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Hurricane JOHN


Hurricane John Discussion Number  11
NWS National Hurricane Center Miami FL       EP122018
300 AM MDT Wed Aug 08 2018

As mentioned in the previous discussion, the eye of John passed
about 9 nmi northeast of Socorro Island around 0030 UTC, with the
island possibly being within or just outside the eyewall. Additional
data from an automated station on the island indicate that the
highest sustained wind reported in 15-minute intervals was 48 kt at
0230 UTC, with another 70-kt gust reported at 0200 UTC. The lowest
pressure measured was 970 mb at 0015 UTC, which is probably a 4-5 mb
too low. Since that time, John's eye has occasionally become
cloud-filled, but deep convection has recently developed in the
eyewall. The initial intensity is only decreased slightly to 85 kt
based on a UW-CIMSS ADT estimate of 87 kt and due to the recent
uptick in eyewall convection.

Although John should remain over warm waters for another 12 hours
or so, the general trend calls for steady weakening due to the
ingestion of more stable air to the north, which is expected to
decrease the instability and inner-core convection. The official
intensity forecast is lower than the previous intensity forecast,
and is similar to a blend of the FSSE and HCCA models.

The initial motion estimate is north-northwestward or 330/10 kt.
John is expected to return to a northwestward motion at a slightly
faster forward speed later this morning, and then continue that
motion for the next 72 hours. After that time, a turn toward the
west-northwestward is forecast due to the weakening and shallow
cyclone being steered by the low-level trade wind flow. The new
official forecast remains in close agreement with the previous
advisory, and lies down the middle of the guidance envelope.

Although the core 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.


INIT  08/0900Z 20.0N 111.6W   85 KT 100 MPH
 12H  08/1800Z 21.1N 112.8W   80 KT  90 MPH
 24H  09/0600Z 22.8N 114.8W   75 KT  85 MPH
 36H  09/1800Z 24.2N 116.8W   65 KT  75 MPH
 48H  10/0600Z 25.3N 119.0W   50 KT  60 MPH
 72H  11/0600Z 26.8N 122.9W   35 KT  40 MPH...POST-TROPICAL
 96H  12/0600Z 27.0N 125.6W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  13/0600Z 27.3N 127.2W   15 KT  15 MPH...POST-TROP/REMNT LOW

Forecaster Stewart