Prognostic Meteorological Discussion
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FXCA20 KWBC 051100
PMDCA

TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
700 AM EDT WED AUG 05 2015

PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI FROM AUG 05/06
UTC:  RETROGRESSING TUTT EXTENDS TO THE EAST-NORTHEAST OF THE
ISLANDS. AS IT RETROGRESSES TOWARDS THE BASIN...THIS IS PRESSING
AGAINST A RIDGE OVER THE EASTERN CARIBBEAN. THE LATTER FAVORS A
STRONG CAP INVERSION. AT LOW LEVELS...BROAD RIDGE OVER THE
ATLANTIC SUSTAINS A TIGHT GRADIENT AND BRISK EASTERLY
TRADES...WHILE ALSO TRIGGERING GENERATION OF STREAMERS AND LIGHT
EARLY MORNING CONVECTION.

TUTT IS TO GRADUALLY MOVE TO THE NORTH-NORTHEAST OF PUERTO
RICO/VIRGIN ISLES DURING THE DAY ON FRIDAY...WHERE IT IS TO REMAIN
THROUGHOUT THE WEEKEND. MID ALTHOUGH THIS IS TO SUSTAIN A FAIRLY
WELL DEFINED MID LEVEL PERTURBATION... THE MID LEVEL RIDGE
ENVELOPING THE FORECAST AREA IS GOING TO HOLD A BIT LONGER THAN AT
UPPER LEVELS. SO EROSION OF CAP INVERSION IS GOING TO BE A SLOW
AND ARDUOUS PROCESS. THE TUTT ALOFT IS TO SUSTAIN A PERTURBATION
IN THE EASTERLY TRADES. THIS ENTERS THE EASTERN CARIBBEAN DURING
THE DAY ON FRIDAY...WITH SHALLOW MOISTURE TO THEN SURGE ACROSS THE
EASTERN CARIBBEAN THROUGH SATURDAY MORNING. EVOLVING MID/UPPER
LEVEL PATTERN IS TO HAVE AN IMPACT ON THE SURFACE RIDGE...WITH
AXIS EXPECTED TO GRADUALLY WEAKEN OVER THE NEXT COUPLE OF DAYS. AS
A RESULT...TRADE WIND EASTERLIES WILL DECREASE TO 10-15KT LATER
TODAY...AND THIS IS TO HOLD THROUGH SATURDAY. THESE WILL BE WEAK
ENOUGH TO ALLOW FOR THE SEA/LAND BREEZE CYCLE TO ESTABLISH ACROSS
THE FORECAST AREA. THE WEAKER TRADES AND INFLOW OF MOISTURE IS TO
LIKELY FAVOR AN INCREASE IN DIURNAL CONVECTION...WITH SHOWERS
CLUSTERING ON WESTERN INTERIOR PORTIONS OF PUERTO RICO. BUT AS THE
LOW LEVEL WINDS VEER TO THE SOUTHEAST...CONVECTION IS TO THEN
CLUSTER OVER NORTHWEST PUERTO RICO LATER ON FRIDAY TO SATURDAY. IN
THIS PATTERN THE GFS REMAINS THE MOST OPTIMISTIC THAT WE ARE TO
HAVE MEASURABLE RAINFALL AMOUNTS...WHILE THE EUROPEAN MODELS
GENERALLY FAVOR TRACE AMOUNTS. THIS IS NOT CONDUCIVE TO A HIGH
CONFIDENCE FORECAST.

SALMON...MS (ANTIGUA AND BARBUDA)
CABRERA...ONAMET (THE DOMINICAN REPUBLIC)
DAVISON...WPC (USA)
$$





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