ZCZC MIATCDEP5 ALL TTAA00 KNHC DDHHMM TROPICAL STORM NORMAN DISCUSSION NUMBER 5 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP152006 800 PM PDT MON OCT 09 2006 NORMAN HAS BEEN EXHIBITING A BURSTING TYPE CONVECTIVE PATTERN DURING THE LAST 6-12 HOURS. THE ADVISORY INTENSITY IS RAISED TO 45 KT BASED ON A BLEND OF THE LASTEST SUBJECTIVE DVORAK INTENSITY ESTIMATES OF 55 KT AND 45 KT FROM TAFB AND SAB RESPECTIVELY ALONG WITH AN EXPERIMENTAL OBJECTIVE ESTIMATE OF 45 KT FROM UW-CIMSS. IT SHOULD BE NOTED THAT THERE IS SOME UNCERTAINTY IN THE INTENSITY ESTIMATE DUE TO THE CURRENT LACK OF A WELL-DEFINED CLOUD PATTERN. NORMAN HAS BEEN EXPERIENCING SOME WESTERLY VERTICAL SHEAR ASSOCIATED WITH A LARGE TROUGH OVER THE WESTERN UNITED STATES. HOWEVER... WATER VAPOR IMAGERY SHOWS THAT A SHORTWAVE DISTURBANCE EMBEDDED WITHIN THE LARGER-SCALE PATTERN IS LIFTING QUICKLY NORTHEASTWARD...AND THIS EVOLUTION IS EXPECTED TO RESULT IN A TEMPORARY WEAKENING OF THE SHEAR. THUS...THE OFFICIAL FORECAST ALLOWS FOR SOME STRENGTHENING OVER THE NEXT DAY OR SO. THEREAFTER...THE SHEAR IS EXPECTED TO INCREASE AGAIN AND NORMAN IS FORECAST TO BE MOVING OVER SLIGHTLY COOLER WATERS. THIS SEEMINGLY UNFAVORABLE ENVIRONMENT SHOULD RESULT IN WEAKENING WITH NORMAN EXPECTED TO BECOME A DISSIPATING REMNANT LOW NEAR THE END OF THE FORECAST PERIOD. NORMAN IS CURRENTLY MOVING AROUND THE WESTERN PERIPHERY OF A WEAK MID-LEVEL RIDGE CENTERED OVER SOUTHERN MEXICO...RESULTING IN A GENERAL NORTHWARD MOTION OR 360/05. THE CYCLONE SHOULD TURN MORE TOWARDS THE NORTHEAST AND ACCELERATE A LITTLE AS IT REACHES THE NORTHERN PORTION OF THE RIDGE DURING THE NEXT DAY OR SO. WHILE THE SYNOPTIC SCALE STEERING APPEARS RELATIVELY STRAIGHTFORWARD...TRACK GUIDANCE CONTINUES TO BE SPREAD A BIT MOST LIKELY DUE TO VARYING FORECAST STRENGTH AND DEPTH OF THE CYCLONE. THE NOGAPS... UKMET...CANADIAN AND GFDN MODELS ALL WEAKEN THE CYCLONE QUICKLY RESULTING IN A TURN TOWARD THE SOUTHEAST BEYOND 36 HOURS. CONVERSELY... THE ECMWF...GFDL...GFS...AND GFS ENSEMBLE MEAN MAINTAIN A MORE VERTICALLY COHERENT VORTEX AND SHOW THE CYCLONE CONTINUING NORTHEASTWARD TOWARD BAJA. THE OFFICIAL FORECAST ASSUMES NORMAN WILL REMAIN DEEP ENOUGH FOR THE NEXT COUPLE OF DAYS AND GAIN ENOUGH LATITUDE TO BE CAUGHT IN THE DEEP-LAYERED WESTERLY FLOW FORECAST TO DEVELOP TO ITS NORTH. FORECAST POSITIONS AND MAX WINDS INITIAL 10/0300Z 16.9N 117.8W 45 KT 12HR VT 10/1200Z 17.6N 117.8W 50 KT 24HR VT 11/0000Z 18.6N 117.3W 50 KT 36HR VT 11/1200Z 19.9N 116.3W 45 KT 48HR VT 12/0000Z 20.8N 115.3W 40 KT 72HR VT 13/0000Z 22.5N 113.0W 25 KT 96HR VT 14/0000Z 25.0N 110.5W 20 KT...REMNANT LOW 120HR VT 15/0000Z...DISSIPATED $$ FORECASTER RHOME/PASCH NNNN
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Page last modified: Tuesday, 10-Oct-2006 02:35:03 UTC