ZCZC MIATCDEP1 ALL TTAA00 KNHC DDHHMM HURRICANE SERGIO DISCUSSION NUMBER 11 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP212006 100 AM PST THU NOV 16 2006 THE SATELLITE SIGNATURE OF SERGIO HAS CONTINUED TO SLOWLY DEGRADE... WITH THE OVERALL CLOUD PATTERN ELONGATED FROM SOUTH TO NORTH AND THE CENTRAL CONVECTION SOMEWHAT RAGGED. AN SSM/I OVERPASS AT 0249Z SHOWED THE BULK OF THE CONVECTION NORTHEAST OF THE CENTER. ANALYSES FROM CIMSS AT THE UNIVERSITY OF WISCONSIN NOW SHOW ABOUT 15 KT OF WESTERLY SHEAR AFFECTING THE SYSTEM DUE TO A DEVELOPING MID/UPPER-LEVEL TROUGH WEST OF THE HURRICANE. SATELLITE INTENSITY ESTIMATES ARE 102 KT FROM TAFB...90 KT FROM SAB...AND 77 KT FROM AFWA. BASED ON THIS THE INITIAL INTENSITY REMAINS 90 KT...ALTHOUGH THIS COULD BE A LITTLE GENEROUS. SERGIO APPEARS TO BE MAKING ITS FORECAST LEFT TURN...WITH THE INITIAL MOTION NOW 045/3. WATER VAPOR IMAGERY SHOWS A MID/UPPER-LEVEL LOW DEVELOPING OVER SOUTHERN BAJA CALIFORNIA WITH A BROAD TROUGH EXTENDING SOUTHWARD TO NEAR 12N111W. THE LARGE-SCALE MODELS AGREE THE LOW SHOULD MOVE SOUTHWARD FOR ANOTHER 24 HR OR SO...THEN TURN WESTWARD AS A MID/UPPER-LEVEL RIDGE BUILDS OVER NORTHWESTERN MEXICO TO THE WEST OF A DEEP-LAYER TROUGH OVER THE EASTERN UNITED STATES AND THE GULF OF MEXICO. DESPITE THIS...A CONSIDERABLE SPREAD REMAINS IN THE MODEL FORECAST TRACKS FOR SERGIO. THE GFDL AND THE NOGAPS ARE ON THE RIGHT SIDE OF THE GUIDANCE ENVELOPE AND ARE THE FASTEST...BRINGING THE CENTER TO THE MEXICAN COAST IN 48-72 HR. THE GFS AND ECMWF ARE ON THE LEFT SIDE OF THE GUIDANCE...WHILE THE UKMET IS DOWN THE MIDDLE AND SLOWER. THE FORECAST TRACK IS BASED ON THE PREMISE THAT THE DEVELOPING LOW WILL TURN SERGIO NORTHWARD FOR 24 HR OR SO...FOLLOWED BY A MOTION TOWARD THE NORTH-NORTHWEST OR NORTHWEST AS THE RIDGE BUILDS. THE NEW TRACK IS SIMILAR TO THE PREVIOUS FORECAST AND IS IN BEST AGREEMENT WITH THE FLORIDA STATE SUPERENSEMBLE. GIVEN THE UNCERTAINTY...INTERESTS ALONG THE SOUTHWESTERN COAST OF MEXICO SHOULD MONITOR THE PROGRESS OF SERGIO IN CASE IT MOVES CLOSER TO THE COAST THAN CURRENTLY FORECAST. THE LARGE-SCALE MODELS FORECAST THE SHEAR TO INCREASE SOMEWHAT OVER THE NEXT 24 HR...SO THE INTENSITY FORECAST NOW CALLS FOR WEAKENING DURING THAT PERIOD. THE MODELS FORECAST AN UPPER-LEVEL RIDGE TO BUILD OVER SERGIO FROM 24-72 HR...WHICH WILL CAUSE SOME SHEAR BUT LIKELY PRODUCE STRONG DIFFLUENCE OR DIVERGENCE OVER THE SYSTEM. THE SHIPS AND SUPERENSEMBLE MODELS FORECAST WEAKENING DURING THIS TIME...WHILE THE GFDL MAINTAINS SERGIO AS A 90-100 KT HURRICANE. ON THE PREMISE THAT THE SHEAR WILL PREVAIL OVER THE DIVERGENCE... THE INTENSITY FORECAST WILL CALL FOR SLOW WEAKENING DURING THIS TIME...ALTHOUGH AT A SLOWER PACE THAN THE PREVIOUS FORECAST. AFTER 72 HR...THE SHEAR IS FORECAST TO INCREASE WHILE THE DIVERGENCE DECREASES...WHICH SHOULD CAUSE A FASTER WEAKENING. FORECAST POSITIONS AND MAX WINDS INITIAL 16/0900Z 12.5N 103.1W 90 KT 12HR VT 16/1800Z 13.1N 103.0W 85 KT 24HR VT 17/0600Z 14.1N 103.3W 80 KT 36HR VT 17/1800Z 15.0N 103.9W 80 KT 48HR VT 18/0600Z 15.9N 104.8W 75 KT 72HR VT 19/0600Z 18.0N 106.5W 70 KT 96HR VT 20/0600Z 19.5N 107.5W 55 KT 120HR VT 21/0600Z 21.0N 110.0W 40 KT $$ FORECASTER BEVEN NNNN
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Page last modified: Thursday, 16-Nov-2006 08:50:03 UTC