ZCZC MIATCDEP4 ALL TTAA00 KNHC DDHHMM HURRICANE HERNAN DISCUSSION NUMBER 9 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP092008 200 PM PDT FRI AUG 08 2008 THE RAGGED EYE FEATURE FROM THIS MORNING HAS PERSISTED INTO THE AFTERNOON...AND LATEST SATELLITE IMAGERY INDICATES THAT THE EYE IS BECOMING BETTER DEFINED. DVORAK SATELLITE CLASSIFICATIONS REFLECT THIS INCREASING ORGANIZATION...WITH TAFB AND SAB COMING IN WITH T4.5 AND T4.0...RESPECTIVELY. ON THIS BASIS...THE INITIAL INTENSITY IS SET AT 75 KT. LIGHT EASTERLY SHEAR AND OTHER FAVORABLE FACTORS PREDICTED ALONG THE FORECAST TRACK SHOULD GIVE HERNAN THE OPPORTUNITY TO INTENSIFY FURTHER DURING THE NEXT 24 TO 36 HOURS. HOWEVER...BETWEEN 36 AND 48 HOURS...HERNAN SHOULD REACH SUB-26C SSTS AND BEGIN A GRADUAL WEAKENING. THE OFFICIAL INTENSITY FORECAST LIES SLIGHTLY ABOVE ALL OBJECTIVE AIDS AS WELL AS THE PREVIOUS ADVISORY. THE HEADING IS 275/10...A MOTION WHICH HAS REMAINED NEARLY UNCHANGED DURING THE PAST DAY OR SO. NEARLY ALL OF THE TRACK GUIDANCE TURNS HERNAN MORE TOWARD THE NORTHWEST VERY SOON...LIKELY IN RESPONSE TO A PRONOUNCED MID- TO UPPER-LEVEL TROUGH LYING WELL NORTHWEST OF THE HURRICANE. HOWEVER...WATER VAPOR CLOUD-TRACKED WINDS SHOW A SMALL MID-LEVEL RIDGE AXIS LYING DIRECTLY NORTH OF HERNAN...WHICH HAS BEEN GUIDING IT ON A MORE WESTERLY COURSE. THIS FEATURE SEEMS TO BE UNDER-REPRESENTED IN THE GLOBAL MODEL FIELDS AND PERHAPS THIS IS WHY THE MODEL GUIDANCE HAS BEEN EXHIBITING A NORTHWARD BIAS WITH HERNAN. CONSEQUENTLY...THE NEW OFFICIAL FORECAST REMAINS ON THE SOUTHERN EDGE OF THE GUIDANCE ENVELOPE. IN 24 TO 48 HOURS...MODEL GUIDANCE IS IN GOOD AGREEMENT ON THE MID-LEVEL RIDGE BUILDING WESTWARD WITH THE HURRICANE AS THE MID- TO UPPER-LEVEL TROUGH TO THE NORTH LIFTS OUT. THIS SHOULD ALLOW THE TRACK TO BEND MORE TOWARD THE WEST AND PERHAPS EVEN TO THE WEST-SOUTHWEST LATE IN THE PERIOD...AS A WEAKER HERNAN BECOMES STEERED BY THE LOW- TO MID-LEVEL FLOW. FORECAST POSITIONS AND MAX WINDS INITIAL 08/2100Z 14.8N 120.9W 75 KT 12HR VT 09/0600Z 15.0N 122.3W 85 KT 24HR VT 09/1800Z 15.4N 124.0W 85 KT 36HR VT 10/0600Z 16.1N 125.7W 75 KT 48HR VT 10/1800Z 16.7N 127.4W 65 KT 72HR VT 11/1800Z 17.0N 130.5W 45 KT 96HR VT 12/1800Z 17.0N 133.0W 35 KT 120HR VT 13/1800Z 16.5N 135.0W 25 KT $$ FORECASTER KIMBERLAIN/BROWN NNNN
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Page last modified: Tuesday, 21-Apr-2009 12:09:38 UTC