800
FXCA20 KWBC 211828
PMDCA
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
128 PM EST TUE JAN 21 2025
FORECAST BULLETIN 21 JANUARY 2025 AT 18:30 UTC
MEDIUM RANGE DISCUSSION: UNDER THE INFLUENCE OF PHASES 5 AND 6 OF
THE MJO...EXPECT ENHANCED UPPER CONVERGENCE TO PERSIST ACROSS THE
AMERICAS THROUGH THE FORECAST CYCLE. THIS GENERALLY ASSOCIATES
WITH ENHANCED SUBSIDENCE AND LOW-LEVEL WIND SHEAR DUE TO AN
ACCELERATION OF THE EASTERLY TRADES. ALTHOUGH THIS FAVORS
GENERALLY DRIER CONDITIONS...AREAS WHERE TRADE WIND CONVERGENCE
PLAYS A ROLE IN ENHANCING PRECIPITATION COULD SEE LOCALLY HEAVIER
PRECIPITATION AMOUNTS.
MID-LEVEL ANALYSIS: OBSERVATIONS AND MODEL SOLUTIONS SHOW THE
RIDGE CENTERING WELL TO THE NORTHEAST OF THE LEEWARD
ISLANDS...WHERE IT IS TO REMAIN THROUGH THE FORECAST CYCLE. THIS
WILL AID TO SUSTAIN A STABLE LAYER ACROSS MOST OF THE
CARIBBEAN...LIMITING THE VERTICAL DEVELOPMENT OF CONVECTION. A
WEAKNESS IN THE RIDGE OVER SOUTHERN MEXICO AND CENTRAL
AMERICA...HOWEVER...WILL ALLOW FOR SOME VERTICAL DEVELOPMENT
ESPECIALLY ONCE CONVECTION ASSOCIATED WITH A ROBUST ARCTIC FRONT
DEVELOPS.
ARCTIC BLAST: A POTENT ARCTIC BLAST IN THE CENTRAL AND EASTERN
UNITED STATES ASSOCIATES WITH AN EXTENSIVE COLD FRONT THAT IS
PROPAGATING SOUTHWARD ACROSS FLORIDA AND THE GULF OF MEXICO ON
TUESDAY AFTERNOON. BY TUESDAY EVENING THE FRONT IS EXPECTED ACROSS
CENTRAL FLORIDA...THE CENTRAL GULF OF MEXICO...EASTERN
TABASCO...SOUTHERN CHIAOAS INTO THE TEHUANTEPEC/CHIVELA LASS
REGION...CENTRAL MEXICO...SOUTHERN ZACATECAS AND ALONG THE SIERRA
MADRE OCCIDENTAL OF SINALOA AND SONORA. BY WEDNESDAY EVENING
EXPECT THE FRONT TO BECOME STATIONARY ACROSS THE NORTHWEST
BAHAMAS...NORTH-CENTRAL CUBA...INTO A WEAKENING BOUNDARY ACROSS
NORTHEAST HONDURAS...NORTHERN EL SALVADOR...SOUTHERN GUATEMALA AND
CENTRAL OAXACA IN MEXICO. BY THURSDAY EVENING EXPECT A STATIONARY
FRONT EXTENDING JUST TO THE NORTH OF GRAND BAHAMA...FAR SOUTHEAST
FLORIDA INTO A WEAKENING BOUNDARY ACROSS WEST CUBA AND THE
NORTHERN YUCATAN PENINSULA. THE LARGEST RAINFALL AMOUNTS WITH THIS
BOUNDARY ARE EXPECTED IN NORTHERN CENTRAL AMERICA AND SOUTHERN
MEXICO...GIVEN ENHANCED LOW-LEVEL MOISTURE CONVERGENCE BUT ALSO
MOISTER AND LESS STABLE CONDITIONS IN THE MID TROPOSPHERE. THROUGH
EARLY WEDNESDAY EXPECT 15 - 30MM/DAY AND MAXIMA OF 40 - 80MM
DEVELOPING IN SOUTHERN VERACRUZ AND NORTHERN CHIAPAS IN
ASSOCIATION WITH ENHANCED LOW-LEVEL MOISTURE CONVERGENCE. IN
NORTHERN GUATEMALA...WESTERN BELIZE AND THE SOUTHERN YUCATAN
PENINSULA EXPECT MAXIMA OF 30 - 60MM...WHILE IN CENTRAL VERACRUZ
EXPECT SIMILAR AMOUNTS. IN CENTRAL AND EASTERN PORTIONS OF THE
YUCATAN PENINSULA EXPECT MAXIMA OF 15 - 30MM. NOTE THAT SHOWERS
AND ALSO THUNDERSTORMS ARE EXPECTED IN ALL OF THESE LOCATIONS. ON
WEDNESDAY THROUGH EARLY THURSDAY EXPECT THE LARTEST ACCUMULATIONS
TO CLUSTGER IN NORTHERN HONDURAS...ISLAS DE LA BAHIA AND
EAST-CENTRAL GUATEMALA...WHERE EXPECT 15 - 20MM/DAY AND MAXIMA OF
30 - 60MM IN THURNDERSTORMS. REMAINING UPSLOPE IN SOUTHERN
VERACRUZ AND NORTH CHIAPAS ASD WELL AS IN CENTRAL GUATEMALA WILL
FAVOR MAXIMA OF 15 - 30MM. ON THURSDAY...THE RETREATING FRONT WILL
COUPLE WITH A MOIST PLUME PROPAGATING WESTWARD ACROSS THE GULF OF
HONDURAS. THIS WILL FAVOR MAXIIMA OF 20 - 35MM/DAY DEVELOPING
ALONG THE ENTIRE EAST COAST OF THE YUCATAN PENINSULA AS WELL AS IN
NORTHERN BELIZE.
