516 WTPZ44 KNHC 212043 TCDEP4 Tropical Storm Roslyn Discussion Number 8 NWS National Hurricane Center Miami FL EP192022 400 PM CDT Fri Oct 21 2022 Satellite imagery shows that Roslyn continues to gradually become better organized, with the center now embedded in a well-defined central dense overcast. In addition, convective banding has increased outside of the CDO, suggesting that the dry air earlier seen in the circulation is mixing out. Various subjective and objective satellite intensity estimates have nudged upward, so the initial intensity is increased to 60 kt. The wind radii have been adjusted downward based on data from a recent ASCAT overpass. The latest imagery and the scatterometer data confirm that Roslyn has been moving to the left of the previous forecast, and the initial position for this advisory is a slight re-location. The initial motion is a somewhat uncertain 295/6. Overall, there is no change in the track forecast philosophy, as Roslyn is still expected to recurve around the western edge of a mid-level ridge that will migrate eastward across Mexico during the next couple of days. This will lead to the center passing near or a little west of Cabo Corrientes in about 36 h, followed by landfall in mainland Mexico. However, a combination of the current westward nudge and an eastward shift in the track guidance results in the new forecast track being to the west of the previous track through 24 h and a little to the east of the previous track after that time. The new forecast is also faster to bring the center to the coast of Mexico, with landfall now shown between 36-48 h. The new forecast track lies near the consensus models through 24 h, and thereafter lies a little to the west of the consensus models. Roslyn has a small inner core, and light vertical wind shear conditions are expected during the next 24-30 h. Since the dry air seems to be mixing out, this should allow Roslyn to steadily to rapidly intensify during this time. The rapid intensification indices in the SHIPS model suggest a good chance of 25-35 kt of strengthening during the next 24 h, and the new intensity forecast calls for a possibly conservative 25 kt of strengthening during this time. After that time, the latest large-scale models forecast increasing shear, and there is uncertainty on how soon land interaction will occur. Based on this, the intensity forecast shows a little more strengthening through 36 h, followed by rapid weakening after the center makes landfall. The system should dissipate completely over the mountains of Mexico between 60-72 h. The new forecast requires a northward extension of the hurricane warnings and watches along the coast of Mexico and for the Islas Marias. Additional watches and warnings could be required tonight and Saturday. Key Messages: 1. Roslyn is forecast to be a hurricane when it passes near and makes landfall along the west-central coast of Mexico late Saturday and Sunday, accompanied by strong winds and a potentially dangerous storm surge. A Hurricane Warning is now in effect for a portion of the west-central coast of Mexico. 2. Heavy rainfall could lead to flash flooding and possible landslides in areas of rugged terrain over coastal southwestern and west-central Mexico. FORECAST POSITIONS AND MAX WINDS INIT 21/2100Z 16.4N 105.0W 60 KT 70 MPH 12H 22/0600Z 17.0N 105.8W 75 KT 85 MPH 24H 22/1800Z 18.3N 106.3W 85 KT 100 MPH 36H 23/0600Z 20.2N 106.1W 90 KT 105 MPH 48H 23/1800Z 22.6N 105.0W 50 KT 60 MPH...INLAND 60H 24/0600Z 25.7N 102.9W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 24/1800Z...DISSIPATED $$ Forecaster Beven