[Tropical] Tropical Cyclone Discussion

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WTNT41 KNHC 281455
TCDAT1
HURRICANE DANIELLE DISCUSSION NUMBER  29
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL062010
1100 AM AST SAT AUG 28 2010

THE VISIBLE AND INFRARED SATELLITE PRESENTATIONS AND A SERIES OF
MICROWAVE IMAGES FROM THE NRL TROPICAL CYCLONE WEBSITE INDICATE
CONTINUED WEAKENING OF THE INNER EYEWALL STRUCTURE OF
DANIELLE...PARTICULARLY OVER THE WESTERN PORTION. THE OUTER
CONCENTRIC RING LOCATED ABOUT 60 NMI FROM THE CENTER OF THE
CYCLONE...HOWEVER...IS WELL DEFINED AND SYMMETRIC...AND APPEARS TO
BE CLOSE TO COMPLETING AN EYEWALL REPLACEMENT CYCLE.
CONSEQUENTLY...THERE MAY BE A SMALL WINDOW OF OPPORTUNITY FOR
STRENGTHENING DURING THE NEXT 12-18 HOURS BEFORE THE NORTHEASTERLY
SHEAR INCREASES SIGNIFICANTLY AND THE SYSTEM BEGINS ITS TRACK OVER
COOLER WATER. IT IS WORTH NOTING...HOWEVER...THAT THE SHIPS MODEL
PROBABILITY OF RAPID INTENSIFICATION DURING THE NEXT 24 HOURS HAS
DECREASED FROM 14 TO 4 PERCENT...SUGGESTING A SMALL CHANCE OF THIS
SCENARIO COMING TO FRUITION. AS A COMPROMISE...THE INITIAL AND
FORECAST INTENSITY WILL MAINTAIN A WIND SPEED OF 95 KT FOR 12
HOURS...THEN SHOW A GRADUAL WEAKENING TREND THEREAFTER. BY THE 96
HOUR PERIOD...DANIELLE WILL LIKELY TRANSITION INTO A LARGE AND
POWERFUL EXTRATROPICAL CYCLONE OVER THE NORTH ATLANTIC...AND THE
FORECAST SHOWS ONLY SLOW WEAKENING DURING THIS EVENT.

THE INITIAL MOTION ESTIMATE IS NORTH-NORTHEASTWARD OR 020/8.
DANIELLE SHOULD BEGIN TO ACCELERATE TOWARD THE NORTH-NORTHEAST LATER
TODAY IN RESPONSE TO A DEEP LAYER BAROCLINIC TROUGH MOVING
OFF OF THE EASTERN SEABOARD OF THE UNITED STATES. A TEMPORARY
REDUCTION IN FORWARD SPEED IS FORECAST NEAR THE 36-48 PERIOD AS A
MID-LEVEL RIDGE PASSES TO THE NORTH OF THE CYCLONE. AT DAY
3...ANOTHER MAJOR SHORTWAVE TROUGH IS EXPECTED TO MOVE OUT OF
NORTHEAST CANADA...CAUSING DANIELLE TO AGAIN ACCELERATE
EAST-NORTHEASTWARD. THE AFOREMENTIONED SHORTWAVE TROUGH SHOULD
CAUSE DANIELLE TO SHARPLY TURN NORTHWARD TOWARD THE END OF THE
PERIOD. THE OFFICIAL NHC FORECAST HAS BEEN ADJUSTED A LITTLE TO THE
RIGHT BECAUSE OF THE 6 HOUR MOTION AND IS BASED ON A BLEND OF THE
DYNAMICAL MODELS...PRIMARILY THE GFS...ECMWF...AND THE CANADIAN
BEYOND DAY 3.


FORECAST POSITIONS AND MAX WINDS

INITIAL      28/1500Z 29.3N  60.5W    95 KT
 12HR VT     29/0000Z 31.2N  59.5W    95 KT
 24HR VT     29/1200Z 34.6N  57.2W    90 KT
 36HR VT     30/0000Z 37.7N  54.9W    85 KT
 48HR VT     30/1200Z 39.5N  53.0W    75 KT
 72HR VT     31/1200Z 42.5N  42.5W    70 KT
 96HR VT     01/1200Z 51.0N  30.5W    65 KT...POST-TROP/EXTRATROP
120HR VT     02/1200Z 55.0N  35.5W    55 KT...POST-TROP/EXTRATROP

$$
FORECASTER ROBERTS/AVILA


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