268
FXCA20 KWBC 161914
PMDCA
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
314 PM EDT TUE SEP 16 2025
FORECAST BULLETIN 16 SEPTEMBER 2025 AT 1915 UTC:
SYNOPSIS:
THE PRECIPITATION EXPECTED OVER MUCH OF THE REGION OVER THE NEXT
FEW DAYS WILL CONTINUE TO OCCUR DUE TO OROGRAPHIC AND LOCAL
EFFECTS. HOWEVER, THE PRESENCE OF A DEEP TROUGH IN THE
MID-LATITUDES, MOISTURE DUE TO THE PRESENCE OF THE MONSOON TROUGH,
AND A WESTWARD MOVING TROPICAL WAVE WILL AID IN INCREASING
PRECIPITATION TOTALS IN MEXICO AND CENTRAL AMERICA. IN THE BAHAMAS
AND THE GREATER ANTILLES, THE INTERACTION OF THE DEEP TROUGH WILL
BRING DAILY PRECIPITATION AND POTENTIALLY SEVERE WEATHER TO CUBA
AND THE BAHAMAS. WHILE THE ENTRANCE OF A TROPICAL WAVE WILL BRING
PRECIPITATION TO HISPANIOLA AND PUERTO RICO AT THE END OF THE
WEEK. IN SOUTH AMERICA, LOW-LEVEL MOISTURE ENTERING INTO THE WEST
COAST OF COLOMBIA WILL BRING HIGH PRECIPITATION TO THE NORTHWEST
OF SOUTH AMERICA, WHILE IN NORTHCENTRAL SOUTH AMERICA, MOST
PRECIPITATION WILL BE CAUSED BY LOCALLY INDUCED CONVECTION.
MEXICO AND CENTRAL AMERICA:
THE MAIN PRECIPITATION WILL BE CAUSED BY A DEEP TROUGH IN THE
MIDLATITUDES EXTENDING FROM THE SOUTHERN UNITED STATES AND WITH A
BASE IN THE YUCATAN PENINSULA FOR THE NEXT FEW DAYS, RESULTING IN
HEAVY PRECIPITATION FOR MUCH OF SOUTHEAST MEXICO AND GUATEMALA. IN
THE YUCATAN PENINSULA AND GUATEMALA, THE INTERACTION BETWEEN THE
UPPER-LEVEL TROUGH AND THE RIDGE TO THE WEST OF IT WILL ALLOW FOR
UPPER-LEVEL DIVERGENCE TO PERSIST IN THE AREA. THE UPPER TROUGH IS
BEING VERTICALLY PROJECTED INTO THE LOWER LEVELS IN THE FORM OF AN
INVERTED TROUGH. WITH LOWER LEVEL CONVERGENCE ALONG WITH AMPLE
MOISTURE ADVECTION, THIS SHOULD RESULT IN HEAVY PRECIPITATION IN
THE YUCATAN PENINSULA AND INLAND, INCLUDING CAMPECHE, CHIAPAS, AND
GUATEMALA, PARTICULARLY TODAY INTO WEDNESDAY. THE PRECIPITATION
TOTALS IN THE INTERIOR REGION, INCLUDING CAMPECHE AND GUATEMALA,
WILL PEAK TODAY AT ABOUT 30-60MM. BY FRIDAY, THE PRESENCE OF THE
MONSOON TROUGH AND CYCLONIC CIRCULATION ASSOCIATED WITH IT WILL
BRING SIGNIFICANT AMOUNTS OF MOISTURE TO THE SOUTHERN COAST OF
THIS REGION, INCLUDING OAXACA AND CHIAPAS IN MEXICO, GUATEMALA, EL
SALVADOR, AND PARTS OF HONDURAS AND NICARAGUA. THE LARGEST AMOUNTS
OF MOISTURE ARE EXPECTED TO ENTER INTO THE REGION IN THE EARLY
MORNING ON FRIDAY, AND WITH ADDITIONAL OROGRAPHIC EFFECTS, WILL
DROP HEAVY PRECIPITATION OF UP TO 30-60MM ON FRIDAY, WITH LOCALLY
HIGHER AMOUNTS POSSIBLE IN THE GULF OF FONSECA REGION. IN
NORTHWESTERN MEXICO, MID-LEVEL SHORTWAVE TROUGHING THROUGHOUT MUCH
OF THE COAST IN SONORA, SINALOA, JALISCO, AND BAJA CALIFORNIA SUR,
WILL HELP TO PROMOTE INSTABILITY. THERE IS ADDITIONAL AND
SIGNIFICANT LOW-LEVEL MOISTURE, ASSOCIATED WITH THE WESTWARD
MOVING TROPICAL STORM MARIO, ADVECTING INTO THE REGION FLOWING
FROM THE SOUTHEAST ON TUESDAY. ONSHORE FLOW WITH DIURNAL EFFECTS
WILL AID IN THE DEVELOPMENT OF CONVECTION EACH DAY IN THE FORECAST
PERIOD, OF UP TO 20-45MM IN THE SINALOA, SOUTHWEST CHIHUAHUA, AND
NORTHWEST DURANGO REGION. IN COSTA RICA AND PANAMA, THE
COMBINATION OF THE PRESENCE OF THE MONSOON TROUGH, MOISTURE
AVAILABILITY, AND UPPER-LEVEL DIVERGENCE WILL RESULT IN
PRECIPITATION IN EACH OF THE THREE DAYS IN THE FORECAST PERIOD,
WITH THE HIGHEST AMOUNTS REACHING 30-60MM ON WEDNESDAY AND
THURSDAY.
