289
FXCA20 KWBC 181837
PMDCA
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
136 PM EST MON DEC 18 2023
FORECAST BULLETIN 18 DEC 2023 AT 1830 UTC: A POTENT POLAR TROUGH
EXTENDS OVER THE EASTERN USA WITH ITS BASE INTO THE WESTERN
CARIBBEAN. THIS IS SUSTAINING A LONG-FETCH SURFACE FRONT THAT IS
PROPAGATING INTO THE FAR SOUTHWEST CARIBBEAN...AS WELL AS A SHEAR
LINE. BY MONDAY EVENING EXPECT THE FRONT ALONG 24N 70W...TURKS AND
CAICOS...WINDWARD PASSAGE...EAST JAMAICA...SAN ANDRES...COSTA
RICA-NICARAGUA BORDER. THE SHEAR LINE IS EXPECTED FROM THE HAITIAN
PENINSULA INTO GUNA YALA IN PANAMA. BY TUESDAY EVENING EXPECT THE
FRONT TO BECOME STATIONARY ALONG THE TURKS AND
CAICOS...HAITI...13N 80W...BOCAS DEL TORO. THE SHEAR LINE IS
EXPECTED ACROSS THE NORTHEAST DOMINICAN REPUBLIC...BARAHONA...INTO
GUNA YALA IN PANAMA. BY WEDNESDAY EVENING...EXPECT A WEAKENING
STATIONARY FRONT EXTENDING ALONG SAMANA IN THE DOMININCAN
REPUBLIC...BARAHONA...NEAR SAN ANDRES AND PROVIDENCIA...BOCAS DEL
TORO. THE WEAKENING SHEAR LINE IS EXPECTED ALONG 13N 78W INTO
CENTRAL PANAMA. ON MONDAY...THE BASE OF THE UPPER TROUGH WILL
CONTINUE INTERACTING WITH THE FRONTAL MOIST PLUME IN
HAITI...SOUTHEAST CUBA...TURKS AND CAICOS AND INAGUA. THIS WILL
FAVOR 15-20MM/DAY AND MAXIMA OF 30-60MM. MOIST SOUTHERLY FLOW IN
THE SOUTHERN DOMINICAN REPUBLIC WILL INTERACT WITH OROGRAPHY TO
FAVOR 15-30MM/DAY AND ISOLATED MAXIMA OF 40-80MM. NOTE THAT
SEVERAL MODELS ARE TENDING TO UNDERESTIMATE RAINFALL UNDER THESE
SCENARIOS. ALSO ON MONDAY...THE SHEAR LINE WILL FAVOR 10-15MM/DAY
AND ISOLATED MAXIMA OF 20-40MM IN NORTHEAST AND NORTH-CENTRAL
PANAMA. ONSHORE FLOW AND UPSLOPE WILL FAVOR MAXIMA OF 30-60MM IN
BOCAS DEL TORO AND 05-10MM/DAY WITH MAXIMA OF 15-25MM IN
NORTHERN...EASTERN AND SOUTHERN COSTA RICA. IN NORTH-CENTRAL
HONDURAS AND ISLAS DE LA BAHIA EXPECT MAXIMA OF 15MM. ON
TUESDAY...EXPECT 15-30MM/DAY AND MAXIMA OF 50-100MM IN NORTHERN
HISPANIOLA...AS ONSHORE FLOW DEVELOPS AND PRECIPITABLE WATER
REMAINS IN THE 50-55MM RANGE. IN SOUTHWEST HISPANIOLA EXPECT
MAXIMA OF 25-50MM. FRONTAL CONVECTION IN BOCAS DEL TORO WILL FAVOR
MAXIMA OF 40-80MM...WHILE IN NORTHEAST PANAMA...THE SHEAR LINE
WILL FAVOR MAXIMA OF 30-60MM. IN THE CARIBBEAN BASIN OF COSTA RICA
EXPECT 10-15MM/DAY AND MAXIMA OF 20-40MM. ON WEDNESDAY...EXPECT
FRONTAL CONVECTION AND NORTHEASTERLY TRADES TO FAVOR 15-20MM/DAY
AND MAXIMA OF 25-50MM IN NORTHERN PORTIONS OF HISPANIOLA. IN SAN
ANDRES AND PROVIDENCIA...AS WELL AS IN THE CARIBBEAN BASIN OF
COSTA RICA AND PANAMA EXPECT 05-10MM/DAY AND MAXIMA OF 15-30MM.
