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Hurricane Teddy Discussion Number  34
NWS National Hurricane Center Miami FL       AL202020
500 PM AST Sun Sep 20 2020

Satellite images show that Teddy is continuing to maintain a 
central core, albeit eroded on the western side due to shear and 
dry air. However, the latest microwave data show a more distinct 
eye than conventional data would indicate, along with an open 
eyewall.  The initial intensity is held at 90 kt, pending Air 
Force Reserve Hurricane Hunter aircraft data this evening.

The hurricane has turned north-northwestward and is likely to 
turn northward tonight and north-northeastward tomorrow due to an 
approaching large mid-latitude trough. By early Tuesday, the 
cyclone should turn back to the north-northwest as it rotates 
around the same trough, then turn northeastward early Wednesday 
ahead of yet another trough moving into from eastern Canada.  
Track model guidance remains in very good agreement, and only a 
slight westward adjustment was made to the forecast. 

The global models are in excellent agreement on Teddy transitioning 
into a large non-tropical low between Bermuda and Nova Scotia in 
about 2 days.  In many respects, the upcoming trough interaction 
reminds me of an extratropical transition like Sandy 2012, 
thankfully happening at a good distance from land, with the 
GFS/ECMWF models showing pressures into the 940s tomorrow, a slight 
increase in maximum winds, and a large increase in the size of the 
tropical-storm-force winds.  Beyond Tuesday, the hurricane should 
become post-tropical near or south of Nova Scotia and be absorbed by 
a larger extratropical low after day 4 to the northeast of 
Newfoundland.  Little change was made to the official forecast, 
other than show a small increase tomorrow as the peak extratropical 
forcing deepens the cyclone.  It is still worth noting every model 
has a rather large and strong post-tropical cyclone near Nova Scotia 
in 2-3 days, with hazards that will extend a very long way from the 
center.
 
Extremely dangerous surf conditions with 20-ft waves have been 
reported on the south shore of Bermuda, and officials are 
encouraging residents to avoid going into or near the water.

Key Messages:
 
1. The center of Teddy is forecast to move east of Bermuda on
Monday. Tropical storm conditions are likely on the island beginning
this evening and could continue into Monday evening.
 
2. Teddy is expected to transition to a powerful post-tropical
cyclone as it moves near or over portions of Atlantic Canada 
late Tuesday through Thursday, where there is an increasing risk of 
direct impacts from wind, rain, and storm surge. A Tropical Storm 
Watch has been issued for portions of Nova Scotia, and heavy rain is 
also expected across sections of Atlantic Canada.
 
3. Large swells produced by Teddy are expected to affect portions of
Bermuda, the Leeward Islands, the Greater Antilles, the Bahamas, 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.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  20/2100Z 29.0N  63.4W   90 KT 105 MPH
 12H  21/0600Z 30.1N  63.5W   85 KT 100 MPH
 24H  21/1800Z 32.8N  62.6W   90 KT 105 MPH
 36H  22/0600Z 36.9N  63.0W   90 KT 105 MPH
 48H  22/1800Z 40.0N  64.0W   85 KT 100 MPH
 60H  23/0600Z 42.7N  63.5W   75 KT  85 MPH...POST-TROP/INLAND
 72H  23/1800Z 46.0N  61.3W   60 KT  70 MPH...POST-TROP/EXTRATROP
 96H  24/1800Z 54.5N  50.5W   40 KT  45 MPH...POST-TROP/EXTRATROP
120H  25/1800Z...DISSIPATED
 
$$
Forecaster Blake
 
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