[Tropical] Tropical Cyclone Discussion

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WTNT44 KNHC 251451
TCDAT4

TROPICAL STORM DEBBY DISCUSSION NUMBER   9
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL042012
1000 AM CDT MON JUN 25 2012

THERE HAS BEEN NO SIGNIFICANT DEEP CONVECTION NEAR THE CENTER OF
DEBBY FOR OVER 12 HOURS. WHAT CONVECTION REMAINS IS PRIMARILY
LOCATED IN A FRAGMENTED BAND WELL EAST OF THE CENTER...AND
SOUNDINGS ALONG THE GULF COAST INDICATE THAT THE ENTRAINMENT OF DRY
MID-LEVEL AIR IS AFFECTING THE STORM. IN ADDITION...THE SLOW
MOVEMENT OF DEBBY HAS INDUCED OCEANIC UPWELLING AND COOLING
UNDERNEATH THE CYCLONE AND MAY HAVE CONTRIBUTED TO THE OBSERVED
WEAKENING. LATEST DATA FROM THE RECONNAISSANCE AIRCRAFT INDICATE
THAT THE MAXIMUM WINDS ARE NEAR 40 KT. WITH DRY AIR LURKING AND
WESTERLY SHEAR ON THE INCREASE OVER THE NEXT COUPLE DAYS...
SIGNIFICANT RE-INTENSIFICATION OF THE CYCLONE PRIOR TO LANDFALL
SEEMS UNLIKELY. THE NEW NHC FORECAST IS ADJUSTED DOWNWARD IN LINE
WITH CURRENT TRENDS AND THE LATEST INTENSITY GUIDANCE.

AIRCRAFT AND SATELLITE FIXES HAVE SHOWN LITTLE OVERALL MOVEMENT OVER
THE PAST 12 TO 18 HOURS... ALTHOUGH RECENT SATELLITE IMAGERY
INDICATES AN EAST-NORTHEASTWARD TO NORTHEASTWARD SHORT-TERM MOTION.
AT THE MOMENT...IT IS UNCLEAR WHETHER THE CURRENT MOTION REPRESENTS
A MEANDERING OR A MORE DECIDED MOTION. ON THE LARGE SCALE...DEBBY
IS TRAPPED IN A REGION OF WEAK STEERING IN BETWEEN A STRONG
MID-LEVEL RIDGE OVER THE PLAINS AND ONE OVER THE SUBTROPICAL
CENTRAL ATLANTIC. GLOBAL MODELS DEPICT AN AMPLIFYING TROUGH
OFFSHORE THE EASTERN SEABOARD CAUSING DEBBY TO MOVE GENERALLY
EASTWARD THROUGH THE FORECAST PERIOD...WITH THE CENTER EMERGING
OVER THE SOUTHWEST ATLANTIC BY DAY 5. THE ECMWF/GFS SOLUTIONS BEGIN
TO LIFT OUT THE WESTERN ATLANTIC TROUGH IN ABOUT 72 HOURS...WHICH
COULD LEAVE DEBBY IN WEAK STEERING CURRENT AGAIN AFTER THAT TIME.
SINCE YESTERDAY... THE GUIDANCE HAS COME INTO BETTER
AGREEMENT...WITH ONLY THE UKMET NOW SHOWING A WESTWARD MOTION. IN
ADDITION...THE LATEST GFS ENSEMBLE MEMBERS FAVOR AN EASTWARD MOTION
BY ABOUT A 3 TO 1 RATIO. THE NEW FORECAST TRACK REPRESENTS A
SUBSTANTIAL CHANGE FROM THE PREVIOUS ONE BUT IS STILL SLOWER THAN
THE MULTI-MODEL CONSENSUS IN THE SHORT TERM.


FORECAST POSITIONS AND MAX WINDS

INIT  25/1500Z 28.6N  85.2W   40 KT  45 MPH
 12H  26/0000Z 28.8N  85.1W   35 KT  40 MPH
 24H  26/1200Z 28.9N  84.9W   35 KT  40 MPH
 36H  27/0000Z 29.0N  84.7W   35 KT  40 MPH
 48H  27/1200Z 29.2N  84.4W   35 KT  40 MPH
 72H  28/1200Z 29.5N  83.5W   35 KT  40 MPH
 96H  29/1200Z 29.5N  82.5W   30 KT  35 MPH...INLAND
120H  30/1200Z 29.5N  81.0W   30 KT  35 MPH

$$
FORECASTER KIMBERLAIN/FRANKLIN


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