ALSO IN ASSOCIATION WITH THE PERSISTENT NORTHERLY FLOW ACROSS THE
GULF OF HONDURAS...EXPECT SHALLOW CONVECTION AND PRECIPITATION ON
A DAILY BASIS IN PORTIONS OF NORTHERN HONDURAS AND ISLAS DE LA
BAHIA. INITIALLY EXPECT MAXIMA OF 15MM. THIS INCREASES TO
05-10MM/DAY AND MAXIMA OF 15-25MM THEREAFTER.
A SECOND COLD FRONT IS EXPECTED TO EXIT THE SOUTH COAST OF THE USA
LATE ON MONDAY AND PROPAGATE RAPIDLY INTO THE NORTHERN CARIBBEAN.
BY TUESDAY EVENING EXPECT THE FRONT ACROSS THE CENTRAL
BAHAMAS...CENTRAL CUBA...PINAR DEL RIO...INTO THE CENTRAL GULF OF
MEXICO. BY WEDNESDAY EVENING EXPECT IT ALONG THE TURKS AND
CAICOS...SOUTHEAST CUBA...ISLAS DE LA BAHIA...INTO A DISSPATING
BOUNDARY ACROSS THE CENTRAL YUCATAN PENINSULA INTO THE WESTENR
GULF OF MEXICO. THIS SYSTEM WILL HAVE VERY LIMITED EFFECTS ON
PRECIPITATION GIVEN ITS PROPAGATION WITHIN A MUCH DRIER
ENVIRONMENT THAN THE SOUTHERN FRONT.
A FRONTAL SHEAR LINE CONTINUES TO EXTEND FROM THE TROPICAL NORTH
ATLANTIC INTO THE WINDWARD ISLANDS...WHERE IT IS FORECAST TO
PERSIST THROUGH EARLY WEDNESDAY...TO THEN START LOSING DEFINITION.
THIS WILL CONTINUE TO BE THE FOCUS FOR MODERATE PRECIPITATION. ON
MONDAY EXPECT MAXIMA OF 15-25MM...DECREASING TO MAXIMA OF 15-20MM
ON TUESDAY. ON WEDNESDAY...THE REMAINING MOIST PLUME WILL FAVOR
MAXIMA OF 15MM.
IN NORTHERN SOUTH AMERICA...WESTERLY FLOW CONTINUES IN THE UPPER
TROPOSPHERE FROM CENTRAL COLOMBIA INTO THE NORTHERN AMAZON BASIN.
AS THE BOLIVIAN HIGH/SUBTROPICAL UPPER RIDGE GAINS STRENGTH OVER
SOUTHERN PERU/BOLIVIA THROUGH WEDNESDAY...EXPECT VENTILATION TO
INCREASE...FAVORING AN INCREASING TREND IN ACCUMULATION PRIMARILY
IN THE AMAZON BASIN. MODERATE TO LOCALLY HEAVY AMOUNTS ARE
EXPECTED IN THE PACIFIC BASIN OF SOUTHWEST COLOMBIA AND ECUADOR ON
A DAILY BASIS...FAVORED BY ITCZ CONVERGENCE AND PRECIPITABLE WATER
EXCEEDING 50MM IN COASTAL REGION/OFFSHORE. THIS WILL FAVOR MAXIMA
OF 20-50MM ON MONDAY...MAXIMA OF 30-60MM ON TUESDAY AND MAXIMA OF
20-40MM ON WEDNESDAY.
POSITIONS OF TROPICAL/EASTERLY WAVES INITIALIZED AT 12 UTC
NONE
GALVEZ...WPC (USA)
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