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Tropical Storm GREG Forecast Discussion


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Tropical Storm Greg Discussion Number  33
NWS National Hurricane Center Miami FL       EP072017
800 AM PDT Tue Jul 25 2017

Greg's convective pattern continues to deteriorate, and all of the
thunderstorm activity appears limited to the west and northwest of
the low-level center.  Dvorak final-T numbers have decreased, and
it is assumed that Greg has weakened to a 35-kt tropical storm.
Southerly shear is increasing over Greg, and it is expected
increase further to around 30-35 kt and turn out of the northwest
in about 48 hours.  In addition, the low- to mid-level environment
continues to get drier, and Greg is moving toward cooler waters.
All of this means that additional weakening is anticipated, and Greg
is likely to degenerate into a remnant low by 48 hours.  The
remnant low will likely persist through the remainder of the
forecast period.

The best estimate of the initial motion is 295/9 kt.  A low- to
mid-level trough located north and northeast of Greg appears to be
allowing the cyclone to gain latitude at the moment.  However, as
Greg continues to weaken, it is likely to turn west and
west-southwest as it becomes steered by the low-level trade winds.
Although there is some spread in the track guidance during the
remnant low stage, especially regarding the system's forward speed,
the NHC track forecast remains in the middle of the guidance
envelope, nearest HCCA and the various consensus models.

FORECAST POSITIONS AND MAX WINDS

INIT  25/1500Z 15.4N 136.8W   35 KT  40 MPH
 12H  26/0000Z 16.3N 137.8W   35 KT  40 MPH
 24H  26/1200Z 17.1N 139.1W   35 KT  40 MPH
 36H  27/0000Z 17.5N 140.5W   30 KT  35 MPH
 48H  27/1200Z 17.5N 142.0W   30 KT  35 MPH...POST-TROP/REMNT LOW
 72H  28/1200Z 16.8N 144.7W   25 KT  30 MPH...POST-TROP/REMNT LOW
 96H  29/1200Z 16.0N 147.5W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  30/1200Z 15.0N 150.5W   20 KT  25 MPH...POST-TROP/REMNT LOW

$$
Forecaster Berg

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