643
FXCA20 KWBC 121807
PMDCA
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
206 PM EDT FRI SEP 12 2025
FORECAST BULLETIN 12 SEPTEMBER 2025 AT 1800 UTC:
THE NATIONAL HURRICANE CENTER CONTINUES TO MONITOR TROPICAL STORM
MARIO, WHICH IS MOVING VERY CLOSE TO THE WESTERN COAST OF MEXICO.
ALTHOUGH THE STORM IS SMALL, IT IS DRAWING IN HIGHER THAN AVERAGE
MOISTURE ALONG THE PACIFIC COAST OF MEXICO AND WILL CONTINUE TO
SUPPORT SHOWERS AND THUNDERSTORMS TODAY AND SATURDAY. OVER THE
NEXT THREE DAYS, FROM TODAY THROUGH MONDAY MORNING, WIDESPREAD
RAINFALL IS EXPECTED ACROSS MANY PARTS OF CENTRAL AMERICA AND
SOUTHERN AND WESTERN MEXICO. ABUNDANT TROPICAL MOISTURE WILL
COMBINE WITH LOCAL TERRAIN EFFECTS AND UPPER LEVEL DYNAMICS TO
PRODUCE REPEATED ROUNDS OF SHOWERS AND THUNDERSTORMS. THREE DAY
RAINFALL TOTALS COULD REACH AS HIGH AS 150 MM IN ISOLATED PORTIONS
OF PANAMA AND COSTA RICA, AND UP TO 100 MM IN SOUTHERN GUATEMALA.
ACROSS PORTIONS OF SOUTH AND WESTERN MEXICO, FROM CHIAPAS
NORTHWARD INTO THE SIERRA MADRE OCCIDENTAL, THREE DAY RAINFALL
TOTALS OF 75 TO 100 MM ARE POSSIBLE, WITH LOCALLY HIGHER AMOUNTS
NEAR COASTAL AND MOUNTAINOUS AREAS. A FEW STRONG THUNDERSTORMS
ACROSS HISPANIOLA AND EASTERN CUBA COULD ALSO PRODUCE ISOLATED
RAINFALL TOTALS UP TO 100 MM DURING THE THREE DAY PERIOD.
THE SYNOPTIC SCALE PATTERN ACROSS THE TROPICAL REGION WILL FAVOR
DAILY RAINFALL OVER MUCH OF THE AREA. PRECIPITABLE WATER VALUES
WILL REMAIN NEAR OR ABOVE NORMAL THROUGH THE WEEKEND ACROSS
NORTHERN CENTRAL AMERICA, SOUTHERN AND WESTERN MEXICO, PANAMA,
COSTA RICA, NORTHWESTERN SOUTH AMERICA, AND MANY OF THE CARIBBEAN
ISLANDS. ONE EXCEPTION WILL BE AN AREA OF SLIGHTLY DRIER AIR
CAUSED BY SAHARAN DUST, WHICH IS PRESENT OVER NICARAGUA, HONDURAS,
PARTS OF THE LEEWARD ISLANDS, AND JAMAICA. THIS DRY AIR WILL
SUPPRESS RAINFALL THROUGH AT LEAST SATURDAY IN THOSE LOCATIONS,
BUT WILL GRADUALLY LIFT OUT BY LATE SATURDAY INTO SUNDAY. BY
SUNDAY, MOISTURE VALUES WILL BEGIN TO DECREASE TOWARD NEAR TO
SLIGHTLY BELOW NORMAL ACROSS NORTHERN CENTRAL AMERICA AND SOUTHERN
MEXICO, WHILE REMAINING SLIGHTLY ABOVE NORMAL FROM NICARAGUA
SOUTHWARD INTO NORTHWESTERN SOUTH AMERICA, THE CARIBBEAN ISLANDS,
THE BAHAMAS, AND NORTHWESTERN MEXICO.
