Hurricane SERGIO

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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
 
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FORECASTER RHOME
 
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