Hurricane Teddy Forecast Discussion


000
WTNT45 KNHC 201455
TCDAT5

Hurricane Teddy Discussion Number  33
NWS National Hurricane Center Miami FL       AL202020
1100 AM AST Sun Sep 20 2020

The satellite signature of Teddy has degraded from an eye pattern 
overnight into a central dense overcast this morning.  Air Force 
Reserve Hurricane Hunter aircraft data indicate that the hurricane 
has weakened, and the initial wind speed is set to 90 kt, perhaps 
generously.  The aircraft data does still show that Teddy remains a 
large hurricane, with hurricane-force winds extending outward in the 
northeastward quadrant to about 70 n mi.

While the forecast intensity does not change much over the next 
couple of days, the hurricane should undergo significant changes 
during that time.  Teddy should not lose any more strength by late 
today due to favorable positioning with an approaching trough, and 
the gale-force winds should greatly expand due to this trough 
interaction. In 2 or 3 days, after the system occludes and becomes 
post-tropical, the cyclone should weaken because of a loss of  
extratropical forcing while over the cooler water south of Nova 
Scotia.  Eventually Teddy will probably get absorbed by a larger 
extratropical low around day 5.  Model guidance is fairly tightly 
packed around the official wind forecast, which leans on the global 
models given the substantial extratropical contributions, plus or 
minus 5 kt throughout the forecast period.

The hurricane has resumed a northwestward motion or 320/8 kt. Teddy 
is likely to turn northward today and north-northeastward tomorrow 
due to the aforementioned 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.  Although the 
forecast evolution is complex, model guidance is in remarkably good 
agreement, and no substantial changes were made to the previous 
forecast. Regardless of the details, every model has a rather large 
and strong post-tropical cyclone south of Nova Scotia in about 3 
days.


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 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.


FORECAST POSITIONS AND MAX WINDS

INIT  20/1500Z 28.3N  62.8W   90 KT 105 MPH
 12H  21/0000Z 29.2N  63.4W   85 KT 100 MPH
 24H  21/1200Z 31.0N  62.9W   85 KT 100 MPH
 36H  22/0000Z 34.8N  62.1W   85 KT 100 MPH
 48H  22/1200Z 38.8N  63.0W   85 KT 100 MPH
 60H  23/0000Z 41.7N  63.4W   75 KT  85 MPH...POST-TROP/EXTRATROP
 72H  23/1200Z 44.5N  62.0W   60 KT  70 MPH...POST-TROP/EXTRATROP
 96H  24/1200Z 53.0N  53.0W   40 KT  45 MPH...POST-TROP/EXTRATROP
120H  25/1200Z 60.5N  39.5W   35 KT  40 MPH...POST-TROP/EXTRATROP

$$
Forecaster Blake

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