[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT43 KNHC 150854
TCDAT3

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.


KEY MESSAGES:

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.


FORECAST POSITIONS AND MAX WINDS

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

This weather bulletin was brought to you by:
www.nashvilleweather.net