ZCZC MIATCDEP1 ALL TTAA00 KNHC DDHHMM HURRICANE SERGIO DISCUSSION NUMBER 10 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP212006 700 PM PST WED NOV 15 2006 AFTER LOOKING VERY IMPRESSIVE EARLIER TODAY...SERGIO'S SATELLITE PRESENTATION HAS DEGRADED RAPIDLY DURING THE LAST SEVERAL HOURS. THE EYE IS NO LONGER PRESENT AND THE OVERALL CLOUD PATTERN HAS BECOME INCREASINGLY ELONGATED SOUTHWEST TO NORTHEAST. IT IS DIFFICULT TO KNOW WHETHER THIS IS A TEMPORARY FLUCTUATION OR THE BEGINNING OF A LONGER-TERM WEAKENING TREND. THE INITIAL INTENSITY IS CONSERVATIVELY SET AT 90 KT IN LINE WITH AN AVERAGE OF THE AVAILABLE SUBJECTIVE DVORAK ESTIMATES. WATER VAPOR IMAGERY AND UW-CIMSS SATELLITE DERIVED WINDS INDICATE THAT THE LARGE-SCALE PATTERN DOES NOT APPEAR TO BE EVOLVING AS PREVIOUSLY SHOWN BY THE GLOBAL MODELS. THE SHORTWAVE TROUGH DROPPING SOUTHWARD OVER THE BAJA PENINSULA HAS NOT CLOSED OFF AND THE WEAK RIDGE HAS NOT YET FORMED OVER MEXICO. INSTEAD...A LARGE TROUGH OVER THE CENTRAL UNITED STATES EXTENDS ACROSS MEXICO INTO THE EASTERN PACIFIC. AS A RESULT...STRONG WESTERLY SHEAR IS NOW BEARING DOWN ON THE CYCLONE...AND MAY ALREADY BE AFFECTING IT. NONETHELESS...THE GFDL MODEL CONTINUES TO SHOW SERGIO STRENGTHENING WHILE MOVING NORTHWARD INTO THIS INCREASINGLY SHEARED ENVIRONMENT. SINCE ANY APPRECIABLE NORTHWARD MOTION WOULD TAKE THE CYCLONE INTO A SEEMINGLY HOSTILE ENVIRONMENT...THIS SOLUTION DOES NOT APPEAR TO BE THE MOST LIKELY SCENARIO. INSTEAD...THE OFFICIAL FORECAST IS CLOSER TO THE FSU SUPERENSEMBLE MODEL AND CALLS FOR NO ADDITIONAL STRENGTHENING DURING THE NEXT 12-24 HOURS FOLLOWED BY WEAKENING AS THE CYCLONE BEGINS TO ENCOUNTER EVEN STRONGER SHEAR AND A DRY/STABLE AIR AIRMASS. SERGIO HAS BEEN MOVING SLOWLY EASTWARD THIS EVENING WITH THE LAST COUPLE OF SATELLITE IMAGES SUGGESTING A GRADUAL NORTHWARD TURN. THE INITIAL MOTION ESTIMATE IS 060/4. AS MENTIONED ABOVE...THE LARGE-SCALE STEERING PATTERN IS COMPLEX...RESULTING IN QUITE A BIT OF SPREAD AMONG THE AVAILABLE TRACK MODELS. THE GUIDANCE ENVELOPE IS FLANKED ON THE EAST SIDE BY THE GFDL AND NOGAPS MODELS WHICH SHOW SERGIO CLIPPING THE SOUTHWESTERN COAST OF MEXICO. CONVERSELY...THE GFS...ITS ENSEMBLE MEAN...AND NOW THE ECMWF MODEL SHOW A MORE WESTWARD TRACK. THE OFFICIAL FORECAST ASSUMES THAT SERGIO WILL GRADUALLY WEAKEN AND THUS TURN NORTHWEST IN LINE WITH THE FSU SUPERENSEMBLE AND MEDIUM BAM MODEL. WHILE IT IS MUCH TOO SOON TO SAY WHETHER SERGIO WILL OR WILL NOT AFFECT MEXICO... INTERESTS ALONG THE SOUTHWESTERN COAST SHOULD MONITOR THE PROGRESS OF THIS SYSTEM. FOR THE HISTORICALLY CURIOUS...SERGIO IS THE STRONGEST EASTERN NORTH PACIFIC BASIN HURRICANE ON RECORD FOR SO LATE IN THE SEASON. FORECAST POSITIONS AND MAX WINDS INITIAL 16/0300Z 12.3N 103.2W 90 KT 12HR VT 16/1200Z 12.7N 103.1W 90 KT 24HR VT 17/0000Z 13.7N 103.3W 90 KT 36HR VT 17/1200Z 14.6N 103.8W 85 KT 48HR VT 18/0000Z 15.9N 104.9W 75 KT 72HR VT 19/0000Z 18.0N 106.5W 65 KT 96HR VT 20/0000Z 19.5N 107.5W 55 KT 120HR VT 21/0000Z 21.0N 109.0W 45 KT $$ FORECASTER RHOME NNNN
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Page last modified: Thursday, 16-Nov-2006 02:40:04 UTC