Prognostic Meteorological Discussion
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FXCA20 KWBC 121123
PMDCA

TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
622 AM EST FRI FEB 12 2016

PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI FROM FEB 12/06
UTC: SUBTROPICAL RIDGE CONTINUES TO YIELD TO AMPLIFYING POLAR
TROUGH OVER THE WESTERN ATLANTIC. AS IT AMPLIFIES ACROSS THE
NORTHERN CARIBBEAN ISLES...A SUBTROPICAL JET MAXIMA IS TO
GRADUALLY ROUND THE BASE OF THE TROUGH. THE JET NOSES JUST NORTH
OF THE FORECAST AREA ON SATURDAY TO SUNDAY...WITH ITS RIGHT EXIT
REGION TO SUSTAIN A WEAK UPPER CONVERGENT PATTERN. AT MID
LEVELS...SIMILAR EVOLUTION IS EXPECTED...WITH BROAD/LOW AMPLITUDE
TROUGH TO MEANDER ACROSS THE NORTHERN ISLANDS DURING THE NEXT FEW
DAYS. AS THE JET PULLS TO THE NORTH...MID LEVEL CYCLONIC VORTICES
ARE TO STREAM ACROSS HISPANIOLA-PUERTO RICO-NORTHERN LEEWARD ISLES
DURING THE DAY ON SUNDAY AND PART OF MONDAY. BUT IN A WEAK
CYCLONIC ADVECTIVE PATTERN MID LEVEL FORCING WILL COME IN SHORT
SUPPLY. AT LOW LEVELS EASTERLY TRADES ARE TO GENERALLY
PREVAIL...WITH 850 HPA WINDS TO PEAK AROUND 10-15KT OVER THE NEXT
COUPLE OF DAYS. ON SUNDAY THE WINDS VEER TO THE EAST-SOUTHEAST AS
DEEPENING POLAR TROUGH TO THE NORTH INDUCES AN INVERTED/PREFRONTAL
TROUGH ACROSS THE EASTERN CARIBBEAN. ALTHOUGH THE SURFACE FRONT
STALLS FAR TO THE NORTH...A PREFRONTAL SHEAR LINE IS FORECAST TO
BRIEFLY ENTER THE MONA PASSAGE/WESTERN PUERTO RICO ON SUNDAY
AFTERNOON. THIS...IN COMBINATION WITH THE INDUCED/PREFRONTAL
TROUGH WILL FAVOR AN INCREASE IN LOW LEVEL MOISTURE CONVERGENCE
ACROSS THE FORECAST AREA...WITH PWAT EXPECTED TO RANGE BETWEEN
25-35MM.

AS MOISTURE RISES...AND MID LEVEL DYNAMICS BECOME SOMEWHAT MORE
FAVORABLE... THE GLOBAL MODELS SHOW AN INCREASE IN TRADE WIND
SHOWER ACTIVITY ACROSS THE ENTIRE FORECAST AREA. THE
GFS...HOWEVER...IS THE ONLY ONE SHOWING MEASURABLE AMOUNTS ON
SUNDAY-TUESDAY...WHILE THE EUROPEAN MODELS ONLY FORESEE TRACE
ACCUMULATION. LACKING UPPER VENTILATION...THE ATMOSPHERE IS HAVING
A HARD TIME SUSTAINING A WELL ORGANIZED CONVECTIVE PROCESS. IN
RESPONSE...GDI PROJECTIONS ONLY SHOWS CHANCE OF SHOWERS ON SUNDAY
AND A SOMEWHAT HIGHER PROBABILITY OF A FEW BOOMERS ON TUESDAY.
CONSIDERING CYCLE-TO-CYCLE INCONSISTENCIES...AND LACK OF
SUPPORT...THE PROBABILITY OF THE GFS VERIFYING DURING THE MEDIUM
RANGE PERIOD IS LOW.

HUNTE...BMS (BARBADOS)
DAVISON/GALVEZ...WPC (USA)
$$




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