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Tropical Storm Rosa Forecast Discussion Number 24
2018-10-01 04:34:08| National Hurricane Center (East Pacific)
Issued at 800 PM PDT Sun Sep 30 2018 547 WTPZ45 KNHC 010234 TCDEP5 Tropical Storm Rosa Discussion Number 24 NWS National Hurricane Center Miami FL EP202018 800 PM PDT Sun Sep 30 2018 All of Rosa's associated deep convection is located within the northeastern quadrant of the circulation, moving out ahead of the center due to 25-30 kt of southwesterly shear. Subjective and objective intensity estimates have decreased since the previous advisory but encompass a wide range from about 45 kt to 65 kt. The initial intensity is lowered to 55 kt, the average of these estimates and similar to the latest UW-CIMSS SATCON estimate. Rosa's center is now over sub-24C waters, heading for waters around 21C along the Baja California coast, and the shear is forecast to increase further in the coming days. As a result, Rosa is expected to weaken below tropical storm intensity between 24-36 hours, after it has reached the Baja California coast. All of the cyclone's deep convection is likely to be sheared away soon thereafter, making Rosa a remnant low between 36-48 hours, if not sooner. The remnant low should dissipate over Arizona by 48 hours. Rosa continues to move north-northeastward, or 025/10 kt. The flow on the eastern side of a large mid-level trough located off the U.S. West Coast should continue to steer Rosa north-northeastward, with some acceleration beginning by Monday night. Although there are still some speed differences among the models, particularly between the faster GFS and slower ECMWF, the guidance remains tightly clustered overall, and the new NHC track forecast is very close to the multi-model consensus aids. 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 01/0300Z 26.0N 117.6W 55 KT 65 MPH 12H 01/1200Z 27.3N 116.8W 45 KT 50 MPH 24H 02/0000Z 29.1N 115.6W 35 KT 40 MPH 36H 02/1200Z 31.5N 114.1W 30 KT 35 MPH...NEAR THE SONORA COAST 48H 03/0000Z 34.2N 112.4W 25 KT 30 MPH...POST-TROP/INLAND 72H 04/0000Z...DISSIPATED $$ Forecaster Berg
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