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Tropical Storm Greg Discussion Number  29
NWS National Hurricane Center Miami FL       EP072017
800 AM PDT Mon Jul 24 2017

Greg's convective structure is gradually deteriorating, likely due
to very dry air in the surrounding atmosphere.  However, the
initial intensity remains 40 kt on this advisory, primarily since
subjective and objective final-T numbers still range between T2.0
and T3.0.  Along with the dry environment, deep-layer vertical
shear is expected to turn out of the west and increase in 36-48
hours, and Greg will be moving over marginally warm waters of
around 26 deg C.  Therefore, gradual weakening is anticipated, and
Greg will likely be a tropical depression in about 48 hours and
then a remnant low by day 3.  This forecast is just an update of
the previous one and is very close to the ICON intensity consensus.

Based on the latest center fixes, Greg's motion has been
oscillating between westward and west-northwestward, and the
12-hour motion estimate is 280/10 kt.  A more definitive
west-northwestward motion is likely to begin soon and continue for
the next 48 hours as the ridge axis to Greg's north changes from a
north-south orientation to a more east-west orientation.  After 48
hours, the remnant low of Greg should then be steered westward and
west-southwestward by the lower-level trade winds.  The track
guidance envelope shifted northeastward between 12-48 hours on this
cycle, and as a result the new NHC track forecast has been adjusted
in that direction during that period.  Otherwise, there are no
significant changes from the previous forecast.

FORECAST POSITIONS AND MAX WINDS

INIT  24/1500Z 14.6N 133.2W   40 KT  45 MPH
 12H  25/0000Z 15.1N 134.5W   40 KT  45 MPH
 24H  25/1200Z 15.9N 135.8W   35 KT  40 MPH
 36H  26/0000Z 16.7N 137.2W   35 KT  40 MPH
 48H  26/1200Z 17.3N 138.7W   30 KT  35 MPH
 72H  27/1200Z 17.4N 142.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
 96H  28/1200Z 16.5N 145.0W   20 KT  25 MPH...POST-TROP/REMNT LOW
120H  29/1200Z 15.5N 147.0W   20 KT  25 MPH...POST-TROP/REMNT LOW

$$
Forecaster Berg

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