CARIBBEAN: FAST LOW-LEVEL WIND SPEEDS ARE EXPECTED IN THE
CARIBBEAN THROUGH THE FORECAST CYCLE...PARTICULARLY ACROSS THE
LESSER ANTILLES AND PUERTO RICO...EXTENDING WEST INTO SAN ANDRES
AND PROVIDENCIA. ENHANCED VERTICAL WIND SHEAR AND THE INFLUENCE OF
THE MID-LEVEL RIDGE WILL GENERALLY LIMIT PRECIPITATION AMOUNTS.
NEVERTHELESS...EXPECT ISOLATED MODERATE ACCUMULATION IN EASTERN
SLOPES OF STEEP TERRAIN DUE TO ENHANCED UPLIFT/TERRAIN
ENHANCEMENT. IN THE CENTRAL LESSER ANTILLES EXPECT ISOLATED MAXIMA
OF 15MM ON TUESDAY INCREASING TO 15 - 25MM ON WEDNESDAY AND
DECREASING TO 15 - 20MM ON THURSDAY. IN EASTERN COSTA
RICA/SOUTHEAST NICARAGUA EXPECT MAXIMA OF 15 - 20MM ON WEDNESDAY
INCREASING TO 15 - 30MM ON THURSDAY AND DECREASING TO 15 - 25MM ON
FRIDAY.
NORTHWEST SOUTH AMERICA: SEASONALLY QUIET CONDITIONS ARE EXPECTED
GIVEN THE CONTINUED PRESENCE OF DRY AIR IN THE MID-TROPOSPHERE AND
UPPER CONVERGENT MJO CONDITIONS. THE LARGEST RAINFALL
ACCUMULATIONS ARE EXPECTED IN INTERIOR PORTIONS OF COASTAL
ECUADOR...GIVEN HIGH VALUES OF PRECIPITABLE WATER AND LIMITED
VERTICAL WIND SHEAR. ACCORDINTLY...EXPECT MAXIMA OF 25-50MM ON
WEDNESDAY. THIS DECREASES TO MAXIMA OF 15 - 20MM ON THURSDAY AND
THEREAFTER. NOTE THAT A GRADUAL DESTABILIZATION OF THE MID-UPPER
TROPOSPHERE WILL LIKELY YIELD TO AN INCREASE IN THE COVERAGE OF
CONVECTION IN WESTERN COLOMBIA...YET MAXIMA IF LIKELY TO REMAIN IN
THE 15 - 20MM/DAY RANGE.
NORTHEAST SOUTH AMERICA: THE ITCZ IS MEANDERING NORTHWARD ACROSS
THE ATLANTIC BASIN...FROM AMAPA IN BRASIL ON TUESDAY TO EXTEND
INTO NORTHERN FRENCH GUIANA AND SURINAME BY THURSDAY.
INITIALLY...MOST OF THE STRONGEST CONVECTION IS EXPECTED TO
CLUSTER IN SOUTHERN SURINAME AND PARA-BRASIL...WHERE HIGHER VALUES
OF PRECIPITABLE WATER...MOISTURE CONVERGENCE AND VENTILATION ARE
EXPECTED. YET...AS THE ITCZ INTERACTS WITH THE BASE OF AN UPPER
TROUGH ON THURSDAY AND THE EASTERLY TRADES ACCELERATE...EXPECT A
RISK FO ECHO TRAINING DEVELOPING. FROM THURSDAY MORNING INTO
FRIDAY MORNING EXPECT POTENTIAL MAXIMA OF 50 - 100MM IN FRENCH
GUIANA...SURINAME AND FAR EASTERN GUYANA.
GALVEZ...(WPC)
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