ZCZC MIATCDEP4 ALL TTAA00 KNHC DDHHMM TROPICAL STORM HERNAN DISCUSSION NUMBER 3 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP092008 200 AM PDT THU AUG 07 2008 HERNAN'S CLOUD PATTERN CONTINUES TO GRADUALLY INCREASE IN ORGANIZATION. THE CENTER IS ESTIMATED TO BE NEAR THE NORTHEASTERN EDGE OF A NEAR-CENTRAL REGION OF VERY COLD-TOPPED CONVECTION...AND THIS HAS BEEN CONFIRMED BY MICROWAVE IMAGERY. UPPER-LEVEL OUTFLOW IS FAIRLY PRONOUNCED OVER THE WESTERN SEMICIRCLE OF THE STORM BUT IS IMPEDED ON THE EASTERN SIDE. CURRENT INTENSITY IS SET AT 45 KT BASED ON THE LATEST DVORAK ESTIMATES FROM TAFB AND SAB. EAST- NORTHEASTERLY VERTICAL SHEAR CONTINUES TO HAVE SOME IMPACT... HOWEVER THE SHIPS MODEL INDICATES SOME RELAXATION OF THE SHEAR WITHIN THE NEXT DAY OR TWO. THEREFORE THE ENVIRONMENT SHOULD BE AMENABLE FOR GRADUAL STRENGTHENING IN THE NEAR FUTURE. THE OFFICIAL INTENSITY FORECAST IS SIMILAR TO THE PREVIOUS ONE AND IS ON THE HIGH SIDE OF THE VARIOUS OBJECTIVE INTENSITY FORECAST TECHNIQUES. AFTER ABOUT 48 HOURS...HERNAN SHOULD BEGIN TO PASS OVER COOLER WATERS SO A GRADUAL DECLINE IN STRENGTH IS FORECAST TO COMMENCE AT THAT TIME. INITIAL MOTION IS AROUND 295/12. A MID-TROPOSPHERIC RIDGE TO THE NORTH AND NORTHEAST OF HERNAN SHOULD PERSIST OVER THE NEXT COUPLE OF DAYS. LATER IN THE PERIOD...HERNAN IS LIKELY TO BE NEARING THE WESTERN PERIPHERY OF THE RIDGE. HOWEVER BY THAT TIME...THE CYCLONE WILL BE WEAKENING AND BECOMING SHALLOWER...AND BEING MOVED MORE BY LOW-LEVEL EASTERLIES. THEREFORE A MORE WESTWARD MOTION IS INDICATED IN 4 TO 5 DAYS. THE OFFICIAL FORECAST TRACK IS SIMILAR TO BUT A LITTLE FASTER THAN THE PREVIOUS NHC TRACK. THIS IS FAIRLY CLOSE TO THE DYNAMICAL MODEL CONSENSUS. THE GFDL MODEL IS AN OUTLIER AS IT SHOWS A MORE NORTHWESTWARD TRACK THAN THE REST OF THE MODEL SUITE. FORECAST POSITIONS AND MAX WINDS INITIAL 07/0900Z 14.5N 114.0W 45 KT 12HR VT 07/1800Z 15.1N 115.5W 50 KT 24HR VT 08/0600Z 15.8N 117.5W 55 KT 36HR VT 08/1800Z 16.5N 119.4W 65 KT 48HR VT 09/0600Z 17.2N 121.4W 65 KT 72HR VT 10/0600Z 18.5N 125.0W 55 KT 96HR VT 11/0600Z 19.0N 128.0W 40 KT 120HR VT 12/0600Z 19.5N 131.0W 25 KT...REMNANT LOW $$ FORECASTER PASCH NNNN
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Page last modified: Tuesday, 21-Apr-2009 12:09:38 UTC