Anti-Cyclone On-Deck
Posted by JAC on 8/27/2009, 10:59 am
TROPICAL STORM DANNY DISCUSSION NUMBER   5
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL052009
1100 AM EDT THU AUG 27 2009

DANNY HAS BECOME A LITTLE BETTER ORGANIZED THIS MORNING.  THE LOW-LEVEL CIRCULATION LOOKS BETTER DEFINED THAN IT DID YESTERDAY...
AND THE CONVECTION IS CLOSER TO THE CENTER.  THAT BEING SAID...THE CENTER IS STILL EXPOSED...THE CONVECTION HAS MORE OF A LINEAR CHARACTER THAN THE CURVED BANDS CHARACTERISTIC OF A TROPICAL CYCLONE...AND THE STRONGEST WINDS ARE STILL WELL REMOVED FROM THE CENTER.  THE INITIAL INTENSITY IS HELD AT 50 KT PENDING THE NEXT AIR FORCE RESERVE HURRICANE HUNTER MISSION AT 18Z...ALTHOUGH RECENT QUIKSCAT DATA SUGGESTS THIS COULD BE A LITTLE GENEROUS.

THE EXPOSED LOW-LEVEL CENTER HAS BEEN MOVING ALMOST DUE WESTWARD FOR THE PAST FEW HOURS.  IT IS UNCLEAR IF THIS IS REPRESENTATIVE OF THE ACTUAL MOTION OF DANNY OR A SHORT-TERM TREND.  SO...THE INITIAL MOTION IS AN UNCERTAIN 310/11.  DESPITE THE PROBLEMATIC INITIAL MOTION...THE TRACK GUIDANCE MODELS ARE 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 NEW ENGLAND AND THE CANADIAN MARITIMES ON ITS WAY INTO THE NORTH ATLANTIC.  THE NAM...NOGAPS...AND CANADIAN MODELS ARE ON THE LEFT SIDE OF THE GUIDANCE ENVELOPE... CALLING FOR THE CENTER TO PASS NEAR CAPE HATTERAS AND THEN OVER NEW ENGLAND.  THE GFS...GFDL...AND HWRF ARE ON THE RIGHT SIDE...CALLING FOR THE CENTER TO STAY OFFSHORE UNTIL IT REACHES NOVA SCOTIA.  THE NEW FORECAST TRACK IS ADJUSTED TO THE LEFT OF THE PREVIOUS TRACK FOR THE FIRST 48 HR BASED ON THE INITIAL POSITION AND MOTION...AND IT LIES DOWN THE MIDDLE OF THE GUIDANCE ENVELOPE.  WHILE THE FORECAST TRACK DOES NOT CURRENTLY SHOW DANNY MAKING LANDFALL IN THE UNITED STATES...ADDITIONAL MOTION TO THE LEFT OF THE TRACK COULD BRING THE CENTER NEAR OR OVER THE U. S.
EASTERN SEABOARD.

DANNY IS CURRENTLY IN AN AREA OF UPPER-LEVEL CONFLUENT FLOW ASSOCIATED WITH THE PERSISTENT CYCLONIC SHEAR AXIS SEEN IN WATER VAPOR IMAGERY.  THE LARGE-SCALE MODELS FORECAST THIS FEATURE TO BE REPLACED BY AN UPPER-LEVEL ANTICYCLONE DURING THE NEXT 24-30 HR...
AND IF THIS VERIFIES IT WILL GIVE DANNY ITS BEST CHANCE TO STRENGTHEN.  BASED ON THIS...THE INTENSITY FORECAST CALLS FOR DANNY TO STRENGTHEN DURING THE 24-48 HR PERIOD...WITH A PEAK INTENSITY OF
65 KT.  THE GUIDANCE AGREES THAT DANNY SHOULD START LOSING TROPICAL CHARACTERISTICS AND INTENSITY AFTER 48 HR AS IT BECOMES EMBEDDED IN A STRONG BAROCLINIC ENVIRONMENT.  OVERALL...THE INTENSITY FORECAST IS IN BEST AGREEMENT WITH THE INTENSITY CONSENSUS...WITH THE PEAK INTENSITY BELOW THAT OF THE HWRF AND GFDL MODELS.


FORECAST POSITIONS AND MAX WINDS

INITIAL      27/1500Z 27.5N  73.1W    50 KT
12HR VT     28/0000Z 28.7N  73.9W    50 KT
24HR VT     28/1200Z 30.3N  74.5W    55 KT
36HR VT     29/0000Z 33.2N  74.3W    60 KT
48HR VT     29/1200Z 36.9N  72.4W    65 KT
72HR VT     30/1200Z 45.0N  64.5W    60 KT...EXTRATROPICAL
96HR VT     31/1200Z 50.0N  53.0W    45 KT...EXTRATROPICAL
120HR VT     01/1200Z 52.5N  37.0W    30 KT...EXTRATROPICAL

$$
FORECASTER BEVEN
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Wimpy Danny needs a shot of spinach - JAC, 8/27/2009, 7:19 am
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CaneTalk: Anti-Cyclone On-Deck
Anti-Cyclone On-Deck
Posted by JAC on 8/27/2009, 10:59 am
TROPICAL STORM DANNY DISCUSSION NUMBER   5
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL052009
1100 AM EDT THU AUG 27 2009

