000 WTPZ42 KNHC 160257 TCDEP2 Hurricane Norma Discussion Number 7 NWS National Hurricane Center Miami FL EP172017 900 PM MDT Fri Sep 15 2017 Infrared satellite imagery indicates that banding associated with Norma has increased during the past few hours. The convective cloud tops have cooled and the band surrounding the center has become a little more solid with the formation of a ragged banding eye. Dvorak data T-numbers from both TAFB and SAB are 4.0, and with the recent increase in organization the initial wind speed is increased to 65 kt. Norma becomes the eighth hurricane in the eastern Pacific this season. Norma should remain over warm water and within a low shear environment during the next 24 to 36 h. These conditions favor strengthening, but the large size of Norma is likely to keep the intensification rate in check. Increasing vertical shear and cooler waters are expected to impart gradual weakening after 48 hours. The latest NHC intensity forecast is similar to the previous advisory and is close to the SHIPS guidance. Norma has been moving slowly north-northwestward, with an initial motion estimate of 335/2 kt. The hurricane is forecast to move slowly northward during the next couple of days, while it remains along the western side of a mid-level ridge. After that time, the ECMWF develops a narrow ridge to the north of Norma which causes the hurricane to turn northwestward. Meanwhile, the GFS keeps Norma on a north track over the Baja California peninsula. The trend of the track guidance has been westward during the past several cycles, so the NHC forecast lies slightly west of the consensus, and closer to the ECMWF that has been more consistent over the past few runs. Given the large spread in the guidance later in the period, the confidence in the track forecast after 48 hours remains low. The 48-hour forecast track and wind radii are very close to the southern tip of the Baja California peninsula. However, with the persistent westward shifts in the guidance, a tropical storm watch does not appear to be needed at this time. We will assess future model trends for the possibility of a watch issuance later tonight or tomorrow. FORECAST POSITIONS AND MAX WINDS INIT 16/0300Z 19.0N 110.2W 65 KT 75 MPH 12H 16/1200Z 19.3N 110.4W 70 KT 80 MPH 24H 17/0000Z 20.0N 110.5W 75 KT 85 MPH 36H 17/1200Z 21.0N 110.9W 75 KT 85 MPH 48H 18/0000Z 22.0N 111.3W 70 KT 80 MPH 72H 19/0000Z 23.7N 112.3W 60 KT 70 MPH 96H 20/0000Z 24.6N 112.6W 45 KT 50 MPH 120H 21/0000Z 25.5N 111.5W 30 KT 35 MPH...INLAND $$ Forecaster Brown