848
WTNT45 KNHC 222054
TCDAT5

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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