Tropical Storm DANNY

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TROPICAL STORM DANNY DISCUSSION NUMBER  10
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL052009
500 PM EDT FRI AUG 28 2009
 
AFTER STALLING EARLIER THIS AFTERNOON...THE CENTER OF DANNY IS
FINALLY MOVING SLOWLY NORTHWARD OR NORTH-NORTHEASTWARD. DATA FROM AN
AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT SUGGEST THAT DANNY IS
STILL A MINIMAL TROPICAL STORM...BASED ON A 33-KT OBSERVATION FROM
THE SFMR IN THE SOUTHEASTERN QUADRANT.
 
THE INTENSITY FORECAST SHOWS THE POSSIBILITY FOR A LITTLE
STRENGTHENING IN THE SHORT TERM...AS THE INCREASING UPPER-LEVEL
DIVERGENCE COULD SUPPORT THE REDEVELOPMENT OF CONVECTION NEAR THE
CENTER. HOWEVER...BY 24 HOURS...DANNY WILL BE MOVING INTO A VERY
UNFAVORABLE ENVIRONMENT FOR A TROPICAL CYCLONE...WITH THE SHIPS
MODEL SHOWING WIND SHEAR INCREASING TO 35 KT BY THAT TIME. BY 36
HOURS...DANNY WILL BE OVER SSTS OF NEAR 20C...AND INTERACTING WITH
THE DEEP-LAYER BAROCLINIC TROUGH OVER THE EASTERN U.S.  MOST OF
THE LATEST GLOBAL MODELS AND PHASE SPACE DIAGRAMS SHOW THAT DANNY
WILL BE EXTRATROPICAL BY THAT TIME. THERE IS THE POTENTIAL FOR SOME
INTENSIFICATION OF DANNY LATE IN THE FORECAST PERIOD AS AN
EXTRATROPICAL CYCLONE OVER THE NORTH ATLANTIC.
 
THE GUIDANCE WAS INITIALIZED WITH A LONG TERM MOTION OF 315/08...
AND REMAINS IS GOOD AGREEMENT ON THE RAPID ACCELERATION OF DANNY
NORTHWARD AND NORTH-NORTHEASTWARD. IN FACT...THE MODEL SPREAD IS
SMALLER NOW THAN IT WAS EARLIER TODAY. THE OFFICIAL TRACK IS SLOWER
THAN THE MODEL CONSENSUS THROUGH MOST OF THE PERIOD DUE TO THE SLOW
INITIAL MOTION. FROM 24 TO 36 HOURS...THE NEW FORECAST IS SHIFTED
TO THE RIGHT OF THE PREVIOUS FORECAST TRACK...BUT DANNY IS STILL
EXPECTED TO MOVE CLOSE TO THE SOUTHEASTERN COAST OF NEW ENGLAND AND
APPROACH NOVA SCOTIA IN 36-48 HOURS.
 
DATA FROM THE AIRCRAFT SUGGEST THAT THE ONLY 34-KT WINDS ARE LOCATED
IN THE SOUTHEASTERN QUADRANT. THE LACK OF WINDS ON THE WEST SIDE OF
DANNY LESSEN THE THREAT FOR TROPICAL STORM WIND REACHING THE NORTH
CAROLINA OUTER BANKS. HOWEVER...THE WATCH IS LEFT IN PLACE IN CASE
THE WIND FIELD BECOMES BETTER DEFINED ON THE WESTERN SIDE OF DANNY.
AS DANNY BECOMES EXTRATROPICAL...ITS EXPANDING WIND FIELD MAY
IMPACT THE COAST OF NEW ENGLAND. THESE POTENTIAL IMPACTS WILL BE
HANDLED WITH GALE WARNINGS AND OTHER PRODUCTS ISSUED BY LOCAL NWS
OFFICES IN THAT REGION.
 
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      28/2100Z 30.4N  75.4W    35 KT
 12HR VT     29/0600Z 32.7N  75.8W    40 KT
 24HR VT     29/1800Z 37.3N  73.2W    40 KT
 36HR VT     30/0600Z 41.9N  68.2W    40 KT...EXTRATROPICAL
 48HR VT     30/1800Z 46.5N  61.4W    40 KT...EXTRATROPICAL
 72HR VT     31/1800Z 50.5N  49.5W    40 KT...EXTRATROPICAL
 96HR VT     01/1800Z 53.0N  35.0W    45 KT...EXTRATROPICAL
120HR VT     02/1800Z 55.0N  22.0W    50 KT...EXTRATROPICAL
 
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FORECASTER BRENNAN
 
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