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| #199128 (Received by flhurricane at: 10:40 PM 04.Jul.2008) TCDAT2 TROPICAL STORM BERTHA DISCUSSION NUMBER 8 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL022008 1100 PM EDT FRI JUL 04 2008 MICROWAVE IMAGERY OVER THE LAST 12-24 HOURS INDICATES THAT BERTHA HAS BEEN STAIR-STEPPING ITS WAY ACROSS THE ATLANTIC OSCILLATING BETWEEN A WESTWARD AND NORTHWESTWARD HEADING WITH EACH NEW CONVECTIVE BURST. IRONING ALL THIS OUT YIELDS AN INITIAL MOTION ESTIMATE OF 280/18...A LITTLE FASTER THAN BEFORE. THERE HAS BEEN LITTLE OVERALL CHANGE IN THE FORECAST PHILOSOPHY. A STRONG RIDGE TO THE NORTH SHOULD KEEP THE CYCLONE ON A GENERAL WESTWARD TO WEST- NORTHWESTWARD MOTION DURING THE NEXT 2-3 DAYS. WHILE MOST OF THE DYNAMICAL MODELS STILL SHOW A WEAKNESS DEVELOPING IN THE RIDGE NORTH OF BERTHA IN ABOUT THREE DAYS...THEY HAVE BEEN TRENDING TOWARDS A MORE WESTWARD MOTION OF BERTHA DUE TO A WEAKER AND SHALLOWER DEPICTION OF THE CYCLONE. THE EXCEPTION IS THE HWRF WHICH FORECASTS A STRONGER AND DEEPER BERTHA TURNING NORTHWESTWARD BEYOND 72 HOURS DUE TO THE WEAKNESS. THE OFFICIAL FORECAST IS NUDGED A LITTLE WESTWARD BUT IS STILL NORTH OF MOST OF THE GUIDANCE SINCE ONLY A MODEST INCREASE IN STRENGTH WOULD ALLOW BERTHA TO RESPOND TO THE DEEPER AND MORE NORTHWARD STEERING. BERTHA CONTINUES TO EXHIBIT A CONVECTIVE BURSTING PATTERN WITH THE LATEST BURST BEGINNING AROUND 2300 UTC. AVAILABLE SATELLITE INTENSITY ESTIMATES SUGGEST THAT THE SYSTEM HAS CHANGED LITTLE IN STRENGTH WITH THE INITIAL INTENSITY HELD AT 45 KT. BERTHA IS FORECAST TO MOVE OVER MARGINALLY WARM SSTS DURING THE NEXT 24 HOURS WHICH IS EXPECTED TO LIMIT INTENSIFICATION. THEREAFTER...SSTS GRADUALLY INCREASE ALONG THE PROJECTED TRACK AND BERTHA IS EXPECTED TO SLOWLY STRENGTHEN. VERTICAL SHEAR IS FORECAST TO INCREASE TOWARDS THE END OF THE FORECAST SO ARRESTED DEVELOPMENT IS SHOWN BEYOND 72 HOURS. THIS FORECAST IS SIMILAR TO THE PREVIOUS ONE AND IS IN CLOSEST AGREEMENT WITH THE HWRF MODEL. FORECAST POSITIONS AND MAX WINDS INITIAL 05/0300Z 16.0N 33.5W 45 KT 12HR VT 05/1200Z 16.4N 36.2W 45 KT 24HR VT 06/0000Z 17.0N 39.8W 45 KT 36HR VT 06/1200Z 17.6N 43.6W 50 KT 48HR VT 07/0000Z 18.1N 47.3W 55 KT 72HR VT 08/0000Z 20.0N 53.5W 60 KT 96HR VT 09/0000Z 22.0N 58.5W 60 KT 120HR VT 10/0000Z 24.0N 63.0W 60 KT $$ FORECASTER RHOME |
