Issued at 1100 AM AST Thu Aug 07 2025
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