Tropical Storm Greg Forecast Discussion (Text)

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WTPZ42 KNHC 220833

Tropical Storm Greg Discussion Number  20
NWS National Hurricane Center Miami FL       EP072017
200 AM PDT Sat Jul 22 2017

Microwave imagery indicates that the center of the tropical storm
is located to the south of the main area of deep convection.  The
current intensity estimate is kept at 45 kt, based on a Dvorak
estimate from TAFB.  Greg is being affected by southerly
shear associated with an upper-level low/trough located to the
north-northwest, which is clearly seen in water vapor imagery.  The
global dynamical guidance indicates that the trough will lift
northward over the next day or two, resulting in a decrease of
shear.  However, Greg is expected to reach slightly cooler waters
and begin to ingest drier mid-level air within a couple of days.
Therefore, only slight strengthening is anticipated, followed by
weakening later in the forecast period.  By the end of the period,
the hostile environment should result in the system degenerating
into a remnant low.  The official forecast is near or a little above
the intensity model consensus.

Greg is moving westward or 275/11 kt.  A mid-level ridge to the
north of the tropical cyclone is likely to maintain the westward
motion for the next several days.  In 4-5 days the ridge is
predicted to weaken somewhat, and this should result in a slowing
of the forward speed along with a turn toward the right.  The
official track forecast is close to the simple and corrected
dynamical consensus tracks and is not too different from its


INIT  22/0900Z 15.2N 123.1W   45 KT  50 MPH
 12H  22/1800Z 15.3N 124.8W   45 KT  50 MPH
 24H  23/0600Z 15.4N 127.2W   45 KT  50 MPH
 36H  23/1800Z 15.3N 129.6W   50 KT  60 MPH
 48H  24/0600Z 15.2N 131.6W   50 KT  60 MPH
 72H  25/0600Z 15.7N 134.6W   45 KT  50 MPH
 96H  26/0600Z 17.2N 137.0W   35 KT  40 MPH
120H  27/0600Z 18.0N 139.0W   25 KT  30 MPH...POST-TROP/REMNT LOW

Forecaster Pasch

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Page last modified: Saturday, 22-Jul-2017 08:34:27 UTC