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TROPICAL STORM RICK DISCUSSION NUMBER   6
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP212015
200 PM MST THU NOV 19 2015

Rick is exhibiting a shear pattern, with the low-level center of the
cyclone estimated to be near the southeastern edge of a curved
convective band over the northwestern semicircle of the
circulation.  A 1616 UTC ASCAT-A overpass indicated peak
uncontaminated winds of 36 kt, so the initial intensity is held at
35 kt.  Some further reduction in southeasterly shear over the
cyclone should occur tonight or early Friday while other large-
scale factors remain generally favorable, which could allow for some
additional intensification over the next 24 hours or so.  However,
the broad nature of the cyclone's circulation shown by the
scatterometer data is most likely to result in only slow
strengthening before a substantial increase in west-southwesterly
shear occurs in about 36 to 48 hours.  Even higher shear is expected
over Rick by 72 hours once the storm gains more latitude
and a trough in the eastern Pacific subtropics nears the cyclone
from the west.  A rapid decoupling of the cyclone should occur not
long after that time, and remnant low status is indicated in 96
hours, though this could occur sooner.  The new intensity forecast
is is a bit lower than the previous one and slightly lower than the
multi-model consensus through 48 hours.

ASCAT passes were quite helpful in determining that the location of
Rick's low-level center was farther south and west than previously
estimated.  Those fixes indicate that Rick has turned northwestward
with an initial motion estimate of 320/07.  A mid-level ridge over
mainland Mexico should build north of Rick tonight and tomorrow,
resulting in a west-northwestward turn with an increase in forward
speed.  Once Rick reaches the western periphery of this ridge in
about 3 days, a more poleward track is forecast until dissipation.
The new track forecast is adjusted back to the left, primarily due
the center re-location.

FORECAST POSITIONS AND MAX WINDS

INIT  19/2100Z 14.8N 107.0W   35 KT  40 MPH
 12H  20/0600Z 15.5N 108.3W   40 KT  45 MPH
 24H  20/1800Z 16.2N 109.9W   45 KT  50 MPH
 36H  21/0600Z 16.9N 111.6W   45 KT  50 MPH
 48H  21/1800Z 17.5N 112.8W   40 KT  45 MPH
 72H  22/1800Z 19.0N 114.4W   30 KT  35 MPH
 96H  23/1800Z 21.2N 115.1W   20 KT  25 MPH...POST-TROP/REMNT LOW
120H  24/1800Z...DISSIPATED

$$
Forecaster Kimberlain

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