ZCZC MIATCDEP4 ALL TTAA00 KNHC DDHHMM HURRICANE HERNAN DISCUSSION NUMBER 15 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP092008 200 AM PDT SUN AUG 10 2008 HERNAN CONTINUES TO WEAKEN AS IT MOVES OVER COOLER SSTS AND THE INITIAL INTENSITY IS LOWERED TO 85 KT BASED ON A BLEND OF THE SUBJECTIVE DVORAK FINAL T AND CI NUMBERS. ADDITIONAL WEAKENING IS ANTICIPATED AND HERNAN COULD DROP BELOW HURRICANE STRENGTH WITHIN THE NEXT 24 HOURS. SSTS LEVEL OFF IN ABOUT 2 DAYS THEN BEGIN TO RISE SO A SLOWER RATE OF DECAY IS SHOWN AT THE EXTENDED FORECAST TIMES...AND HERNAN COULD CLING TO ITS STATUS AS A TROPICAL CYCLONE FOR SEVERAL DAYS. THE INITIAL MOTION ESTIMATE IS ESSENTIALLY UNCHANGED 305/09. AN UPPER-LEVEL TROUGH TO THE NORTHWEST OF HERNAN IS FORECAST TO BE REPLACED BY A WEAK RIDGE DURING THE NEXT DAY OR SO RESULTING IN A GRADUAL TURN TOWARDS THE WEST. BEYOND 48 HOURS...A TURN MORE SOUTHWESTWARD IS FORECAST AS THE WEAKENING CYCLONE IS STEERED BY THE NORTHEASTERLY LOW/MID-LEVEL FLOW. THERE REMAINS SPREAD IN THE TRACK GUIDANCE...WITH THE BAM MODELS AND THE HWRF CALLING FOR A SLOWER WESTWARD TURN RESULTING IN THOSE MODELS LYING ALONG THE NORTHERN EDGE OF THE GUIDANCE ENVELOPE. CONVERSELY...THE GFS AND UKMET MODELS SHOW A MUCH SHARPER WESTWARD AND SOUTHWESTWARD TURN WITH THOSE MODELS LYING ALONG THE SOUTHERN EDGE OF THE GUIDANCE ENVELOPE. THE OFFICIAL TRACK FORECAST IS A LITTLE NORTH OF THE MODEL CONSENSUS AND CLOSE TO THE GFDL MODEL THROUGH ABOUT 48 HOURS...THEN ALONG BUT A LITTLE SLOWER THAN THE MODEL CONSENSUS THEREAFTER. FORECAST POSITIONS AND MAX WINDS INITIAL 10/0900Z 17.3N 125.7W 85 KT 12HR VT 10/1800Z 17.7N 126.7W 70 KT 24HR VT 11/0600Z 18.0N 128.1W 60 KT 36HR VT 11/1800Z 18.1N 129.4W 50 KT 48HR VT 12/0600Z 18.0N 130.5W 45 KT 72HR VT 13/0600Z 17.0N 133.0W 40 KT 96HR VT 14/0600Z 16.5N 135.0W 35 KT 120HR VT 15/0600Z 16.0N 138.0W 30 KT $$ FORECASTER RHOME NNNN
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