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 595 
 WTPZ41 KNHC 200844
 TCDEP1
 
 TROPICAL STORM RICK DISCUSSION NUMBER   8
 NWS NATIONAL HURRICANE CENTER MIAMI FL       EP212015
 200 AM MST FRI NOV 20 2015
 
 Rick is sending mixed signals tonight with regard to its
 organization and intensity.  On one hand, the convective banding is
 a little better defined, and Dvorak T-numbers are now T3.0 from SAB
 and T2.5 from TAFB.  On the other hand, recent scatterometer data
 indicate that the maximum winds remain about 35 kt, with the
 tropical-storm-force winds confined to a small area west of the
 center.
 
 The initial motion remains west-northwestward, or 295/11 kt.  A
 mid-level ridge that extends westward across central Mexico is
 forecast to build farther westward over the Pacific waters during
 the next 24 hours, which should keep the cyclone on a west-
 northwestward course for the next couple of days.  By Sunday, the
 western extent of the ridge will be eroded by a shortwave trough,
 causing Rick to turn gradually northwestward and northward on days
 3-5.  The track models all agree on this general scenario, but the
 overall guidance envelope has shifted westward from the previous
 cycle, especially beyond 36 hours.  Therefore, the updated NHC track
 forecast is also shifted westward and lies very close to the TVCE
 model consensus and the Florida State Superensemble.
 
 Deep-layer shear near Rick is very low at the moment and should
 remain generally light for the next 36-48 hours.  In addition, sea
 surface temperatures are sufficiently warm for intensification.
 However, a major limiting factor appears to be the presence of
 mid-level dry air, with the 700-500 mb relative humidity expected to
 remain around 50 percent for the next few days.  Therefore, only
 slight strengthening is anticipated in the short term.  After 48
 hours, a marked increase in southwesterly shear should cause Rick to
 weaken and degenerate to a remnant low, possibly as early as 72
 hours, when the associated deep convection is sheared away from the
 low-level center.  The latest global models suggest that the remnant
 low may now last through 120 hours.  There is not much spread among
 the intensity models, and the official intensity forecast mainly
 follows the IVCN model consensus.
 
 FORECAST POSITIONS AND MAX WINDS
 
 INIT  20/0900Z 15.9N 109.4W   35 KT  40 MPH
  12H  20/1800Z 16.5N 110.8W   40 KT  45 MPH
  24H  21/0600Z 17.1N 112.4W   40 KT  45 MPH
  36H  21/1800Z 17.6N 113.9W   40 KT  45 MPH
  48H  22/0600Z 18.1N 115.1W   40 KT  45 MPH
  72H  23/0600Z 20.1N 116.9W   30 KT  35 MPH...POST-TROP/REMNT LOW
  96H  24/0600Z 22.0N 117.5W   20 KT  25 MPH...POST-TROP/REMNT LOW
 120H  25/0600Z 22.5N 117.0W   15 KT  15 MPH...POST-TROP/REMNT LOW
 
 $$
 Forecaster Berg
 
 
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