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Tropical Storm DEBBY (Text)

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TROPICAL STORM DEBBY DISCUSSION NUMBER   7
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL042012
1000 PM CDT SUN JUN 24 2012
 
THE APPEARANCE OF DEBBY IN SATELLITE AND RADAR IMAGERY HAS DEGRADED
SIGNIFICANTLY THIS EVENING AS A SHARP MID-LEVEL DRY INTRUSION HAS
WORKED ITS WAY INTO THE CENTER OF THE CYCLONE AND ERODED ALL OF THE
INNER CORE DEEP CONVECTION. THE INITIAL INTENSITY IS BEING HELD AT
50 KT FOR THIS FORECAST PACKAGE BASED MAINLY ON CONTINUITY WITH THE
PREVIOUS ADVISORY AND THE RELATIVELY LOW CENTRAL PRESSURE OF 991 MB
REPORTED BY AN AIR FORCE RESERVE RECON AIRCRAFT THIS EVENING.

DEBBY HAS BEEN NEARLY STATIONARY SINCE THE LAST ADVISORY. BOTH 18Z
AND 00Z UPPER-AIR DATA INDICATE MID-LEVEL RIDGING HAS CONTINUED TO
BUILD ACROSS THE SOUTHEASTERN U.S. TO THE NORTH OF DEBBY...AND THIS
HAS LIKELY BEEN THE REASON FOR THE LACK OF ANY SIGNIFICANT MOTION
OVER THE PAST SEVERAL HOURS. ALL OF THE NHC MODEL GUIDANCE...EXCEPT
FOR THE GFS AND GFS-ENSEMBLE MODELS...INDICATE THIS BLOCKING PATTERN
ACROSS THE CENTRAL AND EASTERN U.S. SHOULD CONTINUE AS FAST-MOVING
SHORTWAVE TROUGHS PASS WELL TO THE NORTH OF DEBBY. THE RESULT
SHOULD BE THAT THE CYCLONE WILL MOVE LITTLE DURING THE NEXT COUPLE
OF DAYS...AND THEN ONLY DRIFT SLOWLY NORTHWARD AFTER THAT AS THE
RIDGE OVER THE SOUTHEASTERN U.S. GRADUALLY BREAKS DOWN. ALTHOUGH THE
GFS MODEL HAS BEEN VERY CONSISTENT WITH A FAST NORTHEASTWARD MOTION
ACROSS NORTH FLORIDA THE PAST FEW DAYS...THE LARGE SPRAWLING NATURE
OF THE CYCLONE AND THE BLOCKING RIDGE TO THE NORTH WOULD SUGGEST
THAT THE GFS MODEL MAY BE LIFTING OUT DEBBY TOO QUICKLY. THE
OFFICIAL FORECAST TRACK IS SIMILAR TO BUT SLIGHTLY LEFT OF THE
PREVIOUS ADVISORY TRACK...MAINLY DUE TO THE MORE WESTWARD INITIAL
POSITION.
 
DEBBY HAS FINALLY CONSOLIDATED ALL OF THE MULTIPLE SMALL SWIRLS INTO
A WELL-DEFINED LOW-LEVEL CIRCULATION CENTER. THE GLOBAL MODELS ARE
FORECASTING THE AFOREMENTIONED DEEP DRY SLOT TO GRADUALLY MOISTEN
UP OVER THE NEXT 48 HOURS AS DEEP MOISTURE AND INSTABILITY
CURRENTLY OVER THE FLORIDA PENINSULA ADVECTS WESTWARD INTO THE
INNER CORE. THE COMBINATION OF THESE TWO FEATURES MAY ALLOW FOR
SOME SLIGHT STRENGTHENING BEFORE DEBBY BEGINS TO INTERACT WITH LAND
OR COLD UPWELLING BENEATH THE CYCLONE OCCURS. THE OFFICIAL
INTENSITY FORECAST IS IDENTICAL TO THE PREVIOUS ADVISORY AND
FOLLOWS A BLEND OF THE SHIPS/LGEM STATISTICAL MODELS AND THE
HWRF/GFDL REGIONAL MODELS.

FORECAST POSITIONS AND MAX WINDS
 
INIT  25/0300Z 28.3N  85.9W   50 KT  60 MPH
 12H  25/1200Z 28.6N  85.8W   50 KT  60 MPH
 24H  26/0000Z 28.7N  85.8W   50 KT  60 MPH
 36H  26/1200Z 28.8N  85.8W   55 KT  65 MPH
 48H  27/0000Z 28.9N  85.8W   60 KT  70 MPH
 72H  28/0000Z 29.4N  85.8W   55 KT  65 MPH
 96H  29/0000Z 29.9N  85.8W   35 KT  40 MPH...NEAR COAST
120H  30/0000Z 30.4N  85.6W   30 KT  35 MPH...INLAND
 
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FORECASTER STEWART
 
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