400
FXCA20 KWBC 151925
PMDCA
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
324 PM EDT MON SEP 15 2025
FORECAST BULLETIN 15 SEPTEMBER 2025 AT 1930 UTC:
SYNOPSIS:
THE OVERALL WEATHER PATTERN FROM MONDAY THROUGH WEDNESDAY WILL BE
DOMINATED BY LOW-LEVEL MOISTURE CONVERGENCE, OROGRAPHIC LIFTING
AND DIURNAL HEATING FOR MOST OF THE TROPICAL REGION. THE MOST
SIGNIFICANT RAINFALL IN THE NEXT THREE DAYS IS EXPECTED ACROSS
WESTERN AND SOUTHERN MEXICO, CENTRAL AMERICA, CUBA AND THE
BAHAMAS. THE ENHANCEMENT OF PRECIPITATION ALONG THE PACIFIC COAST
OF MEXICO IS ASSOCIATED WITH TROPICAL STORM MARIO AND A TROPICAL
WAVE BEING MONITORED BY THE NHC FOR POTENTIAL TROPICAL CYCLONE
DEVELOPMENT WITH A 70% CHANCE OF FORMATION IN THE NEXT SEVEN DAYS
ACCORDING TO THE LATEST OUTLOOK. IN CENTRAL AMERICA, AREAS OF
INTEREST FROM TODAY INTO THURSDAY ARE GUATEMALA AND EL SALVADOR.
SIGNIFICANT PRECIPITATION IS EXPECTED OVER COSTA RICA, LARGELY
ASSOCIATED WITH THE MONSOON TROUGH AND THE DEVELOPMENT OF A BROAD
LOW-LEVEL CIRCULATION. IN THE CARIBBEAN, AN UPPER LEVEL TROUGH AND
A SHEAR LINE WILL BRING PRECIPITATION TO CUBA AND BAHAMAS. IN
NORTHERN SOUTH AMERICA, MOST OF THE PRECIPITATION IS DUE TO
LOW-LEVEL MOISTURE CONVERGENCE, WITH HIGHER TOTALS EXPECTED IN THE
NORTHWESTERN SECTIONS OF THE CONTINENT
MEXICO AND CENTRAL AMERICA:
TROPICAL STORM MARIO, IS CURRENTLY LOCATED WEST OF BAJA CALIFORNIA
PENINSULA AND CONTINUES MOVING IN THE PACIFIC, INCREASING MOISTURE
OVER BAJA CALIFORNIA AND THE GULF OF CALIFORNIA. THE INCREASED
MOISTURE ALONG WITH A MID-LEVEL TROUGH AND TOPOGRAPHY WILL ALLOW
PRECIPITATION AND THUNDERSTORMS PARTICULARLY ALONG THE SIERRA
MADRE OCCIDENTAL FROM MONDAY TO THURSDAY. THE ENHANCEMENT OF
MOISTURE FOR WESTERN MEXICO WILL CONTINUE FROM TUESDAY TO THURSDAY
AS A TROPICAL WAVE CURRENTLY LOCATED AROUND 100W MOVES ALONG THE
WESTERN COAST OF MEXICO.
THE SYNOPTIC PATTERN FOR MEXICO IS EXPECTED TO BE DOMINATED FOR
THE NEXT THREE DAYS BY AN UPPER-LEVEL HIGH NORTHWEST OF MEXICO,
AND AN UPPER-LEVEL TROUGH EXTENDING FROM THE SOUTHEASTERN UNITED
STATES AND INTO THE YUCATAN PENINSULA. THE BASE OF THE UPPER LEVEL
TROUGH WILL FAVOR RAINFALL OVER SOUTHERN MEXICO INTO PARTS OF
CENTRAL AMERICA. FROM MONDAY TO TUESDAY A LOW- TO MID- LEVEL
TROUGH IS EXPECTED TO ENHANCE PRECIPITATION MAINLY OVER BELIZE AND
PARTS OF YUCATAN AND GUATEMALA DUE TO THE ADVECTION OF VORTICITY
ASSOCIATED WITH THE TROUGH. ANOTHER LOW-LEVEL TROUGH WILL ENHANCE
LOW-LEVEL CONVERGENCE OVER NICARAGUA FROM MONDAY INTO TUESDAY.
