000 WTNT43 KNHC 070837 TCDAT3 Hurricane Leslie Discussion Number 20 NWS National Hurricane Center Miami FL AL132024 500 AM AST Mon Oct 07 2024 Conventional satellite imagery indicates that Leslie's cloud pattern has changed little during the past few hours. A fortuitous SSMIS microwave image revealed a compact inner core with the eyewall partially open in the south side. Most of the convective curve bands remain confined to the north side of the cyclone. The TAFB and SAB subjective and the UW-CIMSS objective satellite intensity estimates support holding the initial intensity at 80 kt for this advisory. Although the statistical GFS/ECMWF SHIPS intensity models indicate a low-shear surrounding environment through the 60 hr period, the global model forecast sounding reveals 15-20 kt of 400-250 mb mid-tropospheric westerly shear undercutting the diffluent flow aloft. This mid-level disrupting flow could force the drier, stable air identified in the water vapor imagery into Leslie's deep convective core. This negative thermodynamic contribution, along with gradually decreasing oceanic surface temperatures ahead of the cyclone's predicted path should cause Leslie to weaken through the period. The ECMWF and GFS model simulated infrared forecast now indicates that Leslie will lose its organized convection within inhibiting environmental conditions and become a post-tropical cyclone by day 5, and the NHC intensity forecast follows suit. Based on the above-mentioned microwave pass, the initial motion is estimated to be northwestward, or 315/11 kt, just a little left of the previous track. Leslie is expected to move around the southwestern periphery of a subtropical ridge to the northeast of the cyclone and turn gradually north-northwestward to northward toward the end of the week. The official forecast is an update of the previous one and closely follows the various consensus aids. Leslie's wind radii were adjusted based on an earlier CSA/RCM-3 SAR overpass. FORECAST POSITIONS AND MAX WINDS INIT 07/0900Z 15.6N 40.4W 80 KT 90 MPH 12H 07/1800Z 16.6N 41.7W 75 KT 85 MPH 24H 08/0600Z 18.1N 43.4W 60 KT 70 MPH 36H 08/1800Z 19.6N 45.2W 55 KT 65 MPH 48H 09/0600Z 20.9N 46.7W 50 KT 60 MPH 60H 09/1800Z 21.7N 47.9W 50 KT 60 MPH 72H 10/0600Z 22.4N 48.9W 45 KT 50 MPH 96H 11/0600Z 23.9N 50.1W 40 KT 45 MPH 120H 12/0600Z 25.8N 49.9W 40 KT 45 MPH...POST-TROPICAL $$ Forecaster Roberts
Originally Posted at:
NATIONAL HURRICANE CENTER and CENTRAL PACIFIC HURRICANE CENTER
At The NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION
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