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Tropical Storm GREG (Text)


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Tropical Storm Greg Discussion Number  28
NWS National Hurricane Center Miami FL       EP072017
200 AM PDT Mon Jul 24 2017

ASCAT passes at 0542 and 0636 UTC suggest that Greg has weakened a
little.  The highest wind vector in either pass was 36 kt in the
northeast quadrant, and no winds exceeding 32 kt were observed in
any other quadrants.  Based on the ASCAT data, and sampling
considerations, the intensity has been decreased to 40 kt.

The ASCAT passes were very helpful in locating the center of Greg
and the initial motion estimate is 285/8 kt.  No significant change
has been made to the NHC track forecast.  There remains fair
agreement between the models that Greg will continue west-northwest
or northwestward, steered by an extension of a mid-layer ridge
centered to the northwest.  Once the tropical storm weakens to a
remnant low, the low-level flow should turn the remnant circulation
back toward the west or west-southwest until it dissipates.

Greg is not expected to recover from the dry air that is
contributing to its current weakening trend.  The vertical shear is
expected to increase as well in about 24-36 hours, which should
cause further weakening.  The new forecast is a little lower than
the previous one, mainly to account for the lower initial
intensity.  A few models, especially the GFS, suggest that Greg
could open into a trough within the 5-day forecast period, but this
isn't supported by the ECMWF, UKMET, or HWRF.  Out of respect for
those models, the forecast currently calls for Greg to remain a
closed circulation throughout the forecast period, but it would not
be surprising if it dissipated by day 5.

FORECAST POSITIONS AND MAX WINDS

INIT  24/0900Z 14.4N 132.1W   40 KT  45 MPH
 12H  24/1800Z 14.8N 133.5W   40 KT  45 MPH
 24H  25/0600Z 15.4N 135.0W   40 KT  45 MPH
 36H  25/1800Z 16.2N 136.4W   35 KT  40 MPH
 48H  26/0600Z 16.9N 137.8W   30 KT  35 MPH
 72H  27/0600Z 17.4N 140.8W   25 KT  30 MPH...POST-TROPICAL
 96H  28/0600Z 17.0N 144.1W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  29/0600Z 16.0N 147.0W   20 KT  25 MPH...POST-TROP/REMNT LOW

$$
Forecaster Zelinsky

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Page last modified: Wednesday, 13-Dec-2017 12:10:01 UTC