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Tropical Storm John Discussion Number  15
NWS National Hurricane Center Miami FL       EP122018
200 AM PDT Thu Aug 09 2018

The satellite presentation of John continues to degrade, with the
central dense overcast decreasing in both size and intensity.
Scatterometer data also indicate that the low-level center is
southwest of the mid-level center, hinting that the circulation
could be decoupling.  The initial wind speed is set to 60 kt, near
the latest TAFB and CIMSS-ADT estimates.  John is rapidly moving
over cool waters into a dry stable airmass, which should cause
further weakening. The new NHC wind speed prediction follows the
trend of the HFIP corrected-consensus guidance (a top performer this
year), leading to a small reduction in the forecast.  Remnant low
status is forecast after 36 hours when the cyclone moves over
sub-22C waters with little environmental instability.

John has turned leftward, now estimated at 305/14 kt.  The tropical
cyclone should continue to gradually turn toward the west-northwest
over the next few days as it moves around a ridge situated over the
southwestern United States. John's remnants are likely to drift
northward or northwestward at long range in a region of weak
steering currents. The track guidance is in very good agreement and
the official forecast is close to the previous one.

John is producing large swells that are already affecting portions
of the coast of the southern Baja California peninsula. These swells
are predicted to spread northward along the west coast of the
peninsula today and reach portions of the coast of southern
California by tonight.  These swells are likely to cause life-
threatening surf and rip current conditions.  Please consult
products from your local weather office.


FORECAST POSITIONS AND MAX WINDS

INIT  09/0900Z 23.7N 115.9W   60 KT  70 MPH
 12H  09/1800Z 24.8N 117.8W   50 KT  60 MPH
 24H  10/0600Z 25.9N 119.9W   40 KT  45 MPH
 36H  10/1800Z 26.9N 121.8W   35 KT  40 MPH
 48H  11/0600Z 27.5N 123.4W   30 KT  35 MPH...POST-TROP/REMNT LOW
 72H  12/0600Z 28.1N 125.5W   25 KT  30 MPH...POST-TROP/REMNT LOW
 96H  13/0600Z 29.0N 126.0W   20 KT  25 MPH...POST-TROP/REMNT LOW
120H  14/0600Z...DISSIPATED

$$
Forecaster Blake

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