658
WTNT44 KNHC 122033
TCDAT4
TROPICAL STORM SEAN DISCUSSION NUMBER 8
NWS NATIONAL HURRICANE CENTER MIAMI FL AL192023
500 PM AST THU OCT 12 2023
SEAN REMAINS FAIRLY DISORGANIZED ON SATELLITE IMAGERY THIS
AFTERNOON. THE LOW-LEVEL CENTER IS STILL EXPOSED, HOWEVER THERE HAS
BEEN A RECENT BURST OF CONVECTION CLOSER TO THE CENTER. SUBJECTIVE
DVORAK INTENSITY ESTIMATES HAVE INCREASED SINCE THE PREVIOUS CYCLE,
WITH FINAL-T NUMBERS OF T2.5/T2.0 FROM TAFB AND SAB, RESPECTIVELY.
THESE ESTIMATES ARE IN FAIRLY GOOD AGREEMENT WITH THE SCATTEROMETER
DATA FROM EARLIER. THEREFORE, THE INITIAL INTENSITY FOR THIS
ADVISORY IS HELD AT 35 KT.
THE TROPICAL STORM IS MOVING AT A SLIGHTLY FASTER NORTHWESTWARD
MOTION AT 310/10 KT, GAINING A LITTLE MORE LATITUDE SINCE THIS
MORNING. A WEAK RIDGE TO THE NORTHEAST OF THE SYSTEM WILL CONTINUE
TO STEER SEAN NORTHWESTWARD TO WEST-NORTHWESTWARD THROUGHOUT THE
FORECAST PERIOD. MODEL GUIDANCE REMAINS IN FAIRLY GOOD AGREEMENT
WITH THIS SCENARIO. THERE WAS A SLIGHT SHIFT TO THE RIGHT IN THE
SHORT-TERM CENTER POSITIONS TO ACCOUNT FOR THE SLIGHTLY FASTER
NORTHWESTWARD MOTION. OTHERWISE, THE TRACK FORECAST IS SIMILAR TO
THE PREVIOUS AND LIES NEAR THE CONSENSUS AIDS.
WESTERLY VERTICAL WIND SHEAR IS EXPECTED TO PERSIST OVER THE SYSTEM
FOR THE NEXT DAY OR SO, BEFORE DECREASING ALONG SEAN'S FORECAST
TRACK. HOWEVER, THE SYSTEM WILL BE MOVING INTO AN AREA WITH DRIER
MID-LEVEL RH VALUES, A MORE STABLE ENVIRONMENT, AND A LESS FAVORABLE
UPPER-LEVEL WIND PATTERN. SIMULATED SATELLITE IMAGERY FROM THE GFS
AND ECMWF MODELS SUGGEST THAT SEAN COULD STRUGGLE TO PRODUCE
ORGANIZED CONVECTION IN THE COMING DAYS. WHILE SMALL INTENSITY
FLUCTUATIONS ARE POSSIBLE, THE NHC INTENSITY FORECAST REMAINS NEAR
THE HCCA AND IVCN CONSENSUS AIDS, KEEPING SEAN A TROPICAL STORM FOR
THE NEXT DAY OR SO, THEN WEAKENING IT BACK INTO A DEPRESSION.
AFTERWARDS, THE SYSTEM IS FORECAST TO DEGENERATE INTO A
POST-TROPICAL REMNANT LOW AS IT BECOMES DEVOID OF CONVECTION, AND
DISSIPATE INTO A TROUGH BY DAY 4. ALTHOUGH, SOME GLOBAL MODELS
DEPICT THAT THESE TRANSITIONS COULD OCCUR EVEN SOONER THAN FORECAST.
FORECAST POSITIONS AND MAX WINDS
INIT 12/2100Z 13.8N 38.2W 35 KT 40 MPH
12H 13/0600Z 14.5N 39.5W 35 KT 40 MPH
24H 13/1800Z 15.5N 41.2W 35 KT 40 MPH
36H 14/0600Z 16.8N 42.6W 30 KT 35 MPH
48H 14/1800Z 18.0N 43.8W 30 KT 35 MPH
60H 15/0600Z 19.0N 44.8W 25 KT 30 MPH...POST-TROP/REMNT LOW
72H 15/1800Z 19.9N 45.9W 25 KT 30 MPH...POST-TROP/REMNT LOW
96H 16/1800Z...DISSIPATED
FORECASTER KELLY
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