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Hurricane Rosa Forecast Discussion Number 23
2018-09-30 22:33:34| National Hurricane Center (East Pacific)
Issued at 200 PM PDT Sun Sep 30 2018 534 WTPZ45 KNHC 302033 TCDEP5 Hurricane Rosa Discussion Number 23 NWS National Hurricane Center Miami FL EP202018 200 PM PDT Sun Sep 30 2018 An Air Force Reserve Unit Hurricane Hunter aircraft recently investigated Rosa, and found peak 700-mb flight-level winds that still supported minimal hurricane intensity. However, the SFMR-observed surface winds were somewhat lower, which is not surprising since the system has minimal deep convection and is over 24-25 deg SSTs. Given that the central pressure is still fairly low, 982 mb, Rosa is being maintained, perhaps generously, as a hurricane for this advisory. With increasing shear and cooler waters ahead for the system, weakening seems inevitable. The official intensity forecast is similar to the latest HWRF model prediction, and shows Rosa weakening to a depression by the time it reaches the southwest United States. The initial motion is north-northeastward, or 025/10 kt. The track forecast scenario remains essentially unchanged from the previous couple of advisory packages. The flow on the eastern side of a large mid-level trough approaching from the west should steer Rosa on a north-northeastward track for the next couple of days. The official track forecast is very close to the latest dynamical model consensus. The wind radii have been adjusted slightly based on data from a recent ASCAT scatterometer overpass. 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 30/2100Z 25.2N 118.1W 65 KT 75 MPH 12H 01/0600Z 26.5N 117.4W 55 KT 65 MPH 24H 01/1800Z 28.1N 116.2W 45 KT 50 MPH 36H 02/0600Z 29.9N 115.0W 40 KT 45 MPH...INLAND 48H 02/1800Z 32.3N 113.9W 30 KT 35 MPH...INLAND 72H 03/1800Z 37.0N 112.0W 20 KT 25 MPH...POST-TROP/INLAND 96H 04/1800Z...DISSIPATED $$ Forecaster Pasch
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