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.


FORECAST POSITIONS AND MAX WINDS

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

Edited: 08/17/2021 at 08:03 AM by Central Floridave