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| #1206116 (Received by flhurricane at: 5:00 AM 02.Nov.2024) TCDAT2 Subtropical Storm Patty Discussion Number 1 NWS National Hurricane Center Miami FL AL172024 900 AM GMT Sat Nov 02 2024 The low pressure system that the NHC has been monitoring over the northern Atlantic has gradually acquired subtropical characteristics during the past 12-24 h. The low has become detached from fronts and has a shallow warm-core structure, though it remains within a cooler airmass behind a cold front over the eastern Atlantic. Despite SSTs around 21 deg C, instability aloft has allowed the system to sustain some moderate convection that wraps most of the way around its center in geostationary and passive microwave images. Since the wind field is asymmetric and the system remains co-located with an upper-level low, it seems best classified as a subtropical cyclone, which is consistent with ST2.5 classifications from TAFB. Thus, the NHC is initiating advisories on Subtropical Storm Patty. Earlier partial scatterometer data showed 35-40 kt winds in the southern semicircle, and the initial intensity is set at 45 kt since it does not appear the strongest winds were sampled by the instrument. Patty is moving east-southeastward at 105/7 kt. The track guidance is in very good agreement that Patty will move faster toward the east-southeast through early Sunday, bringing the center near or over portions of the Azores. Then, a turn toward the east and east-northeast is expected through early next week as Patty is steered by an upper-level trough. The NHC track forecast lies near the center of the guidance envelope, generally between the simple and corrected consensus aids. Little change in strength is expected today, and Patty is forecast to be a fairly short-lived subtropical cyclone. This is because westerly shear is forecast to increase over the system during the next couple of days, which will likely make it difficult for the system to sustain convection near and around its center. Due to its increasing forward speed, the strongest winds of Patty should generally remain over the southern portion of the circulation during its lifetime. Given the non-tropical origins of this system, the NHC intensity forecast leans more heavily on the GFS and ECMWF global models, which lie on the lower end of the guidance envelope. FORECAST POSITIONS AND MAX WINDS INIT 02/0900Z 39.9N 34.4W 45 KT 50 MPH 12H 02/1800Z 39.1N 31.3W 45 KT 50 MPH 24H 03/0600Z 38.2N 27.3W 40 KT 45 MPH 36H 03/1800Z 38.0N 23.3W 35 KT 40 MPH...POST-TROPICAL 48H 04/0600Z 38.7N 19.1W 35 KT 40 MPH...POST-TROPICAL 60H 04/1800Z 39.8N 15.2W 30 KT 35 MPH...POST-TROP/REMNT LOW 72H 05/0600Z 41.3N 11.5W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 06/0600Z...DISSIPATED $$ Forecaster Reinhart |
