707 
 WTPZ41 KNHC 081448
 TCDEP1
 
 Hurricane Sergio Discussion Number  37
 NWS National Hurricane Center Miami FL       EP212018
 800 AM PDT Mon Oct 08 2018
 
 Sergio's structure has remained nearly steady-state for the past 24
 hours.  A solid ring of deep convection surrounds Sergio's giant
 eye, and there is little evidence of any convective bands.  Despite
 upwelling that is presumably occuring beneath the slow moving
 hurricane, cloud tops have actually cooled over the past few hours,
 and satellite intensity estimates from TAFB and SAB have not
 changed. The initial intensity has therefore been held at 80 kt,
 which also agrees with a 1045 UTC UW-CIMSS SATCON estimate.
 
 As long as Sergio can maintain its annular structure in an
 environment of negligible shear, only very gradual weakening is
 expected, despite presumably cooling waters beneath the cyclone
 associated with its slow movement.  The ECMWF and GFS forecast that
 the shear will begin to increase in about 24 to 36 hours, and the
 cyclone will also be reaching much cooler waters shortly after that
 time.  A faster rate of weakening is therefore anticipated beyond
 48 h, in line with the latest intensity consensus, and Sergio is
 forecast to be a tropical storm when it approaches northwestern
 Mexico in a few days.  The cyclone should weaken quickly after
 landfall, and will likely dissipate over the high terrain of
 mainland Mexico, though a 5 day remnant low point is still shown
 for continuity purposes.
 
 Sergio is moving very little right now, and the slow motion will
 likely continue during the day today.  By tonight, a large trough
 centered over the southwestern United States will cause the
 hurricane to accelerate northeastward.  The track guidance is in
 good agreement on the track of Sergio, although there is still some
 uncertainty associated with the timing for when Sergio will reach
 the west coast of the Baja California peninsula. Only minor changes
 were made to the official track forecast, which lies near the middle
 of the guidance envelope and very close to TVCN.
 
 FORECAST POSITIONS AND MAX WINDS
 
 INIT  08/1500Z 15.3N 128.6W   80 KT  90 MPH
  12H  09/0000Z 15.9N 128.4W   75 KT  85 MPH
  24H  09/1200Z 16.6N 127.6W   70 KT  80 MPH
  36H  10/0000Z 17.4N 126.1W   65 KT  75 MPH
  48H  10/1200Z 18.6N 124.0W   65 KT  75 MPH
  72H  11/1200Z 22.3N 119.0W   55 KT  65 MPH
  96H  12/1200Z 27.5N 113.0W   40 KT  45 MPH...INLAND
 120H  13/1200Z 33.0N 105.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
 
 $$
 Forecaster Zelinsky