000 WTPZ42 KNHC 192033 TCDEP2 Tropical Storm Greg Discussion Number 10 NWS National Hurricane Center Miami FL EP072017 300 PM MDT Wed Jul 19 2017 Deep convection associated with Greg has thinned out again this afternoon, with the low-level center evident near the northwestern portion of a loosely curved convective band. Although Dvorak satellite intensity estimates suggest maximum winds of 45 to 55 kt, recent ASCAT data continued to support a lower intensity of around 40 kt. The cirrus outflow and current structure of the tropical cyclone continue to suggest that there is moderate shear over the system which may be coming from a layer below 200 mb since the analyzed 850 to 200 mb shear is low. The global models predict that there should be a better upper-level wind pattern over Greg within the next couple of days, and as a result, strengthening is forecast. However, the NHC forecast remains below much of the guidance and the intensity consensus since the shear has failed to abate thus far. After 48 hours, the GFS and ECWMF show Greg in very different upper-level environments with the GFS being much more conducive than the ECMWF. Due to this uncertainty, the NHC forecast again is below the intensity consensus at 72 hours and beyond, and it is a low confidence forecast. Greg is moving westward at about 9 kt. There has been no significant change to the track forecast reasoning. Greg is forecast to move west-northwestward during the next couple of days to the south of a mid- to upper-level ridge that extends westward from northern Mexico. Greg should turn westward and accelerate around the northern portion of TD Eight-E's circulation in a few days. The dynamical model guidance is in good agreement on this overall scenario, but there are large along-track or speed differences with the GFS being much slower than the ECMWF. Overall, the track guidance has again trended slower so the NHC forecast has been adjusted accordingly. FORECAST POSITIONS AND MAX WINDS INIT 19/2100Z 14.3N 112.7W 40 KT 45 MPH 12H 20/0600Z 14.4N 113.9W 45 KT 50 MPH 24H 20/1800Z 14.9N 115.9W 50 KT 60 MPH 36H 21/0600Z 15.5N 118.2W 55 KT 65 MPH 48H 21/1800Z 16.0N 120.5W 60 KT 70 MPH 72H 22/1800Z 16.2N 125.5W 60 KT 70 MPH 96H 23/1800Z 16.0N 130.5W 50 KT 60 MPH 120H 24/1800Z 16.0N 135.0W 40 KT 45 MPH $$ Forecaster Brown