ZCZC MIATCDEP1 ALL TTAA00 KNHC DDHHMM HURRICANE SERGIO DISCUSSION NUMBER 14 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP212006 700 PM PST THU NOV 16 2006 AFTER WEAKENING CONSIDERABLY EARLIER TODAY...SERGIO APPEARS TO BE HOLDING ITS OWN AS DEEP CONVECTION HAS REFORMED OVER THE CENTER. THE INITIAL INTENSITY IS HELD AT 70 KT BASED ON THIS TREND. NONETHELESS...THE CYCLONE CONTINUES TO BATTLE STRONG WESTERLY SHEAR...AND WATER VAPOR IMAGERY SUGGESTS THE SHEAR WILL BE EVEN STRONGER ALONG THE PROJECTED TRACK. EVEN THE GFDL HAS FINALLY ACKNOWLEDGED SUCH A HOSTILE ENVIRONMENT AND BACKED OFF FROM ITS EARLIER ROBUST INTENSIFICATION. THE ONLY POTENTIAL FACTOR ARGUING FOR STRENGTHENING WOULD BE FOR THE UPPER-LEVEL TROUGH CURRENTLY TO THE NORTHWEST OF THE CYCLONE TO FRACTURE AND FORM A CLOSED LOW...LEAVING A DOWNSTREAM UPPER-LEVEL RIDGE OVER SERGIO. SOME OF THE GLOBAL MODELS SUGGEST SUCH A LARGE-SCALE ENVIRONMENT COULD UNFOLD IN 1-2 DAYS. HOWEVER...EVEN IF THIS PATTERN MATERIALIZES... SERGIO WOULD STILL HAVE TO OVERCOME INCREASINGLY DRY AND STABLE AIR. THE OFFICIAL FORECAST ASSUMES THAT SERGIO WILL GRADUALLY WEAKEN...BUT IT DOES PAY RESPECT TO THE POTENTIALLY LESS HOSTILE UPPER-LEVEL WINDS BY SHOWING AN INTENSITY PLATEAU AT 36-48 HOURS. THE FSU SUPERENSEMBLE AND SHIPS MODELS SHOW EVEN FASTER WEAKENING THAN INDICATED HERE. SERGIO CONTINUES ITS GRADUAL TURN TOWARD THE NORTH WITH AN INITIAL MOTION ESTIMATE OF 360/4. THERE HAS BEEN LITTLE CHANGE IN THE OVERALL FORECAST TRACK PHILOSOPHY. A MID-LEVEL RIDGE IS EXPECTED TO BUILD SOUTHWARD OVER CENTRAL MEXICO DURING THE NEXT DAY OR SO IMPARTING A TURN TOWARD THE NORTHWEST. HOWEVER...THIS PATTERN WILL ALSO PRODUCE LARGE DISCREPANCIES BETWEEN THE DEEP AND SHALLOW LAYER STEERING FLOWS. ACCORDINGLY...THERE REMAINS CONSIDERABLE SPREAD AMONG THE VARIOUS TRACK MODELS. A STRONGER AND DEEPER CYCLONE WOULD TEND TO TRACK ALONG THE RIGHT SIDE OF THE GUIDANCE ENVELOPE IN LINE WITH THE NOGAPS...GFDL...AND DEEP BAM MODELS. CONVERSELY...A WEAKER AND MORE SHALLOW SYSTEM WOULD TEND TO MOVE CLOSER TO THE LEFT SIDE OF THE GUIDANCE ENVELOPE IN LINE WITH THE GFS...ITS ENSEMBLE MEAN...AND THE SHALLOW BAM MODELS. IT IS HARD TO IMAGINE SERGIO REMAINING A HURRICANE MUCH LONGER IN LIGHT OF THE AFOREMENTIONED HOSTILE ENVIRONMENT. ACCORDINGLY...THE OFFICIAL FORECAST LEANS A LITTLE TO THE LEFT OF THE MODEL CONSENSUS. SERGIO IS AN EXCELLENT REMINDER THAT THE EFFECTS OF A HURRICANE CAN EXTEND FAR FROM THE CENTER...AS RAINBANDS EXTEND WELL TO THE NORTHEAST AND HAVE BEEN AFFECTING COASTAL PORTIONS OF SOUTHWESTERN MEXICO TODAY. IT IS FOR THIS REASON...AND THE HIGHER THAN NORMAL FORECAST UNCERTAINTY...THAT INTERESTS IN MEXICO SHOULD CLOSELY MONITOR THE PROGRESS OF SERGIO. FORECAST POSITIONS AND MAX WINDS INITIAL 17/0300Z 13.8N 102.7W 70 KT 12HR VT 17/1200Z 14.5N 102.9W 65 KT 24HR VT 18/0000Z 15.1N 103.4W 60 KT 36HR VT 18/1200Z 15.8N 104.2W 55 KT 48HR VT 19/0000Z 16.7N 105.0W 55 KT 72HR VT 20/0000Z 18.0N 106.5W 45 KT 96HR VT 21/0000Z 19.5N 108.5W 35 KT 120HR VT 22/0000Z 21.5N 111.0W 25 KT...REMNANT LOW $$ FORECASTER RHOME NNNN
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Page last modified: Friday, 17-Nov-2006 02:50:03 UTC