622
FXCA20 KWBC 231749
PMDCA
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
149 PM EDT TUE SEP 23 2025
FORECAST BULLETIN 23 SEPTEMBER 2025 AT 1800 UTC:
THE BAHAMAS AND THE CARIBBEAN:
A TROPICAL WAVE BREAKING THROUGH THE REGION IS EXPECTED TO IMPACT
THE LESSER AND GREATER ANTILLES FROM TUESDAY INTO FRIDAY. HEAVY
PRECIPITATION IS EXPECTED FROM TUESDAY TO WEDNESDAY OVER THE
LESSER ANTILLES, PARTICULARLY OVER THE LEEWARD ISLAND WITH A
MAXIMUM BETWEEN 30-60MM. AS THE WAVE PROPAGATES
WEST-NORTHWESTWARD, IT WILL CONTINUE CAUSING SIGNIFICANT RAINFALL
ACCUMULATION OVER THE U.S VIRGIN ISLANDS AND PUERTO RICO FROM
WEDNESDAY INTO THURSDAY, AND WILL ENHANCE PRECIPITATION OVER
HISPANIOLA FROM THURSDAY TO FRIDAY. THIS TROPICAL WAVE, CURRENTLY
BEING MONITORED BY THE NATIONAL HURRICANE CENTER, HAS A 60% CHANCE
OF TROPICAL DEVELOPMENT IN THE NEXT SEVEN DAYS AS IT REACHES THE
SOUTHWESTERN ATLANTIC. ANOTHER TROPICAL WAVE CURRENTLY AROUND 48W,
MOVING WEST-NORTHWESTWARD IS ALSO BEING MONITORED BY THE NHC, HAS
A 90% CHANCE OF FORMATION, AND IS EXPECTED TO BRING HIGH VALUES OF
PRECIPITABLE WATER IN THE WESTERN TROPICAL ATLANTIC BY THE END OF
THE WORKWEEK, KEEPING CONDITIONS FAVORABLE FOR THUNDERSTORMS FOR
PUERTO RICO AND THE LESSER ANTILLES.
AN UPPER-LEVEL TROUGH OVER THE SOUTHERN UNITED STATES EXTENDING
WITH A BASE IN THE YUCATAN PENINSULA, SLOWLY PROPAGATING EASTWARD,
WILL ENHANCE UPPER-LEVEL DIVERGENCE OVER CUBA AND THE BAHAMAS IN
THE NEXT THREE DAYS. THIS ALONG WITH LOW-LEVEL TROUGHS AND
MOISTURE ADVECTION, AND LOCAL EFFECTS IS EXPECTED TO PRODUCE
CONVECTIVE ACTIVITY, PARTICULARLY FOR THE BEGINNING OF THE
FORECAST PERIOD. AS PWAT SLIGHTLY DECREASES TOWARDS THE END OF THE
WORKWEEK, LESS RAINFALL ACCUMULATIONS ARE EXPECTED.
MEXICO AND CENTRAL AMERICA:
HURRICANE NARDA, IS FORECAST TO CONTINUE MOVING GENERALLY WESTWARD
AWAY FROM THE COAST OF MEXICO. MOISTURE ASSOCIATED WITH THE
TROPICAL CYCLONE IN COMBINATION WITH OROGRAPHIC LIFTING AND
DIURNAL HEATING WILL ENHANCE CONVECTION IN THAT REGION TODAY AND
WEDNESDAY, WITH LOWER TOTALS COMPARED TO PREVIOUS DAYS.
IN SOUTHERN MEXICO AND GUATEMALA, A MID- TO UPPER- LEVEL TROUGH
WILL RESULT IN A FAVORABLE ENVIRONMENT FOR CONVECTIVE ACTIVITY FOR
THE NEXT THREE DAYS. THIS IN COMBINATION WITH LOW-LEVEL MOISTURE
CONVERGENCE, WILL CAUSE SIGNIFICANT RAINFALL OVER THE REGION,
PARTICULARLY FROM TUESDAY TO WEDNESDAY WITH THE PASSAGE OF A
TROPICAL WAVE CURRENTLY AROUND 91W.
SIGNIFICANT RAINFALL IS EXPECTED OVER SIERRA MADRE OCCIDENTAL,
FROM WEDNESDAY TO FRIDAY WITH MAXIMUM TOTALS FROM 30-60MM EACH
DAY. THIS INCREASE IN PRECIPITATION WILL BE ASSOCIATED WITH THE
DEVELOPMENT OF A LOW-LEVEL TROUGH WEST OF SONORA AND SINALOA, A
HIGH INCREASE IN PWAT, ENHANCED DIVERGENCE IN THE PERIPHERY OF THE
RIDGE AND WITH SUPPORT FROM A MID-LEVEL TROUGH.
THE NORTHEAST OF MEXICO WILL BE ANOTHER AREA OF INTEREST
PARTICULARLY FROM THURSDAY INTO FRIDAY AND THE WEEKEND, AS A COLD
FRONT WILL MOVE INTO THE REGION, INCREASING THE CHANCES OF
RAINFALL.
PRECIPITATION IN PARTS OF CENTRAL AMERICA, INCLUDING NICARAGUA,
HONDURAS WILL BE LIMITED FROM TUESDAY THROUGH THURSDAY DUE TO THE
INTRUSION OF DRY AIR INTO THE REGION, BUT RAINFALL DUE TO LOCALLY
INDUCED CONVECTION CAN BE EXPECTED. OVER COSTA RICA AND PANAMA,
MOST OF THE PRECIPITATION WILL BE DUE TO THE PRESENCE OF THE
MONSOON TROUGH IN THE AREA AND LOW-LEVEL CIRCULATION THAT WILL
FAVOR MOIST ONSHORE FLOW FOR THE NEXT THREE DAYS.
SOUTH AMERICA:
IN TROPICAL SOUTH AMERICA, CONDITIONS WILL BE MORE FAVORABLE,
COMPARED TO PREVIOUS DAYS, FOR THE DEVELOPMENT OF DAILY
CONVECTION, AS MOISTURE INCREASES ACROSS THE REGION THROUGHOUT THE
FORECAST PERIOD. MOST OF THE ACTIVITY IN TROPICAL SOUTH AMERICA IS
EXPECTED FROM THURSDAY TO FRIDAY IN THE WESTERN REGION OF
COLOMBIA, WITH LONG FETCH MOIST FLOW COMING FROM THE EASTERN
PACIFIC, ENHANCING LOW LEVEL MOISTURE CONVERGENCE INTO THE REGION,
ALONG WITH THE SUPPORT OF A MID-LEVEL TROUGH IN THE REGION.
POSITIONS OF TROPICAL/EASTERLY WAVES INITIALIZED AT 12 UTC
TYPE SOF INIT 24/00 24/12 25/00 25/12 26/00 26/12 27/00 22/12
TW 21N 48W 51W 54W 56W 58W 59W 60W 61W 62W
TW 19N 60W 63W 65W 67W 69W 71W 73W 74W ---
TW 17N 91W 93W 95W 97W 99W 101W 104W 106W 108W
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