[Tropical] Tropical Cyclone Discussion

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WTNT41 KNHC 250256
TCDAT1
HURRICANE DANIELLE DISCUSSION NUMBER  14
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL062010
1100 PM AST TUE AUG 24 2010

A SERIES OF MICROWAVE PASSES DURING THE PAST SEVERAL HOURS SHOW THAT
DANIELLE IS BECOMING BETTER-ORGANIZED...WITH HINTS OF AN EYE
FEATURE ON THE 37-GHZ CHANNELS. THIS IS ALSO SUGGESTED BY AN
INCREASE IN DEEP CONVECTION NEAR THE CENTER...ALTHOUGH THE SYSTEM
APPEARS TO STILL BE EXPERIENCING NORTHWESTERLY SHEAR. SATELLITE
CLASSIFICATIONS ARE A LITTLE HIGHER THAN SIX HOURS AGO...AND THE
INITIAL WIND SPEED IS RAISED TO 65 KT.

THE INTENSITY FORECAST IS A CHALLENGING ONE THIS EVENING.  FOR THE
NEXT DAY OR SO...THE HURRICANE WILL BE INTERACTING WITH THE
MID-OCEANIC TROUGH TO ITS NORTHWEST AND EXPERIENCING MODERATE
SOUTHWESTERLY SHEAR. DESPITE WARM SSTS...THESE UPPER-LEVEL
CONDITIONS USUALLY DO NOT FAVOR MUCH INTENSIFICATION.
HOWEVER...MOST OF THE GLOBAL MODELS FRACTURE THE TROUGH IN 36-48
HR...WHICH CAUSES A DECREASE IN SHEAR AS HIGH PRESSURE BUILDS
CLOSER TO DANIELLE AND AN OPPORTUNITY FOR A MORE SIGNIFICANT
RESTRENGTHENING.  THIS IS THE SCENARIO FOLLOWED IN THE NHC
INTENSITY FORECAST...AND IS IN GOOD AGREEMENT WITH A BLEND OF THE
GFDL/LGEM/SHIPS MODELS.

THE INITIAL MOTION OF THE CYCLONE CONTINUES TO THE WEST-NORTHWEST AT
ABOUT 16 KT. A RIDGE OVER THE CENTRAL ATLANTIC SHOULD PROVIDE THE
STEERING FLOW FOR DANIELLE DURING MOST OF THE FORECAST PERIOD. AS
THE RIDGE WEAKENS...A TURN TOWARD THE NORTHWEST IS EXPECTED
TOMORROW...WITH THAT GENERAL MOTION AT A SLOWER SPEED CONTINUING
FOR A FEW DAYS AFTERWARD. THE BIGGEST QUESTION IN THE LONG-TERM IS
HOW MUCH A MID-LATITUDE TROUGH THAT IS FORECAST TO MOVE OFFSHORE OF
THE NORTHEAST UNITED STATES OVER THE WEEKEND WILL AFFECT DANIELLE.
THE OVERALL TREND IN THE MODELS IS FOR A WEAKER TROUGH...WHICH
CAUSES A DELAYED NORTHWARD TURN OF THE CYCLONE.  THE OFFICIAL
FORECAST IS WEST OF THE PREVIOUS ONE INITIALLY...BUT ENDS UP SLOWER
THAN THE PREVIOUS FORECAST AT 120 HOURS.  IT IS IMPORTANT TO NOTE
THAT THE MODEL SPREAD IS INCREASING AT THE LONG-RANGE...SO THE
FORECAST CONFIDENCE AT THAT TIME IS LOWER THAN AVERAGE.


FORECAST POSITIONS AND MAX WINDS

INITIAL      25/0300Z 18.2N  49.8W    65 KT
 12HR VT     25/1200Z 19.4N  51.5W    70 KT
 24HR VT     26/0000Z 21.3N  53.5W    70 KT
 36HR VT     26/1200Z 23.0N  55.3W    75 KT
 48HR VT     27/0000Z 24.4N  57.0W    80 KT
 72HR VT     28/0000Z 27.0N  60.0W    90 KT
 96HR VT     29/0000Z 30.0N  61.5W    90 KT
120HR VT     30/0000Z 33.0N  61.5W    85 KT

$$
FORECASTER BLAKE



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