777 
 WTPZ45 KNHC 290242
 TCDEP5
 
 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
 
 

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