ZCZC MIATCDEP5 ALL TTAA00 KNHC DDHHMM TROPICAL STORM OTIS DISCUSSION NUMBER 5 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 2 AM PDT THU SEP 29 2005 A QUIKSCAT PASS AT 0130Z SUPPORTED AT LEAST 30 KT...WITH A COUPLE OF UNCERTAIN 35 KT VECTORS IN CONVECTION TO THE WEST OF THE CENTER. SINCE THAT TIME THERE HAS BEEN AN INCREASE IN DEEP CONVECTION OVER OR VERY NEAR THE CIRCULATION CENTER...AND THE 6Z CLASSIFICATIONS FROM TAFB AND SAB WERE T2.5...OR 35 KT. BASED ON THE ABOVE...THE DEPRESSION IS UPGRADED TO A TROPICAL STORM. THE CENTER REMAINS DIFFICULT TO LOCATE. THERE HAVE BEEN SEVERAL MICROWAVE PASSES THAT SUGGEST A CENTER TO THE NORTH AND EAST OF MY ESTIMATED POSTION...BUT THESE MAY BE REFLECTING SWIRLS GENERATED IN THE CONVECTION THAT THEN ROTATE COUNTERCLOCKWISE AROUND A BROADER CIRCULATION. AT NIGHT I WOULD PREFER TO MAINTAIN MORE CONTINUITY WITH THE PREVIOUS TRACK THAN JUMP ON ONE OF THESE SWIRLS. EVEN SO...THE TRACK DOES APPEAR TO HAVE TURNED TO THE RIGHT AND THE INITIAL MOTION IS ESTIMATED TO BE 300/5. OTIS REMAINS ON THE SOUTH SIDE OF A MID- TO UPPER-LEVEL RIDGE THAT CURRENTLY EXTENDS WESTWARD FROM NORTHERN MEXICO ACROSS BAJA CALIFORNIA. GLOBAL MODEL GUIDANCE IS IN PRETTY GOOD AGREEMENT THAT THIS RIDGE WILL BE REPLACED BY A TROUGH OR CUTOFF LOW OFF OF SOUTHERN CALIFORNIA OVER THE NEXT 48 HOURS...AND THAT OTIS WILL TURN NORTHWARD ALONG THE EAST SIDE OF THIS TROUGH. THERE IS CONSIDERABLE SPREAD IN THE FORWARD SPEED OF OTIS AMONG THE DYNAMICAL MODELS...ESPECIALLY LATE IN THE FORECAST PERIOD...AND THERE HASN'T BEEN MUCH CONSISTENCY FROM RUN TO RUN. THE NOGAPS...WHICH HAD BEEN ONE OF THE SLOWER MODELS PREVIOUSLY...IS NOW ONE OF THE FASTEST...WHILE THE GFDL...WHICH HAD BEEN THE FASTEST...IS NOW IN THE MIDDLE OF THE PACK. SUCH ERRATIC BEHAVIOR IS A GOOD REASON TO STAY NEAR THE DYNAMICAL MODEL CONSENSUS. ONLY THE 12Z EUROPEAN MODEL TURNS OTIS AWAY FROM THE BAJA PENINSULA. NORTHEASTERLY SHEAR CONTINUES TO AFFECT OTIS...ALTHOUGH THIS SHEAR IS FORECAST TO LESSEN OVER THE NEXT 36 HOURS. SLOW STRENGTHENING IS EXPECTED OVER THE NEXT DAY OR SO WITH A SOMEWHAT FASTER PACE AFTER THAT. BY LATE IN THE FORECAST PERIOD...INCREASING SOUTHERLY SHEAR AND/OR COOLER SSTS ARE EXPECTED TO RESULT IN A WEAKENING TREND. THE OFFICIAL FORECAST IS A BLEND OF THE SHIPS AND GFDL GUIDANCE. FORECASTER FRANKLIN FORECAST POSITIONS AND MAX WINDS INITIAL 29/0900Z 17.5N 107.6W 35 KT 12HR VT 29/1800Z 18.0N 108.6W 40 KT 24HR VT 30/0600Z 18.9N 110.0W 45 KT 36HR VT 30/1800Z 19.7N 111.0W 55 KT 48HR VT 01/0600Z 20.5N 111.7W 65 KT 72HR VT 02/0600Z 22.1N 112.6W 65 KT 96HR VT 03/0600Z 24.5N 113.5W 50 KT 120HR VT 04/0600Z 27.5N 114.0W 35 KT...INLAND $$ NNNN
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Page last modified: Thursday, 29-Sep-2005 08:40:23 UTC