HPC Discussion
Posted by JAC on 6/10/2009, 6:19 am
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
214 PM EDT TUE JUN 09 2009

PATTERN EVOLUTION-FORECAST IS MORE COMPLICATED OVER THE CENTRAL
AND SOUTHERN CARIBBEAN. IN THIS AREA THE MODELS DISAGREE ON RISK
OF CYCLOGENESIS ALONG THE INDUCED/INVERTED TROUGH. LATEST
SATELLITE IMAGES SHOWS A SMALL CYCLONE OFF THE NORTHEAST COAST OF
HONDURAS. UNDER INFLUENCE OF THE UPPER TROUGH...AND IN INTERACTION
WITH A TROPICAL WAVE OVER THE CENTRAL CARIBBEAN...THE GFS
FORECASTS THIS SYSTEM TO RETAIN ITS INTEGRITY WHILE LIFTING TO THE
NORTHEAST TOWARDS JAMAICA THROUGH 36-42 HRS. THE GFS THEN
FORECASTS THE CYCLONE TO STALL. THE NAM INITIALLY FOLLOWS A
SIMILAR EVOLUTION...THEN FORECASTS THE LOW TO MIGRATE WEST TO
SOUTH OF THE CAYMAN ISLANDS BY 78 HRS. THE ECMWF FAILS TO
INITIALIZE THE LOW...AND TRIES TO DEVELOP A CLOSED CIRCULATION
OVER THE SOUTHERN CARIBBEAN BY 54-60 HRS. THIS SYSTEM IS IN A HIGH
SHEAR ENVIRONMENT...SO IT IS SOMEWHAT QUESTIONABLE THAT IT MIGHT
SURVIVE/INTENSIFY AT THE PACE THE GFS/NAM INDICATE. CONDITIONS
MIGHT BE MORE FAVORABLE AFTER 48/60 HRS WHEN THE UPPER LOW CUTS
OFF AND THE INFLOW OF COLD AIR ALOFT STARTS TO WANE.
MEANWHILE...THE SURFACE CYCLONE WILL FAVOR ORGANIZED DEEP
CONVECTION OVER NORTHEAST HONDURAS WHERE WE EXPECT RAINFALL
AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 30-60MM. MOST INTENSE IS
EXPECTED OVER WATER...AND AS THE WEAK VORTEX MIGRATES TOWARDS
JAMAICA THROUGH 36 HRS IT WILL FAVOR A SURGE IN ACTIVITY. AS A
RESULT...BETWEEN 24-60 HRS...WE EXPECT ACCUMULATION OF 20-40MM/DAY
AND MAXIMA OF 150-250MM TO AFFECT JAMAICA... HAITIAN PENINSULA AND
PORTIONS OF EASTERN CUBA. CONVECTION MIGHT PERSIST INTO DAY
03...BUT THIS WILL BE HIGHLY DEPENDENT ON INTENSITY/INTEGRITY OF
THE SURFACE CYCLONE. WE ARE GOING FOR HEAVY RAINS ON DAY 03...AS A
WORST CASE SCENARIO...BUT THIS IS A LOW CONFIDENCE FORECAST. THE
MAXIMA WILL PERSIST AT 150-250MM...WITH POSSIBILITY OF EXPANDING
TOWARDS THE CAYMAN ISLANDS.
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GFS & CMC Back on for West Carib Development - JAC, 6/10/2009, 5:56 am
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