TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
245 PM EDT MON MAY 20 2024

FORECAST BULLETIN 20 MAY 2024 AT 1845 UTC:

THE MAIN STORY THIS WEEK IS THE POTENTIAL RAINFALL EVENT
DEVELOPING ACROSS THE CARIBBEAN. AN AMPLIFYING MID AND UPPER LEVEL
TROUGHS WILL COMBINE WITH AN INCREASE IN MOISTURE ACROSS THE
CENTRAL CARIBBEAN INTO THE TURKS AND CAICOS BY MIDWEEK. THIS MAY
CAUSE SIGNIFICANT RAINFALL WITH SQUALLY WEATHER THIS WEEK ACROSS
THE CARIBBEAN ISLANDS INTO THE SOUTHERN BAHAMAS. THE IMPACT OF
THIS RAINFALL EVENT COULD BE SIGNIFICANT...BECAUSE MOST OF THE
HEAVY PRECIPITATION COULD OCCUR FROM MIDWEEK TO THE END OF THE
WORKWEEK...BUT SOME RAINFALL IS EXPECTED TODAY THROUGH WEDNESDAY
ACROSS THE CARIBBEAN ISLANDS...SO THE SOILS COULD BE SATURATED BY
THE LATTER PART OF THE WORKWEEK...CAUSING ANY SIGNIFICANT RAIN
OVER THE CARIBBEAN ISLANDS TO BE A POSSIBLE HAZARD. THAT BEING
SAID...THERE IS ANOTHER AREA THAT COULD SEE VERY SIGNIFICANT
RAINFALL OVER THE NEXT 3 DAYS...AND THAT IS WESTERN COLOMBIA INTO
PANAMA AND COSTA RICA...PARTICULARLY TODAY. THIS IS DUE TO A LONG
FETCH MOISTURE PLUME THAT WILL HAVE ONSHORE FLOW ACROSS WESTERN
COLOMBIA INTO PANAMA AND COSTA RICA...COMBINED WITH THE AMPLIFYING
MID AND UPPER LEVEL TROUGHS DIGGING INTO THE CARIBBEAN...WHICH
WILL REACH CENTRAL AMERICA.

AT THE SURFACE...THERE IS A LOW PRESSURE OVER THE WESTERN ATLANTIC
THAT WILL MOVE TO THE NE OVER THE NEXT 3 DAYS. THIS WILL ALLOW A
SFC HIGH PRESSURE TO EXTEND INTO THE TROPICAL ATLANTIC BY MIDWEEK.
IN THE MID LEVELS...THERE IS A HIGH PRESSURE OVER THE EAST PACIFIC
AND MEXICO...WHILE A MID LEVEL TROUGH WILL AMPLIFY OVER THE
WESTERN ATLANTIC INTO THE CARIBBEAN THOUGH THURSDAY...WITH ITS
AXIS OVER CUBA AND JAMAICA. IN THE UPPER LEVELS...MOST OF THE
WESTERN CARIBBEAN AND GULF OF MEXICO WILL SEE NW WINDS AS AN UPPER
LEVEL HIGH PRESSURE IS LOCATED OVER THE EAST PACIFIC. THERE IS
HOWEVER AN UPPER TROUGH ACROSS THE NE CARIBBEAN AND THE WESTERN
ATLANTIC...TO THE NORTH OF THE BAHAMAS. THE TROUGH IS EXPECTED TO
CONTINUE AMPLIFYING...WITH THE AXIS OVER EASTERN CUBA AND
JAMAICA...AND THE TROUGH BASE REACHING CENTRAL AMERICA...CAUSING
UPPER LEVEL DIFFLUENCE OVER NORTHWESTERN SOUTH AMERICA. THIS
PATTERN WILL PROMOTE VENTILATION ALOFT AND HELP PERSISTENT
DEVELOPMENT OF SHOWERS AND THUNDERSTORMS OVER THE NORTHWESTERN
SECTIONS OF SOUTH AMERICA AS WELL AS PORTIONS OF CENTRAL AMERICA.
THE OTHER FEATURE THAT WILL CAUSE RAINFALL ACROSS THE TROPICAL
REGION IS THE ITCZ IN THE ATLANTIC AND THE MONSOON TROUGH IN THE
PACIFIC. THERE IS ENOUGH MOISTURE AND CONVECTION ALONG THE
BOUNDARY THAT WILL HELP CAUSE SHOWERS AND THUNDERSTORMS ACROSS THE
NORTHERN SECTIONS OF SOUTH AMERICA. THE CONVECTION ACROSS SOUTH
AMERICA...NOT COUNTING WESTERN COLOMBIA...WILL BE GENERALLY ALONG
THE ITCZ/NET...WITH SOME LOCAL ENHANCEMENTS DUE TO EASTERLY WAVES
AND SFC TROUGHS.

