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Hurricane Lee Discussion Number  29
NWS National Hurricane Center Miami FL       AL132023
Issued by the NWS Weather Prediction Center College Park MD
1100 AM AST Tue Sep 12 2023
 
GOES-16 satellite and radar images from the NOAA Hurricane Hunter
indicate that Lee is trying to consolidate into one large eyewall,
but the eye remains obscured with fragments of the old eyewall
structures.  Peak 700-mb flight-level winds were about 110 kt, 0.5
km radar estimates were near 121 kt and surface SFMR estimates were
about 90 kt, which could be under sampled with such a large
radius of maximum winds.  The initial wind speed is held at 100 kt
as a compromise of the aircraft estimates.
 
Lee is still moving slowly west-northwestward (300/5 kt), with
mid-level ridging established to the north and east of the
hurricane. This steering pattern is expected to change during the
next couple of days as a deep-layer trough moves across the eastern
United States and produces a weakness in this ridge. As a result,
Lee is forecast to turn northward and gradually accelerate during
the middle and latter parts of this week. The track guidance
envelope shows little cross-track spread during the first 3 days of
the forecast period, and this portion of the NHC forecast is fairly
similar to the previous one. While the core of the hurricane is
forecast to pass west of Bermuda, the large wind field of the storm
is likely to bring wind impacts to the island on Thursday,
prompting the Bermuda Weather Service to issue a Tropical Storm
Watch.  The latest NHC track was a compromise between the 6z GEFS
and ECMWF ensembles in the days 4/5 time frame, as it is still too
early to know if any leftward bend will occur as Lee approaches
North America.
 
No significant change in strength is expected in the near-term with
Lee due to its current structure and large wind field.  Going
forward, the large hurricane appears likely to begin upwelling
cooler waters along its path, and in a few days it will encounter
the cool wake left behind by recent western Atlantic hurricanes.
Thus, gradual weakening is forecast through midweek. Later, the
aforementioned trough is expected to produce stronger deep-layer
shear over Lee, and the hurricane is forecast to move over
significantly cooler waters as it passes north of the Gulf Stream.
As a result, more significant weakening is shown at days 4-5, along
with completion of its extratropical transition. Despite the
forecast weakening, it is important to note that the expanding wind 
field of Lee will produce impacts well away from the storm center.
 
 
KEY MESSAGES:
 
1. Dangerous surf and life-threatening rip currents will affect
portions of the northern Leeward Islands, the Virgin Islands, Puerto
Rico, Hispaniola, the Turks and Caicos Islands, the Bahamas,
Bermuda, and most of the U.S East Coast through much of the week.
 
2. There is an increasing risk of strong winds, rainfall, and high
surf impacts to Bermuda later this week, and a Tropical Storm Watch
has been issued for the island.
 
3. It remains too soon to know what level of additional impacts Lee
might have along the northeastern U.S. coast and Atlantic Canada
late this week and this weekend.  However, since wind and rainfall
hazards will extend well away from the center as Lee grows in size,
users should continue to monitor updates to Lee's forecast during
the next several days.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  12/1500Z 24.3N  65.9W  100 KT 115 MPH
 12H  13/0000Z 24.8N  66.6W  100 KT 115 MPH
 24H  13/1200Z 25.9N  67.3W  100 KT 115 MPH
 36H  14/0000Z 27.4N  67.8W   95 KT 110 MPH
 48H  14/1200Z 29.4N  68.2W   90 KT 105 MPH
 60H  15/0000Z 31.6N  68.0W   85 KT 100 MPH
 72H  15/1200Z 34.3N  67.4W   80 KT  90 MPH
 96H  16/1200Z 40.7N  66.6W   65 KT  75 MPH
120H  17/1200Z 45.3N  65.9W   45 KT  50 MPH...POST-TROP/EXTRATROP
 
$$
Forecaster Bann/Blake/Gallina
 
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