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TROPICAL STORM JOSEPHINE DISCUSSION NUMBER 3

Published on September 2, 2008 6:14 PM | Comments

TROPICAL STORM JOSEPHINE DISCUSSION NUMBER 3 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL102008 500 PM EDT TUE SEP 02 2008

JOSEPHINE CONTINUES TO EXHIBIT A RATHER IMPRESSIVE APPEARANCE IN VISIBLE IMAGERY...ALTHOUGH THE INFRARED CLOUD TOPS ARE STILL NOT ALL THAT COLD...WITH SOLID AND FAIRLY SYMMETRIC CONVECTIVE BANDING AND WELL-DEFINED UPPER-LEVEL OUTFLOW IN ALL DIRECTIONS. LACKING ACTUAL WIND DATA ANYWHERE NEAR THE CENTER OF THE CYCLONE...THE INITIAL INTENSITY ESTIMATE IS AN UNCERTAIN 45 KT. SOME DVORAK ESTIMATES AND AN EARLIER AMSU INTENSITY ESTIMATE SUGGEST THE STORM COULD BE A LITTLE STRONGER...BUT WE CAN WAIT UNTIL THE VARIOUS ESTIMATES PERHAPS COME INTO BETTER AGREEMENT. NEVER MIND THE DETAILS...JOSEPHINE APPEARS POISED TO STRENGTHEN SOME MORE. THE STORM IS CURRENTLY LOCATED OVER RATHER WARM SEA-SURFACE TEMPERATURES OF ABOUT 28 CELSIUS...AND THE WATERS WILL REMAIN THAT WARM FOR ABOUT THE NEXT 24 HOURS. COMBINE THAT WITH THE COMPLETE ABSENCE OF WIND SHEAR...AND STRENGTHENING APPEARS LIKELY IN THE SHORT TERM. ALL OF THE OBJECTIVE GUIDANCE MODELS EXCEPT FOR THE HWRF FORECAST A HURRICANE...AND THE INTENSITY CONSENSUS IS AT 65 KT AT 24 HOURS. THIS IS ALSO SHOWN IN THE NEW OFFICIAL FORECAST... WHICH IS AN UPWARD ADJUSTMENT FROM THE PREVIOUS ADVISORY. ALL OF THE INTENSITY GUIDANCE CONTINUES TO FORECAST A WEAKENING TREND AT DAYS 3-5...HOWEVER...IN RESPONSE TO JOSEPHINE PASSING OVER COOLER SSTS IN A COUPLE OF DAYS...AND DUE TO INCREASING SOUTHERLY WIND SHEAR ON THE EASTERN FLANK OF AN UPPER-LEVEL LOW. GIVEN THIS GUIDANCE...THE OFFICIAL FORECAST SHOWS A WEAKER CYCLONE AT FIVE DAYS...AND EVEN 55 KT IS ABOVE NEARLY ALL OF THE MODEL PREDICTIONS.

A SUBTROPICAL RIDGE CENTERED NORTHWEST OF JOSEPHINE IS USHERING THE TROPICAL CYCLONE WEST-NORTHWESTWARD AT ABOUT 290/12. MODELS ARE CLUSTERED FAIRLY TIGHTLY AROUND THIS SAME HEADING AND SPEED FOR THE NEXT 48 HOURS. AFTER THAT...THE GFDL AND HWRF FORECAST A FASTER MOTION THAT EVENTUALLY BECOMES NORTHWESTWARD INTO A WEAKNESS IN THE RIDGE ASSOCIATED WITH THE DEEP-LAYER LOW THAT WILL CROSS THE NORTH-CENTRAL ATLANTIC. THE GLOBAL MODELS ARE EITHER SLOWER OR FARTHER SOUTH. SINCE THE GFDL AND HWRF SEEM TO HAVE THE BEST HANDLE ON THE INITIAL MOTION...THOSE SOLUTIONS ARE SLIGHTLY FAVORED...AND THE OFFICIAL TRACK FORECAST IS A LITTLE RIGHT OF THE CONSENSUS AND IS VERY SIMILAR TO THE PREVIOUS ADVISORY.



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