809 WTNT45 KNHC 201437 TCDAT5 Post-Tropical Cyclone Ernesto Discussion Number 36 NWS National Hurricane Center Miami FL AL052024 300 PM GMT Tue Aug 20 2024 Strong southwesterly vertical wind shear and cold sea-surface temperatures have caused Ernesto to lose tropical characteristics this morning. The cyclone lacks organized convection, and the low-level center is becoming exposed as dry air wraps into the circulation. Also, GFS phase diagrams indicate Ernesto no longer has a warm-core structure. Thus, it appears the cyclone has completed its transition to a post-tropical cyclone. Despite these structural changes, nearby ship observations indicate Ernesto remains a powerful cyclone with storm-force winds in its southern semicircle. Based on these observations, the initial intensity is set at 60 kt. The post-tropical cyclone is moving quickly northeastward (055/32 kt) within the flow between a deep-layer trough over the north Atlantic and a subtropical ridge over the central Atlantic. An even faster east-northeastward motion is forecast through Wednesday as the cyclone remains embedded within strong steering currents. The system is forecast to merge with a frontal system and become extratropical by tonight, and the low should dissipate on Wednesday over the northeastern Atlantic. Although some weakening is expected during the next day or so, the cyclone will maintain a large wind field to the south of its center. This is the last NHC advisory on Ernesto. 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 20/1500Z 49.0N 44.7W 60 KT 70 MPH...POST-TROPICAL 12H 21/0000Z 50.5N 36.0W 50 KT 60 MPH...POST-TROP/EXTRATROP 24H 21/1200Z 52.8N 23.3W 40 KT 45 MPH...POST-TROP/EXTRATROP 36H 22/0000Z...DISSIPATED $$ Forecaster Reinhart