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Tropical Depression FIVE (Text)

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TROPICAL DEPRESSION FIVE DISCUSSION NUMBER   3
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL052010
500 AM EDT WED AUG 11 2010
 
SATELLITE IMAGERY...RADAR DATA...AND REPORTS FROM AN AIR FORCE
RESERVE RECONNAISSANCE AIRCRAFT INDICATE THE DEPRESSION HAS NOT
CHANGED ITS ORGANIZATION SINCE THE LAST ADVISORY. CONVECTION HAS
ERODED CONSIDERABLY...AS HAS THE LOW-LEVEL CIRCULATION...WHICH IS
LIKELY DUE TO COOL DOWNDRAFTS CAUSED BY THE ENTRAINMENT OF DRY
MID-LEVEL AIR TO THE WEST OF THE CYCLONE. THE INITIAL INTENSITY IS
BEING HELD AT A GENEROUS 30 KT BASED ON SURFACE OBS OF 25-27 KT IN
SOME OF THE OUTER RAINBANDS AND A FEW UNCONTAMINATED SFMR WINDS OF
25 KT MEASURED BY THE RECON AIR AIRCRAFT. 

THE INITIAL MOTION ESTIMATE IS AN UNCERTAIN 310/09 DUE TO DIFFICULTY
IN LOCATING THE SURFACE CENTER. DESPITE THE DISRUPTION OF THE
LOW-LEVEL WIND FIELD...00Z UPPER-AIR DATA INDICATES THAT THE
DEPRESSION IS WELL DEFINED FROM 850 MB THROUGH AT LEAST 400 MB. ALL
OF THE MODELS ARE IN GOOD AGREEMENT ON TD-5 MOVING NORTHWEST TO
WEST-NORTHWESTWARD UNTIL LANDFALL AROUND 48 HOURS. HOWEVER...A
GRADUAL DECREASE IN FORWARD SPEED IS EXPECTED BY 36 HOURS AS A
MID-LEVEL SHORTWAVE TROUGH OVER THE CENTRAL DIGS SOUTHEASTWARD AND
CREATES A WEAKNESS IN THE SUBTROPICAL RIDGE ALONG THE CENTRAL GULF
COAST. THE EXACT TIMING OF THE WEAKNESS DEVELOPING WILL DETERMINE
HOW FAR WEST THE CYCLONE MOVES BEFORE TURNING NORTHWARD. THE
OFFICIAL FORECAST TRACK IS A LITTLE TO THE EAST OF THE PREVIOUS
ADVISORY...AND IS ALONG THE WESTERN EDGE OF THE GUIDANCE ENVELOPE.
 
ALTHOUGH THE DEPRESSION IS LACKING CONVECTIVE ORGANIZATION AT THIS
TIME...THE OVERALL STRUCTURE OF THE CYCLONE SUPPORTS THE
REDEVELOPMENT OF CONVECTION LATER TODAY AFTER THE DRY MID-LEVEL AIR
HAS MIXED AND THE LOW-LEVEL WIND FIELD HAS RECOVERED. NONE OF THE
GLOBAL MODELS ARE BULLISH ON THIS SYSTEM BECOMING MUCH STRONGER
THAN ITS CURRENT INTENSITY..DESPITE A VERY FAVORABLE UPPER-LEVEL
FLOW PATTERN THAT IS FORECAST TO DEVELOP ALONG THE GULF COAST BY
36-48 HOURS. THE GFDL AND HWRF MODELS DROP THE PRESSURE TO 986 AND
968 MB...RESPECTIVELY SHORTLY AFTER LANDFALL...AND THE HWRF MODEL
IS FORECASTING THE CYCLONE TO REACH HURRICANE STRENGTH RIGHT AT
LANDFALL. THE OFFICIAL INTENSITY FORECAST IS A BLEND OF THE VARIOUS
INTENSITY MODELS AND IS ONLY SLIGHTLY HIGHER THAN THE PREVIOUS
ADVISORY.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      11/0900Z 26.8N  85.1W    30 KT
 12HR VT     11/1800Z 27.7N  86.4W    30 KT
 24HR VT     12/0600Z 28.7N  88.0W    35 KT
 36HR VT     12/1800Z 29.5N  89.2W    40 KT
 48HR VT     13/0600Z 30.3N  89.4W    45 KT
 72HR VT     14/0600Z 31.0N  89.5W    35 KT...INLAND
 96HR VT     15/0600Z 33.5N  87.5W    20 KT...POST-TROP/REMNT LOW
120HR VT     16/0600Z...DISSIPATED INLAND
 
$$
FORECASTER STEWART
 
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