Official Discussion issued by the National Hurricane Center

Lee (AL132023) DATA RELEASED: 9/12/2023 3:00:00 AM UTC

Copy of official data

Hurricane Lee Discussion Number  27
NWS National Hurricane Center Miami FL       AL132023
1100 PM AST Mon Sep 11 2023

This evening, Lee appears to be in the final stages of completing 
another eyewall replacement cycle (ERC). A GPM microwave pass at 
2201 UTC showed that the outer eyewall remains closed and, while it 
remains quite large, continues to contract slowly as the inner 
eyewall decays within. The initial intensity is held at 100 kt this 
advisory, blending the subjective and objective intensity estimates 
this evening. Another Air Force Reserve Reconnaissance mission is 
scheduled to investigate the storm overnight, and several saildrones 
along Lee's path are also likely to provide additional in-situ 
observations in the hurricane over the next day or so.

Lee continues to move slowly west-northwestward, with the motion 
estimated at 295/6 kt. Lee is expected to continue moving slowly 
west-northwest or northwest over the next 24-36 h while mid-level 
ridging remains in place centered northwest of the hurricane. 
However, the ridge should then become eroded and shift eastward as a 
mid- to upper-level trough swings into the northeastern United 
States. This pattern change should result in Lee turning northward 
and gradually accelerating. The biggest spread in the track 
guidance solutions remains in the along-track direction, with the 
GFS on the faster end, and ECMWF on the slower end. The NHC track 
forecast continues to favor a blend of the simple and corrected 
consensus aids, and is very close to the previous forecast track 
through 72 h, and is just a touch east of the prior track 
thereafter. On this track, Lee is likely to pass near, but west of, 
Bermuda late Thursday and Friday and then be situated offshore of 
the mid-Atlantic states and New England late Friday and Saturday.

With the pending completion of Lee's ERC, expected over the next 
6-12 hours, the NHC intensity forecast continues to show some modest 
re-intensification. This seems reasonable given that sea surface 
temperatures (SSTs) observed by a saildrone in Lee's south outer 
eyewall are still around 29 C. After the next day or so, however, 
coupled atmospheric-ocean models suggest the large wind field of Lee 
will begin to upwell cooler SSTs, and Lee is still forecast to move 
over a cool SST wake left behind by Hurricanes Idalia and Franklin 
later this week. In addition, the approaching mid-latitude trough 
should also result in an increase in shear, and dry air entrainment, 
which should result in more steady weakening later this week and 
over the weekend. This trough interaction will also ultimately lead 
to Lee transitioning to an extratropical cyclone by the end of the 
forecast period as it crosses the north wall of the Gulf Stream. The 
NHC intensity forecast is a bit lower than the prior cycle after 72 
h but remains close to the consensus intensity aids.

Although Lee is expected to weaken later in the week, it is still 
expected to significantly increase in size and hazards will extend 
well away from the storm center by the end of the forecast period.


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. Lee could bring strong winds, rainfall, and high surf impacts to
Bermuda later this week. Interests there should continue to monitor
updates to the forecast of Lee during the next several days.

3. It remains too soon to know what level of additional impacts Lee 
might have along the Northeast U.S. coast and Atlantic Canada late 
this week and this weekend.  However, because wind and rainfall 
hazards will likely 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.


INIT  12/0300Z 23.9N  64.8W  100 KT 115 MPH
12H  12/1200Z 24.4N  65.6W  105 KT 120 MPH
24H  13/0000Z 25.0N  66.5W  105 KT 120 MPH
36H  13/1200Z 26.1N  67.2W  100 KT 115 MPH
48H  14/0000Z 27.5N  67.6W   95 KT 110 MPH
60H  14/1200Z 29.4N  67.9W   90 KT 105 MPH
72H  15/0000Z 31.6N  67.8W   80 KT  90 MPH
96H  16/0000Z 37.6N  66.4W   70 KT  80 MPH
120H  17/0000Z 43.0N  66.0W   60 KT  70 MPH...POST-TROP/EXTRATROP

Forecaster Papin