Tropical Storm IKE Forecast Discussion
000 WTNT44 KNHC 020856 TCDAT4 TROPICAL STORM IKE DISCUSSION NUMBER 4 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 500 AM EDT TUE SEP 02 2008
AL092008
THE STRUCTURE OF IKE HAS NOT CHANGED SIGNIFICANTLY THIS EVENING WITH SUBSTANTIAL CONVECTIVE BANDING EMBEDDED IN A LARGE SURFACE CIRCULATION. THE DVORAK CLASSIFICATIONS FROM TAFB AND SAB REMAIN 3.0 OR 45 KT...WHICH IS THE CURRENT INTENSITY. AN AMSU PASS AT 0020Z PROVIDED SOME CONFIDENCE IN ESTIMATING A TRACK AT 280 DEGREES AT 13 KT. THE TROPICAL STORM WILL BE MOVING BRISKLY OFF TOWARD THE WEST OR WEST-NORTHWEST UNDER THE INFLUENCE OF A DEEP LAYERED SUBTROPICAL RIDGE TO ITS NORTH. AS THE CUTOFF LOW CURENTLY SOUTH OF NOVA SCOTIA KICKS OUT TO THE NORTHEAST...THE SUBTROPICAL RIDGE SHOULD RETROGRADE TOWARD THE WEST OVER THE NEXT FEW DAYS. A MOTION WESTWARD ACROSS THE SUBTROPICAL NORTH ATLANTIC ALONG ABOUT 20N WOULD BE SOMEWHAT UNUSUAL...BUT IS SUPPORTED BY OUR MOST RELIABLE TRACK MODELS. THE TRACK MODEL GUIDANCE IS IN A RELATIVELY TIGHT CLUSTER SLIGHTLY TO THE SOUTH OF THE PREVIOUS MODEL RUNS. THIS TRACK FORECAST IS A BLEND BETWEEN THE MORE SOUTHERLY MODEL CONSENSUS AND THE MORE NORTHERLY PREVIOUS OFFICIAL FORECAST. THE INTENSITY PREDICTION IS MORE PROBLEMATIC. IN THE NEAR TERM...IKE IS IN A CONDUCIVE DYNAMICAL ENVIRONMENT WITH LOW VERTICAL SHEAR AND DIVERGENCE ALOFT...BUT THE THERMODYNAMICS ARE NOT AS FAVORABLE FOR DEVELOPMENT WITH ONLY SLIGHTLY WARM SSTS AND A POCKET OF LOW-LEVEL DRY AIR TO ITS SOUTH. IN THE LONGER TERM...THE OCEAN TEMPERATURES SHOULD WARM TO 29C...BUT THE SHEAR SHOULD INCREASE AS FLOW BETWEEN AN UPPER LOW EAST OF IKE AND THE UPPER RIDGE NORTHWEST OF IKE IS PREDICTED TO PRODUCE 30 KT NORTHEASTERLIES. GRADUAL INTENSIFICATION IS INDICATED THROUGH THE PERIOD...WHICH REFLECTS THE CONSENSUS OF THE SHIPS AND LGEM MODELS CALLING FOR A MINIMAL HURRICANE...AND THE GFDL AND HWRF MODELS WHICH SUGGEST A MUCH STRONGER CYCLONE. THIS INTENSITY FORECAST IS NEARLY THE SAME AS PROVIDED IN THE PREVIOUS ADVISORY. FORECAST POSITIONS AND MAX WINDS INITIAL 12HR VT 24HR VT 36HR VT 48HR VT 72HR VT 96HR VT 120HR VT 02/0900Z 02/1800Z 03/0600Z 03/1800Z 04/0600Z 05/0600Z 06/0600Z 07/0600Z 18.6N 19.0N 19.6N 20.2N 20.8N 21.5N 21.5N 21.5N 43.1W 45.3W 48.2W 51.3W 54.3W 60.5W 66.5W 72.0W 45 55 60 70 75 80 85 90 KT KT KT KT KT KT KT KT