[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT45 KNHC 171502 CCA
TCDAT5

Hurricane Teddy Discussion Number  21...Corrected
NWS National Hurricane Center Miami FL       AL202020
1100 AM AST Thu Sep 17 2020

Corrected to add Key Messages

Since the previous advisory, Teddy's satellite appearance has
steadily improved. There is now a ragged warming eye surrounded by a
ring of convection with cloud tops colder than -60 degrees C. Very
recently the objective satellite intensity estimates from UW-CIMSS
have been rapidly increasing. And although a blend of the 1130 and
1200 UTC Dvorak intensity estimates from SAB and TAFB, respectively,
averaged out to an intensity of about 95 kt, the improved satellite
presentation since that time suggests that the hurricane should have
winds of at least 105 kt, which is the initial intensity for this
advisory, which could even be a little conservative based on the
latest UW-CIMMS ADT and SATCON values of 120 and 111 kt,
respectively. There will be NOAA and Air Force Reserve Hurricane
Hunter aircraft inside Teddy later today, which should provide much
more detail on the structure and intensity of Teddy.

The only negative factor for intensification during the next 24 h is
about 10 to 15 kt of vertical wind shear. However, Teddy has been
able to begin the latest burst of intensification despite that
shear. Therefore additional strengthening is anticipated through
this evening, and Teddy is forecast to become a category 4 hurricane
by tonight. The overall environment does not change significantly
for the next couple of days, so other than some fluctuations
intensity such as due to potential eyewall replacement cycles, no
change in strength is indicated during that time. As Teddy continues
moving northwest over the weekend, it is likely to begin to
encounter some of the cooler waters upwelled by Hurricane Paulette
last week. This could cause the cyclone to slowly weaken. By late
this weekend, increasing vertical wind shear should also contribute
to weakening. Due to the fast increase in intensity this morning,
the latest NHC intensity is a bit higher than all of the guidance
for the first 48 h, but the overall intensity trends are closely
mirrored by the various multi-model consensus. Beyond 48 h, the NHC
forecast closely follows the LGEM guidance.

Teddy continues to move northwestward at 10 kt. The track
forecast and reasoning both remain straightforward and unchanged for
the next 72 h. The latest NHC model guidance is in excellent
agreement that a deep-layer ridge situated over the central Atlantic
will force Teddy on a northwestward track toward the western
Atlantic.  There is a little less divergence among the models on
days 4 and 5 then on previous cycles, and these differences are
due to timing differences in where and how fast the hurricane
begins to recurve ahead of an approaching mid-latitude trough and
frontal system moving off the coast of the eastern United States in
about 3 days.  The new NHC track forecast is little changed from
the previous one, and is in the middle of the tightly clustered
track guidance. On the forecast track, Teddy will make its closest
approach to Bermuda on Monday.

Key Messages:

1. Teddy is expected to approach Bermuda as a hurricane this
weekend and make its closest approach to the island late Sunday or
Monday. While the exact details of Teddy's track and intensity near
the island are not yet known, the risk of strong winds, storm surge,
and heavy rainfall on Bermuda is increasing.

2. Swells produced by Teddy are expected to affect portions of the
Leeward Islands, the Greater Antilles, the Bahamas, Bermuda, and the
southeastern United States late this week and into the weekend.
These swells could cause life-threatening surf and rip current
conditions.

FORECAST POSITIONS AND MAX WINDS

INIT  17/1500Z 19.3N  53.0W  105 KT 120 MPH
 12H  18/0000Z 20.4N  54.0W  115 KT 130 MPH
 24H  18/1200Z 21.8N  55.5W  115 KT 130 MPH
 36H  19/0000Z 23.5N  57.0W  115 KT 130 MPH
 48H  19/1200Z 25.5N  58.9W  110 KT 125 MPH
 60H  20/0000Z 27.3N  60.9W  105 KT 120 MPH
 72H  20/1200Z 28.7N  62.7W  100 KT 115 MPH
 96H  21/1200Z 32.4N  63.4W   95 KT 110 MPH
120H  22/1200Z 38.9N  62.3W   85 KT 100 MPH

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