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Hurricane Teddy Discussion Number  22
NWS National Hurricane Center Miami FL       AL202020
500 PM AST Thu Sep 17 2020
 
Teddy has intensified quickly today, with the cyclone now having a
more symmetrical appearance while the eye has become mostly clear.
The deep convection with cloud tops ranging from -60 to -75 degrees
have surrounded the eye for much of the day, and there are
well-defined outflow channels to the south and east of the
hurricane. Both NOAA and US Air Force Reserve Hurricane Hunter
aircraft have spent time investigating Teddy today as it has been
intensifying and have been able to provide very useful data in
determining both the size and strength of the hurricane. The peak
SFMR winds measured by the aircraft this afternoon were 113 kt, 
while the peak 700 mb flight-level winds were 130 kt. Based on a 
reduction to 117 kt from 700 mb, and assuming some slight 
undersampling may be occurring, the initial intensity has been 
raised to 120 kt.
 
The hurricane is expected to remain in an environment of
low-moderate shear while over warm waters for the 48 h or so. And
since the period of rapid strengthening of Teddy appears to be
ongoing, the hurricane is expected to strengthen some more into
tonight. Once this round of intensification completes, there will
likely be some fluctuations in strength due to eyewall replacement
cycles and other short term changes in structure. After 48 h, the
path of Teddy should take it over some cooler waters caused by
upwelling from Hurricane Paulette last week. This should cause the
cyclone to slowly weaken. By 96 h, vertical wind shear is forecast
to increase ahead of an approaching mid-latitude trough and
associated frontal boundary. This should hasten the weakening trend
of Teddy. By 120 h, the hurricane is expected to have crossed the 26
degree SST isotherm, and will begin to interact with the
aforementioned mid-latitude system causing it to begin an
extratropical transition that may or may not be completed by the end
of the forecast period. The latest NHC intensity forecast has been
increased due to the higher initial intensity, and the forecast
trends fit well with the various intensity consensus and SHIPS
guidance.
 
Teddy continues its northwestward motion, now at 11 kt. The track
guidance is in very good agreement on a continuation of this motion
for the next 72 h as the cyclone is steered by a mid-level ridge
over the central Atlantic. The model guidance has come into better
agreement on the evolution of the large scale features later on in
the forecast period as the hurricane is expected to recurve ahead of
the approaching mid-latitude trough moving off the coast of the
eastern United States in a few days. The new NHC track forecast is
little changed from the previous one, and is in the middle of the
track guidance. On the forecast track, Teddy will make its closest
approach to Bermuda Sunday night into 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. Large 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  17/2100Z 20.1N  54.1W  120 KT 140 MPH
 12H  18/0600Z 21.2N  55.2W  130 KT 150 MPH
 24H  18/1800Z 22.8N  56.6W  125 KT 145 MPH
 36H  19/0600Z 24.5N  58.1W  125 KT 145 MPH
 48H  19/1800Z 26.3N  59.9W  120 KT 140 MPH
 60H  20/0600Z 28.0N  62.1W  110 KT 125 MPH
 72H  20/1800Z 29.5N  63.3W  105 KT 120 MPH
 96H  21/1800Z 33.9N  63.0W   95 KT 110 MPH
120H  22/1800Z 41.3N  62.0W   80 KT  90 MPH
 
$$
Forecaster Latto
 
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