AXPZ20 KNHC 170958

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1005 UTC Tue Jan 17 2017

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
0930 UTC.


A trough extends from 05N77W to southwest to 03N79W to low
pressure near 01N83W 1010 mb. The ITCZ axis extends from 03N97W
to 02N105W to 07N114W to 07N123W to 06N123W to beyond 06N140W.
Scattered moderate convection is within 60 nm south of the axis
between 110W and 123W.



A ridge extends from a 1025 mb high pressure center located at
28N127W southeastward to the Revillagigedo Islands situated about
265 miles southwest of the southern tip of the Baja California
peninsula. Gentle to moderate winds prevail over the forecast
waters off the coast of Baja California and over the Gulf of
Tehuantepec. Light to gentle winds prevail over the waters off
southwest Mexico and the Gulf of California. Seas are in the 5-7
ft range off the coast of Baja California, 2 ft or less over the
Gulf of California, and 4-6 ft elsewhere.

Global models are in good consensus in suggesting that a
weakening cold front will move over the waters off Baja
California Norte by Thursday, then become diffuse ahead of a
stronger cold front that will quickly move across Baja
California and the Gulf of California Friday through Saturday.
The second front will be accompanied by fresh to strong winds and
a large set of northwest swell forecast to bring very large
seas in the range of 12-19 ft to the waters off Baja California
Norte on Saturday, and seas of 8-13 ft to the waters off Baja
California Sur at that same time as depicted in latest wavewatch
model guidance. This could potentially bring hazardous conditions
to mariners navigating through those waters.


Gulf of Papagayo: Northwest winds will pulse to 20-25 kt late
tonight into the early morning hours and again late Wednesday
night across the Gulf of Papagayo before diminishing to moderate
to fresh Thursday afternoon, and to moderate Thursday night into
Friday and diminishing further to light to gentle variable winds
Friday afternoon.

Elsewhere light to gentle northeast to east winds will persist
north of about 07N, and light to gentle south to southeast winds
south of 07N. Seas are around the 3-4 ft range, except for
slightly higher seas north of 07N with little change expected
through Thursday.


High pressure of 1024 mb centered north of the area near 30N134W
extends a ridge southeast to near the Revillagigedo Islands. The
pressure gradient between lower pressure in the vicinity of the
ITCZ is supporting an area of fresh to strong trade winds from
11N to 15N west of 126W, with seas of 10-12 ft. Fresh trades
are elsewhere from 06N to near 21N west of 113W with seas of 8-11
ft in a northwest to north swell. The fresh to strong trades will
decrease in coverage during the next couple of days with model
guidance depicting them to shift to west of 136W from 09N to
12N, and with seas of 9-10 ft. The fresh trades will be confined
from 07N to 20N and west of 122W also at that time, with seas of
8-10 ft in mixed northeast and northwest swell.

Looking ahead, the areal coverage of the fresh to strong trade
winds and associated seas will decrease Thursday as the high
pressure north of the area weakens ahead of an advancing cold
front. Northwest swell with resultant seas of 8-12 ft will
accompany the front as it moves eastward across the waters north
of 25N Wednesday and Thursday while weakening, followed by a
second front expected to sweep southeastward over the far
northeast waters to the east of 130W late Thursday night into
Friday. Wavewatch model guidance shows an extensive set of
northwest swell that will propagate southeastward through the
waters north of about 20N behind the second front. Seas with
this swell event are expected to be in the 10-17 ft range,
building to 15-20 ft in the far northern waters east of 130W
late Friday into Saturday.

A deep layer low situated over eastern Arizona extends a trough
southwestward to 25N117W to 22N125W, then becomes rather narrow
as it continues to 21N135W and west to beyond the area at
20N140W. A very active jet stream branch is rounding the base of
the trough. Strong west to southwest with this jet are
transporting abundant moisture from the deep tropics eastward and
northeastward towards the far eastern portion of the area from
12N to 22N. Scattered showers and isolated thunderstorms are
possible with this moisture plume. A considerable amount of mid
to upper level cloudiness is being advected to the northeast with
the jet stream winds. These clouds have moved inland over much
of central Mexico as observed on satellite water vapor imagery. A
weak surface trough is analyzed at 06Z along a position from
13N118W to 08N122W. The trough is under a very pronounced upper
level diffluent flow pattern. Scattered showers and thunderstorms
are noted within 150 nm west of the trough. The upper level
trough will gradually translate eastward over the next couple of
days as high pressure ridging builds eastward over the western
and central portions of the area in the wake of the previously
mentioned cold fronts. Mid to upper level cloudiness will remain
over the eastern portion of the area on Thursday. The weak
surface trough will move westward about 15-20 kt through the next
48 hours, then become diffuse in the trade wind flow. Another
surface trough is forecast to develop in the vicinity of 111W-
114W and from 06N to 11N late on Thursday.