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FXCA20 KWBC 091232
PMDCA

TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
832 AM EDT THU MAY 09 2024

WEEKLY DISCUSSION FOR PUERTO RICO AND THE USVI MAY 09/12UTC:

SYNOPSIS: SATELLITE IMAGERY AND MODELS SHOW THAT AN EXTENSIVE
MID-UPPER TROUGH CONTINUES EXTENDING FROM BERMUDA INTO THE
NORTHEAST CARIBBEAN. SHORT WAVE VORTICES ARE PROPAGATING EASTWARD
ALONG THE BASE OF THE MAIN TROUGH. THE EASTERNMOST SHORT WAVE
TROUGH EXTENDS ALONG 58-60W. AS THE TROUGH EXITS THE DRIER AIR
MASS TO THE WEST IS SUSTAINING DRYING TREND OF THE MID AND UPPER
TROPOSPHERE OVER THE LOCAL ISLANDS. THAT BEING SAID...PRECIPITABLE
WATER VALUES REMAIN CLOSE TO 50MM OR ABOVE NORMAL FOR THIS TIME OF
THE YEAR. THIS IS IN ASSOCIATION WITH A ZONALLY ORIENTED MOIST
PLUME PRODUCED BY A PERSISTENT STATIONARY FRONT THAT HAS LOST
BAROCLINICITY IN THE LAST TWO DAYS. INCREASINGLY UPPER CONVERGENT
CONDITIONS ARE ALSO PLAYING A ROLE IN LIMITING VERTICAL
DEVELOPMENT...THUS EXPECT A NOTICEABLE DECREASE IN THE COVERAGE
AND INTENSITY OF DIURNAL CONVECTION TODAY WITH RESPECT TO EARLIER
THIS WEEK.

FORECAST: AFTER SEVERAL DAYS UNDER THE INFLUENCE OF THE MOIST
PLUME AND PROPAGATING SHORT WAVE MID-UPPER TROUGHS IN THE
WESTERLIES...THE MID-UPPER TROPOSPHERIC PATTERN IS FORECAST TO
GRADUALLY EVOLVE INTO A DRIER ONE. MODELS AGREE ON THE MID-LEVEL
RIDGE CURRENTLY LOCATED OVER MEXICO/GULF OF MEXICO/WESTERN
CARIBBEAN CONTINUING TO BUILD EASTWARD INTO THE CENTRAL AND
EASTERN CARIBBEAN...SETTING FOOTHOLD OVER PUERTO RICO BETWEEN
SUNDAY AND MONDAY...TO PERSIST INTO AT LEAST MID-WEEK. THIS IS
CONSISTENT WITH AN EXPECTED STRENGTHENING OF THE TRADE WIND CAP
EARLY NEXT WEEK...RESULTING IN A NOTICEABLE DECREASE IN VERTICAL
DEVELOPMENT AND COVERAGE OF DEEP CONVECTION STARTING ON SUNDAY.
AVAILABLE MOISTURE IS FORECAST TO DECREASE...BUT TO REMAIN WITHIN
CLIMATOLOGICAL NORMALS. HOWEVER...LESS FAVORABLE DYNAMICS FOR
ASCENT WILL YIELD TO MORE CONSERVATIVE RAINFALL ACCUMULATION
STARTING SUNDAY.

IN THE MEAN TIME...THE MID-UPPER TROUGH PATTERN IS FORECAST TO
PERSIST THROUGH SATURDAY. LIMITED AVAILABLE MOISTURE AND LIMITED
SATURATION/CLOUD COVER IN THE MID AND UPPER TROPOSPHERE WILL
ACTUALLY STIMULATE DIURNAL HEATING...FAVORING HIGH RAINFALL RATES
IN AFTERNOON THUNDERSTORMS THAT DEVELOP ESPECIALLY ON THURSDAY AND
FRIDAY. UNDER THE INFLUENCE OF WEAK SOUTHEASTERLY TRADES ON
THURSDAY AND FRIDAY...EXPECT STRONG DIURNAL BREEZE CONVERGENCE TO
FOCUS IN INTERIOR PORTIONS OF NORTHERN AND NORTHWEST PUERTO RICO
WHERE AFTERNOON CONVECTION IS EXPECTED. EXPECT DIURNAL MAXIMA IN
THE 1-2 INCH RANGE...ALTHOUGH ISOLATED MAXIMA NEAR 3 INCHES CANNOT
BE RULED OUT.

GALVEZ...WPC (USA)


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