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Eastern North Pacific Tropical Weather Discussion



000
AXPZ20 KNHC 221626
TWDEP 

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1605 UTC Wed Nov 22 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 1200 UTC surface analysis and satellite imagery through 
1515 UTC.

...SPECIAL FEATURE...

Gulf of Tehuantepec Gale Warning: Strong N to NE winds have 
begun to spread across NW portions of the Gulf of Mexico this 
morning and will quickly push S across the Mexican coastal 
waters behind a cold front throughout the day. The front is 
expected to reach the western Bay of Campeche this afternoon 
with strong northerly winds then blasting through the Chivelas 
Pass and across the Gulf of Tehuantepec. Gale force winds to 40 
kt will develop quickly by late afternoon and increase to 35 to 
45 kt gale force shortly before sunset. Gale force winds will 
spread farther downstream of the coast overnight to about 13N, 
and seas building to near 17 ft, with winds then diminishing 
slightly into early Thu afternoon. Minimal gale conditions will 
then persist through mid morning on Fri then diminish to 20 kt 
or less late Sat morning. The resultant NE swell will propagate 
SW, mixing with long-period cross equatorial swell, with seas 8 
ft or higher well downstream of the Gulf of Tehuantepec along 
08N between 94W and 102W on Fri evening before beginning to 
subside. Strong N winds are forecast to resume again on Sat 
evening with gale conditions at sunrise on Sun and continuing 
through sunrise on Tue. 

INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... 

The monsoon trough extends from low pres near 11N76.5W 1010 MB 
across Panama to 08N83.5W TO 08.5N97W, then transitions to ITCZ, 
TO 07N116W TO 09N130W TO 11N140W. Scattered moderate convection 
was across far eastern areas E of a line from 02.5N78.5W TO 
10N87W.  Scattered moderate to strong convection was noted 
within 60 nm of a line from 08N130W to 17.5N136W. 

...DISCUSSION...

OFFSHORE WATERS WITHIN 250 NM OF MEXICO...

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

A NW to SE orientated ridge axis extending about 270 nm seaward 
of the Pacific coast of Mexico will be interrupted today as a 
weak trough forms extending S from the central Baja Peninsula to 
near 20N112W, and persists through Fri night before filling. 
Expect mild seas of 3 to 4 ft seas at 12 seconds W of Baja 
through Thu morning, except near 2 ft nearshore, then building 
in new NW swell at 14 to 15 seconds Fri, peaking at 4 to 7 ft 
across the waters W of Baja Fri night. Seas will then gradually 
subside some Sat into Sun. Long-period NW swell in the form of 7 
to 9 ft seas will reach 30N120W on Sun night, and spread S 
across the waters W of Baja with 8 to 13 ft seas at 17 to 19 
seconds forecast W of Baja late Mon night.

Scattered moderate isolated strong thunderstorms persist within 
150 nm of the Mexican coast this morning between 98W and 102.5W 
and are expected to linger in the general area today as an upper 
trough supporting the Gulf of Mexico cold front sinks S across N 
and central Mexico. 

Gulf of California: Moderate to fresh NW flow prevails across 
across all but southern portions of the gulf this morning as 
high pressure is building across N Mexico behind a cold front. 
Winds will diminish slightly this evening through Thu night as 
the ridge shifts SE. The pressure gradient will then relax 
further, with light and variable winds on Fri through Mon. 
Strong to near gale NW flow expected N of 30N on Mon night, with 
gale conditions possible on Tue afternoon with seas building to 
10 ft across the long fetch waters.  

OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND 
WITHIN 750 NM OF ECUADOR...

Gulf of Fonseca...Fresh NW winds forecast to begin around 
sunrise on Mon.  

Gulf of Papagayo: Fresh to locally strong NE nocturnal drainage 
flow forecast to begin on Thu night into early Fri afternoon, and
then resume on Fri night and continue through Tue with strong 
winds are expected to reach as far SW as 09N91W.

Light and variable winds, and 3 to 5 ft seas, are expected 
elsewhere through Sun to the N of the monsoon trough which has 
been meandering between 09N and 11N, while moderate southerly 
winds, and 3 to 6 ft seas, are forecast S of the monsoon trough.

REMAINDER OF THE AREA... 

A NE to SW aligned ridge will meander from 32N125W to 21N138W 
for the next several days. Strong SW winds, currently across the 
waters N of 30N W of 135W, will diminish to 20 kt or less by 
this afternoon as the ridge weakens allowing a cold front to 
reach 32N140W on Wed. The cold front will stall from 32N137W to 
23N140W on Thu then begin to drift towards the NW as a warm 
front, while elongated low pressure develops along the front 
just NW of the area Thu night through Fri morning. The low will 
move NE and away from the area late Fri night.

Long period NW swell is producing combined seas of 8 to 11 ft 
across the discussion waters W of a line from 30N132W TO 26N135W 
TO 15N137W TO 11N140W this morning and will build to 8 to 15 ft 
at 14 to 15 seconds late tonight. This NW swell, in the form of 
8 to 11 ft seas at 12 to 17 seconds, will propagate across the 
waters W of a line from 32N122W to 14N140W on Thu night before 
beginning to subside. 

Another cold front will move E in to the area reaching from 
32N133W to 25N140W early Sat with 8 to 14 ft seas at 12 to 17 
seconds in the wake of the front. 

$$ Stripling