Prognostic Meteorological Discussion
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TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
706 AM EDT MON OCT 20 2014

PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI. AT UPPER
LEVELS... WANING TUTT LOW NOW CENTERS JUST NORTH OF PUERTO
RICO/USVI...WHILE EXTENDING A SHORT WAVE TROUGH TO THE EASTERN
CARIBBEAN. ANOTHER TUTT LIES TO THE WEST ACROSS THE CENTRAL
CARIBBEAN. AT MID LEVELS...A CELL OF THE SUBEQUATORIAL RIDGE
MAINTAINS ITS FOOTHOLD ACROSS THE ISLAND CHAIN/EASTERN CARIBBEAN.
THIS REMAINS STRONG ENOUGH TO DELAY ONSET OF DIURNAL
CONVECTION...BUT NOT STRONG ENOUGH TO SUPPRESS IT. AT LOW
LEVELS...NORTHEASTERLY TRAILS PREVAIL ACROSS THE FORECAST
AREA...WITH WINDS OF 10-15KT. ALSO AT LOW LEVELS...TROPICAL WAVE
LIES NOW ALONG 45W/46W. THIS IS INTERACTING WITH ANOTHER TUTT TO
THE NORTH...ENHANCING CONVECTIVE DEVELOPMENT ALONG THE ATLANTIC
ITCZ.

AT UPPER LEVELS...TUTT LOW NORTH OF THE ISLANDS IS TO GRADUALLY
PULL TO THE EAST-NORTHEAST THROUGH TUESDAY MORNING AS ANOTHER
TROUGH APPROACHES FROM THE WEST. THE LATTER MOVES ACROSS THE
FORECAST AREA BY MIDDAY ON TUESDAY. THE TROUGH THEN CONTINUES EAST
INTO THE LESSER ANTILLES/EASTERN CARIBBEAN AS A BROAD RIDGE
ESTABLISHES TO THE WEST. THROUGH THURSDAY EVENING THIS IS TO
DISPLACE THE TROUGH FARTHER TO THE EAST WHILE GRADUALLY EXPANDING
ACROSS THE EASTERN CARIBBEAN. THIS...IN-TURN...IS TO SUSTAIN UPPER
CONVERGENT PATTERN AND LARGE SCALE SUBSIDENCE ACROSS THE FORECAST
AREA. MODELS THEN PROJECT A SHARP DROP IN AVAILABLE MOISTURE
THROUGH THE DAY ON WEDNESDAY...WHEN A PWAT MINIMA OF 35-35MM IS TO
ENVELOP THE NORTHEAST CARIBBEAN ISLES. LOW LEVEL WINDS ARE TO THEN
VEER TO THE EAST-SOUTHEAST AS THE WEEK PROGRESSES.

AS THE PATTERN EVOLVES...THE MOST ACTIVE CONVECTION IS EXPECTED
OVER THE NEXT TWO DAYS...WITH DEEP CONVECTION TO CLUSTER ALONG THE
CORDILLERA IN PUERTO RICO. THIS IS TO GENERALLY FAVOR RAINFALL
AMOUNTS OF 0.25-0.50 AN INCH...WITH LOCALIZED MAXIMA OF 1.0 TO
1.5. ALTHOUGH GENERALLY PATTERN IS TO HOLD THROUGH TUESDAY
AFTERNOON...THE HIGHER AMPLITUDE TROUGH TO FOLLOW IS LIKELY TO
FAVOR MORE WIDESPREAD CONVECTION ACROSS THE FORECAST AREA.
ACTIVITY IS TO THEN WANE ON WEDNESDAY TO THURSDAY AS UPPER
CONVERGENT PATTERN IS TO GENERALLY FAVOR WEATHER CONDITIONS.

THE TROPICAL WAVE ENTERS THE FORECAST AREA DURING THE MEDIUM RANGE
PERIOD EARLY ON FRIDAY. AS MID/UPPER CONVERGENT PATTERN IS LIKELY
TO HOLD THROUGH THE END OF THE WEEK...MOST ACTIVE CONVECTION IS
EXPECTED FAR TO THE SOUTH.

JN BAPTISTE...MS (SAINT LUCIA)
MEDINA...ONAMET (REPUBLICA DOMINICANA)
DAVISON...WPC (USA)

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