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Tropical Depression NINETEEN-E Forecast Discussion

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WTPZ44 KNHC 261445

800 AM PDT MON SEP 26 2016

Scatterometer data from around 0600 UTC indicated that the area of
low pressure located near 140W had a well-defined circulation, with
peak reliable wind vectors of 28 kt.  Deep convection associated
with this system has since become much better organized.  Satellite
classifications are T2.0 and T2.5, and the low is designated as a
tropical depression based on these satellite data.

Light northwesterly shear, warm waters of around 28 deg C and an
increasingly diffluent flow aloft over the cyclone support
intensification during the next 2 to 3 days.  The large divergence
expected over the depression is related to a mid-level cyclone seen
in water vapor imagery near 18N 140W that is forecast to retrograde.
The only negative factor is marginal mid-level moisture that
is forecast to decrease further.  Once the system gains sufficient
latitude after 72 hours, it is likely to become vulnerable to much
stronger westerly flow aloft.  In fact, with 30 to 40 kt of westerly
shear forecast over the cyclone by day 4, rapid weakening should
occur, and the system is forecast to be a remnant low by that time.
The NHC intensity forecast is a blend of the statistical and
dynamical guidance through 72 hours and is below both sets of output
after that time.

The low was moving just south of due west during the last 24 hours,
but appears to have recently turned toward the northwest.  Given
the sudden change in heading, the initial motion estimate of 305/04
is rather uncertain.  Global models show the cyclone turning
northward within 24 hours and then moving north-northeastward after
that for the next few days while it rotates around the mid-level
low to the northwest of the cyclone.  Once the cyclone weakens
appreciably after 72 hours, a turn toward the west is likely when
the remnant low is steered by the trade wind flow.  The NHC track
forecast is a left of the multi-model consensus, close to a
consensus without the GFDL model.


INIT  26/1500Z 11.6N 139.6W   30 KT  35 MPH
 12H  27/0000Z 12.0N 139.8W   40 KT  45 MPH
 24H  27/1200Z 12.8N 139.5W   45 KT  50 MPH
 36H  28/0000Z 13.6N 138.8W   50 KT  60 MPH
 48H  28/1200Z 14.4N 138.2W   55 KT  65 MPH
 72H  29/1200Z 16.1N 138.0W   50 KT  60 MPH
 96H  30/1200Z 17.2N 139.5W   35 KT  40 MPH...POST-TROP/REMNT LOW
120H  01/1200Z 17.3N 142.3W   20 KT  25 MPH...POST-TROP/REMNT LOW

Forecaster Kimberlain