[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT43 KNHC 142052
TCDAT3

Hurricane Lee Discussion Number  38
NWS National Hurricane Center Miami FL       AL132023
500 PM AST Thu Sep 14 2023

There has been little overall change to the satellite presentation
of Lee since the previous advisory.  Deep convection continues to
develop near the center, but it is primarily confined to the
northern portion of the circulation.  Southwesterly shear and dry
air entrainment is disrupting the convective banding over the
southern portion of the storm.  The initial intensity was lowered
to 75 kt on the 1800 UTC intermediate advisory, and was based
on data from the Air Force Reserve reconnaissance aircraft that was
in the storm through midday.  The initial wind speed remains at
that value for this advisory.  The next reconnaissance mission is
scheduled to investigate Lee this evening. The early aircraft data
along with a couple of fortuitous ASCAT overpasses showed that the
wind field of Lee has continued to expand.  The 50-kt wind radii
extend outward up to 170 n mi over the eastern semicircle of the
storm.  NOAA buoy 41048 located about 75 miles (120 km) west of the
center of Lee has recently reported a peak one-minute sustained wind
of 58 kt and a gust to 76 kt and wave heights of around 30 ft.
Bermuda, located more than 220 miles east-northeast of the center
has also reported sustained tropical-storm force winds today.

Lee is moving northward at about 13 kt, which is slightly faster
than before.  Lee should continue to pick up some forward speed as
it moves northward around the western side of a mid-level ridge
over the central Atlantic during the next 12-24 hours.  After that
time a slight bend to the north-northwest is likely late Friday or
early Saturday, and this motion should bring the center of Lee near
or over southwestern Nova Scotia late Saturday.  After that time,
Lee is forecast to turn northeastward over Atlantic Canada.  The
track guidance is still in good agreement, and no significant
changes to the previous official forecast were required.

Increasing southwesterly vertical wind shear and dry air entrainment
could cause some additional weakening, but baroclinic forcing
during the early stages of Lee's extratropical transition may help
to maintain the cyclone's intensity through Friday.  By Friday
night Lee will be moving over significantly cooler sea surface
temperatures, and gradual weakening is expected after that time.
Lee is forecast to complete its transition into an extratropical
cyclone when it nears Atlantic Canada.  Regardless of Lee's
designation when it approaches New England and Atlantic Canada, it
will remain a very large and dangerous cyclone through landfall.


KEY MESSAGES:

1. Tropical storm conditions, heavy rainfall, and high surf will
continue to impact Bermuda through Friday morning, and a Tropical
Storm Warning is in effect for the island.

2. Hurricane conditions and coastal flooding are possible in
portions of eastern Maine, southern New Brunswick, and western Nova
Scotia on Saturday, and a Hurricane Watch is in effect for that
area.  Tropical storm conditions and coastal flooding are expected
to begin in southern New England on Friday afternoon, and spread
northward along the coast of New England through Saturday where
Tropical Storm warnings are in effect.

3. 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 Friday night into Saturday night.


FORECAST POSITIONS AND MAX WINDS

INIT  14/2100Z 31.7N  68.3W   75 KT  85 MPH
 12H  15/0600Z 33.8N  67.9W   75 KT  85 MPH
 24H  15/1800Z 37.0N  66.9W   75 KT  85 MPH
 36H  16/0600Z 40.3N  66.6W   70 KT  80 MPH
 48H  16/1800Z 43.3N  66.4W   60 KT  70 MPH...POST-TROP/EXTRATROP
 60H  17/0600Z 46.0N  65.0W   45 KT  50 MPH...POST-TROP/EXTRATROP
 72H  17/1800Z 48.6N  61.4W   40 KT  45 MPH...POST-TROP/EXTRATROP
 96H  18/1800Z 53.7N  48.0W   35 KT  40 MPH...POST-TROP/EXTRATROP
120H  19/1800Z...DISSIPATED

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