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TROPICAL STORM KAY DISCUSSION NUMBER   4
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP122016
900 AM MDT FRI AUG 19 2016

Shortwave infrared imagery and a 0850 UTC AMSR2 microwave image
show that Kay's center of circulation continues to be sheared
to the northeast of the deep convection.  The coldest cloud tops
are confined to a curved band wrapping in toward the center from the
southern half of the system.  The initial intensity remains at 35
kt and is based on a consensus of Final-T number (T2.5) satellite
intensity estimates from TAFB and SAB.  Global models and the SHIPS
guidance indicate that the shear should relax within the next 24
hours.  Therefore, some strengthening is expected through day 2.
For the remaining portion of the forecast, Kay should gradually
weaken as it moves into a more stable thermodynamic environment and
over cooler sea surface temperatures of around 25C.  The large-scale
models are also showing increasing upper-level easterlies at that
time.  The NHC intensity forecast is based on the IVCN consensus and
reflects Kay degenerating into a remnant low in 96 hours.

The initial motion is a little uncertain, but based on the
earlier microwave images and surface observations from Socorro
Island, Kay appears to be moving at 320/7 kt.  The Socorro Island
observations during the past few hours indicate that the center of
Kay is passing very close to the island.  The cyclone should move
northwestward around the western portion of a mid- to upper-level
tropospheric ridge over northwestern Mexico during the next couple
of days.  The GFS and its ensemble mean have shifted considerably
toward the left, closer to the other global and regional guidance,
and consequently, have reduced the earlier noted large model spread.
Beyond day 3, Kay is forecast to turn slowly toward the
west-northwest in response to the low-level tradewind flow steering
the shallow remnant low.  The official forecast is close to the TVCN
consensus and is slightly faster than the previous advisory beyond
the 48 hour period due primarily to the significant shift in the
GFS.


FORECAST POSITIONS AND MAX WINDS

INIT  19/1500Z 19.1N 111.5W   35 KT  40 MPH
 12H  20/0000Z 19.7N 112.0W   40 KT  45 MPH
 24H  20/1200Z 20.5N 112.6W   40 KT  45 MPH
 36H  21/0000Z 21.0N 113.0W   40 KT  45 MPH
 48H  21/1200Z 21.6N 113.6W   35 KT  40 MPH
 72H  22/1200Z 22.2N 114.7W   30 KT  35 MPH
 96H  23/1200Z 23.0N 116.5W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  24/1200Z 23.7N 118.9W   20 KT  25 MPH...POST-TROP/REMNT LOW

$$
Forecaster Roberts

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