198
FXCA20 KWBC 181841
PMDCA
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
141 PM EST TUE NOV 18 2025
FORECAST BULLETIN 18 NOVEMBER 2025 AT 1840 UTC:
THE BAHAMAS AND CARIBBEAN:
A LOW-LEVEL TROUGH IS EXPECTED TO BRING PRECIPITATION TO THE
LEEWARD ISLANDS AND EASTERN PUERTO RICO BY ADVECTING MOISTURE AND
ENHANCING LOW-LEVEL MOISTURE CONVERGENCE. ANOTHER INDUCED
LOW-LEVEL TROUGH WILL BRING SOME INSTABILITY TO THE DOMINICAN
REPUBLIC, AND TURKS AND CAICOS. HOWEVER LIMITED MOISTURE WILL KEEP
THE TOTAL ACCUMULATED RAINFALL BELOW 15MM. OVER WESTERN CUBA,
LIGHT RAINFALL IS EXPECTED DUE TO A LOW-LEVEL TROUGH TO THE
SOUTHWEST OF CUBA. AFTER WEDNESDAY, A DRYING TREND IS EXPECTED
OVER MOST OF THE CARIBBEAN AND THE BAHAMAS.
MEXICO AND CENTRAL AMERICA:
AN UPPER-LEVEL TROUGH OVER SOUTHWESTERN U.S., REFLECTED IN MID-
AND LOW-LEVELS WILL BE ENHANCING INSTABILITY OVER BAJA CALIFORNIA
AND PORTIONS OF SONORA, AS THE TROUGH PROPAGATES EASTWARD FROM
TODAY THROUGH THURSDAY. FROM WEDNESDAY THROUGH THURSDAY, A
LOW-LEVEL TROUGH WILL ALSO ENHANCE LOW-LEVEL MOISTURE CONVERGENCE
OVER COAHUILA AND COMBINED WITH THE UPPER-LEVEL DIVERGENCE SHOULD
ENHANCE PRECIPITATION IN THE AREA. UPPER LEVEL DIVERGENCE WILL
CONTINUE OVER NORTHERN MEXICO FROM THURSDAY THROUGH FRIDAY AS
ANOTHER UPPER-LEVEL TROUGH APPROACHES THE WESTERN U.S. COAST, AND
PRECIPITATION IS EXPECTED TO CONTINUE. ALTHOUGH PRECIPITATION IS
EXPECTED EACH DAY OF THE FORECAST PERIOD FOR THOSE REGIONS, THE
HEAVIEST RAINFALL IS EXPECTED FROM WEDNESDAY THROUGH THURSDAY WITH
A TOTAL PRECIPITATION AROUND 30MM OVER SONORA AND COAHUILA. A
SLIGHT RISK OF SEVERE WEATHER EXISTS FOR SONORA.
OVER CENTRAL AMERICA CONDITIONS ARE EXPECTED TO REMAIN RELATIVELY
STABLE, WITH DRY AIR BEING PRESENT IN THE REGION AND AN
UPPER-LEVEL HIGH DOMINATING THE SYNOPTIC PATTERN. LIGHT
PRECIPITATION CAN BE EXPECTED TODAY OVER WESTERN GUATEMALA, AS A
LOW-LEVEL TROUGH MOVES ALONG THE PACIFIC COAST, AND OVER NICARAGUA
AS A LOW-LEVEL TROUGH ENHANCES LOW-LEVEL CONVERGENCE BRINGING SOME
MOISTURE FROM THE CARIBBEAN. THE TOTALS, HOWEVER, ARE EXPECTED TO
REMAIN ON THE LOWER END, WITH MAXIMUM PRECIPITATION STAYING BELOW
20MM.
FURTHER SOUTH IN CENTRAL AMERICA, THE MONSOON TROUGH WILL SUPPORT
RAINFALL OVER COSTA RICA AND PANAMA. THERE IS SOME DISCREPANCY,
PARTICULARLY AFTER WEDNESDAY, BETWEEN THE MODELS IN REGARDS TO
WHERE THE MAXIMUM PRECIPITATION WILL HAPPEN. THE GFS SUGGESTS THAT
MOST OF IT WILL REMAIN OFFSHORE, WHILE THE ECMWF BRINGS THE
PRECIPITATION TO THE CARIBBEAN COAST OF PANAMA. THE DIFFERENCE IS
LIKELY LINKED TO THE STRENGTH OF THE FLOW AT LOW-LEVELS AND THE
PRECIPITABLE WATER AVAILABLE IN THE REGION.
TROPICAL SOUTH AMERICA:
A PLUME OF MOISTURE ASSOCIATED WITH A LOW-LEVEL TROUGH IS EXPECTED
TO REACH GUYANA, EASTERN VENEZUELA AND TRINIDAD AND TOBAGO TODAY.
ADDITIONAL SUPPORT FROM UPPER-LEVELS IS ALSO EXPECTED WITH
INCREASING UPPER-LEVEL DIFFLUENCE, WHICH WILL ENHANCE THE
DEVELOPMENT OF CONVECTIVE ACTIVITY IN THE AREA. TOTALS REACHING
40MM CAN BE EXPECTED FROM TODAY THROUGH WEDNESDAY, WITH LOCALIZED
HIGHER AMOUNTS. THE PLUME OF MOISTURE WILL REMAIN IN THE AREA
CAUSING SOME PRECIPITATION, BUT LESS CONVECTIVE ACTIVITY IS
EXPECTED COMPARED TO THE PREVIOUS DAY. THIS IS MOSTLY BECAUSE
UPPER-LEVEL DIVERGENCE IS EXPECTED TO REMAIN OFFSHORE FROM
WEDNESDAY THROUGH FRIDAY AS AN UPPER-LEVEL TROUGH DEVELOPS IN THE
ATLANTIC EXTENDING INTO THE CARIBBEAN AND PROPAGATES EAST, WITH
ITS DIVERGENT SIDE OFF THE NORTHEASTERN COAST OF SOUTH AMERICA.
HEAVY PRECIPITATION IS EXPECTED EACH DAY OF THE FORECAST PERIOD
OVER THE WESTERN COAST OF COLOMBIA, AS LOW-LEVEL WESTERLIES ADVECT
MOISTURE FROM THE PACIFIC OCEAN TOWARDS THE COAST OF COLOMBIA.
THE REST OF TROPICAL SOUTH AMERICA CAN EXPECT RAINFALL AND
THUNDERSTORMS DUE TO DIURNAL HEATING, MOISTURE ADVECTION,
LOW-LEVEL CONVERGENCE AND LOCAL EFFECTS. MOST OF THE
PRECIPITATION, HOWEVER, IS EXPECTED TO HAPPEN OVER THE WESTERN
PORTION OF SOUTH AMERICA THROUGHOUT THE FORECAST PERIOD. AN
ENHANCEMENT IN UPPER-LEVEL DIVERGENCE IS EXPECTED FROM THURSDAY
THROUGH FRIDAY OVER WESTERN COLOMBIA AND PORTIONS OF ECUADOR,
WHICH COULD ENHANCE THE CONVECTIVE ACTIVITY IN THE AREA.
POSITIONS OF TROPICAL/EASTERLY WAVES INITIALIZED AT 12 UTC
TYP SOF INIT 19/00 19/12 20/00 20/12 21/00 21/12 22/00
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