883
FXCA20 KWBC 181741
PMDCA
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
141 PM EDT TUE APR 18 2023
FORECAST BULLETIN FROM 18 APR 2023 AT 1740 UTC: A SURFACE HIGH
PRESSURE ACROSS THE ATLANTIC CONTINUES PROMOTING EASTERLY WINDS
ACROSS THE CARIBBEAN...AND SOUTHEASTERLY WINDS ACROSS THE WESTERN
GULF OF MEXICO. THE SOUTHEASTERLY WINDS ACROSS THE GULF OF MEXICO
WILL TURN SOUTHERLY BY FRIDAY AS A LOW PRESSURE SYSTEM AND FRONTAL
BOUNDARY MOVES EAST ACROSS THE SOUTHERN US. A WEAK SURFACE LOW
PRESSURE ACROSS THE EASTERN PACIFIC IS WEAKENING...AND THE WINDS
ACROSS NORTHWESTERN SOUTH AMERICA WILL MOVE FROM THE EAST AND
OFFSHORE. THIS WOULD ALLOW FOR A DECREASE IN THE SHOWER AND
THUNDERSTORM ACTIVITY ACROSS THE WEST COAST OF ECUADOR AND
COLOMBIA...BUT WOULD ALLOW FOR OCCASIONAL THUNDERSTORMS TO THE
EAST OF THE CORDILLERA IN ECUADOR AND PERU. ACROSS THE NORTH
CENTRAL TO NORTHEAST OF SOUTH AMERICA...THE WINDS WILL COME FROM
THE CARIBBEAN SIDE...WHICH WILL ALLOW FOR MOISTURE TO COMBINE WITH
DIURNAL HEATING AND CAUSE SHOWERS AND THUNDERSTORMS FROM GUYANA
EAST TO NORTH CENTRAL BRAZIL. AN UPPER TROUGH WITH AXIS ACROSS THE
GULF OF MEXICO IS SLOWLY MOVING EAST AS IT WEAKENS. AN UPPER RIDGE
IS PRESENT OVER THE WESTERN ATLANTIC...ALSO MOVING EAST. THE UPPER
TROUGH WILL BE IN THE WEST ATLANTIC BY WEDNESDAY AND AROUND THE
BAHAMAS BY FRIDAY. THERE IS ALSO A MID LEVEL TROUGH ACROSS THE
EASTERN GULF OF MEXICO INTO THE WESTERN CARIBBEAN THAT CONTINUES
TO WEAKEN AS IT MOVES TO THE EAST. THE MID AND UPPER LEVEL TROUGHS
ARE CAUSING THE EGDI INDEX TO SUGGEST ISOLATED TO SCATTERED
THUNDERSTORMS ACROSS SOUTHEASTERN CUBA AND THE SOUTHERN BAHAMAS
LATE TODAY AND TONIGHT.
ACROSS THE ATLANTIC...THERE IS A COLD FRONT EXTENDING FROM THE
CENTRAL ATLANTIC...TO THE SOUTHWEST INTO THE NORTHERN
BAHAMAS...THEN A STATIONARY FRONT MOVES THROUGH THE BAHAMAS AND
CUBA INTO THE WESTERN CARIBBEAN. THIS FRONT WILL REMAIN STATIONARY
IN ITS WESTERNMOST END FOR THE NEXT FEW DAYS AS IT WEAKENS. AHEAD
OF THE FRONT THERE IS A SURFACE TROUGH THAT WILL COMBINE WITH THE
DIVERGENT SIDE OF THE MID LEVEL TROUGH...WHICH WILL ALSO HELP IN
THE DEVELOPMENT SHOWERS AND THUNDERSTORMS ACROSS THE BAHAMAS TODAY
AND TONIGHT. THE SOUTHERN BAHAMAS WILL HAVE THE HIGHEST AMOUNTS OF
RAINFALL TODAY WITH TOTALS FORECAST AT 05-10MM AND MAX OF
15-25MM...WHILE THE NORTHERN HALF WILL OBSERVE UP TO 10MM OF RAIN
TODAY. ON WEDNESDAY AND THURSDAY...THE BAHAMAS GENERALLY ARE
FORECAST TO OBSERVE MAXIMA OF 15-25MM WITH BRIEF SHOWERS AT TIMES.
