ZCZC MIATCDEP5 ALL TTAA00 KNHC DDHHMM TROPICAL STORM NORMAN DISCUSSION NUMBER 6 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP152006 200 AM PDT TUE OCT 10 2006 NORMAN HAS SUSTAINED SOME DEEP CONVECTION OVER THE LAST SEVERAL HOURS...ALTHOUGH THE COVERAGE HAS BEEN GENERALLY ON THE DECREASE. SHORTWAVE IR IMAGERY AND AN SSMI OVERPASS AT 0400 UTC SUGGEST THE CYCLONE IS BEGINNING TO FEEL THE EFFECTS OF SOUTHWESTERLY SHEAR OVER THE NORTHERN SEMICIRCLE...WITH THE CONVECTION BEGINNING TO BECOME DISPLACED SLIGHTLY NORTH-NORTHEAST OF THE LOW-LEVEL CENTER. THE ADVISORY INTENSITY IS HELD AT 45 KT BASED ON DVORAK ESTIMATES OF 55 KT AND 45 KT FROM TAFB AND SAB...BUT LEANING TOWARD THE LOWER ESTIMATE BASED ON A QUIKSCAT PASS AT 0230 UTC THAT DID NOT REVEAL ANY WINDS GREATER THAN 45 KT. THE SHIPS MODEL SUGGESTS THAT BEYOND ABOUT 12 HOURS THE SHEAR WILL STEADILY INCREASE THROUGH THE END OF THE FORECAST PERIOD. NORMAN WILL ALSO PASS OVER SLIGHTLY COOLER SSTS BEYOND 12 HOURS. THE OFFICIAL FORECAST CONTINUES TO REFLECT THESE UNFAVORABLE ENVIRONMENTAL FACTORS AND ANTICIPATES WEAKENING BEYOND 24 HOURS. THE INTENSITY FORECAST IS A BLEND OF THE SHIPS AND GFDL GUIDANCE...AND FOLLOWS THE FSU SUPERENSEMBLE CLOSELY. NORMAN IS CURRENTLY MOVING VERY SLOWLY TO THE NORTH...TEMPORARILY WITHIN A WEAKNESS IN THE STEERING FLOW...IN BETWEEN THE FAR WESTERN PERIPHERY OF A WEAK MID-LEVEL RIDGE JUST OFF THE COAST OF CENTRAL MEXICO...AND SOUTH OF THE DEEP-LAYER TROUGH EXTENDING FROM CALIFORNIA SOUTHWARD OVER BAJA. A QUIKSCAT AMBIGUITY ANALYSIS AND THE SSMI OVERPASS AT 0400 UTC HELPED VERIFY THAT NORMAN HAS BEEN MOVING SLIGHTLY SLOWER THAN PREVIOUSLY INDICATED...AND THE INITIAL MOTION ESTIMATE IS ONLY 360/2. HOWEVER...ALL OF THE TRACK MODEL GUIDANCE SUGGESTS THIS SLOWDOWN IS TEMPORARY AND FORECAST A GRADUAL TURN TOWARD THE NORTHEAST DURING THE NEXT DAY OR TWO. HOWEVER...THE MODELS GREATLY DISAGREE ON HOW FAR NORTH NORMAN WILL TRAVEL AND HOW FAST. THE NEW OFFICIAL FORECAST IS SLOWER THAN THE PREVIOUS ADVISORY TO COME INTO BETTER AGREEMENT WITH MOST OF THE GUIDANCE. FORECAST POSITIONS AND MAX WINDS INITIAL 10/0900Z 16.5N 117.8W 45 KT 12HR VT 10/1800Z 17.5N 117.6W 45 KT 24HR VT 11/0600Z 18.4N 116.8W 45 KT 36HR VT 11/1800Z 19.1N 115.9W 40 KT 48HR VT 12/0600Z 19.9N 114.9W 35 KT 72HR VT 13/0600Z 21.0N 113.0W 25 KT...DISSIPATING 96HR VT 14/0600Z 22.5N 111.0W 20 KT...REMNANT LOW 120HR VT 15/0600Z...DISSIPATED $$ FORECASTER KNABB/WILLIS NNNN
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Page last modified: Tuesday, 10-Oct-2006 09:05:03 UTC