219
WTNT44 KNHC 120232
TCDAT4
TROPICAL DEPRESSION SEAN DISCUSSION NUMBER 5
NWS NATIONAL HURRICANE CENTER MIAMI FL AL192023
1100 PM AST WED OCT 11 2023
SEAN IS A HIGHLY SHEARED TROPICAL CYCLONE, WITH THE CENTER LOCATED
WELL TO THE WEST OF THE ASSOCIATED DEEP CONVECTION. SIMILAR TO WHAT
WAS OBSERVED THIS MORNING, TWO RECENT ASCAT PASSES SHOWED MAXIMUM
WINDS A LITTLE OVER 25 KT AND A POORLY DEFINED SURFACE CIRCULATION.
BASED ON THESE DATA, SEAN IS BEING DESIGNATED AS A 30-KT TROPICAL
DEPRESSION.
THE INITIAL MOTION REMAINS WEST-NORTHWESTWARD (295 DEGREES) AT 11
KT. WEAK MID-LEVEL RIDGING TO THE NORTH IS EXPECTED TO KEEP SEAN ON
A WEST-NORTHWESTWARD OR NORTHWESTWARD HEADING FOR THE NEXT SEVERAL
DAYS, WITH SOME DECREASE IN FORWARD SPEED. THE NHC TRACK FORECAST
IS VERY CLOSE TO THE PREVIOUS PREDICTION THROUGH 48 HOURS, BUT THEN
DEVIATES A LITTLE TO THE RIGHT ON DAYS 3 AND 4. THE GFS AND ECMWF
ARE BOTH ON THE FAR RIGHT SIDE OF THE GUIDANCE ENVELOPE, AND IT'S
POSSIBLE THAT ADDITIONAL RIGHTWARD ADJUSTMENTS COULD BE POSSIBLE IN
SUBSEQUENT FORECASTS.
STRONG DEEP-LAYER SHEAR OUT OF THE WEST OR WEST-SOUTHWEST IS
EXPECTED TO CONTINUE FOR THE NEXT 36 HOURS OR SO, WITH SOME
ABATEMENT POSSIBLE AFTER THAT. BY THEN, HOWEVER, DRIER AIR WILL
HAVE INFILTRATED THE CIRCULATION, AND SEAN WILL BEGIN TO STRUGGLE TO
MAINTAIN ORGANIZED DEEP CONVECTION. DUE TO THE HOSTILE ATMOSPHERE,
AND BASED ON THE LATEST INTENSITY GUIDANCE, SEAN IS HELD AS A 30-KT
DEPRESSION FOR THE NEXT 60 HOURS, WITH DEGENERATION TO A REMNANT LOW
BY DAY 3. DISSIPATION TO A TROUGH IS NOW FORECAST BY DAY 5. SOME
OF THE GLOBAL MODELS SUGGEST THAT EACH OF THESE TRANSITIONS COULD
OCCUR EVEN SOONER THAN WHAT IS SHOWN IN THE OFFICIAL FORECAST.
FORECAST POSITIONS AND MAX WINDS
INIT 12/0300Z 12.0N 36.2W 30 KT 35 MPH
12H 12/1200Z 12.4N 37.4W 30 KT 35 MPH
24H 13/0000Z 13.1N 39.0W 30 KT 35 MPH
36H 13/1200Z 14.0N 40.5W 30 KT 35 MPH
48H 14/0000Z 15.0N 42.0W 30 KT 35 MPH
60H 14/1200Z 16.1N 43.1W 30 KT 35 MPH
72H 15/0000Z 17.2N 44.1W 25 KT 30 MPH...POST-TROP/REMNT LOW
96H 16/0000Z 18.5N 46.8W 25 KT 30 MPH...POST-TROP/REMNT LOW
120H 17/0000Z...DISSIPATED
FORECASTER BERG
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