Official Discussion issued by the National Hurricane Center

Teddy (AL202020) DATA RELEASED: 9/20/2020 3:00:00 AM UTC

Copy of official data

Hurricane Teddy Discussion Number  31
NWS National Hurricane Center Miami FL       AL202020
1100 PM AST Sat Sep 19 2020

Some convective cells have been developing within Teddy's large 
outer eye, and it is possible that this convection is forming an 
inner eyewall.  In any event, observations from an Air Force 
Hurricane Hunter aircraft indicate that the maximum winds have 
decreased slightly, to near 100 kt.  The hurricane is expected to 
remain in a low shear environment until tomorrow evening, and to 
more or less maintain its intensity for 12-24 hours.  Thereafter, 
increasing shear associated with an upper-level trough to the west 
should cause weakening.  Although the shear is predicted by the 
global models to become fairly strong after 48 hours, the system 
has a a very large and intense circulation so only slow weakening 
is expected.  By 72 hours, Teddy should merge with a frontal zone to 
the east of New England and become a strong extratropical cyclone.  
The official intensity forecast is close to the model consensus.

The system's wind field will likely become even larger as the wind 
field of Teddy interacts within a high pressure system behind a cold 
front during the next few days. This could prolong the period of 
strong winds over Bermuda into Monday night.

Teddy continues on a general northwestward track or about 315/11 kt. 
The hurricane should move on the western side of a subtropical high 
pressure area for the next day or so, and then begin to accelerate 
northward ahead of a strong mid-tropospheric trough that develops 
into a cutoff low off the northeast U.S. coast in a couple of days.  
The interaction of Teddy with this low will likely result in a 
slight leftward bend of the track  around days 2-3.  In 4-5 days, 
post-tropical Teddy is likely to turn north-northeastward to 
northeastward in the flow on the east side of a broad 500 mb trough. 
The official track forecast is a blend of the simple and corrected 
dynamical model consensus predictions.

The extent of 12-foot or higher seas associated with Teddy 
continues to increase.  See the Key Message below regarding swells 
caused by the hurricane.

Key Messages:

1. While the center of Teddy is forecast to move east of Bermuda
late Sunday or Monday, tropical storm conditions are likely on the
island beginning Sunday evening.

2. Teddy is expected to transition to a powerful post-tropical
cyclone as it moves near or over portions of Atlantic Canada early
next week, where there is an increasing risk of direct impacts from
wind, rain, and storm surge. Residents there should closely monitor
the progress of Teddy and updates to the forecast.

3. Large swells produced by Teddy are expected to affect portions
of the Leeward Islands, the Greater Antilles, the Bahamas, Bermuda,
the east coast of the United States, and Atlantic Canada during the
next few days. These swells could cause life-threatening surf and
rip current conditions.


INIT  20/0300Z 27.3N  61.2W  100 KT 115 MPH
12H  20/1200Z 28.3N  62.3W  100 KT 115 MPH
24H  21/0000Z 29.6N  63.0W   95 KT 110 MPH
36H  21/1200Z 31.6N  62.4W   90 KT 105 MPH
48H  22/0000Z 35.7N  61.8W   90 KT 105 MPH
60H  22/1200Z 39.7N  62.5W   80 KT  90 MPH
72H  23/0000Z 42.5N  62.8W   70 KT  80 MPH...POST-TROP/EXTRATROP
96H  24/0000Z 49.5N  56.0W   50 KT  60 MPH...POST-TROP/EXTRATROP
120H  25/0000Z 57.0N  42.5W   40 KT  45 MPH...POST-TROP/EXTRATROP

Forecaster Pasch