Tropical Depression THIRTEEN

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TROPICAL DEPRESSION THIRTEEN DISCUSSION NUMBER   2
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
11 PM EDT SUN AUG 28 2005
 
TROPICAL DEPRESSION THIRTEEN CONTINUES TO STRUGGLE WITHIN THE
MODERATE NORTHEASTERLY SHEAR ENVIRONMENT.  SHORTWAVE INFRARED
IMAGERY DEPICTS A RATHER DISORGANIZED CLOUD PATTERN...WITH DEEP
CONVECTION DISPLACED TO THE SOUTHWEST OF THE CIRCULATION CENTER. 
SATELLITE CLASSIFICATIONS AND THE INITIAL INTENSITY REMAIN UNCHANGED
FROM THE PREVIOUS PACKAGE.  THE INTENSITY FORECAST IS A LITTLE
PROBLEMATIC.  AVAILABLE DYNAMICAL MODELS SUGGEST DISSIPATION WITHIN
48 HOURS AS THE SYSTEM INTERACTS WITH A MID-ATLANTIC TROUGH TO THE
NORTHWEST.  SHIPS SUGGESTS THAT THE SHEAR WILL DECREASE BY MID
PERIOD...GRADUALLY BRINGING THE SYSTEM TO 61 KT IN 120 HOURS.  THE
INTENSITY FORECAST IS SIMILAR TO THE PREVIOUS ADVISORY AND THE
GFDL...INDICATING SLOW STRENGTHENING TO A TROPICAL STORM IN 48
HOURS.
 
INITIAL MOTION IS ESTIMATED AT 310/10.  THE TROPICAL DEPRESSION IS
EXPECTED TO MOVE WITHIN THE STEERING FLOW AROUND THE SOUTHWESTERN
EDGE OF THE SUBTROPICAL RIDGE.  GLOBAL MODELS AND THE GFDL SUGGEST
A RELATIVELY SHARP TURN TO THE NORTH IN 48 HOURS NEAR 54W JUST
BEFORE DISSIPATION.  ANOTHER POSSIBLE SCENARIO IS THAT THE SYSTEM
COMPLETELY SHEARS FROM THE MID-LEVEL CIRCULATION AND CONTINUES ON A
WEST-NORTHWESTWARD MOTION WITH THE LOW-LEVEL FLOW.  THE OFFICIAL
FORECAST IS A BLEND OF THE GFS BETA ADVECTION MODELS...THE
GFDL...AND THE PREVIOUS FORECAST CALLING FOR A GRADUAL TURN
NORTHWESTWARD WITHIN A WEAKNESS IN THE RIDGE IN 72 HOURS.
 
FORECASTER ROBERTS/FRANKLIN
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      29/0300Z 15.9N  47.4W    25 KT
 12HR VT     29/1200Z 16.9N  48.7W    25 KT
 24HR VT     30/0000Z 18.1N  50.7W    30 KT
 36HR VT     30/1200Z 19.2N  52.8W    30 KT
 48HR VT     31/0000Z 20.4N  54.8W    35 KT
 72HR VT     01/0000Z 22.5N  58.0W    35 KT
 96HR VT     02/0000Z 24.0N  60.0W    35 KT
120HR VT     03/0000Z 25.5N  62.0W    35 KT
 
 
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