IN THE UPPER LEVELS, A HIGH PRESSURE CENTER IS POSITIONED OVER
NORTHWESTERN MEXICO WHILE AN UPPER TROUGH IS DIGGING THROUGH THE
GULF AND INTO THE YUCATAN PENINSULA. FARTHER EAST, ANOTHER HIGH
PRESSURE LIES JUST EAST OF THE BAHAMAS, AND A LOW PRESSURE CENTER
IS LOCATED IN THE CENTRAL ATLANTIC. BY SUNDAY, THIS PATTERN WILL
SHIFT SLIGHTLY EASTWARD, WITH THE HIGH OVER NORTHWESTERN MEXICO
SLIDING A BIT TO THE EAST AND SOUTH, AND THE GULF TROUGH
CONTINUING EAST BUT STILL DIGGING INTO THE YUCATAN. THE HIGH EAST
OF THE BAHAMAS WILL ALSO DRIFT A LITTLE FARTHER EAST AND BE
CENTERED NORTH OF PUERTO RICO. AT MID LEVELS, A BROAD TROUGH IS
LOCATED JUST WEST OF THE BAJA CALIFORNIA PENINSULA, WHILE A HIGH
PRESSURE EXTENDS FROM THE CENTRAL UNITED STATES INTO NORTHERN
MEXICO. A REFLECTION OF THE GULF TROUGH IS ALSO EVIDENT IN THE MID
LEVELS, AND FARTHER EAST A HIGH PRESSURE REMAINS JUST EAST OF THE
BAHAMAS ALONG WITH A MID LEVEL LOW IN THE CENTRAL ATLANTIC. FOR
THE MOST PART THE FEATURES ARE VERTICALLY STACKED BETWEEN THE MID
AND UPPER LEVELS. A SHORTWAVE MID-LEVEL TROUGH IS ALSO PRESENT
OVER CENTRAL AMERICA. BY SUNDAY, THE HIGH PRESSURE OVER NORTHERN
MEXICO IS FORECAST TO WEAKEN SUBSTANTIALLY, BUT THE MID LEVEL
TROUGH OVER THE EASTERN GULF AND YUCATAN PENINSULA WILL PERSIST.
THE MID LEVEL HIGH EAST OF THE BAHAMAS WILL EXTEND SOUTHWARD FROM
THE EAST CENTRAL ATLANTIC INTO THE GREATER ANTILLES. THE MID LEVEL
TROUGH OVER CENTRAL AMERICA WILL DRIFT A BIT WEST, HOWEVER, WITH
ITS AXIS OVER GUATEMALA AND SOUTHERN MEXICO BY SUNDAY.
RAINFALL TIMING AND AMOUNTS WILL VARY DURING THE THREE DAY PERIOD.
ACROSS WESTERN MEXICO, TODAY INTO SATURDAY WILL BE THE WETTEST
PERIOD, WITH MANY SEPARATE AREAS WITH RAINFALL TOTALS OF 25 TO 50
MM WITH ISOLATED HIGHER AMOUNTS ALONG THE WEST COAST AND INTO THE
SIERRA MADRE OCCIDENTAL. FROM SATURDAY INTO SUNDAY, RAINFALL WILL
DECREASE SLIGHTLY, WITH MANY AREAS STILL RECEIVING 25 TO 35 MM AND
ISOLATED POCKETS NEAR 50 MM. FROM SUNDAY INTO MONDAY, MOST AREAS
CAN EXPECT 15 TO 30 MM WITH ISOLATED PEAKS NEAR 45 MM. ACROSS
CENTRAL AMERICA, TODAY INTO SATURDAY WILL BE THE DRIEST PERIOD FOR
HONDURAS AND NICARAGUA BECAUSE OF THE SAHARAN DUST. ELSEWHERE,
INCLUDING EL SALVADOR, COSTA RICA, AND PANAMA, SCATTERED SHOWERS
AND THUNDERSTORMS WILL BRING 25 TO 50 MM WITH LOCALLY HIGHER
AMOUNTS ALONG THE MOUNTAINOUS AREAS. AS THE DRY AIR DEPARTS FROM
SATURDAY AFTERNOON ONWARD, RAINFALL COVERAGE WILL INCREASE ACROSS
CENTRAL AMERICA, ESPECIALLY FOR COSTA RICA AND PANAMA WHERE
SIGNIFICANT RAINFALL TOTALS SURPASSING 75 MM ARE POSSIBLE ALONG
THE MONSOON TROUGH. OTHER PORTIONS OF CENTRAL AMERICA, SUCH AS EL
SALVADOR AND GUATEMALA, CAN RECEIVE UP TO 50 MM FROM SATURDAY INTO
SUNDAY, WHILE MOST OTHER LOCATIONS SEE 15 TO 35 MM. FROM SUNDAY
INTO MONDAY, RAINFALL ACROSS CENTRAL AMERICA BECOMES MORE
GENERALIZED, WITH MANY AREAS RECEIVING MAXIMUM RAINFALL TOTALS
BETWEEN 20 AND 45 MM, PARTICULARLY ACROSS GUATEMALA, EL SALVADOR,
AND NEAR COSTA RICA AND PANAMA ALONG THE MONSOON TROUGH.
