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Tropical Storm Greg Forecast Discussion


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000
WTPZ42 KNHC 242038
TCDEP2

Tropical Storm Greg Discussion Number  30
NWS National Hurricane Center Miami FL       EP072017
200 PM PDT Mon Jul 24 2017

Even embedded within a relatively dry and stable air mass, Greg's
deep convection has increased again during the day.  Dvorak CI
numbers remain between 35-45 kt, and recent ASCAT data showed
maximum winds near or a little above 35 kt.  Because convection has
recently increased, I see no reason to deviate from the 40 kt we've
been carrying.  Despite the recent convective upswing, the
environment ahead of Greg will become less conducive over the next
day or two.  The atmosphere will continue to get a little drier, and
vertical shear is expected to increase out of the south and west.
In addition, Greg will be moving toward cooler waters.  All of this
means that gradual weakening is anticipated, with Greg likely to
become a tropical depression in 48 hours and a remnant low by day
3. This scenario remains close to SHIPS, HCCA, and the ICON
intensity consensus.

Greg still appears to be moving westward, or 275/10 kt, but the
models insist that the cyclone will soon turn west-northwestward or
northwestward due to weak ridging to its northwest and a low-level
trough to its northeast.  After it becomes a remnant low, Greg's
shallower circulation should turn westward and then
west-southwestward in the low-level trade wind flow.  The updated
NHC forecast is very similar to the previous one and remains close
to the TVCN multi-model consensus.

FORECAST POSITIONS AND MAX WINDS

INIT  24/2100Z 14.5N 134.3W   40 KT  45 MPH
 12H  25/0600Z 15.1N 135.4W   35 KT  40 MPH
 24H  25/1800Z 15.9N 136.8W   35 KT  40 MPH
 36H  26/0600Z 16.7N 138.1W   35 KT  40 MPH
 48H  26/1800Z 17.3N 139.5W   30 KT  35 MPH
 72H  27/1800Z 17.1N 142.6W   25 KT  30 MPH...POST-TROP/REMNT LOW
 96H  28/1800Z 16.0N 145.5W   20 KT  25 MPH...POST-TROP/REMNT LOW
120H  29/1800Z 15.0N 148.0W   20 KT  25 MPH...POST-TROP/REMNT LOW

$$
Forecaster Berg