000 WTNT42 KNHC 070838 TCDAT2 TROPICAL STORM GRACE DISCUSSION NUMBER 8 NWS NATIONAL HURRICANE CENTER MIAMI FL AL072015 500 AM AST MON SEP 07 2015 Deep convection has redeveloped near the center of Grace overnight, and an earlier SSMI microwave overpass showed that the convection was organized in a couple of bands around the center. There are indications in geostationary satellite imagery that the shear is beginning to increase as the cirrus outflow has become restricted over the western portion of the system. The initial wind speed remains 45 kt, which is in agreement with subjective Dvorak satellite intensity estimates from TAFB and SAB. Little change in strength is expected today. Environmental conditions are forecast to become less favorable by tonight as westerly vertical wind shear increases and dry mid-level air over the tropical Atlantic impinges on the circulation. The shear is forecast to increase to 20-30 kt by late Tuesday, and weakening is expected to begin by that time. The NHC intensity forecast is close to the LGEM model and the intensity consensus. Given the strong southwesterly upper-level winds expected near the eastern Caribbean late in the period, it is quite possible that Grace will degenerate to a tropical wave before it reaches the Lesser Antilles. Grace continues to move westward or 275/14 kt. The tropical cyclone is forecast to move generally westward to the south of a large mid- to upper-level ridge over the central Atlantic. The model guidance is in good agreement on this scenario and the NHC forecast is once again essentially an update of the previous NHC advisory. The new track forecast is close to the multi-model consensus. FORECAST POSITIONS AND MAX WINDS INIT 07/0900Z 13.5N 33.9W 45 KT 50 MPH 12H 07/1800Z 13.7N 36.1W 45 KT 50 MPH 24H 08/0600Z 13.9N 39.1W 45 KT 50 MPH 36H 08/1800Z 14.2N 42.2W 45 KT 50 MPH 48H 09/0600Z 14.7N 45.4W 40 KT 45 MPH 72H 10/0600Z 15.5N 51.6W 35 KT 40 MPH 96H 11/0600Z 16.2N 57.2W 35 KT 40 MPH 120H 12/0600Z 16.8N 62.5W 30 KT 35 MPH $$ Forecaster Brown