BAHAMAS AND CARIBBEAN:
THE PRESENCE OF THE PREVIOUSLY MENTIONED DEEP MIDLATITUDE TROUGH
WILL CONTINUE TO EXTEND INTO THE YUCATAN CHANNEL FROM THE SOUTHERN
UNITED STATES, IN WHICH THE DIVERGENT SIDE OF THE TROUGH WILL BE
SITUATED OVER CUBA AND THE BAHAMAS OVER THE NEXT FEW DAYS.
MOISTURE IS EXPECTED TO GRADUALLY INCREASE BEGINNING TODAY DUE TO
THE PROJECTION OF THE TROUGH INTO THE LOWER LEVELS, AND CONTINUE
TO INCREASE THROUGH THE END OF THE WEEK, WHICH AT THAT POINT WILL
BE DUE TO THE WESTWARD MOVEMENT OF AN INCOMING TROPICAL WAVE,
CURRENTLY LOCATED AT AROUND 59W. THIS WILL RESULT IN DAILY
CONVECTION OVER THE NEXT FEW DAYS, WITH TOTALS REACHING UP TO
20-35MM IN CUBA AND 20-45MM IN THE BAHAMAS ON THURSDAY AND FRIDAY.
ADDITIONALLY, THERE IS A MARGINAL RISK OF SEVERE WEATHER FOR CUBA
LOCATIONS TODAY, WEDNESDAY, AND THURSDAY, AND FOR THE BAHAMAS ON
THURSDAY. IN HISPANIOLA AND PUERTO RICO, THE ENTRANCE OF THE
TROPICAL WAVE WILL BRING HEAVY PRECIPITATION TO PUERTO RICO ON
THURSDAY AND HISPANIOLA FRIDAY, WITH THE HIGHEST TOTALS REACHING
25-50MM IN HISPANIOLA.
TROPICAL SOUTH AMERICA:
THE PRESENCE OF THE PANAMANIAN LOW AND THE LOW-LEVEL CIRCULATION
ASSOCIATED WITH IT, PARTICULARLY THE LOW-LEVEL WESTERLY FLOW AND
MOISTURE ADVECTION, WILL BRING PRECIPITATION TO THE WEST COAST OF
COLOMBIA AND ECUADOR FOR THE NEXT THREE DAYS. FOR COLOMBIA, THERE
WILL BE SIGNIFICANT MOISTURE AVAILABLE, WHICH COULD RESULT IN
PRECIPITATION TOTALS REACHING 30-60MM ON THURSDAY AND FRIDAY.
CYCLONIC FLOW FURTHER NORTH, IN NORTHWEST COLOMBIA AND WEST
VENEZUELA, WITH LOW-LEVEL MOISTURE INFLOW WILL BRING PRECIPITATION
OF UP TO 20-45MM DAILY OVER THE NEXT FEW DAYS. IN THE
NORTH-CENTRAL AREAS OF SOUTH AMERICA, THE PRECIPITATION EXPECTED
OVER THE NEXT THREE DAYS WILL BE LARGELY DUE TO AN INFLUX OF
LOW-LEVEL MOISTURE AND CONVERGENCE IN THE LOWER LEVELS, WHICH WILL
RESULT IN LOCAL AND OROGRAPHICALLY INDUCED CONVECTION.
POSITIONS OF TROPICAL/EASTERLY WAVES INITIALIZED AT 12 UTC
TYPE SOF INIT 17/00 17/12 18/00 18/12 19/00 19/12 20/00 20/12
TW 20N 41W 43W 45W 47W 49W 51W 53W 55W 57W
TW 25N 59W 62W 65W 68W 70W 72W 74W 75W 76W
TW 20N 78W 80W 82W 84W 86W 88W 90W 93W 96W
TW 15N 102W 104W 105W 107W 109W 111W 113W 115W 117W
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