Tropical Depression ONE

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TROPICAL DEPRESSION ONE DISCUSSION NUMBER   1
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL012009
1100 AM EDT THU MAY 28 2009
 
DEEP CONVECTION ASSOCICATED WITH THE AREA OF LOW PRESSURE OFF THE
MID-ATLANTIC COAST HAS BEEN PERSISTENT SINCE ABOUT 04Z THIS MORNING
WHILE THE SYSTEM MOVES OVER THE 25-26C WATERS OF THE GULF
STREAM.  DVORAK CLASSIFICATIONS FROM TAFB AND SAB AT 12Z WERE
T2.0 AND T1.5...RESPECTIVELY.  AN AMSU PASS AT 1033Z HELPS TO PLACE
THE CENTER ON THE NORTHWEST EDGE OF THE DEEP CONVECTION.  BASED ON
THESE DATA...THE SYSTEM IS BEING UPGRADED TO A TROPICAL
DEPRESSION...THE FIRST OF THE ATLANTIC HURRICANE SEASON.
 
THE INITIAL MOTION IS 050/15.  THE DEPRESSION IS EMBEDDED IN A
SOUTHWESTERLY STEERING CURRENT AHEAD OF A DEEP-LAYER TROUGH OVER
THE CENTRAL UNITED STATES.  THIS BASIC PATTERN IS EXPECTED TO
PERSIST...AND THE DYNAMICAL MODEL GUIDANCE IS IN PRETTY GOOD
AGREEMENT...AT LEAST THROUGH 36 HOURS...WHEN THE SYSTEM BEGINS TO
LOSE DEFINITION IN MUCH OF THE GUIDANCE.
 
VERTICAL SHEAR OVER THE SYSTEM IS LIGHT...AND THE CYCLONE IS LIVING
OFF THE NARROW GULF STREAM WATERS.  AS LONG AS IT REMAINS THERE SOME
STRENGTHENING IS POSSIBLE.  ALTHOUGH THE SHIPS GUIDANCE DOES NOT
SHOW THE SYSTEM REACHING TROPICAL STORM STRENGTH...THE INITIAL SST
INPUT TO THE MODEL APPEAR TOO COLD.  AS A RESULT...THE OFFICIAL
FORECAST WILL CALL FOR THE SYSTEM TO BECOME A TROPICAL STORM OVER
THE NEXT DAY OR SO.  AFTER THAT...A LOSS OF CONVECTION...AND
TROPICAL CHARACTERISTICS...IS EXPECTED.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      28/1500Z 37.3N  71.0W    30 KT
 12HR VT     29/0000Z 38.5N  68.4W    35 KT
 24HR VT     29/1200Z 40.2N  64.6W    35 KT
 36HR VT     30/0000Z 41.5N  60.0W    30 KT
 48HR VT     30/1200Z 43.0N  55.0W    25 KT...EXTRATROPICAL
 72HR VT     31/1200Z 46.0N  46.0W    25 KT...EXTRATROPICAL
 96HR VT     01/1200Z...DISSIPATED
 
$$
FORECASTER FRANKLIN/BEVEN
 
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