ZCZC MIATCDEP2 ALL
TTAA00 KNHC DDHHMM

Tropical Storm Greg Discussion Number  21
NWS National Hurricane Center Miami FL       EP072017
800 AM PDT Sat Jul 22 2017

A large and strong burst of convection has formed on the northern
side of the center of Greg during the past several hours.  However,
microwave data suggest the center remains mostly exposed on the
southern side of the thunderstorm activity.  Satellite intensity
estimates range between 35-55 kt, so the initial wind speed will be
kept at 45 kt.

While shear is forecast to decrease near Greg over the next 36
hours as a trough lifts out, SSTs are also likely to decrease
along with more dry air in the environment of the cyclone.  The net
result of these competing factors is that little significant
intensity change is expected over the next couple of days.  After
that, most of the models increase the shear again while the storm
moves over colder waters.  Thus Greg should weaken at long range,
and will likely be a remnant low by day 5.  Little change was made
to the previous NHC forecast, which is near or slightly higher than
the model consensus.

Greg is moving westward or 270/11 kt.  A mid-level ridge to the
north of the tropical cyclone is likely to maintain the westward
motion for the next couple of days.  In 3-5 days the ridge is
predicted to weaken somewhat, and this should result Greg slowing
down and turning west-northwestward.  There has been little change
to the model tracks, with the ECMWF/UKMET on the left side of the
guidance, and the GFS-based guidance on the right side.  The
GFS-based guidance has been trending westward, so it makes some
sense to stay on the left side of the consensus.  The latest NHC
forecast is very close to the previous forecast, leaning a little
heavier on the ECMWF, UKMET, their ensembles, and the HFIP-corrected
consensus model.


FORECAST POSITIONS AND MAX WINDS

INIT  22/1500Z 15.1N 124.2W   45 KT  50 MPH
 12H  23/0000Z 15.1N 126.0W   45 KT  50 MPH
 24H  23/1200Z 15.0N 128.2W   45 KT  50 MPH
 36H  24/0000Z 14.9N 130.3W   50 KT  60 MPH
 48H  24/1200Z 15.1N 132.0W   50 KT  60 MPH
 72H  25/1200Z 16.0N 134.8W   45 KT  50 MPH
 96H  26/1200Z 17.3N 137.2W   35 KT  40 MPH
120H  27/1200Z 18.0N 140.0W   25 KT  30 MPH...POST-TROP/REMNT LOW

$$
Forecaster Blake

NNNN