ZCZC MIATCDEP5 ALL TTAA00 KNHC DDHHMM TROPICAL STORM OTIS DISCUSSION NUMBER 7 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 2 PM PDT THU SEP 29 2005 A WELL-DEFINED PARTIALLY EXPOSED LOW-LEVEL CIRCULATION HAS BEEN ROTATING NORTH AND WESTWARD AT 20-25 KT AROUND THE EAST AND NORTH SIDE OF THE MID-LEVEL CENTER DURING THE PAST 6 HOURS. THE INITIAL POSITION AND RESULTANT MOTION ARE BASED MAINLY ON THE LOCATION OF THE MID-LEVEL CIRCULATION NOTED IN MICROWAVE IMAGERY. THE INITIAL INTENSITY OF 45 KT IS BASED ON A BLEND OF SATELLITE INTENSITY ESTIMATES OF 55 KT FROM SAB... 45 KT FROM TAFB... AND 35 KT FROM SAB... RESPECTIVELY. THIS INTENSITY IS ALSO SUPPORTED BY AN UW-CIMSS AMSU INTENSITY ESTIMATE OF 996 MB AND 52 KT AT 29/1545Z. THE INITIAL MOTION ESTIMATE IS 310/11. THE LAST FEW VISIBLE SATELLITE IMAGES SUGGEST THAT THE LOW-LEVEL CENTER MAY BE STARTING TO PULL UNDERNEATH THE MID- AND UPPER-LEVEL CIRCULATION CENTERS. AS SUCH... A DECREASE IN FORWARD SPEED IS EXPECTED TO RESUME DURING THE NEXT 6-12 HOURS. OVERALL... THE FORECAST TRACK AND REASONING REMAIN UNCHANGED FROM THE PREVIOUS SEVERAL FORECAST DISCUSSIONS. OTIS IS FORECAST TO MOVE NORTHWESTWARD AROUND THE SOUTHWESTERN PERIPHERY OF A LARGE MID-LEVEL RIDGE LOCATED OVER NORTHERN MEXICO AND BAJA CALIFORNIA. ALL OF THE GLOBAL MODELS CONTINUE TO FORECAST A SHOTWAVE TROUGH TO DROP SOUTHWARD AND ERODE THE WESTERN PORTION OF THE RIDGE OVER BAJA CALIFORNIA... WHICH IS EXPECTED TO ALLOW OTIS TO TURN NORTHWARD BY 72 HOURS AND POSSIBLY MAKE LANDFALL ALONG THE WEST-CENTRAL COAST OF BAJA CALIFORNIA BETWEEN 96-120 HOURS. THE NHC MODEL GUIDANCE IS IN STRONG AGREEMENT ON THIS SCENARIO... AND THE OFFICIAL FORECAST TRACK IS CLOSE TO THE PREVIOUS TRACK AND IS NEAR THE MIDDLE OF THE TIGHTLY PACKED GUIDANCE ENVELOPE. NORTHEASTERLY UPPER-LEVEL SHEAR CONTINUES TO DECREASE AND... AS A RESULT... THE OUTFLOW PATTERN HAS IMPROVED AND BECOME MORE CIRCULAR. A 25/1545Z SSMI OVERPASS INDICATED A 60 PERCENT MID-LEVEL EYEWALL HAD FORMED...SO AT LEAST AN AVERAGE RATE OF INTENSIFICATION SHOULD OCCUR FOR THE NEXT 36 HOURS OR SO. HOWEVER...GIVEN THAT OTIS WILL BE OVER 28.5-29C SSTS FOR AT LEAST THE NEXT 24 HOURS... A BRIEF PERIOD OF RAPID INTENSIFICATION COULD OCCUR. BY AROUND 72 HOURS... OTIS IS FORECAST TO BEGIN MOVING OVER SUB-26C SSTS... WHICH SHOULD INDUCE STEADY WEAKENING... WITH FASTER WEAKENING EXPECTED AFTER 96 HOURS WHEN SOUTHWESTERLY UPPER-LEVEL IS FORECAST TO INCREASE TO MORE THAN 20 KT. INTERESTS NEAR THE BOTH COASTS OF THE SOUTHERN BAJA CALIFORNIA PENINSULA SHOULD CLOSELY MONITOR THE PROGRESS OF OTIS OVER THE NEXT FEW DAYS. FORECASTER STEWART FORECAST POSITIONS AND MAX WINDS INITIAL 29/2100Z 18.9N 109.4W 45 KT 12HR VT 30/0600Z 19.4N 110.1W 55 KT 24HR VT 30/1800Z 20.1N 111.1W 65 KT 36HR VT 01/0600Z 20.8N 111.8W 75 KT 48HR VT 01/1800Z 21.5N 112.4W 70 KT 72HR VT 02/1800Z 23.3N 113.1W 65 KT 96HR VT 03/1800Z 26.0N 114.0W 50 KT 120HR VT 04/1800Z 29.5N 114.0W 35 KT...INLAND CENTRAL BAJA $$ NNNN
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Page last modified: Thursday, 29-Sep-2005 20:25:21 UTC