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Tropical Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1116Z Apr 03, 2020)
 
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TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
716 AM EDT FRI APR 03 2020

PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI FROM APR 03/11
UTC: A BROAD MID/UPPER LEVEL TROUGH ESTABLISHED OVER THE WESTERN
ATLANTIC...WITH AXIS BOTTOMING OUT OVER THE NORTHERN CARIBBEAN
ISLANDS. THIS IS DRAWING A SHORT WAVE TROUGH ACROSS THE CENTRAL
CARIBBEAN...WITH AXIS SHEARING SHORT WAVE ENERGY AS IT STREAMS
SOUTH OF PUERTO RICO THIS AFTERNOON. AT LOW LEVELS...SURFACE FRONT
IS STREAMING ACROSS THE WESTERN ATLANTIC WHILE TRAILING ACROSS THE
SOUTHEAST BAHAMAS/TURKS TO CUBA. AHEAD OF THIS BOUNDARY...A MOIST
SOUTH-SOUTHEAST FLOW ESTABLISHED OVER THE EASTERN
CARIBBEAN...WHILE TO THE NORTH OF THE ISLANDS A LONG FETCH
WESTERLY FLOW IS TO PERSIST. ACROSS PUERTO RICO THIS WILL FEED
DIURNAL CONVECTION THIS AFTERNOON TO RESULT IN MOSTLY LIGHT
AFTERNOON CONVECTION ACROSS INTERIOR PORTIONS OF THE ISLAND...WITH
LESSER AMOUNTS EXPECTED OVER SAINT CROIX AND VIEQUES.

A BUILDING MID LEVEL RIDGE ACROSS THE GULF OF MEXICO-EASTERN USA
WILL HELP LOCK THE TROUGH IN PLACE OVER THE WESTERN
ATLANTIC/NORTHERN CARIBBEAN THROUGH THE MIDDLE OF NEXT WEEK. FROM
TIME-TO-TIME SHORT WAVE VORTICES ROUNDING THE BASE OF THE TROUGH
ARE TO STREAM ACROSS THE BAHAMAS INTO NORTHERN HISPANIOLA/PUERTO
RICO...WITH INFLOW OF SHORT WAVE ENERGY INCREASING ON
TUESDAY-WEDNESDAY. AT 250 HPA...TIGHTENING GRADIENT TO THE NORTH
WILL HELP SUSTAIN THE GRADUAL INTENSIFICATION OF A SUBTROPICAL JET
MAXIMA TO THE NORTH OF PUERTO RICO LATER THIS EVENING/EARLY
SATURDAY MORNING. THIS IS TO BRIEFLY FAVOR AN UPPER DIVERGENT
PATTERN ON ITS RIGHT ENTRANCE REGION THAT IS TO VENT CONVECTIVE
DEVELOPMENT ON SATURDAY. THIS...HOWEVER...WILL BE SHORT
LASTING...WITH JET MAXIMA TO MEANDER EAST-SOUTH INTO THE NORTHEAST
CARIBBEAN LATER ON SUNDAY. FORECAST AREA WILL THEN REMAIN ON THE
CONVERGENT/SUBSIDENT SIDE OF THE UPPER LEVEL JET...STRENGTHENING
THE MID LEVEL CAP INVERSION OVER THE NORTHEAST CARIBBEAN. AT LOW
LEVELS...SURFACE FRONT MEANDERS SOUTH ACROSS THE BASIN...ENTERING
NORTHERN PUERTO RICO/NORTHERN VI ON SATURDAY EVENING. THROUGH THE
NIGHT...AS THE WINDS BELOW 900 HPA BACK TO THE
NORTH-NORTHWEST...THE FRONT WILL SLIDE ACROSS PUERTO RICO TO THE
CARIBBEAN COAST...WHERE IT IS EXPECTED TO STALL. ALTHOUGH THE
BOUNDARY LAYER WINDS TAKE A NORTHERLY COMPONENT DURING THE
WEEKEND...WINDS AT 850 HPA ARE TO RETAIN A SOUTHWESTERLY
COMPONENT. CONDITIONS DURING THE LATTER PERIODS THEN APPEAR
FAVORABLE FOR AN OVERRUNNING PATTERN TO ESTABLISH...WITH SHALLOW
MOISTURE LIFTING OVER THE MEANDERING FRONT TO SUSTAIN A PWAT
CONTENT OF 1.50-1.75 INCHES. ALTHOUGH THE GFS AND ECMWF BOTH
SUPPORT THIS SCENARIO...THEY DISAGREE ON WHERE THE BEST MOISTURE
CONVERGENCE IS GOING TO TAKE PLACE. THE ECMWF IS SHOWING MOISTURE
POOLING OVER PUERTO RICO AND THE VIRGIN ISLANDS EARLY NEXT
WEEK...WHILE THE GFS HAS THE MOISTURE JUST SOUTH OF THE FORECAST
AREA.

ALTHOUGH THIS IS A HIGH UNCERTAINTY FORECAST...CLIMATE FORECAST
SYSTEM GUIDANCE IS HINTING AT ENVIRONMENTAL CONDITIONS BECOMING
SOMEWHAT MORE CONDUCIVE TO DEVELOPMENT AS THE MJO PATTERN ALOFT
BECOMES MORE FAVORABLE NEXT WEEK. ALSO...TAKING INTO ACCOUNT
INFLOW OF MID LEVEL SHORT WAVE VORTICES DURING THE MEDIUM RANGE
PERIOD AND MEANDERING SHALLOW FRONTAL BOUNDARY OVER THE
BASIN...THE WETTER ECMWF SOLUTION IS FAVORED FOR THE LATTER
PERIODS.

DAVISON...WPC (USA)
GALVEZ...WPC (USA)