978
WTNT42 KNHC 030232
TCDAT2
SUBTROPICAL STORM PATTY DISCUSSION NUMBER 4
NWS NATIONAL HURRICANE CENTER MIAMI FL AL172024
300 AM GMT SUN NOV 03 2024
THE CONVECTIVE STRUCTURE OF PATTY HAS CHANGED SOME OVER THE PAST
SEVERAL HOURS AS THE CENTER PASSES JUST SOUTH OF THE CENTRAL
AZORES. WHILE THE CLOUD TOPS HAVE COOLED, THE CONVECTION IS NOW
MAINLY TO THE NORTHEAST OF THE CENTER, AND THE OVERALL CLOUD PATTERN
IS ELONGATED SOUTH-TO-NORTH. THE SYSTEM REMAINS EMBEDDED IN A
DEEP-LAYER COLD AIR MASS, WITH SURFACE TEMPERATURES IN THE AZORES
CURRENTLY BELOW 20C. SATELLITE INTENSITY ESTIMATES HAVE DECREASED
A LITTLE DUE TO THE DECREASED CONVECTIVE SYMMETRY, AND THIS IS THE
BASIS FOR LOWERING THE INITIAL INTENSITY TO 50 KT.
PATTY IS EXPECTED TO WEAKEN OVER THE NEXT FEW DAYS AS THE PARENT
UPPER-LEVEL LOW DECAYS TO AN OPEN TROUGH, LEAVING THE STORM IN
STRONGER SHEAR. WHILE THIS HAPPENS, IT SHOULD ALSO MOVE INTO A
DRIER AND MORE STABLE AIRMASS. THIS COMBINATION IS EXPECTED TO
CAUSE THE CONVECTION TO DISSIPATE BY 36 H, WITH THE STORM BECOMING
A POST-TROPICAL LOW AT THAT TIME. THE LATEST GLOBAL MODEL GUIDANCE
SUGGESTS THAT THE REMNANT LOW IS LIKELY TO DECAY TO A TROUGH BY 72
H, SO THE NEW INTENSITY FORECAST NOW CALLS FOR DISSIPATION BY THEN.
THE INITIAL MOTION IS NOW 095/17 KT. THE MID-LATITUDE WESTERLY
FLOW IS EXPECTED TO STEER THE CYCLONE EASTWARD FOR 12-24 H,
FOLLOWED BY AN EAST-NORTHEASTWARD MOTION. THE MODELS REMAIN IN
FAIRLY GOOD AGREEMENT, AND THE FORECAST TRACK IS AGAIN NEAR THE
MIDDLE OF THE GUIDANCE ENVELOPE.
KEY MESSAGES:
1. TROPICAL STORM CONDITIONS ARE EXPECTED IN THE AZORES THROUGH THE
WEEKEND, WHERE TROPICAL STORM WARNINGS ARE IN EFFECT.
2. LOCALLY HEAVY RAINS ARE POSSIBLE ACROSS THE AZORES THROUGH THE
WEEKEND.
FORECAST POSITIONS AND MAX WINDS
INIT 03/0300Z 37.9N 27.8W 50 KT 60 MPH
12H 03/1200Z 37.6N 24.7W 45 KT 50 MPH
24H 04/0000Z 37.6N 20.8W 45 KT 50 MPH
36H 04/1200Z 38.5N 16.6W 40 KT 45 MPH...POST-TROPICAL
48H 05/0000Z 40.1N 12.7W 35 KT 40 MPH...POST-TROPICAL
60H 05/1200Z 41.6N 9.5W 30 KT 35 MPH...POST-TROP/REMNT LOW
72H 06/0000Z...DISSIPATED
FORECASTER BEVEN
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