Prognostic Meteorological Discussion
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FXCA20 KWBC 241052
PMDCA

TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
651 AM EDT WED AUG 24 2016

PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI FROM 24/06
UTC: AT UPPER LEVELS...A SHORT WAVE RIDGE OVER THE EASTERN
CARIBBEAN IS VENTING DEEP CONVECTION IN ASSOCIATION WITH A
VIGOROUS TROPICAL WAVE OVER THE ISLAND CHAIN. ACTIVITY IS
CLUSTERING OVER THE LEEWARD ISLES WHILE SLOWLY BUILDING WEST
TOWARDS THE VIRGIN ISLES. THE WAVE MOVES OVER THE VIRGIN ISLES
LATER THIS MORNING AND IT IS TO CONTINUE ACROSS PUERTO RICO LATER
TODAY/EARLY THURSDAY MORNING. AS IT MOVES ACROSS THE VI THE MODELS
CONSISTENTLY FORECAST THE AXIS OF CYCLONIC VORTICITY SHIFTING
NORTH AND WEST...PULLING ACROSS THE NORTHERN VI AND THEN SKIRTING
THE NORTH COAST OF PUERTO RICO. AS A RESULT...THE MODELS AGREE ON
MOST ACTIVE CONVECTION TO AFFECT THE VI AND POSSIBLY NORTHEAST
PORTIONS OF PUERTO RICO LATER THIS MORNING. RAINFALL MAXIMA WILL
RANGE BETWEEN 1-2 INCHES IN A HIT OR MISS SCENARIO AS MULTIPLE
CELLS POP UP NEAR THE ISLANDS. IN THE AFTERNOON...AS THE LOW LEVEL
WINDS VEER TO THE SOUTHEAST...THE ARW VERSION OF THE HRWRF SHOWS A
SECONDARY MAXIMA DEVELOPING ACROSS NORTHWEST PUERTO RICO. ALTHOUGH
POSSIBLE...THIS WILL BE HIGHLY DEPENDENT ON GETTING ENOUGH SOLAR
RADIATION TO START THE SEA BREEZE CONVERGENCE AND TO SUSTAIN THE
CONVECTIVE OVERTURNING. BUT THIS SEEMS UNLIKELY CONSIDERING HIGH
DENSE CLOUD COVER IN ASSOCIATION WITH THIS FEATURE. UNDER THESE
CONDITIONS...IF ACTIVITY DEVELOPS... IT SHOULD CONFINE TO THE
NORTHWEST COAST OF PUERTO RICO.

A SECOND ROUND OF CONVECTION IS POSSIBLE ON THURSDAY AS MOISTURE
TRAILING THE TROPICAL WAVE ADVECTS ACROSS THE FORECAST AREA. PWAT
DURING THAT PERIOD WILL PEAK AROUND TWO INCHES. AS THE STEERING
FLOW REMAINS FROM THE SOUTHEAST...THIS COULD RESULT IN SCATTERED
SHOWERS DEVELOPING ACROSS NORTHERN PUERTO RICO DURING THE LATE
MORNING/EARLY AFTERNOON HOURS. MOST ACTIVE IS LIKELY TO DEVELOP
WEST OF TOA BAJA WITH MAXIMA TO PEAK AROUND 1-3 INCHES.

DURING THE MEDIUM RANGE PERIOD...TROPICAL STORM GASTON REMAINS THE
SYSTEM OF CONCERN. PER THE NHC GUIDANCE THE STORM SHOULD RECURVE
TO THE NORTHWEST EARLY IN THE CYCLE...WITH EXPECTED TRACK KEEPING
IT FAR TO THE EAST.

CONTRERAS...IMN (COSTA RICA)
GALVEZ/DAVISON...WPC (USA)
$$




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