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Hurricane John Discussion Number  13
NWS National Hurricane Center Miami FL       EP122018
300 PM MDT Wed Aug 08 2018

John has shown some improved organization since the last advisory
as the system has formed a 20 n mi wide cloud-filled eye.  Satellite
intensity estimates remain in the 65-77 kt range, so the initial
intensity will be held at 75 kt for this advisory.  Other than
this temporary break in the weakening, there is little change to the
intensity forecast, as the forecast track takes John over
progressively colder sea surface temperatures and into a more stable
air mass. The new intensity forecast is in the center of the
intensity guidance, with John expected to weaken to a tropical storm
in 24 h or less and to a remnant low between 48-72 h.

The initial motion is 325/13, a bit faster than earlier.  A
combination of an upper-level low near 19N 124W and a mid- to
upper-level ridge over northwestern Mexico should steer John
northwestward for the next 36 h or so.  After that, the cyclone or
its remnants is forecast to turn west-northwestward in the low-level
trade wind flow.  Near the end of the forecast period, a slow motion
is expected as the remnants of John move into an area of light
steering currents.  The guidance envelope has shifted a little to
the north from the previous advisory, and the new forecast track is
north of and faster than the previous forecast.

Although the center of John is forecast to remain well offshore of
the Baja California Peninsula, a surge of moisture around John's
outer circulation is expected to bring some locally heavy rainfall
to portions of Baja California Sur during the next couple of days.
Therefore, interests in the southern portion of the Baja California
Peninsula should monitor the progress of John.

John is also 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 late Thursday.  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  08/2100Z 22.0N 113.5W   75 KT  85 MPH
 12H  09/0600Z 23.2N 115.0W   65 KT  75 MPH
 24H  09/1800Z 24.6N 117.2W   55 KT  65 MPH
 36H  10/0600Z 25.8N 119.3W   45 KT  50 MPH
 48H  10/1800Z 26.7N 121.4W   40 KT  45 MPH
 72H  11/1800Z 27.5N 124.5W   30 KT  35 MPH...POST-TROP/REMNT LOW
 96H  12/1800Z 28.0N 126.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  13/1800Z 29.0N 126.0W   15 KT  15 MPH...POST-TROP/REMNT LOW

$$
Forecaster Beven

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