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