Caribbean-On-Line's Caribbean Hurricane Blog



TROPICAL STORM JOSEPHINE DISCUSSION NUMBER 2

Published on September 2, 2008 12:33 PM | Comments

So Josephine is pretty organized and could intensify rapidly to a point - and then the various computer models tend to disagree as to what happens. We need to keep and eye on this one.

TROPICAL STORM JOSEPHINE DISCUSSION NUMBER 2 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL102008 1100 AM EDT TUE SEP 02 2008

VISIBLE IMAGERY REVEALS AN INCREASE IN THE CYCLONE'S ORGANIZATION...WITH VERY WELL-DEFINED CONVECTIVE BANDS AND EVEN A DECEPTIVE CENTRAL FEATURE DISGUISED AS AN EYE. THE CONVECTIVE TOPS ARE NOT EXCEPTIONALLY COLD IN THE INFRARED...BUT DVORAK INTENSITY ESTIMATES ARE A CONSENSUS 35 KT...SO THE DEPRESSION IS UPGRADED TO A TROPICAL STORM...THE TENTH OF THE 2008 ATLANTIC SEASON. JOSEPHINE IS CURRENTLY OVER SEA-SURFACE TEMPERATURES OF ABOUT 28 CELSIUS...AND THE WATERS ALONG THE FORECAST TRACK WILL REMAIN AT LEAST THAT WARM FOR ABOUT THE NEXT 24 HOURS. WIND SHEAR IS ESSENTIALLY NON-EXISTENT OVER THE CYCLONE...SO STEADY STRENGTHENING SEEMS LIKELY IN THE SHORT TERM...AND COULD BE RAPID GIVEN THE INCREASED ORGANIZATION AND THAT THE SHIPS-BASED RI INDEX GIVES A 50% CHANCE OF AN INTENSITY INCREASE OF 30 KT OR MORE IN THE NEXT 24 HOURS. BEYOND 24 HOURS...JOSEPHINE WILL TRAVERSE SLIGHTLY COOLER WATERS...AND DUE TO AN UPPER-LEVEL LOW FORECAST BY THE MODELS TO MOVE IN TANDEM WITH THE TROPICAL CYCLONE...WIND SHEAR WILL PROBABLY INCREASE IN A COUPLE OF DAYS. EVEN THOUGH ALL OF THE OBJECTIVE GUIDANCE CALLS FOR A WEAKENING TREND TO START BY 72 HOURS...TO MAINTAIN SOME CONTINUITY THE NEW OFFICIAL INTENSITY FORECAST SIMPLY SHOWS AN INTENSITY PLATEAU AT 60 KT IN THE LONGER TERM.

THE INITIAL MOTION REMAINS BRISK ALONG A HEADING JUST NORTH OF DUE WEST...OR 280/13...BUT THE INITIAL POSITION HAS BEEN ADJUSTED SLIGHTLY NORTH OF THE PREVIOUS TRACK BASED ON VISIBLE IMAGERY AND AN EARLIER QUIKSCAT PASS. A MID-LEVEL HIGH CENTERED OVER THE EAST-CENTRAL SUBTROPICAL ATLANTIC IS CURRENTLY THE PRIMARY STEERING MECHANISM...BUT THIS FEATURE IS FORECAST BY THE MODELS TO PROCEED WESTWARD AND SHIFT TO THE WESTERN ATLANTIC IN A FEW DAYS. MEANWHILE...THE DEEP-LAYER LOW JUST OFF THE NORTHEASTERN UNITED STATES WILL PROPAGATE EASTWARD AND ERODE THE RIDGE NORTH OF JOSEPHINE...WHICH WILL PROBABLY JUST CAUSE A SLIGHT BEND TO THE RIGHT AND A SLOWER FORWARD MOTION AT DAYS 3-5. MODELS ARE IN VERY GOOD AGREEMENT THROUGH 48 HOURS BUT THEN DIVERGE MARKEDLY...WITH THE GFS TURNING THE CYCLONE WESTWARD AND THE GFDL AND HWRF TAKING IT NORTHWESTWARD. THE OFFICIAL TRACK FORECAST SPLITS THE DIFFERENCE AND FOLLOWS THE CONSENSUS...WHICH IS JUST A LITTLE NORTH OF THE PREVIOUS ADVISORY.



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