749
FXCA20 KWBC 191931
PMDCA
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
230 PM EST FRI DEC 19 2025
FORECAST BULLETIN 19 DECEMBER 2025 AT 1930 UTC:
THE BAHAMAS AND CARIBBEAN:
CONDITIONS ARE EXPECTED TO BE RELATIVELY CALM ACROSS THE BAHAMAS
AND CARIBBEAN WITH THE PRESENCE OF A MID-LEVEL AND UPPER-LEVEL
RIDGE IN THE REGION, PRODUCING A MORE STABLE ENVIRONMENT.
NEVERTHELESS, SOME PRECIPITATION IS EXPECTED EACH DAY THROUGHOUT
THE FORECAST PERIOD DUE TO LOW-LEVEL MOISTURE CONVERGENCE,
LOW-LEVEL TROUGHS, DIURNAL HEATING AND LOCAL EFFECTS. IN THE
EASTERN CARIBBEAN, EASTERLY LOW-LEVEL FLOW WILL ALSO FAVOR PASSING
SHOWERS IN THE REGION.
FROM TODAY THROUGH SATURDAY, TOTAL RAINFALL ACCUMULATIONS OF
AROUND 15MM ARE EXPECTED OVER PORTIONS OF THE BAHAMAS AND CUBA, AS
A STATIONARY FRONT PROMOTES LOW-LEVEL CONVERGENCE IN THE AREA.
WITH THE STATIONARY FRONT OVER THE BAHAMAS THROUGHOUT THE FORECAST
PERIOD, LIGHT PRECIPITATION IS EXPECTED TO CONTINUE. AN ADDITIONAL
15-20MM OF RAINFALL IS FORECASTED FOR SATURDAY THROUGH SUNDAY,
FOLLOWED BY ANOTHER 15MM FROM SUNDAY THROUGH MONDAY
OVER HISPANIOLA, A LOW-LEVEL TROUGH AND THE PRESENCE OF A SHEAR
LINE WILL PROMOTE THE GENERATION OF RAINFALL FROM TODAY THROUGH
SATURDAY. FROM SATURDAY THROUGH SUNDAY, THE SHEAR LINE IS
FORECASTED TO INCREASE LOW-LEVEL CONVERGENCE OVER EASTERN
HISPANIOLA AND WESTERN PUERTO RICO, AS A RESULT, SOME SHOWERS ARE
EXPECTED IN THE REGION. FROM SUNDAY THROUGH MONDAY, THE MAIN
DRIVERS OF PRECIPITATION WILL BE A SERIES OF LOW-LEVEL TROUGHS
PASSING OVER PUERTO RICO AND HISPANIOLA. HOWEVER, WITH STABLE
MID- AND UPPER-LEVELS CONDITIONS, TOTAL RAINFALL ACCUMULATIONS ARE
EXPECTED TO REMAIN BELOW 15MM.
MEXICO AND CENTRAL AMERICA:
A MID-LEVEL TROUGH OVER CENTRAL MEXICO IS EXPECTED TO BRING LIGHT
PRECIPITATION OVER PORTIONS OF MEXICO, PARTICULARLY OVER
NORTHEASTERN MEXICO, WHERE A LOW-LEVEL TROUGH IS EXPECTED.
ACCUMULATIONS ARE FORECASTED TO REACH 15MM, AND A MARGINAL RISK
FOR SEVERE WEATHER EXISTS FROM TODAY THROUGH SATURDAY.
A MORE ACTIVE PATTERN OF PRECIPITATION IS EXPECTED FROM SATURDAY
THROUGH SUNDAY OVER SOUTHERN MEXICO AND PORTIONS OF GUATEMALA AND
BELIZE. THE PRESENCE OF A LOW-LEVEL TROUGH THAT IS EXPECTED TO
INCREASE THE CYCLONIC FLOW AND MOISTURE ADVECTION INTO THE REGION,
IN COMBINATION WITH UPPER-LEVEL DIFFLUENCE WITH THE PRESENCE OF AN
UPPER-LEVEL TROUGH OVER CENTRAL MEXICO AND ALONG THE PERIPHERY OF
A HIGH LOCATED OVER THE WESTERN CARIBBEAN. ACCUMULATIONS ARE
EXPECTED TO BE AROUND 20-45MM.
