Tropical Storm DANNY

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TROPICAL STORM DANNY DISCUSSION NUMBER   3
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL052009
1100 PM EDT WED AUG 26 2009
 
AFTER THE AIR FORCE HURRICANE HUNTER AIRCRAFT LEFT DANNY EARLIER
THIS AFTERNOON...VISIBLE SATELLITE IMAGERY SEEMED TO SUGGEST THAT A
NEW LOW-LEVEL CENTER WAS FORMING FARTHER TO THE NORTHEAST CLOSER TO
THE DEEP CONVECTION.  THE OVERALL CIRCULATION REMAINS DISTORTED AND
LIKELY CONSISTS OF A BROAD CENTER WITH A SHARP SURFACE TROUGH
EXTENDING TO THE SOUTHWEST.  NONETHELESS...A NOAA HURRICANE HUNTER
AIRCRAFT CONDUCTING A RESEARCH MISSION THIS EVENING DID RELAY SOME
RELIABLE SFMR DATA WHICH SUGGESTED THAT THE MAXIMUM WINDS ARE NEAR
45 KT WITHIN THE DEEP CONVECTION ABOUT 100 N MI TO THE NORTHEAST OF
THE CENTER.  A DROPSONDE FROM THIS FLIGHT ALSO INDICATED THAT THE
MINIMUM PRESSURE HAS FALLEN TO NEAR 1006 MB.

THE INITIAL MOTION IS ESTIMATED AT 310/9...BUT THIS IS HIGHLY
UNCERTAIN SINCE THE CENTER APPEARS TO BE REFORMING.  THE FORECAST
TRACK REASONING HAS NOT CHANGED...AND THE MODELS ARE IN GOOD
AGREEMENT THROUGH 72 HOURS.  DANNY IS EXPECTED TO MOVE
NORTHWESTWARD AND THEN TURN NORTHWARD WITHIN 48 HOURS AS IT IS
STEERED BETWEEN THE SUBTROPICAL RIDGE AND A EASTWARD-MOVING
MID-LEVEL LOW CURRENTLY LOCATED OVER THE NORTHERN GULF COAST. 
THEREAFTER...DANNY IS EXPECTED TO ACCELERATE NORTH-NORTHEASTWARD...
PARALLELING THE MID-ATLANTIC AND NEW ENGLAND COASTS...AS IT BECOMES
EMBEDDED IN THE FLOW AHEAD OF A DEEPENING UPPER LEVEL TROUGH OVER
THE GREAT LAKES.  IT SHOULD STILL BE NOTED THAT ANY DEVIATION TO
THE LEFT OF THE FORECAST TRACK THROUGH 72 HOURS WOULD BRING DANNY
CLOSER TO THE U.S. EAST COAST.

ALL THE INTENSITY GUIDANCE CONTINUES TO STRENGTHEN DANNY...BUT IT IS
NOT CLEAR WHY THEY MAKE THE CYCLONE SO STRONG.  THE UPPER-LEVEL
ENVIRONMENT IS EXPECTED TO BE FAVORABLE FOR STRENGTHENING OVER THE
NEXT 36-48 HOURS...BUT THEN THE VERTICAL SHEAR IS FORECAST TO
INCREASE TO 40 KT...AND MUCH MORE...ONCE DANNY ACCELERATES TO THE
NORTH AND NORTHEAST.  THE SHIPS AND LGEM MODELS MYSTERIOUSLY SHOW
THE SYSTEM STRENGTHENING TO 70-75 KT ONCE THE SHEAR INCREASES. 
SINCE THIS DOES NOT SEEM VERY REALISTIC...THE OFFICIAL FORECAST
LIMITS THE INTENSITY AT 65 KT.  ALTHOUGH THE OFFICIAL FORECAST
KEEPS DANNY AS A TROPICAL CYCLONE THROUGH 72 HOURS...THE GLOBAL
MODEL FIELDS AND FSU CYCLONE PHASE SPACE DIAGRAMS SUGGEST THAT
DANNY COULD BE EXTRATROPICAL BY THE TIME IT IS NEAR THE NEW ENGLAND
COAST. 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      27/0300Z 26.0N  71.6W    45 KT
 12HR VT     27/1200Z 26.8N  72.7W    45 KT
 24HR VT     28/0000Z 28.1N  74.0W    50 KT
 36HR VT     28/1200Z 30.0N  74.6W    55 KT
 48HR VT     29/0000Z 32.8N  74.2W    65 KT
 72HR VT     30/0000Z 41.5N  69.5W    65 KT
 96HR VT     31/0000Z 49.0N  58.5W    55 KT...EXTRATROPICAL
120HR VT     01/0000Z 53.5N  43.0W    40 KT...EXTRATROPICAL
 
$$
FORECASTER BERG/PASCH
 
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