AXPZ20 KNHC 211004

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1005 UTC Fri Oct 21 2016

Tropical Weather Discussion for the eastern Pacific Ocean from
the Equator to 32N, east of 140W. The following information is
based on satellite imagery, weather observations, radar, and
meteorological analysis.

Based on 0600 UTC surface analysis and satellite imagery through
0900 UTC.

Numerous moderate to strong thunderstorms continue within 180 nm
across the S semicircle of a small area of low pressure located
near 13.5N114W this morning. Global models suggest the potential
for this low to become better organized over the next two days
as it moves W-NW to NW. However, increasing vertical wind shear
across the N portions of the low may limit development, and is
expected to create a hostile upper environment by 48 hours. This
low has a medium chance of developing into a tropical cyclone
over the next 48 hours.

A gale warning remains in effect for the Gulf of Tehuantepec.
Strong northerly winds are spilling across the Gulf as northerly
winds prevail across SW portions of the Gulf of Mexico this
morning, to the W of a north to south aligned trough across the
eastern Bay of Campeche. N winds have increased to 20-30 kt in
recent hours and are expected to reach minimal gale force by
around sunrise this morning, and persist through Saturday
morning before diminishing to 20-30 kt by Saturday afternoon.
Associated seas will build to 8-12 ft by this afternoon. Strong
high pressure behind a cold front moving southward across the NW
Gulf of Mexico will maintain a strong pressure gradient across
the region and persisting northerly flow across the Gulf for the
next several days. Expect nocturnal winds to pulse to gale force
each night through the weekend with the strongest winds in
occurring overnight through the early morning hours,
particularly between 0600-1200 UTC.

The monsoon trough extends from 12.5N87W to low pres near 12N95W
to 10N104W to low pres near 13.5N114W to low pres near 10.5N131W
to 13N140W. Scattered moderate to strong convection is noted
within 120 nm N and 150 nm S of the trough between 87W and 120W.
Scattered moderate to strong convection is noted within 180 nm
across the SW quadrant of low pres near 12N95W. Numerous
moderate to strong convection is also noted within 180 nm across
the S semicircle of low pres near 13.5N114W.


A weakening ridge extends SE from near 33N137W to just N of the
Revillagigedo Islands at 19N112W. Across the offshore Mexican
waters, gentle to moderate NW to N winds were depicted in
overnight scatterometer data. The combination of these winds and
long period NW swell support seas of 5 to 7 ft along Baja
California and 6-7 ft along the mainland coast. Inside the Gulf
of California, overnight scatterometer data showed fresh NNW
winds throughout most of north and central portions, where seas
are likely 3-5 ft, while moderate winds prevailed across S
portions. The ridge will weaken today as a cold front approaches
the forecast region from the NW, and allow winds and seas to
subside inside the Gulf of California. The front is expected to
stall and weaken near 28N136W over the weekend, with reinforcing
high pres building modestly SE in the wake of the front. A new
pulse of NW swell generated behind the front will spread SE and
yield seas 8-10 ft across N and NW portions by Saturday, and
arrive to the offshore waters of Baja California Norte late
Saturday into Sunday, when seas will build 6-8 ft. Seas are
expected to subside again by Monday night.


Mainly moderate SW winds are noted in scatterometer wind data
overnight S of the monsoon trough and across the waters between
Ecuador and the Galapagos Islands. Seas of 4-7 ft in mixed SW
and NW swell prevail, except to the lee of the Galapagos
Islands. Farther N, a small low pressure center has developed
near 12N95W, and is producing moderate to fresh SW winds roughly
from 05N-12N between 94W and 110W. Seas in this area are in the
7-9 ft range with NW swell. These marine conditions are forecast
to persist during the next few days, as the low moves W to W-NW
around 10 kt.

The pres gradient between the ridge to the N and lower pres near
the monsoon through is generating an area of fresh to locally
strong trade winds from 14N to 27N W of 134W, where seas 7 to 8
ft prevail in mixed NE and NW swell. Winds and seas will
continue to gradually diminish across the west-central waters
during the next couple of days.