING. THROUGH SATURDAY EVENING THE WINDS WILL DECREASE
TO 20-25KT WHILE FRONT IS TO REMAIN NEARLY STATIONARY. LATER ON
SUNDAY IT WILL START TO WEAKEN WHILE RETROGRESSING ACROSS THE
FLORIDA PENINSULA-NORTHERN GULF INTO THE SOUTHERN USA. EARLY IN
THE CYCLE...AS THE FRONT SURGES ACROSS THE GULF OF MEXICO...IT
WILL SUSTAIN A PREFRONTAL SHEAR LINE ACROSS CUBA TO THE WESTERN
CARIBBEAN/NORTHERN HONDURAS. THROUGH FRIDAY EVENING THE SHEAR LINE
IS TO MOVE TO THE SOUTHEAST BAHAMAS/TURKS-EASTERN CUBA-JAMAICA TO
EASTERN NICARAGUA/COSTA RICA. LATER ON SATURDAY...HOWEVER...THE
SHEAR LINE WILL RETROGRESS TO NORTHEAST HONDURAS/NICARAGUA...WHERE
IT IS TO REMAIN WHILE GRADUALLY WEAKENING THROUGH SUNDAY
EVENING/SATURDAY MORNING. THROUGH EARLY SATURDAY...EXPECTING
LARGEST AMOUNTS IN SOUTHERN PORTIONS OF THE GULF OF CAMPECHE
WHERE...UNDER TOPOGRAPHIC UPLIFT...AMOUNTS ARE TO REACH
25-50MM/DAY AND MAXIMA OF 100-175MM.  ALSO ON
FRIDAY-SATURDAY...EXPECTING 05-10MM/DAY AND MAXIMA OF 15-25MM IN
EASTERN MEXICO. IN NORTHERN CUBA/NORTHERN BAHAMAS AND NORTHERN
YUCATAN EXPECTING 05-10MM/DAY AND MAXIMA OF 15-30MM. BY
SATURDAY-SUNDAY EXPECTING LARGEST AMOUNTS IN THE SOUTHERN GULF OF
CAMPECHE WHERE MAXIMA WILL REACH 30-60MM/DAY. IN
BAHAMAS/CUBA/NORTHERN YUCATAN MAXIMA WILL START DECREASING TO
15-25MM.  BY SUNDAY-MONDAY...EXPECTING A SHARP DRYING TREND IN
MEXICO...WHILE ACTIVE CONVECTION WILL PERSIST IN NORTHERN
CUBA/NORTHERN BAHAMAS TO PRODUCE SIMILAR AMOUNTS. SHEAR LINE
ACTIVITY WILL LEAD TO 15-20MM/DAY AND MAXIMA OF 35-70MM IN EASTERN
NICARAGUA AND COSTA RICA ON FRIDAY-SATURDAY. SIMILAR AMOUNTS ARE
EXPECTED IN THE GULF OF HONDURAS UNDER INFLUENCE OF NORTHEASTERLY
TRADE WIND CONVERGENCE. AMOUNTS ARE TO DECREASE ON SATURDAY TO
MAXIMA OF 20-35MM/DAY IN NORTHERN HONDURAS...AND MAXIMA OF 20-40MM
IN EASTERN NICARAGUA AND EASTERN COSTA RICA. DURING THIS
PERIOD...SHEAR LINE WILL ALSO ENHANCE SHOWERS IN JAMAICA/NORTHERN
HISPANIOLA AND SOUTHEASTERN CUBA...TO PRODUCE MAXIMA OF 10MM.
SHEAR LINE CONVECTION ON SUNDAY-MONDAY WILL PRODUCE MAXIMA OF 10MM
ACROSS THE NORTHEASTERN ANTILLES.

