144
FXCA20 KWBC 212012
PMDCA

TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
311 PM EST THU NOV 21 2024

FORECAST BULLETIN 21 NOV 2024 AT 1930 UTC: THE UPPER CONVERGENT
MJO WILL CONTINUE TO FAVOR A DECREASE IN THE COVERAGE OF
PRECIPITATING CONVECTION ACROSS THE AMERICAS. HOWEVER...NOTE THAT
A KELVIN WAVE IS PROPAGATING ACROSS THE BASIN THROUGH THE FORECAST
CYCLE...TO HIGHLIGHT A FEW AREAS LOCALLY. OF MOST INTEREST ARE A
SURFACE FRONT AND LATER A SHEAR LINE WHICH WILL ENHANCE
PRECIPITATION IN THE CARIBBEAN BASINS OF COSTA RICA...PANAMA AND
SOUTHERN NICARAGUA...AND DIURNAL CONVECTION IN COLOMBIA.

THE PATTERN OF UPPER TROUGHS AND RIDGES IN THE WESTERLIES IS VERY
AMPLIFIED ACROSS NORTH AMERICA AND THE NORTH ATLANTIC. EMBEDDED IN
THIS PATTERN...A LARGE MID-UPPER POLAR TROUGH CENTERS ON A LOW
OVER THE GREAT LAKES AND EXTENDS AS FAR SOUTH AS THE GULF OF
HONDURAS. THIS TROUGH IS SUSTAINING A POTENT AND LONG FETCH
SURFACE FRONT THAT IS PROPAGATING ACROSS THE NORTHWEST
BAHAMAS...CUBA AND GULF OF HONDURAS ON THURSDAY. BY THURSDAY
EVENING THE MAIN FRONT IS EXPECTED ACROSS THE NORTHWEST
BAHAMAS...CENTRAL CUBA...CENTRAL YUCATAN PENINSULA INTO THE
SOUTHWEST GULF OF MEXICO...WHILE A WEAKENING BOUNDARY EXTENDS
ACROSS THE CENTRAL BAHAMAS...CAYMAN ISLANDS AND INTO NORTH-CENTRAL
HONDURAS. BY FRIDAY EVENING EXPECT THE FRONT ACROSS THE SOUTHEAST
BAHAMAS...SOUTHEAST CUBA...NORTHERN NICARAGUA. BY SATURDAY EVENING
EXPECT THE FRONT ACROSS THE SOUTHERN TURKS AND CAICOS...WINDWARD
PASSAGE...JUST NORTH OF JAMAICA...INTO A WEAKENING STATIONARY
BOUNDARY EXTENDING INTO NORTHERN NICARAGUA. A SHEAR LINE IS ALSO
EXPECTED WITH THIS SYSTEM. BY FRIDAY EVENING EXPECT THE SHEAR LINE
ACROSS WEST HAITI INTO CENTRAL PANAMA. BY SATURDAY EVENING EXPECT
A SHEAR LINE REORGANIZING FROM SOUTHWEST JAMAICA INTO SOUTHEAST
COSTA RICA...WHILE ANOTHER SHEAR LINE STRUCTURE ORGANIZES ACROSS
22N 65W INTO THE DOMINICAN REPUBLIC.

BOTH FRONT AND SHEAR LINE ARE EXPECTED TO ENHANCE PRECIPITATION IN
THE CARIBBEAN BASIN OF CENTRAL AMERICA. THROUGH EARLY
FRIDAY...ENHANCED MOISTURE CONVERGENCE ALONG THE SOUTHERN FRONT
WILL FAVOR 20-40MM/DAY AND MAXIMA OF 50-100MM IN NORTHERN HONDURAS
AND ISLAS DE LA BAHIA. NORTHEASTERLY LOW-LEVEL FLOW IN
HONDURAS...GUATEMALA AND CHIAPAS WILL FAVOR MAXIMA OF 20-35MM
ALONG NORTHERN AND NORTHEASTERN SLOPES DUE TO OROGRAPHIC
ENHANCEMENT. FRONTAL CONVECTION IN THE CAYMAN ISLANDS WILL FAVOR
MAXIMA OF 20-40MM...WHILE IN THE NORTHWEST BAHAMAS EXPECT MAXIMA
OF 15MM. ON FRIDAY...FRONTAL CONVECTION WILL FAVOR MAXIMA OF
15-30MM IN SOUTHEAST CUBA AND JAMAICA...WHILE IN THE SOUTHEAST
BAHAMAS AND TURKS AND CAICOS EXPECT MAXIMA OF 15-20MM. SIMILAR
AMOUNTS ARE EXPECTED IN EASTERN NICARAGUA. SHEAR LINE CONVECTION
IS EXPECTED TO FAVOR MAXIMA OF 20-45MM IN CENTRAL PANAMA. ALSO ON
WEDNESDAY...ONSHORE FLOW IN THE CARIBBEAN BASIN OF COSTA RICA AND
WEST PANAMA WILL FAVOR MAXIMA OF 35-70MM...WHILE IN CENTRLA
GUATEMALA AND NORTHERN HONDURAS...NORTHERLY FLOW WILL ENHANCE
OROGRAPHIC UPLIFT TO FAVOR MAXIMA OF 20-35MM. ON
SATURDAY...FRONTAL CONVECTION WILL FAVOR MAXIMA OF 15MM IN WEST
HAITI AND IN JAMAICA...AND SIMILAR AMOUNTS IN FAR NORTHEAST
NICARAGUA. SHEAR LINE CONVECTION WILL FAVOR MAXIMA OF 25-50MM IN
SAN ANDRES AND PROVIDENCIA...AND MAXIMA OF 50-10MM/DAY IN THE
CARIBBEAN BASIN OF COSTA RICA. ALSO ON SATURDAY...SHEAR LINE
CONVECTION IN AN ENVIRONMENT OF PRECIPITABLE WATER EXCEEDING 50MM
WILL FAVOR MAXIMA OF 20-35MM IN THE DOMINICAN REPUBLIC AND
SOUTHERN HAITI.

IN NORTHERN SOUTH AMERICA...A CELL OF AN UPPER RIDGE CENTERS OVER
WESTERN VENEZUELA AND IS FORECAST TO MOVE VERY LITTLE THROUGH THE
FORECAST CYCLE. THIS IS FAVORING AN EXTENSIVE REGION OF ENHANCED
UPPER DIFFLUENCE IN NORTHWEST AND NORTHERN COLOMBIA/NORTHWEST
VENEZUELA...WHERE LARGE VALUES OF PRECIPITABLE WATER ARE PRESENT.
IN THE LOWE LEVELS...TWO TROUGHS EXTEND ACROSS THE SOUTHEAST AND
SOUTH CENTRAL CARIBBEAN...AND ARE EXPECTED TO PROPAGATE WESTWARD
SLOWLY...ACCOMPANIED BY AN ASSOCIATED INCREASE IN AVAILABLE
MOISTURE AS THEY MOVE WESTWARD. THIS WILL FAVOR MAXIMA OF 15-30MM
IN NORTHERN COLOMBIA AND NORTHWEST VENEZUELA ON
THURSDAY...INCREASING TO MAXIMA OF 25-50MM IN MOST OF CENTRAL AND
NORTHERN COLOMBIA BY FRIDAY...YIELDING TO MAXIMA OF 20-45MM IN
NORTHWEST VENEZUELA AND NORTHERN AND WESTERN COLOMBIA ON SATURDAY.

EASTERLY/TROPICAL WAVES INITIALIZED AT 12 UTC
NONE

GALVEZ...(WPC)





















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