000 WTPZ44 KNHC 210839 TCDEP4 Tropical Storm Roslyn Discussion Number 6 NWS National Hurricane Center Miami FL EP192022 400 AM CDT Fri Oct 21 2022 Roslyn's structure has evolved since the previous advisory. A more distinct core of deep convection appears to be developing, and infrared satellite images have even shown hints of an eye feature during the past few hours. An elongated convective band now extends around the northeastern and southeastern quadrants of the circulation. Based on consensus Dvorak estimates of T3.5 from TAFB and SAB, and a CI number of 3.4 from the UW-CIMSS ADT, Roslyn is now estimated to have maximum winds of 55 kt. Recent scatterometer data and conventional satellite images indicate that Roslyn's center is a bit to the northeast of where it was estimated to be last evening, and the initial motion is west-northwestward, or 300/6 kt. The track forecast reasoning has not changed. Roslyn is expected to recurve around the western edge of a mid-level area of high pressure that will migrate eastward across Mexico during the next couple of days. In 2 to 3 days, Roslyn and its remnants are then expected to accelerate north-northeastward in the flow ahead of an approaching deep-layer mid-latitude trough. With the exception of the UKMET model (which is a western outlier), there is very little cross-track spread among the other track models, and most of the differences are in the forward speeds after 36 hours. The biggest change in this forecast package is that with the northeastward adjustment of Roslyn's center, the entire official track forecast has been shifted east of the previous prediction, and lies close to the updated TVCE and HCCA consensus aids. If Roslyn is indeed developing a better-defined core, environmental conditions could support rapid intensification (RI). The SHIPS RI indices are now showing a 50 to 60 percent chance of a 30-kt increase in intensity over the next 24 hours, and the HWRF, COAMPS-TC, and HCCA consensus aids are all showing RI. RI is therefore now explicitly forecast, and Roslyn should reach hurricane strength later today. In 36 to 48 hours, an increase in southwesterly shear could induce some weakening, but regardless, Roslyn is expected to reach the coast of west-central Mexico as a hurricane. Rapid weakening is expected after landfall, and although the official forecast shows a remnant low over northern Mexico in 72 hours for continuity, Roslyn is likely to have dissipated by that time. Given the relocation of Roslyn's center and the updates to the forecast, hurricane and tropical storm warnings are now in effect for portions of the west-central coast of Mexico. Hurricane watches have also been extended northward along the coast. 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 and will likely be extended northward later today. 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 21/0900Z 16.2N 103.8W 55 KT 65 MPH 12H 21/1800Z 16.6N 104.6W 70 KT 80 MPH 24H 22/0600Z 17.4N 105.5W 85 KT 100 MPH 36H 22/1800Z 18.7N 106.2W 95 KT 110 MPH 48H 23/0600Z 20.5N 106.2W 95 KT 110 MPH 60H 23/1800Z 23.0N 105.1W 70 KT 80 MPH...INLAND 72H 24/0600Z 25.7N 103.3W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 25/0600Z...DISSIPATED $$ Forecaster Berg