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
  
 

This page was last modified on: Thu, Jul 23 2020 - 2003 UTC
Send comments to: Ryan Lyman