FROM SUNDAY THROUGH MONDAY, PRECIPITATION IS EXPECTED TO CONTINUE
PARTICULARLY OVER VERACRUZ AND TABASCO WITH THE PRESENCE OF THE
LOW-LEVEL TROUGH AND THE SYNOPTIC PATTERN REMAINING SIMILAR TO THE
PREVIOUS DAY. LOWER RAINFALL ACCUMULATIONS ARE FORECASTED AS THE
PRECIPITABLE WATER AVAILABLE WILL DECREASE. OVER THE REST OF
CENTRAL AMERICA LIGHT PRECIPITATION IS EXPECTED TO OCCUR EACH DAY,
MOSTLY DUE TO LOW-LEVEL TROUGHS AND MOISTURE ADVECTION. IN COSTA
RICA AND PANAMA, THE MONSOON TROUGH WILL AID THE DEVELOPMENT OF
RAINFALL AND SHOWERS EACH DAY.
TROPICAL SOUTH AMERICA:
THE MAIN DRIVERS OF PRECIPITATION OVER TROPICAL SOUTH AMERICA ARE
EXPECTED TO BE LOW-LEVEL TROUGHS, LOW-LEVEL MOISTURE CONVERGENCE,
MOISTURE ADVECTION, DIURNAL HEATING AND LOCAL EFFECTS. A DRYING
TREND IS EXPECTED PARTICULARLY OVER EASTERN COLOMBIA AND VENEZUELA
WITH THE PRESENCE OF THE NOCTURNAL JET.
DURING EACH DAY OF THE FORECAST PERIOD, PRECIPITATION IS EXPECTED
OVER WESTERN COLOMBIA AND PORTIONS OF ECUADOR WITH MOISTURE BEING
ADVECTED FROM THE PACIFIC OCEAN, BUT WITH THE LOW-LEVEL FLOW
REMAINING RELATIVELY WEAK AND DISORGANIZED, TOTAL ACCUMULATIONS OF
RAIN ARE EXPECTED TO STAY BELOW 35MM. ANOTHER REGION THAT SHOULD
RECEIVE SOME PRECIPITATION EACH DAY OF THE FORECAST PERIOD IS THE
GUIANAS AND PORTIONS OF THE NORTHEASTERN COAST OF BRAZIL WITH A
PLUME OF MOISTURE ADVECTING HIGH VALUES OF PRECIPITABLE WATER INTO
THE COAST.
AN AREA OF INTEREST TODAY THROUGH SATURDAY IS THE AMAZON REGION OF
PERU, AND BRAZIL WHERE AN ENHANCEMENT IN UPPER-LEVEL DIVERGENCE
AND LOW-LEVEL CONVERGENCE WILL GENERATE INSTABILITY AND ALLOW THE
DEVELOPMENT OF STRONG CONVECTION IN THE AREA. THESE CONDITIONS
WILL ALLOW FOR CONVECTION TO CONTINUE DEVELOPING OVER CENTRAL
BRAZIL, PARTICULARLY AS A LOW-LEVEL TROUGH IS EXPECTED IN THE
REGION FROM SATURDAY THROUGH SUNDAY. MAXIMUM TOTAL RAINFALL IS
EXPECTED TO REACH 30-60MM DURING THIS PERIOD.
POSITIONS OF TROPICAL/EASTERLY WAVES INITIALIZED AT 12 UTC
TYP SOF INIT 20/00 20/12 21/00 21/12 22/00 23/12 23/00
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