ZCZC MIATCDAT2 ALL TTAA00 KNHC DDHHMM TROPICAL STORM FRED DISCUSSION NUMBER 4 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL072009 1100 AM AST TUE SEP 08 2009 SATELLITE IMAGES INDICATE THAT FRED CONTINUES TO BECOME BETTER ORGANIZED WITH IMPRESSIVE CURVED BANDING. IN ADDITION...MICROWAVE DATA SHOW THE POSSIBLE DEVELOPMENT OF INNER CORE FEATURES AND THE FIRST SIGNS OF AN EYE. AN 0808 UTC QUIKSCAT PASS SHOWED MAXIMUM WINDS OF ABOUT 50 KT...AND 1200 UTC SATELLITE ESTIMATES WERE 55 KT FROM BOTH TAFB/SAB. THE LATTER VALUE WILL BE USED AS THE INITIAL INTENSITY. FURTHER STRENGTHENING SEEMS LIKELY GIVEN WARM WATERS AND LIGHT SHEAR FOR THE NEXT 24-36 HRS. THEREAFTER...SSTS DECREASE AND AN UPPER TROUGH CURRENTLY ALONG 40W COULD START TO INDUCE SOUTHWESTERLY SHEAR. THE DYNAMICAL GUIDANCE SHOWS A PEAK INTENSITY OF FRED AS A CATEGORY 2 HURRICANE WHILE THE STATISTICAL GUIDANCE IS LESS ROBUST BUT STILL MAKES FRED A HURRICANE. THE NHC INTENSITY FORECAST IS A BLEND OF THAT GUIDANCE AND IS HIGHER THAN THE PREVIOUS FORECAST FOR THE FIRST FEW DAYS. IN THE LONGER-TERM... VERTICAL WIND SHEAR IS FORECAST TO BE QUITE STRONG WHILE THE CYCLONE IS OVER MARGINAL SSTS. THESE CONDITIONS SHOULD PROMOTE SIGNIFICANT WEAKENING AND THE DAY 3-5 FORECAST IS CLOSE TO THE LGEM MODEL. OVERNIGHT MICROWAVE AND VISIBLE IMAGES SUGGEST AN INITIAL MOTION OF ABOUT 275/12. FOR THE TIME BEING...FRED IS BEING STEERED PRIMARILY BY A MID-TROPOSPHERIC RIDGE TO ITS NORTH. THIS RIDGE SHOULD GRADUALLY DIMINISH WITH TIME AS A MID- TO UPPER-LEVEL TROUGH NEAR 40W MOVES EASTWARD. THE MODELS ARE IN REASONABLE AGREEMENT ON A TRACK TOWARD THE WEST-NORTHWEST...NORTHWEST...THEN TOWARD THE NORTH BY DAY THREE. STEERING CURRENTS BECOME LIGHT AFTER THAT TIME...WITH SOME HINTS OF A RIDGE REBUILDING TO THE NORTH CAUSING A SLOW NORTHWESTWARD MOVEMENT. THE CANADIAN AND THE UKMET ARE THE ONLY TWO MODELS THAT HAVE A SLIGHTLY DIFFERENT EVOLUTION TO THE PATTERN...SHOWING FRED MISSING THE FIRST TROUGH WHICH CAUSES A MORE WESTWARD MOTION...BUT EVEN THOSE MODELS HAVE THE CYCLONE MOVING NORTHWARD BY THE END OF THE PERIOD. THE NHC FORECAST IS A LITTLE WEST OF THE PREVIOUS ONE BUT IS CLOSE TO THE MODEL CONSENSUS. FORECAST POSITIONS AND MAX WINDS INITIAL 08/1500Z 11.9N 28.6W 55 KT 12HR VT 09/0000Z 12.4N 30.3W 65 KT 24HR VT 09/1200Z 13.3N 32.1W 75 KT 36HR VT 10/0000Z 14.4N 33.2W 80 KT 48HR VT 10/1200Z 15.7N 34.0W 75 KT 72HR VT 11/1200Z 17.7N 34.3W 60 KT 96HR VT 12/1200Z 19.0N 34.5W 50 KT 120HR VT 13/1200Z 20.5N 35.5W 40 KT $$ FORECASTER BLAKE NNNN
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Page last modified: Thursday, 31-Dec-2009 12:09:09 UTC