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Hurricane Teddy Discussion Number  42
NWS National Hurricane Center Miami FL       AL202020
500 PM AST Tue Sep 22 2020

Teddy is a very impressive cyclone on satellite images this 
afternoon, even from full-disk images.  The hurricane's circulation 
is over 1000 miles wide, with an enormous distinct comma shape and 
frontal features especially in the eastern semicircle.  As far as 
what to call the system convection has actually deepened near the 
center during the past several hours, and an AMSR pass around 1700 
UTC showed that the system still had a low-level eye feature.  For 
that reason and for simplicity's sake, the system will remain a 
hurricane on this advisory, although it is obviously a hybrid low 
with many characteristics of a non-tropical cyclone.  The initial 
wind speed is lowered to 80 kt, assuming the filling trend reported 
by the last NOAA Hurricane Hunter mission continued.  The wind radii 
are expanded based on ASCAT data, with tropical-storm-force winds 
over eastern Nova Scotia already.
 
The hurricane is forecast to transition into a post-tropical cyclone 
later tonight or early tomorrow due to the cooler waters north of 
the Gulf Stream likely weakening any central convection.  Teddy 
should decay below hurricane-strength before reaching Nova Scotia 
and steadily weaken as it moves over the even colder waters in the 
Gulf of St. Lawrence.  The new intensity forecast is a little lower 
than the previous one and is closest to the GFS model.

Teddy is moving northward now and should turn north-northeastward 
tomorrow ahead of the next trough in the mid-latitudes.  This will 
take Post-Tropical Teddy over Nova Scotia and near Newfoundland 
during the next couple of days, with the cyclone likely being 
absorbed into a larger extratropical cyclone west of Greenland in 
2-3 days.  There are no significant changes to report, though there 
has been a slight westward shift of the track near Newfoundland.
 
The hazards from Teddy are extending at quite a distance from the 
center of this hurricane.  In addition to the 500-mile wind 
radii in the northeastern quadrant, Canadian buoy 44150 has 
recently reported 42 ft (13 m) significant wave heights, with the 
buoy still about 90 n mi from the center.
 
Key Messages:
 
1. Teddy is expected to transition to a powerful post-tropical
cyclone as it moves near or over portions of Atlantic Canada
late today through Thursday. The most significant hazard expected
from Teddy is large destructive waves forecast along the southern
coast of Nova Scotia through Wednesday.
 
2. Very 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 are expected to cause
life-threatening surf and rip current conditions.
 
3. Tropical Storm Watches and Warnings are in effect for portions
of Nova Scotia, Newfoundland, Prince Edward Island and the Magdalen 
Islands, and heavy rainfall across Atlantic Canada is expected 
through Thursday.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  22/2100Z 41.1N  64.2W   80 KT  90 MPH
 12H  23/0600Z 43.1N  63.5W   65 KT  75 MPH...POST-TROPICAL
 24H  23/1800Z 47.0N  60.7W   55 KT  65 MPH...POST-TROP/EXTRATROP
 36H  24/0600Z 51.5N  56.5W   45 KT  50 MPH...POST-TROP/EXTRATROP
 48H  24/1800Z 56.5N  53.5W   45 KT  50 MPH...POST-TROP/EXTRATROP
 60H  25/0600Z...DISSIPATED
 
$$
Forecaster Blake
 
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