THE CARIBBEAN AND THE BAHAMAS WILL EXPERIENCE ISOLATED MODERATE TO
HEAVY RAINFALL. A STATIONARY FRONT ACROSS THE NORTHERN BAHAMAS
WILL BRING OCCASIONAL HEAVY SHOWERS ACROSS THE NORTHERN BAHAMAS
AND PORTIONS OF CUBA, WITH POSSIBLE STRONG THUNDERSTORMS, CAUSING
RAINFALL TOTALS UP TO 25 TO 50 MM TODAY INTO SATURDAY, THEN 20 TO
35MM FROM SATURDAY INTO SUNDAY. STRONG THUNDERSTORMS ARE STILL
POSSIBLE ON SATURDAY, HOWEVER. RAINFALL ACROSS DECREASING TO 10
TO 25 MM BY SUNDAY NIGHT. THE GREATER ANTILLES WILL SEE SCATTERED
TRADE WIND SHOWERS AND A FEW STRONG THUNDERSTORMS, ESPECIALLY OVER
THE ALREADY MENTIONED CUBA, BUT HISPANIOLA MAY ALSO OBSERVE
ISOLATED HEAVY RAIN IN THE MOUNTAINOUS SECTIONS, WHERE ISOLATED
RAINFALL AMOUNTS UP TO 50 MM ARE POSSIBLE TODAY AND AGAIN
SATURDAY. ELSEWHERE ACROSS THE CARIBBEAN, SCATTERED SHOWERS WILL
PRODUCE 10 TO 35 MM TODAY AND SATURDAY, DECREASING TO 10 TO 25 MM
ON SUNDAY INTO MONDAY. ACROSS NORTHERN SOUTH AMERICA, THE WETTEST
CONDITIONS WILL REMAIN OVER WESTERN COLOMBIA AND NORTHWESTERN
ECUADOR WHERE UP TO 50 MM OF RAIN IS EXPECTED TODAY AND AROUND 45
MM ON SATURDAY AND SUNDAY. ELSEWHERE IN NORTHERN SOUTH AMERICA,
SHOWERS AND THUNDERSTORMS DRIVEN BY LOCAL EFFECTS WILL BRING DAILY
RAINFALL TOTALS OF 15 TO 25 MM, WITH ISOLATED 45 MM POSSIBLE
ACROSS VENEZUELA ON SUNDAY ALONG A LOW LEVEL TROUGH.
OVERALL, MUCH OF THE TROPICAL REGION WILL CONTINUE TO RECEIVE SOME
RAINFALL EACH DAY THROUGH MONDAY MORNING. THE WETTEST CONDITIONS
ARE EXPECTED TODAY INTO SATURDAY, FOLLOWED BY A GRADUAL DECREASE
IN RAINFALL COVERAGE AND INTENSITY ON SUNDAY, ALTHOUGH SCATTERED
SHOWERS AND THUNDERSTORMS WILL STILL PERSIST ACROSS MEXICO,
CENTRAL AMERICA, THE CARIBBEAN, AND NORTHERN SOUTH AMERICA.
APPROXIMATE POSITIONS OF TROPICAL/EASTERLY WAVES
TYPE SOF 12/12 13/00 13/12 14/00 14/12 15/00 15/12
TW 20N 55W 57W 59W 62W 54W 66W 68W
TW 22N 44W 46W 48W 50W 52W 54W 56W
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