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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