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 340 
 WTPZ42 KNHC 262033
 TCDEP2
 
 TROPICAL DEPRESSION SEVENTEEN-E DISCUSSION NUMBER   1
 NWS NATIONAL HURRICANE CENTER MIAMI FL       EP172015
 400 PM CDT SAT SEP 26 2015
 
 Satellite imagery suggests that the area of low pressure several
 hundred miles southwest of Acapulco, Mexico, has developed a well-
 defined circulation and has enough organized deep convection to
 be declared a tropical depression.  The initial wind speed is set to
 30 kt in agreement with a Dvorak estimate from TAFB.
 
 Recent fixes suggest an initial motion of 345/03, but it would not
 be surprising if the motion were actually even more northerly. A
 slow northward motion is expected during the next 24 to 36 hours as
 the depression rounds the western side of a weak mid-level ridge
 along 95W.  In about 36 h, the cyclone should encounter the
 increasing westerly or west-southwesterly flow around a mid- to
 upper-level trough over the northwestern Gulf of Mexico and turn
 northeastward, a motion that could bring the cyclone's center inland
 as predicted by the GFS and HWRF in 72 to 84 hours.  An alternative
 scenario, supported by the ECMWF, is for the shear to become
 prohibitively high just after 72 hours and result in a decoupling
 of the cyclone. The shallow remnant circulation would then likely
 drift west-northwestward in the low-level flow away from the coast.
 The official track forecast brings the center close to the coast in
 72 hours but does not explicitly show a landfall.  The overall track
 forecast is weighted more heavily toward the ECMWF solution which
 seems to have a better handle on the depression's initial motion.
 
 Although the waters are plenty warm and the atmospheric moisture
 high, westerly shear associated with the mid- to upper-level trough
 over the Gulf of Mexico is expected to be an increasingly important
 factor in the cyclone's intensification.  The shear should not be
 high enough initially to prevent a climatological rate of
 development during the next day or so.  However, global models show
 at least 20 kt of shear in 36-48 hours, which makes significant
 intensification less likely after that time.  The official intensity
 forecast is between the statistical and dynamical guidance through
 72 h and above the multi-model consensus.  Rapid weakening is
 forecast after that time, either as a result of the cyclone's moving
 inland or the possible decoupling of the cyclone.
 
 FORECAST POSITIONS AND MAX WINDS
 
 INIT  26/2100Z 13.3N 103.0W   30 KT  35 MPH
  12H  27/0600Z 14.0N 103.1W   40 KT  45 MPH
  24H  27/1800Z 14.7N 103.1W   50 KT  60 MPH
  36H  28/0600Z 15.4N 102.9W   55 KT  65 MPH
  48H  28/1800Z 15.9N 102.6W   55 KT  65 MPH
  72H  29/1800Z 16.6N 101.6W   55 KT  65 MPH
  96H  30/1800Z 17.1N 102.1W   30 KT  35 MPH
 120H  01/1800Z 17.2N 102.5W   30 KT  35 MPH...POST-TROP/REMNT LOW
 
 $$
 Forecaster Kimberlain
 
 
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