TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
251 PM EDT TUE MAY 14 2024

FORECAST BULLETIN 14 MAY 2024 AT 1845 UTC: THE OVERALL SYNOPTIC
PATTERN FAVORS ISOLATED TO NO SHOWER ACTIVITY ACROSS THE CARIBBEAN
FOR THE NEXT FEW DAYS...WITH MAINLY LOCAL AND DIURNAL EFFECTS
ALLOWING RAINFALL DEVELOPMENT OVER THE ISLANDS IN THE CARIBBEAN.
ABOVE NORMAL PRECIPITABLE WATER ACROSS SOUTHERN TO EASTERN MEXICO
WILL HELP IN THE DEVELOPMENT OF SHOWER ACTIVITY ACROSS THE
AREA...BUT THE ACTIVITY WILL BE CYCLICAL ACCORDING TO THE MODEL
GUIDANCE...MEANING THAT THE MODELS SUGGEST A DIURNAL AND LOCAL
EFFECT ALSO BEING THE MAIN REASON FOR SHOWER
DEVELOPMENT...GENERALLY IN THE LATE AFTERNOON INTO THE EVENING
HOURS EACH DAY. THAT BEING SAID...THE MAIN STORY WITH REGARDS TO
SIGNIFICANT RAINFALL WILL BE ALONG THE ITCZ/MONSOON TROUGH AND HOW
IT WILL AFFECT NORTHERN SOUTH AMERICA AND SOUTHERN CENTRAL
AMERICA. THE LATEST SATELLITE IMAGERY AS WELL AS THE LATEST MODEL
GUIDANCE SUGGEST THAT THE MORE PERSISTENT SHOWER ACTIVITY WILL BE
ALONG THE ITCZ AND IN AREAS OF VERY DEEP MOISTURE ACROSS NORTHERN
SOUTH AMERICA AND CENTRAL AMERICA. SEVERAL EASTERLY WAVES AND SFC
TROUGHS WILL ENHANCE THE AMOUNTS OF RAIN ACROSS NORTHERN SOUTH
AMERICA...WHILE IN THE PACIFIC SIDE...THE ITCZ/MONSOON
TROUGH...WILL HAVE A STRONG SOUTHERLY COMPONENT...CAUSING THE
CONVERGENCE ZONE TO BE OVER PANAMA...COSTA RICA...AND NEARBY
COUNTRIES. THIS CONVERGENCE ZONE WITH THE DEEP MOISTURE OVER THE
AREA WILL CAUSE PERSISTENT AND SIGNIFICANT SHOWER ACTIVITY OVER
THE NEXT FEW DAYS.

AT THE SURFACE ACROSS THE REGION...THERE IS A LOW PRESSURE ACROSS
THE NORTHWESTERN ATLANTIC...WITH A COLD FRONT EXTENDING SOUTH INTO
THE TROPICAL ATLANTIC...NEAR 25N TO THE NORTHEAST OF THE GREATER
ANTILLES. THERE IS ALSO A STRONG SFC HIGH PRESSURE ACROSS THE
NORTH CENTRAL ATLANTIC. THIS SETUP WOULD CAUSE EASTERLY WINDS
ACROSS THE CARIBBEAN...THOUGH BECOMING SOUTHEAST ACROSS THE
WESTERN CARIBBEAN IN TO THE GULF OF MEXICO AS WELL AS OVER THE
BAHAMAS. A COUPLE OF SFC LOW PRESSURE ACROSS THE EAST CENTRAL TO
SOUTHEAST USA WILL MOVE EAST OVER THE NEXT FEW DAYS...HAVING AN
ASSOCIATED WARM FRONT ACROSS THE WESTERN ATLANTIC AND A COLD FRONT
MOVING IN TO THE GULF OF MEXICO AND A STATIONARY FRONT ACROSS
NORTHEASTERN MEXICO BY WEDNESDAY. THE MID-LEVELS ARE LESS EXCITING
ACROSS THE TROPICAL REGION...WITH A MID LEVEL RIDGE ACROSS THE
CENTRAL CARIBBEAN INTO THE BAHAMAS AND A TROUGH WITH AXIS ACROSS
THE WESTERN TROPICAL ATLANTIC NORTH OF THE NORTHEASTERN CARIBBEAN.
AS THE TROUGH AND RIDGE MOVE EAST OVER THE NEXT COUPLE OF DAYS...A
BROAD MID LEVEL TROUGH WILL THEN MOVE INTO THE NORTHERN SECTIONS
OF THE GULF OF MEXICO AND INTO THE NORTHERN BAHAMAS BY THURSDAY.
THE UPPER LEVELS SEEM TO BE IN PHASE WITH THE MID LEVELS...ALSO
HAVING A TROUGH WITH AXIS ACROSS THE TROPICAL ATLANTIC INTO THE
EASTERN CARIBBEAN...AND A RIDGE OVER THE CENTRAL CARIBBEAN NORTH
IN TO THE BAHAMAS AND THE WESTERN TROPICAL ATLANTIC. THAT
SAID...THERE IS AN UPPER JET ACROSS THE SOUTHEAST USA WITH A BROAD
UPPER TROUGH...WHICH WILL MOVE EAST AND CAUSE THE UPPER TROUGH TO
HAVE ITS AXIS ACROSS THE WESTERN TROPICAL ATLANTIC BY WEDNESDAY
EVENING. THIS FEATURE MAY BE IMPORTANT AS THE GR02T ALGORITHM
SUGGESTS A MARGINAL RISK FOR SVR WX ACROSS THE EXTREME NORTHERN
BAHAMAS TONIGHT INTO WEDNESDAY MORNING AS THE UPPER TROUGH MOVES
IN...CAUSING STRONG DIVERGENCE ALOFT.

