[Tropical] Tropical Cyclone Discussion

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WTNT43 KNHC 080839
TCDAT3

Hurricane Lee Discussion Number  12
NWS National Hurricane Center Miami FL       AL132023
500 AM AST Fri Sep 08 2023

Lee remains an extremely powerful category 5 hurricane.  Satellite
images indicate that Lee has a symmetric inner core with a 10 n mi
circular and clear eye and no indications of concentric eyewalls
forming yet.  Although the hurricane is incredibly powerful, its
wind field is not particularly large with its tropical-storm-force
winds extending roughly 100 n mi from the center. The Air Force
Hurricane Hunters investigated Lee earlier this morning and found
that the pressure has fallen to about 926 mb, based on dropsonde
data.  In addition, the maximum 700-mb flight-level wind reported
was 153 kt and maximum surface SFMR wind was 158 kt, but this
estimate could be inflated.  Blending these measurements, the
initial wind speed is nudged upward to 145 kt.  Both the NOAA and
Air Force Hurricane Hunters will further investigate Lee in a couple
of hours.

Since Lee is expected to remain in favorable atmospheric conditions
while moving over even warmer waters during the next couple of days,
it seems likely that the hurricane will at least maintain its
intensity or become a little stronger during that time.  The
dominant factor for Lee's short term intensity will be internal
dynamics, like eyewall replacement cycles.  These conditions will
often cause fluctuations in the hurricane's strength, which are
challenging to forecast.  There likely will be some weakening beyond
a few days when Lee moves over somewhat cooler waters and into an
environment of slightly higher shear.  Regardless of the details,
Lee is expected to remain a powerful hurricane during the next
several days.

The major hurricane has been on a steady west-northwest path during
the past couple of days as it has been steered by the flow on the
south side of a subtropical ridge over the central Atlantic.  A
continued west-northwest motion is expected, but at a progressively
slower pace during the forecast period as the ridge to the north of
the system weakens.  The models are in fairly good agreement, and
little change was made to the previous NHC track forecast.

Lee is expected to increase in size and become more symmetric over
the weekend and early next week as the hurricane slows down. Recent
wave altimeter data showed peak significant wave heights between 45
and 50 feet near the center.  Dangerously high seas are expected to
continue near the core of the hurricane, and large swells will
spread well away from the system through the forecast period.


KEY MESSAGES:

1. Lee is a dangerous category 5 hurricane, and further
strengthening is possible.  Lee's core is expected to move well
north of the northern Leeward Islands, the Virgin Islands, and
Puerto Rico this weekend and early next week.

2. Dangerous surf and life-threatening rip currents are likely in
the northern Leeward Islands beginning later today.  These
conditions will spread westward and northward, affecting Puerto
Rico, Hispaniola, the Turks and Caicos, the Bahamas, and Bermuda
through the weekend.

3. It is way too soon to know what level of impacts, if any, Lee
might have along the U.S. East Coast, Atlantic Canada, or Bermuda
late next week, particularly since the hurricane is expected to
slow down considerably over the southwestern Atlantic.  Regardless,
dangerous surf and rip currents are expected along most of the U.S.
East Coast beginning Sunday.  Continue to monitor updates to Lee's
forecast during the next several days.


FORECAST POSITIONS AND MAX WINDS

INIT  08/0900Z 17.8N  53.5W  145 KT 165 MPH
 12H  08/1800Z 18.6N  55.1W  155 KT 180 MPH
 24H  09/0600Z 19.6N  57.1W  150 KT 175 MPH
 36H  09/1800Z 20.5N  58.8W  145 KT 165 MPH
 48H  10/0600Z 21.2N  60.2W  145 KT 165 MPH
 60H  10/1800Z 21.9N  61.5W  140 KT 160 MPH
 72H  11/0600Z 22.4N  62.7W  135 KT 155 MPH
 96H  12/0600Z 23.3N  65.1W  130 KT 150 MPH
120H  13/0600Z 24.4N  67.1W  120 KT 140 MPH

$$
Forecaster Cangialosi
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