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Tropical Depression EIGHT

Tropical Depression Eight Discussion Number   2
NWS National Hurricane Center Miami FL       AL082021
500 AM AST Mon Aug 16 2021
Satellite imagery and radar data from Bermuda indicate that the 
tropical depression located about 100 nmi east of Bermuda has been 
moving southward and also remains a sheared tropical cyclone -- the 
ongoing saga of the Atlantic basin thus far this hurricane season. 
Convection has increased and developed closer to the center and a 
late-arriving ASCAT-C overpass indicated surface winds of 26-27 kt 
to the south of the well-defined circulation center. Based on those 
data, the slightly improved convective structure noted in both 
satellite and radar data, and satellite classifications of T2.0/30 
kt, the initial intensity has been increased to 30 kt.
The initial motion estimate is 195/04 kt. The small cyclone is 
starting to make the clockwise turn toward the south-southwest and 
eventually southwest that the global and regional models have been 
advertising the past couple of days. The latest NHC model guidance 
now shows less of a turn to the northwest after 72 hours, with the 
exception of the GFS, GFS-ensemble, and HMON models, which continue 
to take the cyclone northward and northeastward around Bermuda on 
day 4 and 5. The latest NHC track forecast is similar to the 
previous advisory track through 60 hours, and then widens the track 
slightly thereafter, but still shows a complete clockwise turn. This 
track scenario is to the right of the consensus models at all 
forecast periods, and is of low confidence on days 4 and 5.

The vertical wind shear is forecast to remain at or below 10 kt for 
the next 36 hours or so, and that is most likely the time when the 
cyclone will strengthen. Thereafter, an increase in the shear to 20 
kt or more is expected to cap the intensification process. The HWRF 
model turn the cyclone into a major hurricane by 72 hours, but this 
scenario is considered to be an extreme outlier given the amount of 
shear forecast to affect the system on days 3-5. So far this season, 
the HWRF model has been very shear resistant and has had a high 
intensity bias. The official intensity forecast closely follows a 
blend of the IVCN and HCCA consensus models through 60 hours, and 
then is below those models due to the high-bias contribution of the 
HWRF model.

INIT  16/0900Z 32.4N  62.9W   30 KT  35 MPH
 12H  16/1800Z 31.6N  63.1W   35 KT  40 MPH
 24H  17/0600Z 31.0N  63.7W   40 KT  45 MPH
 36H  17/1800Z 30.7N  64.5W   45 KT  50 MPH
 48H  18/0600Z 30.7N  65.5W   50 KT  60 MPH
 60H  18/1800Z 30.8N  66.7W   55 KT  65 MPH
 72H  19/0600Z 31.1N  68.0W   55 KT  65 MPH
 96H  20/0600Z 32.0N  69.0W   55 KT  65 MPH
120H  21/0600Z 34.0N  68.5W   55 KT  65 MPH
Forecaster Stewart