[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT43 KNHC 151444
TCDAT3

Hurricane Lee Discussion Number  41
NWS National Hurricane Center Miami FL       AL132023
1100 AM AST Fri Sep 15 2023

Lee remains a very large hurricane over the western Atlantic.  The
strongest winds extend out to roughly 70 miles from the center,
hurricane-force winds around 100 miles and tropical-storm-force
winds more than 300 miles.  Data from both the NOAA and Air Force
Hurricane Hunters indicate that the core winds have decreased
slightly, and a blend of the latest flight-level and SFMR winds
support an intensity of 70 kt. Satellite images indicate that the
hurricane is asymmetric with most of the convection on the north
side.

The hurricane has been wobbling around, but it has generally been
moving north-northeastward at 16 kt during the past 12-18 hours on
the western side of a subtropical ridge.  A northward to
north-northeastward motion at about the same forward speed is
expected until Lee makes landfall in Atlantic Canada in 24 to 36
hours.  After landfall, Lee is forecast to accelerate to the
northeast when it moves in the flow on the east side of an
approaching trough.  The models are tightly clustered, and no
significant changes were made to the previous NHC track forecast.

Southerly vertical wind shear and dry air are eroding deep
convection on the hurricane's south side.  These environmental
conditions are expected to persist while Lee moves over sharply
cooler waters during the next day or so.  Therefore, steady
weakening is forecast and Lee will likely become extratropical
around the time it makes landfall.  The NHC intensity forecast is a
little lower than the previous one, and fairly close to the GFS
model prediction.  Lee is expected to remain a 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 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 could produce localized urban and small
stream flooding in eastern Maine 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 during the next few hours.


FORECAST POSITIONS AND MAX WINDS

INIT  15/1500Z 36.0N  66.9W   70 KT  80 MPH
 12H  16/0000Z 38.5N  66.4W   70 KT  80 MPH
 24H  16/1200Z 41.8N  66.2W   65 KT  75 MPH
 36H  17/0000Z 45.1N  65.7W   55 KT  65 MPH...POST-TROP/EXTRATROP
 48H  17/1200Z 47.8N  62.8W   45 KT  50 MPH...POST-TROP/EXTRATROP
 60H  18/0000Z 50.8N  57.8W   40 KT  45 MPH...POST-TROP/EXTRATROP
 72H  18/1200Z 53.4N  51.3W   35 KT  40 MPH...POST-TROP/EXTRATROP
 96H  19/1200Z...DISSIPATED

$$
Forecaster Cangialosi
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