531
WTNT44 KNHC 071448
TCDAT4
POST-TROPICAL CYCLONE DEXTER DISCUSSION NUMBER 15
NWS NATIONAL HURRICANE CENTER MIAMI FL AL042025
1100 AM AST THU AUG 07 2025
SATELLITE IMAGERY AND SURFACE OBSERVATIONS INDICATE THAT DEXTER HAS
COMPLETED ITS TRANSITION TO AN EXTRATROPICAL CYCLONE. STRONG
WESTERLY WIND SHEAR IS LEAVING AN EXPOSED, ELONGATED CENTER WITH ALL
CONVECTION IN THE EASTERN SEMICIRCLE. THE CONVECTION IS DECREASING
IN STRENGTH AND AREAL COVERAGE, AND IT IS ALSO BECOMING MORE
ASYMMETRIC. A WARM FRONT CLEARLY EXTENDS EAST-NORTHEASTWARD FROM
DEXTER, AND THERE ALSO APPEARS TO BE A DEVELOPING COLD FRONT
EXTENDING TOWARDS THE SOUTHWEST, AS NOTED IN AN EARLIER AMSR2
MICROWAVE PASS. SURFACE MARINE OBSERVATIONS SHOW TEMPERATURES IN
THE UPPER 50S AND LOWER 60S JUST A COUPLE HUNDRED N MI NORTHWEST OF
DEXTER'S CENTER. A RECENT PARTIAL ASCAT PASS SHOWED WINDS UP TO 45
KT, BUT THIS PASS DID NOT SAMPLE THE ENTIRE CIRCULATION. THE
INITIAL INTENSITY OF THE EXTRATROPICAL CYCLONE IS INCREASED TO 50 KT
BASED ON THE ASCAT DATA AS WELL AS GLOBAL MODEL ANALYSES, WHICH
SUGGEST THE WINDS HAVE LIKELY REACHED 50 KT.
DEXTER IS MERGING WITH AN APPROACHING MID- TO UPPER-LEVEL TROUGH.
GLOBAL MODELS SHOW STRENGTHENING OVER THE NEXT 12-24 H DUE TO
BAROCLINIC FORCING DUE TO THE TROUGH INTERACTION. THEREAFTER, THE
CYCLONE WILL BEGIN TO STEADILY WEAKEN LATE FRIDAY INTO THE WEEKEND
AS THE UPPER-LEVEL TROUGH DAMPENS OUT. THE NHC INTENSITY FORECAST IS
NEAR THE HIGH END OF THE GUIDANCE DURING THE FIRST 24 HOURS OF THE
FORECAST, AND NEAR THE MIDDLE OF THE GUIDANCE ENVELOPE THEREAFTER.
THE CYCLONE IS FORECAST TO WEAKEN TO A TROUGH IN 4 TO 5 DAYS.
THE INITIAL MOTION IS 070/15. A MOTION BETWEEN NORTHEAST AND
EAST-NORTHEAST IS EXPECTED DURING THE NEXT 24-36 HOURS AS DEXTER
INTERACTS WITH THE AFOREMENTIONED TROUGH. AFTER THAT TIME, A SLIGHT
BEND MORE TOWARD THE EAST IS EXPECTED AS THE CYCLONE IS STEERED BY
THE MID-LATITUDE FLOW. THE NEW NHC FORECAST IS A BIT SLOWER THAN
THE PREVIOUS ONE, AND LIES IN BETWEEN THE SIMPLE AND CORRECTED
CONSENSUS AIDS.
THIS IS THE FINAL NHC ADVISORY ON DEXTER. ADDITIONAL INFORMATION ON
THIS SYSTEM CAN BE FOUND IN HIGH SEAS FORECASTS ISSUED BY THE
NATIONAL WEATHER SERVICE, UNDER AWIPS HEADER NFDHSFAT1, WMO HEADER
FZNT01 KWBC, AND ONLINE AT OCEAN.WEATHER.GOV/SHTML/NFDHSFAT1.PHP
FORECAST POSITIONS AND MAX WINDS
INIT 07/1500Z 41.4N 50.4W 50 KT 60 MPH...POST-TROP/EXTRATROP
12H 08/0000Z 42.6N 47.3W 60 KT 70 MPH...POST-TROP/EXTRATROP
24H 08/1200Z 44.2N 43.8W 60 KT 70 MPH...POST-TROP/EXTRATROP
36H 09/0000Z 45.2N 39.9W 50 KT 60 MPH...POST-TROP/EXTRATROP
48H 09/1200Z 45.9N 35.4W 45 KT 50 MPH...POST-TROP/EXTRATROP
60H 10/0000Z 46.5N 30.9W 35 KT 40 MPH...POST-TROP/EXTRATROP
72H 10/1200Z 47.1N 26.8W 30 KT 35 MPH...POST-TROP/EXTRATROP
96H 11/1200Z 48.0N 20.0W 30 KT 35 MPH...POST-TROP/EXTRATROP
120H 12/1200Z...DISSIPATED
FORECASTER HAGEN
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