IN TERMS OF RAINFALL...THE MOST SIGNIFICANT AMOUNTS TODAY INTO
TUESDAY MORNING ARE FORECAST TO BE ACROSS NORTHWESTERN SOUTH
AMERICA AND THE SOUTHERN COUNTRIES OF CENTRAL AMERICA...WITH
PORTIONS OF WESTERN COLOMBIA AND PANAMA POSSIBLY OBSERVING AS MUCH
AS 75-125MM OF RAIN. IT IS WORTH MENTIONING THAT THE MODEL
GUIDANCE WAS SUGGESTING EVEN HIGHER VALUES OF RAIN...SO ISOLATED
HIGHER AMOUNTS OF RAIN THAN WHAT WE FORECAST WILL NOT BE RULED
OUT. OTHER AREAS IN NORTHERN SOUTH AMERICA...SUCH AS NORTHWESTERN
VENEZUELA...PORTIONS OF ECUADOR...AND PORTIONS OF WESTERN PANAMA
AND EASTERN COSTA RICA IN CENTRAL AMERICA COULD OBSERVE MAX VALUES
BETWEEN 30 AND 80MM. MOST OTHER AREAS WILL RECEIVE MODEST AMOUNTS
OF RAIN TODAY...RELATIVELY SPEAKING. THE RAINFALL STARTS TO PICK
UP ACROSS THE CARIBBEAN ON TUESDAY...WITH MAX DAILY RAINFALL
VALUES GENERALLY BETWEEN 20 AND 45MM. NORTHWESTERN SOUTH AMERICA
IS FORECAST TO OBSERVE LESS RAIN ON TUESDAY...AS WELL AS SOUTHERN
CENTRAL AMERICA...WITH MAX VALUES GENERALLY RANGING BETWEEN 30 AND
60MM...BUT A SMALL AREA ALONG THE BOUNDARY OF PANAMA AND COSTA
RICA COULD OBSERVE AS MUCH AS 100MM. BY WEDNESDAY INTO
THURSDAY...THE RAINFALL FORECAST INCREASES SIGNIFICANTLY FOR THE
CARIBBEAN NATIONS DUE TO THE AFOREMENTIONED PATTERN OF MID AND
UPPER TROUGHS WITH MOISTURE ADVECTION. DAILY MAX TOTALS COULD
REACH AS MUCH AS 125MM ACROSS HISPANIOLA...WHILE OTHER AREAS IN
THE CARIBBEAN SUCH AS PUERTO RICO AND USVI...JAMAICA...AND EASTERN
CUBA COULD OBSERVE BETWEEN 30 AND 60MM OF RAIN...WITH THE
POTENTIAL OF SQUALLY WEATHER AND SVR THUNDERSTORMS. THE FORECAST
RAINFALL DECREASES SIGNIFICANTLY ACROSS NORTHERN SOUTH AMERICA AND
CENTRAL AMERICA...WITH MAX RAINFALL TOTALS GENERALLY BETWEEN 20
AND 45MM. IT IS ALSO WORTH MENTIONING...THAT THROUGH THE NEXT 3
DAYS...MEXICO SEEMS TO STAY RELATIVELY QUIET...WITH A FEW AREAS OF
CENTRAL TO SOUTHERN MEXICO HAVING MAX VALUES IN THE FORECAST
GENERALLY IN THE 15-35MM RANGE.

ALAMO...WPC (USA)