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| #1158958 (Received by flhurricane at: 4:58 AM 26.Oct.2023) TCDAT5 Post-Tropical Cyclone Tammy Discussion Number 32 NWS National Hurricane Center Miami FL AL202023 500 AM AST Thu Oct 26 2023 Tammy appears to have completed its transition to a post-tropical cyclone, merging with the nearby front. The cloud pattern has become more comma shaped, with a long linear convective band, and is no longer producing deep convection near the center. The cyclone is now frontal but likely still has a warm core, indicating that it is a warm seclusion-type of extratropical cyclone. Despite the transition, it remains a strong cyclone, and the initial intensity is 75 kt, based on current intensity satellite estimates. The cyclone has slowed down and made a northward turn overnight, and recently the system is turning more north-northwestward. The estimated long-term motion is 355/10 kt. Over the next day or so, Tammy is forecast to slow down and move generally northwestward to west-northwestward. Beyond 36 h there continues to be high uncertainty in the track forecast, with no more clarity from the latest global model runs. The global models continue to have enormous spread, and ensemble solutions that diverge in opposite directions. Given the uncertainty, there is little change from the previous forecast at this time range. Although post-tropical, Tammy remains a powerful cyclone. In the near term, the increasing shear and drier air associated with a deep-layer trough to the west should continue to cause convection to dissipate, and the system to weaken over the next few days. Global model fields indicate Tammy could shed its frontal structure by 36 h. A reduction in wind shear is forecast soon thereafter, and convection could redevelop near Tammy`s center in about 2-3 days while it moves over 25-26C sea surface temperatures. Though it is not explicitly forecast, there is some potential based on the GFS and ECMWF simulated satellite imagery that Tammy could reacquire tropical characteristics this weekend or early next week. The chances of the system transitioning back to a tropical cyclone will be evaluated in routine Tropical Weather Outlooks. This is the last NHC advisory. 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 26/0900Z 30.5N 58.4W 75 KT 85 MPH...POST-TROP/EXTRATROP 12H 26/1800Z 31.2N 59.6W 65 KT 75 MPH...POST-TROP/EXTRATROP 24H 27/0600Z 31.5N 61.0W 55 KT 65 MPH...POST-TROP/EXTRATROP 36H 27/1800Z 31.9N 62.2W 55 KT 65 MPH...POST-TROPICAL 48H 28/0600Z 32.3N 62.1W 50 KT 60 MPH...POST-TROPICAL 60H 28/1800Z 32.4N 61.2W 50 KT 60 MPH...POST-TROPICAL 72H 29/0600Z 32.4N 60.4W 45 KT 50 MPH...POST-TROPICAL 96H 30/0600Z 32.3N 59.6W 40 KT 45 MPH...POST-TROPICAL 120H 31/0600Z 32.2N 58.4W 35 KT 40 MPH...POST-TROPICAL $$ Forecaster Kelly |
