918
WTNT45 KNHC 232039
TCDAT5
HURRICANE TAMMY DISCUSSION NUMBER 22
NWS NATIONAL HURRICANE CENTER MIAMI FL AL202023
500 PM AST MON OCT 23 2023
MODERATE SOUTHWESTERLY VERTICAL WIND SHEAR SEEMS TO BE DISRUPTING
TAMMY'S CIRCULATION. DEEP CONVECTION IS BEING PULLED NORTHWARD AWAY
FROM THE ESTIMATED LOW-LEVEL CENTER AND MID-LEVEL DRY AIR IS WORKING
ITS WAY AROUND THE SOUTHERN SIDE OF THE CYCLONE. SATELLITE
INTENSITY ESTIMATE HAVE DECREASED THIS CYCLE TO 55 AND 65 KT FROM
SAB AND TAFB, RESPECTIVELY. THE INITIAL INTENSITY HAS THEREFORE
BEEN LOWERED TO 65 KT. WHILE ASCAT MISSED THE MAJORITY OF THE
HURRICANE'S CORE, IT DID SHOW WINDS ON THE WESTERN PORTION OF THE
CIRCULATION HAVE DECREASED AND THE RADII HAVE BEEN ADJUSTED INWARD
ACCORDINGLY.
TAMMY IS MOVING NORTH-NORTHEASTWARD AT 6 KT. A TURN TOWARD THE
NORTHEAST IS FORECAST SHORTLY AS TAMMY IS STEERED BY A MID-LEVEL
RIDGE CENTERED OVER THE CENTRAL SUBTROPICAL ATLANTIC AND THE FLOW
AHEAD OF A MID-LATITUDE TROUGH OVER THE WESTERN ATLANTIC. BETWEEN
48-60 H, THE MODEL SOLUTIONS BEGIN TO BIFURCATE. THE ECMWF TURNS
THE HURRICANE NORTHWARD AND THEN WESTWARD BY THE END OF THE FORECAST
PERIOD. THE GFS AND REGIONAL MODELS TEND TO TURN TAMMY TOWARD THE
NORTH AND NORTHEASTWARD BY DAY 5. THE OFFICIAL FORECAST STILL
FAVORS THE ECMWF FORECAST AND IS SIMILAR TO THE PREVIOUS ADVISORY.
MODELS SUGGEST THAT ENVIRONMENTAL CONDITIONS WILL BE RELATIVELY
UNFAVORABLE. THE DEEP-LAYER VERTICAL WIND SHEAR IS FORECAST TO
INCREASE AND SURROUNDING MID-LEVEL MOISTURE TO DECREASE THROUGH MOST
OF THE FORECAST PERIOD. HOWEVER, IN A DAY OR SO, WHEN THE HURRICANE
BEGINS TO INTERACTS WITH THE TROUGH TO ITS WEST, UPPER-LEVEL
DIVERGENCE COULD ENHANCE CONVECTION AND CAUSE SOME STRENGTHENING
THROUGH ABOUT 48 H. TAMMY IS THEN EXPECTED TO GRADUALLY WEAKEN AND
COMPLETE ITS TRANSITION INTO AN EXTRATROPICAL CYCLONE BY DAY 3. THE
NHC INTENSITY FORECAST IS SIMILAR TO THE PREVIOUS PREDICTION, WITH A
SLIGHTLY LOWER PEAK INTENSITY OF 75 KT.
FORECAST POSITIONS AND MAX WINDS
INIT 23/2100Z 22.3N 63.6W 65 KT 75 MPH
12H 24/0600Z 23.0N 62.9W 70 KT 80 MPH
24H 24/1800Z 24.0N 61.7W 75 KT 85 MPH
36H 25/0600Z 25.3N 60.3W 75 KT 85 MPH
48H 25/1800Z 26.8N 59.0W 75 KT 85 MPH
60H 26/0600Z 28.9N 58.6W 70 KT 80 MPH
72H 26/1800Z 30.3N 59.3W 60 KT 70 MPH...POST-TROP/EXTRATROP
96H 27/1800Z 31.7N 62.1W 50 KT 60 MPH...POST-TROP/EXTRATROP
120H 28/1800Z 32.5N 65.2W 45 KT 50 MPH...POST-TROP/EXTRATROP
FORECASTER BUCCI
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