Atlantic Basin Tropical Cyclones

Tropical Storm Lee Forecast Discussion



000
WTNT43 KNHC 052054
TCDAT3

Tropical Storm Lee Discussion Number   2
NWS National Hurricane Center Miami FL       AL132023
500 PM AST Tue Sep 05 2023

1-min GOES-16 satellite imagery shows that the tropical cyclone has 
been improving in structure throughout the day, with additional 
curved banding features and a new burst of convection near the 
center.  A late-arriving ASCAT-C pass indicated maximum winds 
supporting 35 kt, and the satellite presentation has notably 
improved since that time.  The initial wind speed is set to 40 kt 
to match the satellite trends.

Lee is moving west-northwestward at about 14 kt.  There are no 
significant changes to the NHC track forecast with a mid-level ridge 
over the central Atlantic likely to persist to the north of the 
storm.  This ridge should provide a steady steering current, with a 
general west-northwestward course expected through the weekend with 
some reduction in forward speed.  The spread in the model guidance 
remains low, and the official forecast is adjusted a bit to the 
northeast closer to the model consensus.  Still, it is too early to 
determine exactly how close this system will be to the Leeward 
Islands given the average track forecast error at those time ranges.

It is becoming a question of when and not if rapid intensification 
(RI) occurs with Lee.  A well-defined outflow pattern has developed 
over the circulation, and there are some hints on a recent SSMI/S 
microwave pass that parts of an inner core are forming.  There's 
still some notable northeasterly shear that could keep Lee in 
check for the next day or two, so the NHC intensity forecast will 
stay at a more moderate rate of intensification during that time.  
All of the models decrease the shear by Friday, so RI is explicitly 
forecast at that time frame while Lee is moving over extremely warm 
waters.  The new forecast is adjusted higher than the last advisory, 
near the model consensus, but there's a notable contingent of 
guidance higher than this forecast.  There is increasing confidence 
on Lee becoming a very powerful hurricane by this weekend.

KEY MESSAGES:

1. Lee is forecast to become a major hurricane by this weekend and 
could bring impacts to the Leeward Islands by that time. While it 
is too soon to determine the location and magnitude of these 
possible impacts, interests in this area should monitor the 
progress of Lee and further updates to the forecast.


FORECAST POSITIONS AND MAX WINDS

INIT  05/2100Z 13.2N  41.8W   40 KT  45 MPH
 12H  06/0600Z 13.7N  43.7W   50 KT  60 MPH
 24H  06/1800Z 14.4N  46.2W   60 KT  70 MPH
 36H  07/0600Z 15.2N  48.5W   70 KT  80 MPH
 48H  07/1800Z 16.2N  51.0W   80 KT  90 MPH
 60H  08/0600Z 17.2N  53.6W   90 KT 105 MPH
 72H  08/1800Z 18.3N  56.0W  110 KT 125 MPH
 96H  09/1800Z 20.4N  60.5W  120 KT 140 MPH
120H  10/1800Z 22.2N  64.3W  125 KT 145 MPH

$$
Forecaster Blake



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