WTPZ42 KNHC 241436

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.


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