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 917 
 WTPZ45 KNHC 280235
 TCDEP5
 
 Tropical Storm Miriam Discussion Number   8
 NWS National Hurricane Center Miami FL       EP152018
 800 PM PDT Mon Aug 27 2018
 
 Miriam hasn't changed much over the past several hours. Last-light
 visible imagery and a couple of microwave overpasses around 0000 UTC
 show that the tropical storm remains lightly sheared from the
 northwest. Although outflow from the deepest inner-core convection
 seems to have become better established, cloud tops from outer bands
 to the north and east are still moving toward the center of the
 cyclone, indicating there is still shear below the outflow layer.
 The initial intensity has been held at 55 kt, in agreement with
 nearly all of the objective and subjective satellite estimates.
 
 Miriam continues to move westward, and the forward speed is now 10
 kt. The guidance remains in very good agreement on the track of
 Miriam for the next 36 hours, with only slight speed differences
 between the various models.  Beyond that time, the tropical storm
 should begin to turn north-northwestward toward a break in the
 subtropical ridge created by a mid- to upper-level trough over the
 central Pacific.  The model spread increases drastically at this
 point, with the ECMWF showing a quicker turn and a faster
 north-northwestward motion than the GFS, with most of the other
 guidance in between.  For now, the NHC forecast has not been
 significantly changed, and remains near the corrected consensus,
 HCCA.
 
 The moderate shear currently affecting Miriam is forecast by the
 global models to continue for the next 24 h or so, preventing the
 cyclone from strengthening significantly.  Between 24 and 72 h, this
 shear is forecast to decrease, allowing the cyclone to strengthen at
 a quicker rate.  By the end of the forecast period, Miriam should
 quickly weaken as it encounters higher shear and cooler SSTs.  The
 HWRF is a notable outlier, showing much faster intensification, but
 it is possible this model is not properly representing the shear
 currently affecting Miriam.  That said, if the shear decreases
 sooner than expected, it is possible that Miriam could intensify
 much faster than currently anticipated.  The new NHC intensity
 forecast is close to the intensity consensus, and shows a slightly
 slower initial intensification rate for Miriam, and a faster decay
 by day 5, than the previous advisory.
 
 FORECAST POSITIONS AND MAX WINDS
 
 INIT  28/0300Z 14.0N 132.5W   55 KT  65 MPH
  12H  28/1200Z 14.0N 134.1W   60 KT  70 MPH
  24H  29/0000Z 14.0N 136.2W   65 KT  75 MPH
  36H  29/1200Z 14.2N 138.1W   75 KT  85 MPH
  48H  30/0000Z 15.0N 139.5W   85 KT 100 MPH
  72H  31/0000Z 17.5N 141.1W   85 KT 100 MPH
  96H  01/0000Z 21.5N 142.0W   65 KT  75 MPH
 120H  02/0000Z 26.0N 144.0W   40 KT  45 MPH
 
 $$
 Forecaster Zelinsky
 
 
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