Hurricane Teddy Discussion Number  18
NWS National Hurricane Center Miami FL       AL202020
500 PM AST Wed Sep 16 2020

Recent satellite imagery is suggesting that Teddy is undergoing some 
westerly vertical wind shear, as indicated by outflow being more 
limited in the western portion of the circulation. The latest 
UW-CIMSS shear analysis suggests the magnitude of this shear could 
be about 10-15 kt, which could help to explain the lack of increase 
in organization of the cyclone today. The most recent Dvorak 
satellite intensity estimates provided CI values of 4.5-5.0, 
indicating that the initial intensity is still around 85 kt. 

The environmental conditions are not forecast to change much for 
Teddy over the next couple of days. The cyclone is forecast to move 
over warm waters within a somewhat dry atmospheric environment, 
while moderate shear is expected to continue due to an upper trough 
to its northwest. Based on these only somewhat favorable conditions 
for strengthening, along with what we have witnessed with the lack 
of intensification today, the NHC intensity forecast over the next 
few days is being lowered. Beyond day 3, there is evidence to 
suggest that Teddy may move over some cooler waters due to upwelling 
caused by Paulette. And, by day 4 global models are forecasting a 
further increase in vertical wind shear. These two factors should 
cause the cyclone to weaken late in the forecast period. This 
updated intensity forecast is in good agreement with the HFIP 
corrected consensus, HCCA. 

Teddy is moving northwestward at about 11 kt. This motion is 
forecast to continue for the next few days, as the cyclone is 
steered by a mid-level ridge to its north and northeast. Late in the 
forecast period, the portion of the ridge north of Teddy is expected 
to erode as a mid-latitude trough digs across the northeastern 
United States. This evolution should cause the cyclone to turn 
north-northwest and possibly north by day 5. The track guidance is 
tightly clustered through day 3, but increases quite a bit after 
that time, likely due to how the models are handling the approaching 
trough. The latest GFS delays a turn and shows a more westerly 
track, with the cyclone southwest of Bermuda by day 5, while the 
rest of the global models turn the system north sooner and take the 
system just east of Bermuda. The NHC track forecast is close to the 
previous one and is near the various multi-model track consensus 
aids. On the forecast track, Teddy could make a close to approach to 
Bermuda in about 5 days. However, based on the model spread at that 
time frame and average track error of about 200 n mi at 120 h, it 
is certainly too soon to know what impacts Teddy may have on the 
island. 


FORECAST POSITIONS AND MAX WINDS

INIT  16/2100Z 17.5N  50.8W   85 KT 100 MPH
12H  17/0600Z 18.6N  52.0W   90 KT 105 MPH
24H  17/1800Z 20.0N  53.4W  100 KT 115 MPH
36H  18/0600Z 21.5N  54.9W  105 KT 120 MPH
48H  18/1800Z 23.0N  56.3W  105 KT 120 MPH
60H  19/0600Z 24.8N  58.0W  100 KT 115 MPH
72H  19/1800Z 26.5N  60.2W  100 KT 115 MPH
96H  20/1800Z 29.5N  63.6W   90 KT 105 MPH
120H  21/1800Z 33.3N  64.6W   85 KT 100 MPH

$$
Forecaster Latto