285 WTPZ41 KNHC 102040 TCDEP1 Tropical Storm Pamela Discussion Number 3 NWS National Hurricane Center Miami FL EP162021 400 PM CDT Sun Oct 10 2021 The cyclone has strengthened since last night, with deep convection persisting over the system's low-level center for much of the morning. Over the past few hours, there has been evidence of some northeasterly shear impacting the cyclone, and the center has become partially exposed. Despite this shear, a 1528 UTC scatterometer overpass revealed an area of 35 to 38-kt winds in the northeastern quadrant. Therefore, the depression has been upgraded to 40-kt Tropical Storm Pamela. Pamela is moving west-northwestward, or 290/13 kt to the south of a strong mid-tropospheric ridge. A weakness is forecast to develop in the ridge early this week as a mid- to upper-level trough digs southward over the western United States and northern Mexico. The cyclone is forecast to slow its forward motion and turn northwest, and then north into this weakness late Monday through Tuesday. By Tuesday night, Pamela should begin to get caught in the southwesterly flow between the ridge and trough and turn northeastward. The track model guidance continues to be in very good agreement on this scenario and the latest NHC forecast track is nearly unchanged from the previous one. Based on the forecast track, the center of the cyclone should pass near or south of the southern tip of the Baja California peninsula Tuesday night or early Wednesday, then reach the coast of west-central mainland Mexico by late Wednesday. The current northeasterly wind shear is about 10-15 kt based on the most recent UW-CIMMS analysis, and this is also recognized by both the EC and GFS-SHIPS guidance. This magnitude of shear is forecast to persist for the next 18-24 h before subsiding to under 10 kt by 36 h. Pamela will be passing over very warm waters near 30 C until it reaches the coast of Mexico while embedded in a moist atmospheric environment. Therefore, despite the shear, steady strengthening is expected, and a faster rate of intensification is possible after 36 h. The latest NHC intensity forecast is close to the IVCN consensus solution, but is slightly below the HFIP corrected consensus HCCA, which indicates that Pamela could become a major hurricane prior to landfall along the coast of mainland Mexico. Key Messages: 1. Pamela is forecast to be at or near major hurricane intensity when it reaches the coast of west-central mainland Mexico by late Wednesday, and could bring life-threatening storm surge, flash flooding, and dangerous winds to a portion of that area. Residents in this area should monitor the progress of this system and ensure they have their hurricane plan in place. 2. Pamela is expected to pass near or south of the southern tip of the Baja California peninsula as a hurricane Tuesday night or early Wednesday, and could bring strong winds and heavy rainfall to the extreme southern portion of the peninsula. Watches could be required for portions of this area tonight or early Monday. FORECAST POSITIONS AND MAX WINDS INIT 10/2100Z 15.5N 105.9W 40 KT 45 MPH 12H 11/0600Z 16.0N 107.4W 50 KT 60 MPH 24H 11/1800Z 16.9N 108.8W 60 KT 70 MPH 36H 12/0600Z 18.1N 109.7W 70 KT 80 MPH 48H 12/1800Z 19.6N 109.9W 80 KT 90 MPH 60H 13/0600Z 21.2N 109.3W 90 KT 105 MPH 72H 13/1800Z 23.3N 108.0W 95 KT 110 MPH 96H 14/1800Z 28.1N 103.1W 25 KT 30 MPH...POST-TROP/INLAND 120H 15/1800Z...DISSIPATED $$ Forecaster Latto