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#109495 (Received by flhurricane at: 4:52 AM 08.Sep.2006) TCDAT1 TROPICAL STORM FLORENCE DISCUSSION NUMBER 19 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL062006 500 AM EDT FRI SEP 08 2006 AS DEPICTED IN INFRARED SATELLITE IMAGERY...FLORENCE HAS A VERY LARGE CIRCULATION BUT CONTINUES TO STRUGGLE IN ORGANIZATION. EVEN THOUGH DVORAK ESTIMATES REMAIN AT 35 KNOTS FROM BOTH TAFB AND SAB...THE INITIAL INTENSITY IS KEPT AT 45 KT WITH THE EXPECTATION THAT SOME STRENGTHENING AND CONSOLIDATION OF THE CLOUD STRUCTURE WILL SOON COMMENCE. WATER VAPOR IMAGERY SHOWS FLORENCE SANDWICHED BETWEEN AN UPPER-LEVEL LOW JUST TO ITS SOUTHWEST AND A RATHER STRONG RIDGE TO ITS NORTH. THESE FEATURES HAVE HELPED INCREASE THE FORWARD MOTION AND IT IS NOW ESTIMATED TO BE 300/14. A VERY DEEP TROUGH IS NOW DIGGING SOUTHWARD INTO THE CENTRAL GULF OF MEXICO...AND TAKING A LOOK AT THE INITIALIZATION OF SOME OF THE GLOBAL MODELS...PARTICULARLY THE GFS...THE TROUGH MAY BE UNDERESTIMATED. WITH THAT SAID...THE MODEL GUIDANCE IS IN CLOSE AGREEMENT IN THE FIRST 72 HOURS...GRADUALLY SLOWING FLORENCE AS IT APPROACHES THE WESTERN PERIPHERY OF THE RIDGE AND TURNING THE CYCLONE TO NORTH AND APPROACH BERMUDA. ONCE FLORENCE IS NORTH OF THE ISLAND THE MODELS DIFFER IN THE ACCELERATION RATE AT DAYS 4 AND 5. THE OFFICIAL TRACK FORECAST STAYS IN LINE WITH THE MOTION REPRESENTED BY THE GFS...NOGAPS... AND FSU SUPERENSEMBLE WITH FLORENCE STARTING TRANSITION TO AN EXTRATROPICAL CYCLONE AROUND DAY 5. ONCE AGAIN...THE INTENSITY FORECAST IS PROBLEMATIC. SINCE FLORENCE IS SUCH A LARGE CIRCULATION...STRENGTHENING WILL TAKE LONGER TO OCCUR. THE OFFICIAL INTENSITY FORECAST IS A BLEND OF THE SHIPS AND GFDL GUIDANCE. FOR SOME UNKNOWN REASON...THE FSU SUPERENSEMBLE SIGNIFICANTLY STRENGTHENS FLORENCE AFTER RECURVATURE OCCURS. THIS SOLUTION IS DISCOUNTED AS THE SHEAR IS EXPECTED TO INCREASE TO OVER 40 KNOTS AFTER 3 DAYS. THE BERMUDA WEATHER SERVICE WILL LIKELY ISSUE WATCHES OR WARNINGS WITHIN THE NEXT 24 HOURS. FORECAST POSITIONS AND MAX WINDS INITIAL 08/0900Z 22.1N 57.6W 45 KT 12HR VT 08/1800Z 23.1N 59.5W 50 KT 24HR VT 09/0600Z 24.4N 61.7W 55 KT 36HR VT 09/1800Z 25.8N 63.6W 65 KT 48HR VT 10/0600Z 27.4N 64.6W 75 KT 72HR VT 11/0600Z 31.0N 65.0W 90 KT...NEAR BERMUDA 96HR VT 12/0600Z 37.0N 62.0W 85 KT 120HR VT 13/0600Z 45.0N 53.0W 80 KT...BECOMING EXTRATROPICAL $$ FORECASTER MAINELLI/BEVEN |