AS THE POLAR TROUGH MOVES TO THE WESTERN ATLANTIC IT IS TO
CONTINUE PRESSING AGAINST THE SUBTROPICAL RIDGE TO THE SOUTH.
THROUGH SATURDAY THE RIDGE WILL YIELD TO THE BROAD TROUGH....AND
LATER IN THE DAY IT IS TO CENTER ON A CLOSED HIGH NEAR 34N 42W. AS
THE HIGH RELOCATES...TRADE WINDS CAP OVER THE NORTHERN CARIBBEAN
ISLES IS EXPECTED TO WEAKEN. THIS WILL ALLOW FOR DEEPEN
INSTABILITY AND GRADUAL ENHANCEMENT OF DIURNAL CONVECTION ACROSS
THE GREATER ANTILLES DURING THE DAY ON SATURDAY. BUT ON
SUNDAY...AS THE TROUGH BEGINS TO PULL TO THE EAST-NORTHEAST...THE
RIDGE WILL THEN START TO BOUNCE BACK WHILE ANCHORING ON A NASCENT
HIGH OVER THE SOUTHEAST BAHAMAS/TURKS AND CAICOS. THIS WILL THEN
STRENGTHEN THE CAP INVERSION ACROSS THE NORTHERN CARIBBEAN
ISLANDS...FAVORING EROSION OF AVAILABLE MOISTURE. AT LOW
LEVELS...A HIGH WILL ROLL ACROSS THE CENTRAL TO SOUTHEAST USA
LATER ON SATURDAY...INTO THE WESTERN ATLANTIC ON SUNDAY. AS IT
MOVES NORTH OF THE ISLANDS LATER IN THE CYCLE THIS WILL TIGHTEN
THE PRESSURE GRADIENT ACROSS THE CARIBBEAN...SUSTAINING A BASIN
WIDE WIND SURGE. ACROSS THE NORTHERN CARIBBEAN ISLES THE BOUNDARY
LAYER WINDS INCREASE TO 20-25KT LATER ON SUNDAY...AND WILL PEAK
BETWEEN 25-30KT ON MONDAY. STRONG WINDS ARE TO ALSO ENVELOP THE
SOUTHERN CARIBBEAN AND MOST OF CENTRAL AMERICA. AS THE WINDS
INTENSIFY AND CAP INVERSION STRENGTHENS THIS IS TO THEN FAVOR A
GRADUAL DRYING TREND ACROSS NORTHERN SOUTH AMERICA AND THE EASTERN
CARIBBEAN ISLES. CONVECTION DURING THE LATTER PART OF THE FORECAST
WILL LIMIT TO STREAMERS FORMING OVER THE ISLANDS AND SPREADING
ACROSS THE BASIN. BUT THESE ARE TO RESULT IN RAINFALL AMOUNTS OF
00-05MM/DAY AND LOCALIZED MAXIMA OF 10MM.

TROPICAL/EASTERLY WAVES INITIALIZED AT 12UTC:

INITIAL   24     36     48     60     72     84     96    TYPE
70W      73W    76W    79W    82W    84W    87W    89W     EW

AN EASTERLY WAVE ALONG 70W WILL SURGE ACROSS THE EASTERN-CENTRAL
CARIBBEAN THROUGH SATURDAY EVENING. MEANWHILE...ACROSS THE ABC
ISLES/NORTHERN VENEZUELA INTO NORTHERN COLOMBIA THIS IS TO TRIGGER
RAINFALL AMOUNTS OF 15-20MM/DAY AND MAXIMA OF 25-50MM THROUGH
SATURDAY MORNING. ACROSS COLOMBIA INTO THE DARIEN IN EASTERN
PANAMA...MOST INTENSE IS EXPECTED ON SATURDAY-SUNDAY...WHEN IT IS
TO FAVOR RAINFALL AMOUNTS OF 15-20MM/DAY AND MAXIMA OF 25-50MM.
OVER COSTA RICA/NICARAGUA THE EASTERLY WAVE IS TO COMBINE WITH A
PREFRONTAL SHEAR LINE ON SATURDAY-MONDAY TO TRIGGER RAINFALL
AMOUNTS OF 15-30MM/DAY AND MAXIMA OF 40-80MM ON SUNDAY-MONDAY. THE
WAVE WILL QUICKLY PULL ACROSS EL SALVADOR/HONDURAS ON
SUNDAY/MONDAY...TO TRIGGER SIMILAR RAINFALL AMOUNTS ON
SUNDAY-MONDAY...DECREASING TO MAXIMA OF 35-70MM ON MONDAY-TUESDAY.

JIMENEZ...IMN (COSTA RICA)
MIRANDA...INAMEH (VENEZUELA)
DAVISON/GALVEZ...WPC (USA)

$$




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