ZCZC MIATCDAT3 ALL
TTAA00 KNHC DDHHMM
 
Hurricane Lee Discussion Number  42
NWS National Hurricane Center Miami FL       AL132023
500 PM AST Fri Sep 15 2023
 
Lee remains a very large hurricane over the western Atlantic. ASCAT 
data from this morning showed the wind field expanding, with the 
hurricane-force winds around 100 miles and tropical-storm-force 
winds more than 300 miles outward from the center. New data from 
the Air Force Hurricane Hunters indicate that the core winds remain 
steady with an intensity of 70 kt. Lee continues to be an 
asymmetric hurricane with most of the convection on the north side 
of the system.
 
The hurricane continues to wobble around, but it is generally moving
northward at 17 kt during the last 12-18 hours on the western side
of a subtropical ridge. Lee will continue to move northward around
the same speed until it makes landfall in Atlantic Canada in
approximately 24 to 30 hours. Once Lee makes landfall, it is still
expected to accelerate to the northeast as it moves in the flow on
the east side of an approaching trough. The models remain in quite
good agreement, and the NHC track forecast was only slightly
shifted to the left to follow the new guidance through landfall.
Otherwise, no significant changes were made.
 
Southerly vertical wind shear and dry air continue eroding deep 
convection on Lee's south side. These environmental conditions will 
persist while Lee moves over sharply cooler waters when it crosses 
the north wall of the Gulf Stream during the next day or so. 
Therefore, gradual weakening is forecast and Lee will likely become 
a strong extratropical cyclone around the time it makes landfall. 
The NHC intensity forecast is slightly lower than the previous one 
and continues to be fairly close to the GFS model. However, Lee is 
expected to remain a very large and dangerous system over the next 
couple of days.
 
KEY MESSAGES:
 
1. Hurricane conditions are possible across portions southern New
Brunswick, and much of 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 evening, 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 could produce localized urban and small
stream flooding in portions of eastern Maine, New Brunswick and
western Nova Scotia Saturday.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  15/2100Z 37.9N  66.7W   70 KT  80 MPH
 12H  16/0600Z 40.5N  66.5W   70 KT  80 MPH
 24H  16/1800Z 43.5N  66.3W   60 KT  70 MPH
 36H  17/0600Z 46.2N  64.7W   45 KT  50 MPH...POST-TROP/EXTRATROP
 48H  17/1800Z 49.0N  60.9W   40 KT  45 MPH...POST-TROP/EXTRATROP
 60H  18/0600Z 51.7N  54.4W   40 KT  45 MPH...POST-TROP/EXTRATROP
 72H  18/1800Z 53.9N  47.1W   35 KT  40 MPH...POST-TROP/EXTRATROP
 96H  19/1800Z...DISSIPATED
 
$$
Forecaster A Reinhart/Cangialosi
 
NNNN