762 WTPZ45 KNHC 301432 TCDEP5 Hurricane Rosa Discussion Number 22 NWS National Hurricane Center Miami FL EP202018 800 AM PDT Sun Sep 30 2018 Rosa continues to be affected by increasing southwesterly shear and cooler waters. Most of the deep convection has been eroded over the southern semicircle of the circulation. The current intensity estimate is reduced to 65 kt in agreement with ADT estimates from UW/CIMSS. An Air Force Reserve Unit Hurricane Hunter aircraft will investigate Rosa later today to provide a better estimate of the intensity of the system. Since the vertical shear is predicted to continue to increase and SSTs should cool to below 23 deg C by Monday, additional weakening is likely before Rosa reaches the Baja California peninsula. The official intensity forecast is near the high end of the numerical guidance. The hurricane is moving just east of north, or around 010/11 kt. The track forecast reasoning is unchanged from the previous advisory package. Rosa is likely to be steered north-northeastward in the flow ahead of a large mid-level trough approaching from the west. This should take the center of the cyclone across Baja California in the Tropical Storm Warning area by Monday night. Rosa or it's remnant should move over the Desert Southwest on Tuesday. The official track forecast is similar to the previous one and roughly in the middle of the dynamical guidance. Key Messages: 1. The main hazard expected from Rosa or its remnants is very heavy rainfall in Baja California, northwestern Sonora, and the U.S. Desert Southwest. These rains are expected to produce life-threatening flash flooding and debris flows in the deserts, and landslides in mountainous terrain. For more information about potential rainfall in that area, please see products from the Weather Prediction Center and your local NWS forecast office. 2. Tropical storm conditions are expected over portions of the central and northern Baja California peninsula on Monday, possibly spreading to the northern Gulf of California Monday night. Interests in those locations should monitor the progress of Rosa. FORECAST POSITIONS AND MAX WINDS INIT 30/1500Z 24.4N 118.6W 65 KT 75 MPH 12H 01/0000Z 25.9N 117.9W 60 KT 70 MPH 24H 01/1200Z 27.5N 116.7W 55 KT 65 MPH 36H 02/0000Z 29.3N 115.4W 45 KT 50 MPH 48H 02/1200Z 31.8N 114.0W 30 KT 35 MPH...INLAND 72H 03/1200Z 36.5N 111.5W 20 KT 25 MPH...POST-TROP/INLAND 96H 04/1200Z...DISSIPATED $$ Forecaster Pasch