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Subtropical Storm Leslie Forecast Discussion Number 3
2018-09-24 04:44:37| National Hurricane Center (Atlantic)
Issued at 1100 PM AST Sun Sep 23 2018 255 WTNT43 KNHC 240244 TCDAT3 Subtropical Storm Leslie Discussion Number 3 NWS National Hurricane Center Miami FL AL132018 1100 PM AST Sun Sep 23 2018 There has been little change in the organization of the subtropical cyclone over the past several hours. Patches of deep convection continue to develop over the southeastern portion of the circulation but there is a lack of convective banding elsewhere. The initial intensity remains 35 kt, which is based on a partial ASCAT pass that detected 25-30 kt winds over the northwestern portion of the storm this evening. Leslie is not forecast to strengthen over the next day or so due to dry air and moderate vertical shear. By 48 hours, some increase in wind is predicted as Leslie interacts with an approaching baroclinic zone. Leslie jogged west-southwestward for a few hours this evening, but has since turned southwestward and slowed down. The system is forecast to move little over the next 24 hours, then begin a faster eastward motion on Monday night and Tuesday as a mid-latitude trough and associated cold front digs southeastward over the central Atlantic. The global models indicate that the front will overtake Leslie in about 48 hours, and the NHC forecast calls for the system to become an extratropical low at that time. The evolution of the system becomes even more complex after that, as the GFS shows Leslie being absorbed by a new non-tropical low pressure area to the north, while some of other global models maintain post-tropical Leslie as the primary low pressure area. For now, the NHC forecast maintains continuity with the previous advisories and calls for the system to merge with the larger front/low by 72 h, but there is a high level of uncertainty in the exact evolution and structure of the system. Regardless of the details of the evolution, a large non-tropical low pressure area with gale- to storm-force winds is expected to be over the east-central Atlantic later this week. FORECAST POSITIONS AND MAX WINDS INIT 24/0300Z 33.3N 48.5W 35 KT 40 MPH 12H 24/1200Z 33.1N 48.5W 35 KT 40 MPH 24H 25/0000Z 33.1N 47.8W 35 KT 40 MPH 36H 25/1200Z 32.9N 46.0W 35 KT 40 MPH 48H 26/0000Z 33.1N 43.2W 40 KT 45 MPH...POST-TROP/EXTRATROP 72H 27/0000Z...MERGED WITH FRONT AND LARGER LOW $$ Forecaster Brown
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