231
WTNT42 KNHC 081434
TCDAT2
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
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