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Hurricane Rosa Forecast Discussion Number 19
2018-09-29 22:42:25| National Hurricane Center (East Pacific)
Issued at 200 PM PDT Sat Sep 29 2018 389 WTPZ45 KNHC 292042 TCDEP5 Hurricane Rosa Discussion Number 19 NWS National Hurricane Center Miami FL EP202018 200 PM PDT Sat Sep 29 2018 The strengthening trend seen earlier has at least slowed, as Rosa has shown little change in organization since the last advisory. The hurricane continues to have a well-defined 30-40 n mi wide eye inside a central dense overcast with cloud tops as cold as -75C. The various satellite intensity estimates have changed little, so the initial intensity remains 90 kt. The hurricane has good to excellent cirrus outflow in the northeastern semicircle, and the outflow has recently improved in the southwestern semicircle. Rosa is now crossing the 26C isotherm, so additional significant strengthening appears unlikely. After 12 h, the combination of decreasing sea surface temperatures and increasing shear should cause steady to rapid weakening, and the intensity forecast continues to call for the cyclone to weaken below hurricane strength before the center reaches the Baja California peninsula in just over 48 h. After landfall, the surface circulation is forecast to dissipate near the 72-h point in agreement with all of the dynamical models. However, the mid-level circulation and the associated rainfall will continue moving across the southwestern United States after the surface circulation dissipates. The initial motion is 350/10. During the forecast period, the hurricane will recurve into the westerlies between a deep-layer ridge over northern Mexico and a large mid- to upper-level trough over California and the adjacent Pacific. This should result in a continued northward motion through tonight, followed by a turn toward the north-northeast on Sunday. The new forecast track is a little to the left of the previous track for the first 12 h, but otherwise is changed little from the previous track. On the forecast track, the center of Rosa or its remnants will move near or over the central and northern portions the Baja California peninsula on Monday and Monday night, and then move into the southwestern United States on Tuesday. Key Messages: 1. The main hazard expected from Rosa or its remnants is very heavy rainfall in Baja California, northwestern Mexico, and the 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. Rosa could also bring tropical storm conditions to portions of the central and northern Baja California peninsula starting on Monday. Interests in those locations should monitor the progress of Rosa. FORECAST POSITIONS AND MAX WINDS INIT 29/2100Z 21.4N 118.7W 90 KT 105 MPH 12H 30/0600Z 22.9N 118.9W 85 KT 100 MPH 24H 30/1800Z 24.8N 118.3W 70 KT 80 MPH 36H 01/0600Z 26.7N 117.1W 55 KT 65 MPH 48H 01/1800Z 28.8N 116.0W 40 KT 45 MPH 72H 02/1800Z 34.5N 113.0W 20 KT 25 MPH...POST-TROP/INLAND 96H 03/1800Z...DISSIPATED $$ Forecaster Beven
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Category:Transportation and Logistics