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TROPICAL STORM KAY DISCUSSION NUMBER  12
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP122016
900 AM MDT SUN AUG 21 2016

Kay is holding its own.  A new burst of very cold-topped convection
has developed since the last advisory, coinciding with the diurnal
convective maximum.  An earlier microwave pass suggested some tilt
between the low- and mid-level centers, indicative that
southeasterly shear diagnosed over the storm could be slightly
stronger than indicated in analyses. Satellite classifications are
T2.5/35 kt and T3.0/45 kt from SAB and TAFB, respectively, and ADT
values are around T3.0.  A blend of these data is used to set the
initial intensity estimate to 40 kt.

Kay is living on borrowed time.  Within 24 hours, the cyclone
should cross the 26-deg C isotherm and encounter a drier and more
stable air mass.  Weakening should have begun by then if not
before, and a rapid decay is expected in 24 to 48 hours when Kay
moves roughly perpendicular to a steep gradient of lower SSTs and is
affected by increasingly unfavorable thermodynamics conditions.
Remnant low status is indicated in 48 hours, and the system should
dissipate just after 72 hours per the global models. The new NHC
intensity forecast maintains the cyclone's current intensity for
the next 12 hours, but overall is similar to the previous one and
the bulk of the intensity guidance after that time.

Kay is moving west-northwestward to northwestward, with an initial
motion estimate of 305/06.  For the next day or so, this general
motion should continue while the cyclone is steered by the weak flow
around the western periphery of a mid-level ridge over northern
Mexico.  After the cyclone weakens, the shallow system should turn
westward with some increase in forward speed due to a building
low-level ridge.  The NHC track forecast is essentially an update of
the previous one, close to a blend of the GFS and ECMWF model
solutions.


FORECAST POSITIONS AND MAX WINDS

INIT  21/1500Z 21.2N 114.6W   40 KT  45 MPH
 12H  22/0000Z 21.6N 115.5W   40 KT  45 MPH
 24H  22/1200Z 22.0N 116.5W   35 KT  40 MPH
 36H  23/0000Z 22.4N 117.8W   35 KT  40 MPH
 48H  23/1200Z 22.9N 119.4W   30 KT  35 MPH...POST-TROP/REMNT LOW
 72H  24/1200Z 23.6N 122.8W   25 KT  30 MPH...POST-TROP/REMNT LOW
 96H  25/1200Z...DISSIPATED

$$
Forecaster Kimberlain

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