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Tropical Storm Kristy Discussion Number   4
NWS National Hurricane Center Miami FL       EP132018
200 PM PDT Tue Aug 07 2018

Geostationary satellite and microwave images indicate that Kristy
has well-defined curved bands, but the convection in these bands
has decreased during the past several hours.  A recent ASCAT pass
showed maximum winds of about 40 kt.  Based on that data and Dvorak
classifications, the initial intensity is again held at 45 kt.

Kristy has been moving just south of due west during the past 12
hours, and the initial motion estimate is 260/11 kt.  The models
agree that a decrease in forward speed and a turn to the
west-northwest is expected to begin tonight or on Wednesday, but
that is about all they agree on for the future track of Kristy.
There remains significant spread in the models about how the storm
will interact with Hurricane John to its northeast.  The GFS
continues to show Kristy being pulled northward and then
northeastward into the outer circulation of John. On the other hand,
the ECMWF has been consistent in showing little interaction between
the tropical cyclones, and keeps Kristy moving on a westward or
west-northwestward path.  The NHC official track forecast lies
between these scenarios and is close to the recent run of the UKMET
model.  This forecast has been adjusted to the north and east of the
previous one to get closer to the middle of the guidance envelope.
It should be noted that the track forecast is of low confidence
given the very different model solutions.

Kristy's struggles are likely due to the influences of dry air and
moderate shear.  The SHIPS model shows the shear decreasing during
the next couple of days, which could allow the storm to gradually
strengthening during that time period.  Beyond a couple of days,
however, cooler waters and a more stable airmass should end the
strengthening trend and result in weakening.  The NHC intensity
forecast is largely an update of the previous one and lies close to
the HCCA model.

FORECAST POSITIONS AND MAX WINDS

INIT  07/2100Z 13.7N 127.1W   45 KT  50 MPH
 12H  08/0600Z 13.9N 128.2W   50 KT  60 MPH
 24H  08/1800Z 14.5N 129.2W   55 KT  65 MPH
 36H  09/0600Z 15.4N 129.9W   60 KT  70 MPH
 48H  09/1800Z 16.4N 130.2W   65 KT  75 MPH
 72H  10/1800Z 18.5N 130.2W   60 KT  70 MPH
 96H  11/1800Z 21.0N 130.8W   55 KT  65 MPH
120H  12/1800Z 23.0N 132.5W   45 KT  50 MPH

$$
Forecaster Cangialosi

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