Official Discussion issued by the National Hurricane Center

Lee (AL132023) DATA RELEASED: 9/15/2023 9:00:00 AM UTC

Copy of official data

Hurricane Lee Discussion Number  40
NWS National Hurricane Center Miami FL       AL132023
500 AM AST Fri Sep 15 2023

Lee appears to be in the very initial stages of extratropical 
transition.  The cloud pattern is becoming increasingly asymmetric, 
and scatterometer data from last evening showed a band of strong 
winds developing along a boundary to the northwest of the center.  
Lee's initial intensity remains 75 kt based on continuity from last 
evening's reconnaissance and scatterometer data, but NOAA and Air 
Force Reserve Hurricane Hunter aircraft should be in the storm in a 
couple of hours to again sample the wind field.

Lee has been wobbling a bit since yesterday afternoon, but the 
smoothed motion is northward (010 degrees) at a faster speed of 14 
kt.  Additional northward acceleration is expected during the next 
24-36 hours as Lee moves along the western periphery of a mid-level 
ridge, and approaches a trough currently over New England.  The 
track model guidance continues to be in very good agreement on 
bringing Lee's center very near the western end of Nova Scotia by 
Saturday afternoon, although the new NHC forecast is a little 
faster than the previous prediction.  In 2-3 days, Lee is forecast 
to turn north-northeastward and northeastward across Atlantic 
Canada as it moves between the aforementioned ridge and a mid-level 
trough moving across Quebec. 

Although southerly shear is forecast to increase markedly through 
the day, baroclinic influences during Lee's extratropical transition 
are likely to keep the intensity relatively steady for the next 24 
hours or so.  During that time, the NHC intensity forecast is near 
the top end of the guidance suite, closest to the GFS and ECMWF 
solutions, and there is some possibility that a band of strong winds 
could develop near the front on the western side of the circulation 
over the Gulf of Maine.  Extratropical transition is forecast to be 
complete by 36 hours (although it could be sooner), and Lee is 
likely to be weakening--but still near or just below hurricane 
force--as it is approaching Nova Scotia due to the continued shear 
and much colder ocean temperatures.  Lee is expected to continue 
weakening while it moves across Atlantic Canada, and global model 
fields indicate that it is likely to be absorbed by another 
developing area of low pressure near Newfoundland and Labrador just 
after 72 hours. 


1. Hurricane conditions are possible across portions of Down East 
Maine, southern New Brunswick, and western Nova Scotia on Saturday 
within the Hurricane Watch area.  Tropical storm conditions and 
coastal flooding are expected to begin in southern New England 
within the Tropical Storm Warning area this afternoon, and spread 
northward along the coast of New England and over portions of 
Atlantic Canada through Saturday.  These conditions are likely to 
lead to downed trees and potential power outages.

2. Heavy rainfall from Lee may produce localized urban and small
stream flooding across eastern New England and into portions of New
Brunswick and Nova Scotia from tonight into Saturday night.

3. Tropical storm conditions and high surf will continue to impact 
Bermuda through this morning.


INIT  15/0900Z 34.4N  67.5W   75 KT  85 MPH
12H  15/1800Z 36.8N  67.0W   75 KT  85 MPH
24H  16/0600Z 40.3N  66.7W   75 KT  85 MPH
36H  16/1800Z 43.4N  66.4W   60 KT  70 MPH...POST-TROP/EXTRATROP
48H  17/0600Z 46.3N  64.8W   50 KT  60 MPH...POST-TROP/INLAND
60H  17/1800Z 49.3N  61.1W   40 KT  45 MPH...POST-TROP/EXTRATROP
72H  18/0600Z 52.2N  55.0W   35 KT  40 MPH...POST-TROP/EXTRATROP
96H  19/0600Z...DISSIPATED

Forecaster Berg