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ZCZC MIATCDEP5 ALL TTAA00 KNHC DDHHMM Hurricane Rosa Discussion Number 16 NWS National Hurricane Center Miami FL EP202018 800 PM PDT Fri Sep 28 2018 The satellite appearance of Rosa continues to degrade due to an ongoing eyewall cycle with weaker convection noted near the eyewall and an apparent moat region. Dvorak estimates continue to fall, and a blend from all agencies gives 95 kt as an initial wind speed. Continued weakening is in the forecast while Rosa moves across progressively cooler SSTs into a higher shear and drier environment. There is some chance that the weakening could pause if the eyewall cycle finishes, but that's less likely as the cyclone encounters the less favorable environment. Thus Rosa is forecast to continue to gradually weaken until it approaches Baja California as a tropical storm. The intensity guidance is in good agreement on this scenario, and the new NHC prediction is basically an update of the previous one after accounting for the initial winds. Rosa has turned to the north-northwest and accelerated, with an initial motion of 340/8. The cyclone should turn to the north tomorrow and move faster to the north-northeast on Sunday ahead of a mid- to upper-level trough approaching the west coast of the United States. There are no substantial guidance changes to consider, and with the model consensus being quite reliable so far, it makes sense to stay near that aid, which is also very close to the previous forecast. 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 in a few days. Interests in those locations should monitor the progress of Rosa. FORECAST POSITIONS AND MAX WINDS INIT 29/0300Z 18.4N 118.0W 95 KT 110 MPH 12H 29/1200Z 19.5N 118.4W 85 KT 100 MPH 24H 30/0000Z 21.4N 118.8W 75 KT 85 MPH 36H 30/1200Z 23.3N 118.6W 65 KT 75 MPH 48H 01/0000Z 25.1N 117.9W 55 KT 65 MPH 72H 02/0000Z 28.9N 116.1W 40 KT 45 MPH 96H 03/0000Z 36.0N 112.0W 15 KT 15 MPH...POST-TROP/REMNT LOW 120H 04/0000Z...DISSIPATED $$ Forecaster Blake NNNN