728 WTPZ44 KNHC 201449 TCDEP4 Tropical Storm Roslyn Discussion Number 3 NWS National Hurricane Center Miami FL EP192022 1000 AM CDT Thu Oct 20 2022 Convection associated with the cyclone has become a bit better organized since the last advisory, with a strong cluster having developed near the center. Various subjective and objective satellite intensity estimates are now near 35 kt, and based on this the depression is upgraded to Tropical Storm Roslyn with an initial intensity of 35 kt. Although the system has strengthened, recent microwave and conventional satellite imagery suggests that multiple low-level swirls are present near the center, indicating that the inner core has not yet tightened up. The initial motion is now 275/5 kt along the southern edge of a mid-level ridge to the north and northwest of the storm. In addition, a deep-layer low pressure area is currently located southwest of California, and west of the ridge. These features are forecast to move slowly eastward during the next few days, with the deep-layer steering flow near Roslyn changing from easterly to southeasterly to southerly and eventually to southwesterly. This evolution should cause the storm to recurve between the ridge and the low and make landfall in western Mexico. The track guidance is generally in good agreement with this scenario. However, there is some spread regarding how quickly Roslyn will recurve. The GFS is on the right side of the guidance envelope with the center passing near Cabo Corrientes, while the UKMET and ECMWF are farther west. The new forecast track is similar to the previous forecast and calls for the center to pass just west of Cabo Corrientes in about 72 h, followed by landfall in mainland Mexico before 96 h. The new forecast track is near or a little to the east of the consensus models. Roslyn is currently over warm sea surface temperatures in a moist environment with light vertical wind shear. These conditions are likely to persist for the next 72 h or so, and they should allow Roslyn to steadily intensify. After 72 h, the intensity forecast becomes more uncertain due to a forecast increase in shear, the possibility of dry air entrainment, and the possibility of land interaction. The new NHC forecast is generally similar to the previous forecast, although it has a slightly lower peak intensity before landfall in mainland Mexico due to a downward trend in the guidance. After landfall, rapid weakening is expected, with the cyclone dissipating over the mountains of Mexico between 96-120 h. Key Messages: 1. Roslyn is forecast to become a hurricane before it passes near or over the west-central coast of Mexico late Saturday and Sunday, accompanied by strong winds and a potentially dangerous storm surge. Interests along the coast of southwestern and west-central Mexico should closely monitor the progress of this system, and hurricane or tropical storm watches could be required for portions of this coastline later today. 2. Heavy rainfall from Roslyn could lead to flash flooding and possible landslides in areas of rugged terrain over coastal southwestern Mexico. FORECAST POSITIONS AND MAX WINDS INIT 20/1500Z 15.2N 102.0W 35 KT 40 MPH 12H 21/0000Z 15.4N 102.8W 45 KT 50 MPH 24H 21/1200Z 15.7N 103.7W 55 KT 65 MPH 36H 22/0000Z 16.3N 104.6W 65 KT 75 MPH 48H 22/1200Z 17.2N 105.5W 75 KT 85 MPH 60H 23/0000Z 18.6N 106.0W 80 KT 90 MPH 72H 23/1200Z 20.3N 105.9W 85 KT 100 MPH 96H 24/1200Z 24.0N 104.0W 35 KT 40 MPH...INLAND 120H 25/1200Z...DISSIPATED $$ Forecaster Beven