ZCZC MIATCDAT1 ALL TTAA00 KNHC DDHHMM 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 NNNN
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