Tropical Storm Leslie Forecast Discussion

000
WTNT43 KNHC 120839
TCDAT3

Tropical Storm Leslie Discussion Number  40
NWS National Hurricane Center Miami FL       AL132024
500 AM AST Sat Oct 12 2024

Leslie has held steady through the night.  The storm has maintained 
a small burst of deep convection near the low-level center, with 
cold cloud top temperatures of less than -80 degrees C.  While the 
satellite intensity estimates have trended downward, the initial 
intensity is held at 45 kt in deference to the earlier scatterometer 
data.

The storm is accelerating to the northeast at 21 kt in the flow 
ahead of an approaching deep-layer trough over the northwestern 
Atlantic.  On Sunday, Leslie should turn east-northeastward to 
eastward and continue this motion through the remainder of the 
forecast period.  Model guidance has shifted northward with a slight 
increase in forward speed this advisory cycle.  The latest NHC 
forecast has been nudged northward and now lies between the previous 
prediction and on the southern side of the tightly clustered 
guidance envelope.  Leslie, or its remnants, is now expected to move 
near or over the Azores late Sunday through early Monday.

Leslie has a few more hours in a marginal environmental.  Later 
today, deep-layer vertical wind shear is forecast to steadily 
increase and the storm is passing over the 26 degree C isotherm 
towards cooler waters.  Global models suggest Leslie will lose its 
deep convection and merge with a frontal system in about a day.  The 
official forecast now reflects the timing of this transition. It 
should be noted that while the models show a closed low pressure 
area through 72 h, the circulation could degenerate into an open 
trough before then due to the fast forward speed.


FORECAST POSITIONS AND MAX WINDS

INIT  12/0900Z 31.3N  45.9W   45 KT  50 MPH
 12H  12/1800Z 33.8N  42.3W   45 KT  50 MPH
 24H  13/0600Z 36.5N  36.6W   40 KT  45 MPH...POST-TROP/EXTRATROP
 36H  13/1800Z 37.6N  31.0W   40 KT  45 MPH...POST-TROP/EXTRATROP
 48H  14/0600Z 37.7N  25.5W   35 KT  40 MPH...POST-TROP/EXTRATROP
 60H  14/1800Z 37.1N  21.0W   35 KT  40 MPH...POST-TROP/EXTRATROP
 72H  15/0600Z 37.1N  16.4W   30 KT  35 MPH...POST-TROP/EXTRATROP
 96H  16/0600Z...DISSIPATED

$$
Forecaster Bucci