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Tropical Depression THIRTEEN-E


Tropical Depression Thirteen-E Discussion Number   1
NWS National Hurricane Center Miami FL       EP132017
800 AM PDT Fri Aug 18 2017

Deep convection associated with the disturbance located over the
open eastern Pacific Ocean has become better organized early this
morning, and a primary convective band now wraps around the western
half of the circulation.  Shortwave-IR and first-light visible
imagery suggest that a complex, but closed surface circulation
exists. NHC is therefore initiating advisories on Tropical
Depression Thirteen-E.

The initial intensity is set at 30 kt, in agreement with the max
winds measured in an earlier ASCAT pass and the latest Dvorak
classification from TAFB.  Light easterly vertical wind shear has
thus far limited convection to the western half of the circulation,
but the GFS and ECMWF agree that the shear will lessen as the system
moves farther west.  Overall, the environment appears conducive for
intensification for the next 3 days or so, and the NHC forecast
indicates that the cyclone will become a hurricane by the end of
this weekend.  After that time, the cyclone will begin to weaken
over much cooler waters.  The NHC forecast is very close to the
multi-model consensus, IVCN.

Since the center has only recently formed, the initial motion
estimate is a fairly uncertain 285/13 kt.  There is fairly good
agreement among the global models that the tropical cyclone will
move generally westward to west-northwestward for the next 72 h
along the southern boundary of a mid-level ridge that extends
westward well into the eastern Pacific basin.  A weakness in the
ridge is forecast to develop in about 3 days that should cause
the cyclone to slow and turn more toward the northwest and
eventually toward the north-northwest.  The official forecast is
close to a blend of the GFS and ECMWF models.


INIT  18/1500Z 14.8N 116.5W   30 KT  35 MPH
 12H  19/0000Z 15.4N 118.4W   35 KT  40 MPH
 24H  19/1200Z 15.9N 121.0W   45 KT  50 MPH
 36H  20/0000Z 16.6N 123.6W   55 KT  65 MPH
 48H  20/1200Z 17.3N 126.1W   65 KT  75 MPH
 72H  21/1200Z 19.1N 130.3W   75 KT  85 MPH
 96H  22/1200Z 21.4N 132.4W   65 KT  75 MPH
120H  23/1200Z 23.6N 133.3W   45 KT  50 MPH

Forecaster Zelinsky