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 791 
 WTPZ42 KNHC 150852
 TCDEP2
 
 Tropical Storm Tara Discussion Number   4
 NWS National Hurricane Center Miami FL       EP222018
 400 AM CDT Mon Oct 15 2018
 
 The satellite presentation of the tropical cyclone has improved
 somewhat overnight, with convection continuing to burst over the
 western and northwestern portions of the circulation.  The center
 is slightly more embedded within the southeastern portion of the
 cold cloud tops, but easterly shear continues to restrict
 convection over the eastern portion of the system.  A couple of
 ASCAT passes around 0400 UTC were helpful in locating the center of
 the cyclone and both indicated peak winds of 25 to 30 kt to the
 west of the center.  Dvorak classifications at 0600 UTC were
 T2.5 (35 kt) from both SAB and TAFB, and given the increase in
 organization, the system has been upgraded to a 35-kt tropical
 storm. The nineteenth named storm of the 2018 eastern North Pacific
 hurricane season.
 
 Recent microwave imagery and the ASCAT data show that Tara has not
 moved much, and the initial motion estimate is stationary for
 this advisory.  Although the tropical storm is located within an
 area of weak steering currents and little overall motion is
 expected during the next couple of days, the track guidance has
 become much more divergent this cycle.  The GFS and UKMET models
 have trended northward and now bring Tara near the southwestern
 coast of Mexico within the next day or so.  On the other hand, the
 ECMWF takes Tara southeastward and southward away from the coast.
 The various consensus aids have trended northward in the
 short-term, and the new NHC track forecast has been nudged in that
 direction through 36 hours, but it is not as far north as the GFS,
 GFS ensemble mean, and UKMET models.  After 48 hours, a ridge is
 forecast to build westward across central Mexico, which should cause
 Tara to turn west-northwestward at a slightly faster forward speed.
 Given the spread in the guidance and its recent trends, the track
 forecast is of low confidence.
 
 The intensity forecast is also very challenging and of low
 confidence this morning. Tara is expected to remain under the
 influence of easterly shear during the next day or two.  The shear,
 however, is not expected to be strong enough to prevent gradual
 strengthening.  After that time, the intensity forecast depends on
 how close to the coast the cyclone moves.  If Tara gets too close to
 southwestern Mexico, the small cyclone is likely to weaken.  If it
 stays offshore, however, the shear is forecast to decrease which
 should allow for additional strengthening.  Since the NHC track
 forecast keeps Tara offshore, it calls for gradual strengthening
 through 72 hours, but it is not as aggressive as before since most
 of the guidance is lower than before.  Increasing southwesterly
 shear by days 4 and 5 should lead to weakening, and although the NHC
 forecast keeps Tara a tropical storm trough the period, most of the
 global models weaken and dissipate the system by the end of the
 week.
 
 Due to the uncertainties in the track forecast, the government of
 Mexico has issued a Tropical Storm Watch for a portion of the coast
 of southwest Mexico.  Regardless of how close Tara tracks to
 southwestern Mexico, heavy rainfall will be the primary threat along
 the coast of southwestern Mexico due to the system's slow motion,
 and life-threatening flash flooding will be possible in mountainous
 areas.
 
 
 FORECAST POSITIONS AND MAX WINDS
 
 INIT  15/0900Z 17.5N 104.2W   35 KT  40 MPH
  12H  15/1800Z 17.8N 104.4W   40 KT  45 MPH
  24H  16/0600Z 17.9N 104.5W   45 KT  50 MPH
  36H  16/1800Z 17.9N 104.7W   45 KT  50 MPH
  48H  17/0600Z 18.0N 105.3W   50 KT  60 MPH
  72H  18/0600Z 18.3N 106.5W   55 KT  65 MPH
  96H  19/0600Z 19.0N 108.0W   50 KT  60 MPH
 120H  20/0600Z 19.0N 108.0W   45 KT  50 MPH
 
 $$
 Forecaster Brown
 
 
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