Tropical Storm DANNY

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TROPICAL STORM DANNY DISCUSSION NUMBER   6
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL052009
500 PM EDT THU AUG 27 2009
 
REPORTS FROM AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT INDICATE
THAT THE CIRCULATION OF DANNY HAS BECOME BETTER DEFINED TODAY...
WITH STRONGER WINDS IN THE PREVIOUSLY WEAK SOUTHWESTERN QUADRANT. 
ASIDE FROM THAT...THE CYCLONE REMAINS VERY DISORGANIZED.  THE MAIN
CONVECTION IS IN A LINE 130-170 N MI EAST THROUGH SOUTH OF THE
CENTER...AND THE STRONGEST WINDS ARE 100 N MI OR MORE FROM THE
CENTER OVER THE NORTHERN SEMICIRCLE.  THE AIRCRAFT DATA...AS WELL
AS DATA FROM THE QUIKSCAT AND ASCAT SCATTEROMETERS...SUGGEST THAT
THE MAXIMUM WINDS HAVE DECREASED TO 40-45 KT.  THE INITIAL
INTENSITY WILL BE REDUCED TO 45 KT.

THE CENTER HAS MOVED SLOWLY WESTWARD SINCE SUNRISE...WITH THE
INITIAL MOTION ESTIMATED AT 270/2.  THE TRACK GUIDANCE MODELS
REMAIN IN EXCELLENT AGREEMENT THAT DANNY SHOULD TURN NORTHWARD OVER
THE NEXT 24-36 HR IN ADVANCE OF A COMPLEX DEEP-LAYER TROUGH MOVING
INTO THE EASTERN UNITED STATES.  AFTER THAT...THE STORM SHOULD
ACCELERATE NORTHEASTWARD INTO THE WESTERLIES...PASSING NEAR OR OVER
CAPE HATTERAS...SOUTHEASTERN NEW ENGLAND...AND THE CANADIAN
MARITIMES ON ITS WAY INTO THE NORTH ATLANTIC.  WITH THE MORE
WESTERLY INITIAL POSITION...THE TRACK GUIDANCE ENVELOPE HAS SHIFTED
SOMEWHAT WESTWARD DURING THE FIRST 48 HR...AND THE NEW FORECAST
TRACK IS ADJUSTED WESTWARD AS WELL.  WHILE THE TRACK IS STILL DOWN
THE MIDDLE OF THE GUIDANCE ENVELOPE...THE GFS...UKMET...NOGAPS...
AND CANADIAN MODELS ARE ALL TO THE LEFT OF THE NEW TRACK.  SOME
ADDITIONAL ADJUSTMENT TOWARD THE LEFT...TOWARD THE EAST COAST OF
THE U. S....MAY BE REQUIRED IF THIS TREND CONTINUES.
 
DANNY REMAINS IN AN AREA OF UPPER-LEVEL CONFLUENT FLOW ASSOCIATED
WITH THE PERSISTENT CYCLONIC SHEAR AXIS SEEN IN WATER VAPOR
IMAGERY.  IN ADDITION...BOTH WATER VAPOR IMAGERY AND SSM/IS TOTAL
PRECIPITABLE WATER IMAGERY SUGGEST THAT THE ENVIRONMENT NEAR DANNY
IS DRY.  THESE FACTORS...COMBINED WITH THE CURRENT LACK OF
ORGANIZATION...SUGGESTS THAT STRENGTHENING WILL BE SLOW AT BEST
DURING THE NEXT 24 HR.  THERE IS A WINDOW OF OPPORTUNITY FOR DANNY
TO STRENGTHEN FROM 24-36 HR AS IT IS FORECAST TO MOVE UNDER AN
UPPER-LEVEL ANTICYCLONE.  AFTER THAT...IT WILL ENCOUNTER STRONG
SOUTHWESTERLY FLOW ASSOCIATED WITH THE DEEP-LAYER TROUGH...WHICH
SHOULD CAUSE WEAKENING AND EXTRATROPICAL TRANSITION.  THE NEW
INTENSITY FORECAST CALLS FOR DANNY TO NOT REACH HURRICANE
STRENGTH...WITH A PEAK INTENSITY OF 60 KT IN 48 HR.  IT SHOULD BE
NOTED THAT THE GFDL AND HWRF STILL FORECAST DANNY TO BECOME A
HURRICANE BY 36 HR.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      27/2100Z 27.5N  73.5W    45 KT
 12HR VT     28/0600Z 28.5N  74.7W    45 KT
 24HR VT     28/1800Z 30.7N  75.0W    50 KT
 36HR VT     29/0600Z 34.4N  74.1W    55 KT
 48HR VT     29/1800Z 38.8N  71.6W    60 KT
 72HR VT     30/1800Z 46.5N  61.5W    50 KT...EXTRATROPICAL
 96HR VT     31/1800Z 50.0N  49.0W    40 KT...EXTRATROPICAL
120HR VT     01/1800Z 51.0N  32.0W    35 KT...EXTRATROPICAL
 
$$
FORECASTER BEVEN
 
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