PRECIPITATION WILL CONTINUE OVER GUATEMALA FROM TUESDAY THROUGH
WEDNESDAY AS A LOW-LEVEL TROUGH WILL CONTINUE TO INTRODUCE HIGH
MOISTURE INTO THE REGION, FAVORING MOISTURE CONVERGENCE. FROM
WEDNESDAY INTO THURSDAY AN AREA OF INTEREST IS EL SALVADOR, AS THE
BASE OF THE UPPER LEVEL TROUGH WILL REACH THE REGION, AND A
TROPICAL WAVE WILL MOVE INTO CENTRAL AMERICA, INCREASING THE
POTENTIAL FOR MCS.
ALONG COSTA RICA AND PANAMA, HIGH PRECIPITABLE WATER IS EXPECTED
ALONG THE MONSOON TROUGH, WHILE A DEVELOPING BROAD LOW LEVEL
CIRCULATION WILL FAVOR MOIST ONSHORE FLOW, INCREASING THE RAINFALL
COVERAGE AND AMOUNT OVER THE REGION.
BAHAMAS AND THE CARIBBEAN:
TWO TROPICAL WAVES WILL BRING ENOUGH MOISTURE TO PRODUCE
PRECIPITATION IN COMBINATION TO DIURNAL HEATING AND LOCAL EFFECTS
DURING THE FORECAST PERIOD PARTICULARLY IN THE EASTERN CARIBBEAN.
AN ENHANCEMENT IN PRECIPITATION WILL BE SEEN FROM WEDNESDAY TO
THURSDAY AS A RETROGRADING TUTT WILL MOVE INTO THE AREA WITH THE
AXIS POSITIONED OVER PUERTO RICO ON THURSDAY, AFFECTING MOSTLY
DOMINICAN REPUBLIC, PUERTO RICO AND THE LESSER ANTILLES.
FROM TUESDAY TO THURSDAY, CUBA AND THE BAHAMAS ARE FORECAST TO
EXPERIENCE INCREASED PRECIPITATION. THIS IS DUE TO A COMBINATION
OF FACTORS: THE PASSAGE OF TROPICAL WAVES, THE DEVELOPMENT OF A
SHEAR LINE ON WEDNESDAY THAT WILL PERSIST THROUGH THURSDAY,
ENHANCED UPPER-LEVEL DIVERGENCE ASSOCIATED WITH AN UPPER-LEVEL
TROUGH EXTENDING FROM SOUTHEAST UNITED STATES INTO THE YUCATAN
THROUGHOUT THE FORECAST PERIOD, AND THE LIKELY PRESENCE OF
MID-LEVEL SHORTWAVE TROUGHS OVER CUBA AND THE NORTHERN BAHAMAS. A
MARGINAL RISK FOR SEVERE WEATHER EXISTS FOR CUBA AND THE NORTHERN
BAHAMAS FROM TUESDAY TO WEDNESDAY, INCREASING TO A SLIGHT RISK FOR
SEVERE WEATHER FROM WEDNESDAY TO THURSDAY.
TROPICAL SOUTH AMERICA:
MOST OF THE ACTIVITY IN TROPICAL SOUTH AMERICA IS EXPECTED IN THE
WESTERN REGION OF COLOMBIA, WITH LONG FETCH MOIST FLOW COMING
FROM THE EASTERN PACIFIC ENHANCING LOW LEVEL MOISTURE CONVERGENCE
INTO THE REGION PARTICULARLY FROM TUESDAY INTO THURSDAY. ACROSS
THE REST OF TROPICAL SOUTH AMERICA, SHOWERS AND THUNDERSTORMS WILL
BE OBSERVED EACH DAY THROUGH THE FORECAST PERIOD. THE PRIMARY
DRIVERS WILL BE LOW-LEVEL MOISTURE CONVERGENCE, DIURNAL HEATING,
AND LOCAL TOPOGRAPHIC EFFECTS.
POSITIONS OF TROPICAL/EASTERLY WAVES INITIALIZED AT 12 UTC
TYPE SOF INIT 16/00 16/12 17/00 17/12 18/00 18/12 19/00 19/12
TW 20 38 40 42 43 44 45 47 49 51
TW 25 52 55 58 61 64 67 70 72 74
TW 20 71 73 76 79 82 85 88 91 94
TW 15 100 102 103 104 106 108 109 111 113
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