935
WTNT45 KNHC 211454
TCDAT5

Hurricane Teddy Discussion Number 37
NWS National Hurricane Center Miami FL AL202020
1100 AM AST Mon Sep 21 2020

Teddy has weakened some since yesterday. While the maximum 700-mb
winds from the latest Air Force Reserve Hurricane Hunter aircraft
mission were 93 kt, the peak SFMR values were only 68 kt. A blend of
these data with some undersampling due to the large size of Teddy
gives an initial wind speed of 80 kt.

The hurricane is beginning to accelerate to the north-northeast as
the long-awaited mid-latitude trough begins to pick up the cyclone.
All of the guidance is in very good agreement that Teddy will
benefit from this interaction, growing in both size and maximum
winds due to this trough and warmer waters in the Gulf Stream.
Thus, the hurricane should intensify overnight, and the new
intensity forecast is close to the latest GFS model. Afterward,
the baroclinic energy source is exhausted, and Teddy should move
north of the Gulf Stream by Wednesday, helping to complete its
post-tropical transition. The cyclone should weaken while it
accelerates to the north-northeast across eastern Nova Scotia, the
Gulf of St. Lawrence, and Newfoundland before dissipating in 3-4
days. No significant changes were made to the track forecast.

Teddy's size will likely increase substantially during the next
couple of days as it moves northward and interacts with the
aforementioned frontal system. Gale force winds are likely along
portions of the near shore waters of the northeast U.S. Please see
products from your local office for more information about marine
hazards.

Key Messages:

1. The center of Teddy is forecast to move east of Bermuda today.
Wind gusts of tropical-storm-force have been reported on the
island, and tropical storm conditions could continue today.

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 is in effect for portions of Nova Scotia, and heavy
rainfall across Atlantic Canada is expected with Teddy between
Tuesday and Thursday after it becomes a strong post-tropical
cyclone.

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 will likely cause life-threatening surf and
rip current conditions.


FORECAST POSITIONS AND MAX WINDS

INIT 21/1500Z 31.1N 62.7W 80 KT 90 MPH
12H 22/0000Z 34.4N 62.4W 85 KT 100 MPH
24H 22/1200Z 38.2N 63.7W 90 KT 105 MPH
36H 23/0000Z 40.7N 64.3W 80 KT 90 MPH
48H 23/1200Z 43.7N 63.0W 65 KT 75 MPH...POST-TROP/EXTRATROP
60H 24/0000Z 47.5N 60.5W 55 KT 65 MPH...POST-TROP/EXTRATROP
72H 24/1200Z 51.5N 55.5W 45 KT 50 MPH...POST-TROP/INLAND
96H 25/1200Z...DISSIPATED

$$
Forecaster Blake
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