Eastern North Pacific Tropical Weather Discussion (Text)

AXPZ20 KNHC 200254

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
0235 UTC Mon Nov 20 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 0000 UTC surface analysis and satellite imagery through
0215 UTC.


Gulf of Tehuantepec Gale Warning: Strong high pressure is surging
down eastern Mexico while a cold front is moving through the SW 
Gulf of Mexico N of the area. While there have been no recent 
observations in the Gulf of Tehuantepec, available guidance 
indicates that gale force winds up to 40 kt are blowing across
the Tehuantepec area. Winds may approach strong gale force during
the overnight hours through around sunrise, then will diminish
below gale force by Mon afternoon as the gradient significantly 
slackens. Seas will rapidly build to up to 17 ft during the 
strongest winds tonight. Northerly winds will pulse to fresh to 
near gale force Mon night, then will diminish to 20 kt or less 
Tue morning. Northerly flow will then pulse to fresh to strong 
starting Wed morning with another gale force wind event possible 
Wed night through Fri night.


The monsoon trough axis extends from 09N75W to 06N90W to
09N106W. 09N106W TO 11N115W TO 10N130W TO 12N140W. The 
intertropical convergence zone axis extends from 09N106W to 
11N115W to 10N130W to 12N140W. Scattered moderate convection is 
within an area bounded by 14N118W to 11N126W to 07N127W to 
05N123W to 05N118W to 09N115W to 14N118W.



Please read the Special Features section above for information 
regarding the Gulf of Tehuantepec Gale Warning. 

A NW to SE oriented ridge just beyond 250 nm seaward will 
maintain moderate to locally fresh NW flow W of the Baja 
Peninsula through the evening when the pressure gradient will 
relax, supporting moderate NW flow later tonight through sunrise
Mon. Light N winds winds then are expected through Thu. A trough
is forecast to form from the central Baja Peninsula southward, 
on Thu night and Fri, accompanied by a light W to NW wind shift.
Expect seas in the 4 to 7 ft range today, with these conditions 
resuming again late in the week, with 3 to 5 ft seas during early
and mid part of the week. 

Gulf of California: Fresh to strong NW winds across the gulf from
25.5N to 29N W of 110W will diminish by midnight as the pressure
gradient relaxes. Moderate NW flow is then forecast across the 
entire gulf waters, becoming light by Mon evening. Moderate to 
locally fresh NW flow will resume across the entire gulf on Tue 
and Wed, then diminishing Thu through Fri.


Gulf of Papagayo:  Moderate to locally fresh NE drainage winds 
are forecast during the overnight hours tonight and on Mon 
night, then light drainage flow expected during the overnight 
hours through Thu night, with moderate to fresh nocturnal 
drainage resuming on Fri night.

Light and variable winds and 3 to 5 ft seas are expected 
elsewhere to the N of the monsoon trough, which has been 
meandering between 09N and 11N. Moderate to locally fresh 
southerly winds and 4 to 7 ft seas are forecast S of the monsoon
trough through the week. 


A tight pressure gradient is in place between a dissipating cold
front W of 140W and ridging to the E across the northern waters.
Associated scattered moderate convection is within an area
bounded by 30N133W to 30N140W to 17N140W to 30N133W. The tight 
pressure gradient is supporting fresh to strong southerly flow in
the NW corner of the discussion waters, along with 8 to 10 ft 
seas. Winds will increase to near gale force with seas also 
building to 12 ft by early Mon with a lengthening fetch area. The
front will dissipate prior to reaching 140W.

Additional cold fronts will approach 140W through the week, but
will stall through Wed night as high pressure holds. A weakening
front will manage to cross 140W by early Thu with an associated
area of large NW swell intruding prior to its arrival. NW swell
will build seas to 16 ft near 30N140W by Thu morning. The highest
seas will decay through the end of the week, but the edge of seas
of 8 ft or greater will manage to stretch across the waters N of
10N and W of 125W by Fri morning.

Elsewhere, moderate to fresh trades are supporting 4 to 7 ft seas
in mixed swell. Trades will diminish slightly early in the week
as the overall pressure gradient weakens allowing for seas to 
subside to less than 6 ft.


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Page last modified: Monday, 20-Nov-2017 02:54:43 UTC