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 predecessor.


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