DANNY HAS BECOME A LITTLE BETTER ORGANIZED THIS MORNING.  THE LOW-LEVEL CIRCULATION LOOKS BETTER DEFINED THAN IT DID YESTERDAY...
AND THE CONVECTION IS CLOSER TO THE CENTER.  THAT BEING SAID...THE CENTER IS STILL EXPOSED...THE CONVECTION HAS MORE OF A LINEAR CHARACTER THAN THE CURVED BANDS CHARACTERISTIC OF A TROPICAL CYCLONE...AND THE STRONGEST WINDS ARE STILL WELL REMOVED FROM THE CENTER.  THE INITIAL INTENSITY IS HELD AT 50 KT PENDING THE NEXT AIR FORCE RESERVE HURRICANE HUNTER MISSION AT 18Z...ALTHOUGH RECENT QUIKSCAT DATA SUGGESTS THIS COULD BE A LITTLE GENEROUS.

THE EXPOSED LOW-LEVEL CENTER HAS BEEN MOVING ALMOST DUE WESTWARD FOR THE PAST FEW HOURS.  IT IS UNCLEAR IF THIS IS REPRESENTATIVE OF THE ACTUAL MOTION OF DANNY OR A SHORT-TERM TREND.  SO...THE INITIAL MOTION IS AN UNCERTAIN 310/11.  DESPITE THE PROBLEMATIC INITIAL MOTION...THE TRACK GUIDANCE MODELS ARE 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 NEW ENGLAND AND THE CANADIAN MARITIMES ON ITS WAY INTO THE NORTH ATLANTIC.  THE NAM...NOGAPS...AND CANADIAN MODELS ARE ON THE LEFT SIDE OF THE GUIDANCE ENVELOPE... CALLING FOR THE CENTER TO PASS NEAR CAPE HATTERAS AND THEN OVER NEW ENGLAND.  THE GFS...GFDL...AND HWRF ARE ON THE RIGHT SIDE...CALLING FOR THE CENTER TO STAY OFFSHORE UNTIL IT REACHES NOVA SCOTIA.  THE NEW FORECAST TRACK IS ADJUSTED TO THE LEFT OF THE PREVIOUS TRACK FOR THE FIRST 48 HR BASED ON THE INITIAL POSITION AND MOTION...AND IT LIES DOWN THE MIDDLE OF THE GUIDANCE ENVELOPE.  WHILE THE FORECAST TRACK DOES NOT CURRENTLY SHOW DANNY MAKING LANDFALL IN THE UNITED STATES...ADDITIONAL MOTION TO THE LEFT OF THE TRACK COULD BRING THE CENTER NEAR OR OVER THE U. S.
EASTERN SEABOARD.

DANNY IS CURRENTLY IN AN AREA OF UPPER-LEVEL CONFLUENT FLOW ASSOCIATED WITH THE PERSISTENT CYCLONIC SHEAR AXIS SEEN IN WATER VAPOR IMAGERY.  THE LARGE-SCALE MODELS FORECAST THIS FEATURE TO BE REPLACED BY AN UPPER-LEVEL ANTICYCLONE DURING THE NEXT 24-30 HR...
AND IF THIS VERIFIES IT WILL GIVE DANNY ITS BEST CHANCE TO STRENGTHEN.  BASED ON THIS...THE INTENSITY FORECAST CALLS FOR DANNY TO STRENGTHEN DURING THE 24-48 HR PERIOD...WITH A PEAK INTENSITY OF
65 KT.  THE GUIDANCE AGREES THAT DANNY SHOULD START LOSING TROPICAL CHARACTERISTICS AND INTENSITY AFTER 48 HR AS IT BECOMES EMBEDDED IN A STRONG BAROCLINIC ENVIRONMENT.  OVERALL...THE INTENSITY FORECAST IS IN BEST AGREEMENT WITH THE INTENSITY CONSENSUS...WITH THE PEAK INTENSITY BELOW THAT OF THE HWRF AND GFDL MODELS.


FORECAST POSITIONS AND MAX WINDS

INITIAL      27/1500Z 27.5N  73.1W    50 KT
12HR VT     28/0000Z 28.7N  73.9W    50 KT
24HR VT     28/1200Z 30.3N  74.5W    55 KT
36HR VT     29/0000Z 33.2N  74.3W    60 KT
48HR VT     29/1200Z 36.9N  72.4W    65 KT
72HR VT     30/1200Z 45.0N  64.5W    60 KT...EXTRATROPICAL
96HR VT     31/1200Z 50.0N  53.0W    45 KT...EXTRATROPICAL
120HR VT     01/1200Z 52.5N  37.0W    30 KT...EXTRATROPICAL

$$
FORECASTER BEVEN
49
In this thread:
Wimpy Danny needs a shot of spinach - JAC, 8/27/2009, 7:19 am
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