[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT43 KNHC 131438
TCDAT3

Hurricane Lee Discussion Number  33
NWS National Hurricane Center Miami FL       AL132023
1100 AM AST Wed Sep 13 2023

Lee continues to exhibit concentric eyewalls, but there are some dry
slots between those features.  An SSMIS microwave image around 10Z
showed that both eyewalls were open, however, recent infrared
satellite images indicate that the inner eyewall appears to be
becoming better organized during the past few hours.  The initial
wind speed is held at 100 kt, but this is near the high end of the
latest satellite intensity estimates.  The Air Force Hurricane
Hunters are scheduled to investigate Lee this afternoon, and the
data they collect should provide a better assessment of the
hurricane's intensity and structure.

Satellite images suggest that Lee seems to be beginning its
northward turn on the western side of a subtropical ridge situated
over the central Atlantic.  The latest initial motion estimate is
345/6 kt.  Lee should gradually increase in forward speed while
moving northward on the west side of the ridge during the next
couple of days, taking the core of the system to the west of Bermuda
Thursday and Thursday night.  The combination of a shortwave trough
and a building ridge extending into Atlantic Canada could cause Lee
to turn slightly to the left Friday night and Saturday, which will
likely bring Lee close to southeastern New England before it reaches
Maine and Atlantic Canada later in the weekend.  Confidence is
increasing in the forecast track, and the model spread is mostly
along-track, associated with the system's forward speed/timing.
Overall, little change was made to the previous NHC track forecast,
and it remains very near the various consensus models.

Lee is expected to gradually weaken as it moves into an environment
of increasing vertical wind shear, slightly drier air, and over
progressively cooler waters during the next few days.  However, the
large size of the system suggests that the weakening process should
be slow.  In addition, Lee is expected to grow in size as it gains
latitude during the next few days.  The NHC intensity forecast is
largely the same as the previous one and fairly close to the HCCA
and IVCN models.  Regardless of the details, there is high
confidence that Lee will be a large hurricane near the coast of New
England Friday night and Saturday.

It should again be noted that the 34- and 50-kt wind speed
probabilities beyond 36 hours in the text and graphical products are
likely underestimating the risk of those winds occurring.  This is
because the forecast wind field of Lee is considerably larger than
average compared to the wind field used to derive the wind speed
probability product.


KEY MESSAGES:

1. Dangerous surf and life-threatening rip currents will affect
portions of the northern Leeward Islands, the Virgin Islands, Puerto
Rico, Hispaniola, the Turks and Caicos Islands, the Bahamas,
Bermuda, the U.S East Coast, and Atlantic Canada into the weekend.

2. Tropical storm conditions, heavy rainfall, and high surf are
expected to impact Bermuda beginning early Thursday, and a Tropical
Storm Warning is in effect for the island.

3. There is an increasing risk of wind, coastal flooding, and rain
impacts from Lee in portions of New England and Atlantic Canada
beginning on Friday and continuing through the weekend.  Watches
will likely required for portions of these areas later today or
tonight. Due to Lee's large size, hazards will extend well away
from the center, and there will be little to no significance on
exactly where the center reaches the coast.


FORECAST POSITIONS AND MAX WINDS

INIT  13/1500Z 26.4N  67.2W  100 KT 115 MPH
 12H  14/0000Z 27.6N  67.7W   95 KT 110 MPH
 24H  14/1200Z 29.6N  68.2W   90 KT 105 MPH
 36H  15/0000Z 31.8N  68.2W   85 KT 100 MPH
 48H  15/1200Z 34.6N  67.6W   80 KT  90 MPH
 60H  16/0000Z 37.9N  67.1W   75 KT  85 MPH
 72H  16/1200Z 41.1N  67.2W   70 KT  80 MPH
 96H  17/1200Z 46.1N  66.6W   50 KT  60 MPH...POST-TROP/INLAND
120H  18/1200Z 52.1N  56.4W   35 KT  40 MPH...POST-TROP/INLAND

$$
Forecaster Cangialosi
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