822 
 WTPZ42 KNHC 200834
 TCDEP2
 
 TROPICAL STORM POLO DISCUSSION NUMBER  17
 NWS NATIONAL HURRICANE CENTER MIAMI FL       EP172014
 200 AM PDT SAT SEP 20 2014
 
 Polo continues to lose organization due to the effects of 25-30 kt
 of easterly vertical wind shear.  The low-level center is exposed
 to the northeast of the convection, and the convection has
 decreased in both coverage and intensity over the last 24 hours.
 In addition, water vapor imagery shows upper-level dry air moving
 over the low-level center.  Satellite intensity estimates are 55 kt
 from TAFB and 45 kt from SAB.  Based on these data and trends since
 the last advisory, the initial intensity is reduced to a somewhat
 uncertain 45 kt.
 
 The initial motion is 315/6.  Polo should gradually turn west-
 northwestward in the next 24-36 hours as a mid-level ridge builds
 north of the cyclone.  Late in the forecast period, the dynamical
 guidance shows the shallow remnant low turning south-southwestward
 as a low-level ridge to the west becomes the dominant steering
 mechanism.  During the first 48 hours, the new track forecast is
 again a little to the north of the previous forecast, and it lies a
 little to the south of the center of the guidance envelope.  After
 that time, the new forecast is similar to the previous forecast.
 
 The large-scale models forecast the shear to continue for the next
 72 hours while Polo moves over cooler sea surface temperatures and
 into a dryer air mass.  This combination should cause steady
 weakening, with the cyclone forecast to weaken to a tropical
 depression in about 36 hours and to degenerate into a remnant low by
 72 hours.  The new intensity forecast is an update of the previous
 advisory and is a blend of the SHIPS, LGEM, and intensity consensus
 guidance.
 
 Based on the forecast track and wind radii, tropical storm force
 winds are most likely to remain south of the Baja California
 peninsula.  However, any deviation to the north of the forecast
 track could bring tropical storm force winds to the southern Baja
 California peninsula.
 
 
 FORECAST POSITIONS AND MAX WINDS
 
 INIT  20/0900Z 20.5N 108.6W   45 KT  50 MPH
  12H  20/1800Z 21.1N 109.5W   40 KT  45 MPH
  24H  21/0600Z 21.8N 110.7W   35 KT  40 MPH
  36H  21/1800Z 22.2N 112.0W   30 KT  35 MPH
  48H  22/0600Z 22.5N 113.2W   25 KT  30 MPH
  72H  23/0600Z 22.5N 115.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
  96H  24/0600Z 21.5N 115.5W   20 KT  25 MPH...POST-TROP/REMNT LOW
 120H  25/0600Z 20.5N 116.0W   20 KT  25 MPH...POST-TROP/REMNT LOW
 
 $$
 Forecaster Beven