Skip Navigation Links weather.gov 
NOAA logo - Click to go to the NOAA homepage National Weather Service   NWS logo - Click to go to the NWS homepage
The Weather Prediction Center
 
Tropical Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1100Z Apr 07, 2020)
 
Version Selection
Versions back from latest:  0   1   2   3   4   5   6   7   8   9   10   
 
Abbreviations and acronyms used in this product


TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
700 AM EDT TUE APR 07 2020

PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI FROM APR 07/11
UTC: SINUSOIDAL MID/UPPER LEVEL PATTERN PREVAILS...WITH MEANDERING
RIDGE OVER THE GULF OF MEXICO-SOUTHEAST USA FAVORING THE SOUTHWARD
AMPLIFICATION OF A TROUGH OVER THE WESTERN ATLANTIC TO THE
NORTHERN CARIBBEAN ISLES. AT 250 HPA...A SUBTROPICAL JET MAXIMA
ROUNDING THE BASE OF THE TROUGH REPOSITIONED JUST SOUTH OF THE
FORECAST AREA...WITH CONVERGENCE ON ITS LEFT ENTRANCE REGION
HELPING SUSTAIN A MID LEVEL TRADE WINDS INVERSION. AT LOW
LEVELS...THIS SUSTAINS A BROAD TROUGH NORTH OF THE ISLANDS...WITH
A MEANDERING FRONT STRETCHING ACROSS THE ATLANTIC TO JUST NORTH OF
THE VIRGIN ISLES-PUERTO RICO INTO THE DOMINICAN REPUBLIC. A
SECONDARY BOUNDARY IS APPROACHING FROM THE NORTH...AND IT WILL
HELP REINFORCE THE FORMER LATER THIS AFTERNOON. THE POLAR TROUGH
TO THE NORTH SUSTAINS AN INDUCED/INVERTED TROUGH OVER THE EASTERN
CARIBBEAN. THIS...IN-TURN...SUSTAINS A MOIST SOUTHEASTERLY FLOW
ACROSS THE ISLAND CHAIN...WITH MOISTURE POOLING OVER THE FORECAST
AREA AND MEANDERING FRONT TO THE NORTH. THE PWAT CONTENT OF
1.50-1.75 INCHES REMAINS SLIGHTLY ABOVE NORMAL FOR THIS TIME OF
THE YEAR. FURTHERMORE...THE PWAT LAYERED PRODUCT FROM CIRA IS
SHOWING MOISTENING OF THE MID LEVELS UPSTREAM OVER THE
BAHAMAS-TURKS...SUGGESTING EROSION OF TRADE WINDS INVERSION FROM
THE WEST AS A MID LEVEL VORTEX STREAMS TOWARDS THE BASIN. ALTHOUGH
FAVORING A SIMILAR PATTERN...THE MODELS DIVERGE ON ITS IMPACT
ACROSS THE FORECAST AREA. THE GLOBAL MODELS GENERALLY DOWNPLAY
POTENTIAL FOR MEASURABLE RAINFALL AMOUNTS DURING THE DAY...WHILE
THE NMM AND ARW VERSIONS OF THE HRWRF SHOW A HIGHER RISK OF HEAVY
CONVECTION TO AFFECT INTERIOR PORTIONS OF PUERTO RICO. CONSIDERING
ADVERSE JET DYNAMICS ALOFT...WE ARE LEANING TOWARDS A WEAKER
SOLUTION THAN WHAT IS SUGGESTED BY THE HIGHER RESOLUTION MODELS.
NOTE THAT THE ECMWF IS HAVING ISSUES WITH CONVECTIVE
FEEDBACK...AND ITS SOLUTION IS QUESTIONABLE DURING THE SHORT RANGE
PERIOD.

THROUGH WEDNESDAY THE ENVIRONMENTAL CONDITIONS ARE TO BECOME MORE
FAVORABLE AND CONDUCIVE FOR CONVECTION TO DEVELOP...WITH MID LEVEL
CYCLONIC VORTEX ROUNDING THE BASE OF THE TROUGH TO STREAM ACROSS
THE FORECAST AREA. THE GLOBAL AND REGIONAL MODELS RESPOND TO MORE
FAVORABLE ENVIRONMENT...SHOWING AN INCREASE IN DIURNAL CONVECTION
ACROSS THE FORECAST AREA.  IN AN EAST-NORTHEAST BOUNDARY LAYER
FLOW...SOUTHEASTERLY AT 850 HPA...AND WESTERLY AT 700 HPA THIS
WILL RESULT IN ENOUGH VERTICAL WIND SHEAR TO FAVOR LONGER LASTING
CONVECTION. MOST ACTIVE TO INITIALLY CLUSTER OVER INTERIOR
PORTIONS OF PUERTO RICO. BUT AS CONVECTION BUILDS...THE WESTERLY
MID LEVEL FLOW WILL STEER THE CONVECTIVE CELLS TOWARDS THE SAN
JUAN METRO AREA DURING THE AFTERNOON AND POTENTIALLY INTO THE
EARLY EVENING HOURS.

ON THURSDAY...MID LEVEL RIDGE BUILDS ACROSS THE GREATER
ANTILLES...DISPLACING THE POLAR TROUGH EAST INTO THE CENTRAL
ATLANTIC. THIS WILL BE ACCOMPANIED BY RAPID INTENSIFICATION OF THE
TRADE WINDS CAP THROUGH FRIDAY. AS THE INVERSION
STRENGTHENS...PWAT CONTENT PLUMMETS DURING THE LATTER PART OF THE
WEEK. AT LOW LEVELS...SHORT WAVE RIDGE OVER THE ISLAND CHAIN THEN
FAVORS A STRONGER SOUTHERLY FLOW ACROSS THE EASTERN CARIBBEAN INTO
THE FORECAST AREA...DISPLACING THE SURFACE FRONT FARTHER TO THE
NORTH EARLY ON FRIDAY. LIGHTER WINDS ARE THEN EXPECTED LATER IN
THE WEEK...WITH STEERING FLOW BECOMING ILL DEFINED. DURING THE
LATTER PERIODS...LAND/SEA BREEZES WILL CONTROL THE LOW LEVEL FLOW.
ACTIVITY STARTS TO EBB ON FRIDAY...WITH DIURNAL HEATING TRIGGERED
CONVECTION LIMITING TO THE CORDILLERA OVER PUERTO RICO...EL YUNQUE
AND NORTH COAST OF THE ISLAND...WHILE OVER THE VIRGIN
ISLES...VIEQUES AND CULEBRA ACTIVITY IS TO CLUSTER OVER HIGHER
ELEVATIONS. BUT IN A HOSTILE ENVIRONMENT...ONLY EXPECTING LIGHT
RAINFALL AMOUNTS.

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