ZCZC MIATCDEP2 ALL TTAA00 KNHC DDHHMM 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 NNNN
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