THE AFOREMENTIONED UPPER TROUGH HAS MOVED EAST AND THE IMPACT IS
NOT STRONG ACROSS CENTRAL AMERICA. THEREFORE...THE NORTHERN
COUNTRIES OF CENTRAL AMERICA ARE EXPECTED TO OBSERVE OCCASIONAL
BRIEF SHOWERS...AMOUNTING TO 05-10MM WITH MAXIMA OF 15MM TODAY.
THE SAME IS EXPECTED FOR PORTIONS OF COSTA RICA AND PANAMA.
WEDNESDAY AND THURSDAY WOULD HAVE SIMILAR AMOUNTS OF RAIN AND
LOCATION OF RAINFALL ACROSS CENTRAL AMERICA...EXCEPT FOR GUATEMALA
AND EL SALVADOR WHERE THUNDERSTORMS COULD PRODUCE UP TO 25MM
ACROSS ISOLATED AREAS ON WEDNESDAY.
THE CARIBBEAN IS EXPECTED TO BE SOMEWHAT UNSTABLE ESPECIALLY ON
WEDNESDAY ONWARD. THIS IS BECAUSE A MID LEVEL RIDGE WILL INHIBIT
DEEP CONVECTION TODAY...BUT THE RIDGE WILL MOVE EAST AND ALLOW A
TROUGH TO MOVE IN ITS PLACE. THIS IN TURN WILL CAUSE SOME
INSTABILITY AND THUNDERSTORMS ARE FORECAST FOR
HISPANIOLA...POSSIBLE CAUSING RAINFALL MAXIMA OF AS MUCH AS
25-50MM ON WEDNESDAY. HOWEVER...NEAR THE NORMAL MOISTURE AND THE
MID LEVEL RIDGE OVER THE AREA TODAY...WILL CAUSE RAINFALL MAXIMA
UP TO 15-25MM ACROSS THE GREATER ANTILLES. THE REST OF THE
CARIBBEAN...ESPECIALLY THE LESSER ANTILLES...WILL OBSERVE 00-05MM
WITH MAXIMA UP TO 10-15MM EACH DAY.
IN SOUTH AMERICA...THERE WILL BE SOME CONVECTION ALONG THE
NET...BUT THE AMOUNTS OF RAIN WILL NOT BE IMPRESSIVE ACROSS MOST
OF NORTHERN SOUTH AMERICA TODAY OR WEDNESDAY...THOUGH INCREASING
ON THURSDAY. IN GENERAL...DAILY RAINFALL WILL BE IN THE ORDER OF
05-10MM WITH MAXIMA OF 15-25MM ALONG THE NET. THE EXCEPTIONS ARE
PORTIONS OF THE GUIANAS...AND PORTIONS OF NORTHEASTERN
BRAZIL...WHERE HIGHER AMOUNTS OF RAIN...WITH MAXIMA AROUND 20-45MM
ARE EXPECTED. AS MENTIONED ABOVE...THE WESTERN COAST OF ECUADOR
AND COLOMBIA WILL SEE A DECREASE IN THUNDERSTORM ACTIVITY TODAY
AND WEDNESDAY...RAINFALL FORECAST RANGING TO 05-10MM WITH MAXIMA
UP TO 25MM TODAY...THEN MAXIMA BETWEEN 15-35MM ACROSS WESTERN
COLOMBIA WHILE MAX OF 20-45MM FORECAST FOR WESTERN ECUADOR ON
WEDNESDAY. THURSDAY LOOKS WETTER WITH ECUADOR OBSERVING MAXIMA OF
40-80MM WHILE WESTERN COLOMBIA WILL OBSERVE MAXIMA BETWEEN
50-100MM. HOWEVER...RAINFALL TO THE EAST OF THE CORDILLERA WILL BE
A LITTLE MORE CONSISTENT. EASTERN ECUADOR IS EXPECTING 15-20MM
WITH MAXIMA UP TO 50MM TODAY...THEN MAXIMA OF 40-80MM ON WEDNESDAY
AND THURSDAY.
ALAMO/ACOSTA...WPC (USA)
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