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| #198851 (Received by flhurricane at: 4:52 PM 03.Jul.2008) TCDAT2 TROPICAL STORM BERTHA DISCUSSION NUMBER 3 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL022008 500 PM EDT THU JUL 03 2008 THE CLOUD TOPS ASSOCIATED WITH BERTHA HAVE WARMED THIS AFTERNOON...HOWEVER...BANDING FEATURES REMAIN WELL-DEFINED IN VISIBLE IMAGERY AND A RECENT SSMIS MICROWAVE OVERPASS. A SHIP LOCATED ABOUT 45 NM NORTHEAST OF THE CENTER AT 1700 UTC REPORTED SUSTAINED WINDS OF 29 KT. THE LATEST DVORAK ESTIMATES FROM TAFB AND SAB ARE 35 KT...WHICH REMAINS THE INITIAL ADVISORY INTENSITY. THE FORECAST SCENARIO REMAINS UNCHANGED AS BERTHA IS EXPECTED TO CONTINUE MOVING WEST-NORTHWESTWARD SOUTH OF A MID-LEVEL RIDGE OVER THE EASTERN ATLANTIC DURING THE NEXT FEW DAYS. THEREAFTER...A WEAKNESS IN THE RIDGE BETWEEN ABOUT 50W-60W WILL PLAY A ROLE IN THE FUTURE TRACK OF BERTHA. THE UKMET...ECMWF...AND HWRF MODELS DEPICT A WEAKER AND SHALLOWER BERTHA...KEEPING THE CYCLONE ON A GENERAL WEST-NORTHWESTWARD TRACK. THE GFS AND GFDL MAINTAIN A STRONGER TROPICAL CYCLONE THAT TURNS NORTHWESTWARD INTO THE WEAKNESS. THE OFFICIAL FORECAST ASSUMES THAT BERTHA WILL BE STRONG AND DEEP ENOUGH TO BE STEERED BY THE MID-LEVEL FLOW...FOLLOWING CLOSELY THE GFDL AND THE GFS. SHEAR IS EXPECTED TO REMAIN LIGHT...BUT BERTHA IS FORECAST TO TRACK OVER SSTS OF 25 DEGREES C....WHICH IS THE MAIN LIMITING FACTOR FOR THE NEXT COUPLE OF DAYS. THEREAFTER...THE SSTS ALONG THE TRACK ARE EXPECTED TO INCREASE BUT SHEAR IS FORECAST TO BE STRONGER LATER IN THE PERIOD. THE SHIPS... LGEM...AND GFDL MODELS PREDICT BERTHA TO REACH HURRICANE STRENGTH IN 3-5 DAYS. THE NEW INTENSITY FORECAST IS UNCHANGED AND CONSERVATIVE DUE TO THE AFOREMENTIONED LIMITING FACTORS. THE CENTER OF BERTHA SHOULD MOVE AWAY FROM THE SOUTHERN CAPE VERDE ISLANDS TONIGHT...HOWEVER OUTER RAINBANDS WILL CONTINUE TO BRING GUSTY WINDS AND LOCALLY HEAVY RAINFALL TO PORTIONS OF THE SOUTHERN CAPE VERDE ISLANDS DURING THE NEXT 24 HOURS. FORECAST POSITIONS AND MAX WINDS INITIAL 03/2100Z 13.6N 25.6W 35 KT 12HR VT 04/0600Z 14.1N 27.6W 40 KT 24HR VT 04/1800Z 15.0N 30.8W 45 KT 36HR VT 05/0600Z 16.0N 34.2W 45 KT 48HR VT 05/1800Z 16.9N 37.7W 50 KT 72HR VT 06/1800Z 18.8N 44.5W 55 KT 96HR VT 07/1800Z 21.5N 49.5W 55 KT 120HR VT 08/1800Z 25.0N 52.5W 55 KT $$ FORECASTER BROWN |