AS MENTIONED ABOVE...THE MAIN CONVECTION AND SHOWER DEVELOPMENT IS
EXPECTED ALONG THE ITCZ. HOWEVER...ACROSS SOUTHERN CENTRAL
AMERICA...THE CONVERGENCE OF THE ITCZ WILL MOVE NORTH AND INTO
COSTA RICA AND PANAMA...TO PRODUCE PERSISTENT SHOWER ACTIVITY OVER
THE AREA EVERY DAY FOR THE REST OF THE WORKWEEK. WITH THE HIGHEST
RAINFALL ACCUMULATIONS...NEAR 60MM OVER THE PACIFIC COASTAL SIDE
OF PANAMA AND COSTA RICA TODAY INTO WEDNESDAY MORNING...WHILE THE
HIGHER ELEVATIONS OF THOSE COUNTRIES MAY OBSERVE MAX VALUES
BETWEEN 60 AND 80MM ON WEDNESDAY AND THURSDAY DURING THE DAY. THE
CHANCES OF RAIN INCREASE FOR NICARAGUA...SOUTHERN GUATEMALA AND EL
SALVADOR ON WEDNESDAY AND THURSDAY AS MOISTURE INCREASES...THOUGH
THE RAINFALL AMOUNTS WILL BE GENERALLY UNDER 25MM.

ACROSS MEXICO...THE ONSHORE WIND FLOW ACROSS SOUTHERN AND EASTERN
MEXICO WILL COINCIDE WITH AN ABOVE NORMAL AMOUNT OF PRECIPITABLE
WATER. THE MID AND UPPER LEVELS ARE RELATIVELY BENIGN...WITH HIGH
PRESSURE IN THE MID LEVELS AND ZONAL FLOW IN THE UPPER
LEVELS...WHICH WILL TRANSLATE TO DAILY RAINFALL ACROSS PORTIONS OF
SOUTHERN AND EASTERN MEXICO HEAVILY INFLUENCED BY DIURNAL EFFECTS.
FOR THAT REASON THE LATEST GUIDANCE INSISTS IN RAINFALL DURING THE
AFTERNOON INTO THE VERY EARLY MORNING. THE DAILY RAINFALL MAX WILL
BE UP TO 35MM TODAY AND WEDNESDAY ACROSS ISOLATED AREAS...WHILE
THURSDAY INTO FRIDAY LOOKS A BIT DRIER. THERE IS AN UPPER LEVEL
JET ACROSS NORTHERN MEXICO...BUT IT IS VERY DRY ACROSS THAT AREA
AND THE MODEL GUIDANCE DOES NOT SUGGEST RAINFALL OVER THOSE
SECTORS.

ONE LAST THING TO NOTE...THE NATIONAL HURRICANE CENTER IS
MONITORING AN AREA OF POSSIBLE TROPICAL CYCLONE DEVELOPMENT ACROSS
THE EASTERN PACIFIC...TO THE SOUTH OF SOUTHERN MEXICO. AT THIS
TIME THERE IS CONSIDERABLE UNCERTAINTY...BUT THE OUTLOOK BY THE
HURRICANE CENTER SAYS THAT AN AREA OF LOW PRESSURE IS FORECAST TO
FORM ALONG A TROUGH SEVERAL HUNDRED MILES TO THE SOUTH OF THE GULF
OF TEHUANTEPEC...AND THAT SOME GRADUAL DEVELOPMENT IS POSSIBLE AS
THE LOW MOVES TO THE WEST-NORTHWEST AS IT REMAINS SOUTH OF THE
COAST OF MEXICO THROUGH EARLY NEXT WEEK. WE WILL CONTINUE TO
MONITOR THIS AREA AND WILL FOLLOW THE OUTLOOKS AND LATEST
FORECASTS FROM THE NATIONAL HURRICANE CENTER.

ALAMO...WPC (USA)