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Potential Tropical Cyclone Eight Discussion Number   1
NWS National Hurricane Center Miami FL       AL082018
1100 AM AST Fri Sep 07 2018

Satellite imagery and surface observations indicate that the area of
low pressure that moved off the west coast of Africa has developed a
closed circulation that appears to be well defined. However, the
convective organization, given Dvorak classifications of only T1.0,
do not support calling the system a tropical cyclone at this point.
However, given that the system is expected to be a tropical storm
near the southern Cabo Verde Islands in 36 to 48 hours, advisories
are being initiated on this system as a potential tropical cyclone
at this time, and a tropical storm warning has been issued for those
islands.

Environmental conditions of light to moderate easterly shear and
SSTs of 27-28C should support development of this system, and the
NHC forecast shows it becoming a tropical storm by 12 hours.
Gradual strengthening is indicated by the bulk of the intensity
guidance through the next 3-4 days. After that time, the shear is
forecast to increase and the system will be moving into somewhat
cooler waters, so some weakening is expected by day 5. The NHC
forecast is close to the latest HCCA guidance and a little higher
than the IVCN consensus.

The initial motion estimate is a somewhat uncertain 275/09 given
that the surface circulation is just forming. The synoptic pattern
over the eastern Atlantic features a ridge to the north of the
disturbance, which is expected to weaken by the end of the period.
This steering pattern should result in a westward to west-
northwestward motion for the next 72 hours with an increase in
forward speed, followed by a decrease in forward speed and a
slightly more poleward motion as the system responds to the weakness
in the ridge. The initial NHC track forecast is close to the latest
HCCA track consensus aid and near the middle of the guidance
envelope.

FORECAST POSITIONS AND MAX WINDS

INIT  07/1500Z 13.1N  17.8W   30 KT  35 MPH...POTENTIAL TROP CYCLONE
 12H  08/0000Z 13.3N  18.6W   35 KT  40 MPH...TROPICAL STORM
 24H  08/1200Z 13.8N  20.3W   40 KT  45 MPH
 36H  09/0000Z 14.2N  22.6W   45 KT  50 MPH
 48H  09/1200Z 14.6N  25.4W   50 KT  60 MPH
 72H  10/1200Z 16.0N  32.0W   55 KT  65 MPH
 96H  11/1200Z 18.0N  37.0W   60 KT  70 MPH
120H  12/1200Z 20.0N  41.0W   55 KT  65 MPH

$$
Forecaster Brennan

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