Eastern North Pacific Tropical Weather Discussion (Text)

AXPZ20 KNHC 250929

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1005 UTC Sat Nov 25 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
0900 UTC.


A ship crossing now the Gulf of Tehuantepec is reporting sustained
winds of 24 kt. Winds will diminish to 20 kt or less late this 
morning, and increase again to 20 to 25 kt tonight. The next 
Gulf of Tehuantepec gale event is forecast to begin by mid-day 
Sunday. As a result, a gale warning has been issued. A building 
ridge across the western Gulf of Mexico and the eastern slopes of
the Sierra Madre Mountains will allow northerly winds to begin 
to spill through the Isthmus of Tehuantepec and across the Gulf 
of Tehuantepec by early Sun morning. The latest computer model 
guidance is suggesting another 30 to 40 kt gap wind event on Sun 
night, with seas building to 16 or 17 ft. Gale conditions will 
persist on Mon, with the area of fresh to strong winds extending 
downwind of the gulf to near 10N99W. Winds should diminish below 
gale force by late Tue morning. 


The monsoon trough extends from 09N84W to 07N90W to 09N95W to
08N105W. The ITCZ continues from 08N105W to 10N120W to 11N130W 
to beyond 10N140W. Scattered moderate convection is occurring 
within about 75 nm south of ITCZ axis between 110W and 133W. 
Similar convection is noted from 13N to 16N between 110W and 



See Special Features paragraph above for information on the 
Gulf of Tehuantepec Gale Warning. 

A weak ridge continues across the offshore waters of Baja 
California producing mainly light and variable winds. Seas are in
the 4 to 7 ft range in NW swell. Seas are forecast to subside 
some today into Sun. Another set of long-period NW swell in the 
form of 7 to 9 ft seas will reach 30N120W by Mon morning, and 
spread S across the offshore forecast waters W of Baja with 8 to 
13 ft seas at 17 to 19 seconds Mon night and Tue.

Winds will increase very slightly over the weekend, mainly due 
to daytime heating. However early on Monday, stronger high 
pressure will begin to build across the region from the NW and 
act to increase NW winds to 20-25 kt across the waters N of 26N, 
including the Sebastian Vizcaino Bay, by the late afternoon and 
evening hours.

Gulf of California: light southerly winds are noted across the 
entire Gulf. The pressure gradient will relax further, with 
light and variable winds expected through Mon. Strong to near 
gale force NW flow is expected to develop across the northern 
Gulf Mon night, with fresh to locally strong winds spreading 
southward across the central and southern portions of the Gulf 
through Tue night. Seas will quickly build to near 8 ft across 
the northern Gulf by Tue morning and then 5-7 ft through central 
portions by Tue night. 


Fresh to locally strong NE winds are occurring across and 
downstream of the Gulf of Papagayo early this morning, with the 
assistance of the nocturnal drainage flow. Seas have built to 6-
7 ft downstream of the gulf. Expect a typical nocturnal maximum 
of around 25 kt across the region through early Tue morning, 
diminishing to 15-20 kt by mid afternoon. Seas will maximize to 
around 7 ft each morning near sunrise, and will likely build to 
8 ft early Monday morning, and early Tue morning. Moderate to 
locally fresh NE winds are expected across the Gulf of Fonseca 
each night through Tue. 

Light to gentle N to NE winds, and 3 to 5 ft seas are expected 
elsewhere through Sun night to the N of the monsoon trough which 
has been meandering between 09N and 11N. Moderate southerly 
winds, and 4 to 6 ft seas, are forecast S of the monsoon trough.


A cold front is over the NW waters and extends from 30N136W to 
21N140W while a reinforcing or secondary cold front is approaching
30N140W. Fresh to strong S to SW winds are noted N of 27N W of 
135W. The secondary front will reach the far NW corner of the 
area this morning followed by fresh to strong NW winds and seas 
up to 10 or 11 ft. The fronts are forecast to merge on Sun as 
they move eastward and approach 125W.

The most recent altimeter data indicated seas of 8 to 11 ft N of
20N W of 128W, and seas of 8 to 10 ft from 12N to 20N W of 128W.  
Seas of 8 ft or greater in long period NW swell are propagating 
across the waters NW of a line from 20N125W to 05N140W. This 
swell event will begin to subside, with seas 8 ft or greater 
mainly S of 14N and W of 125W by tonight. At that time, another 
set of NW swell is expected to reach the far NW waters.


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Page last modified: Saturday, 25-Nov-2017 09:30:06 UTC