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Eastern North Pacific Tropical Weather Discussion



000
AXPZ20 KNHC 232116
TWDEP 

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
2205 UTC Thu Nov 23 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 1800 UTC surface analysis and satellite imagery through
2115 UTC.

...SPECIAL FEATURE...

Gulf of Tehuantepec Gale Warning: 30 to 40 kt northerly winds 
continue across the Gulf of Tehuantepec and downstream to near 
13N96W this afternoon, and will gradually shrink in areal 
coverage to minimal gale conditions tonight through mid morning 
on Fri. Winds will then diminish to 20 kt or less late Sat 
morning. Maximum seas of 14-16 ft near 14N95.5W area occurring 
this afternoon will subside very slowly late tonight and early
Fri to around 12-13 ft. 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 95W and 105W on Fri night before beginning to subside. 
Expect winds 20 kt or less and seas less than 8 ft only briefly 
on Sat afternoon. Strong N winds are forecast to resume again on 
Sat night with gale conditions expected just after sunrise on 
Sun. Latest guidance is suggesting another 30 to 40 kt event on 
Sun night with the gales diminishing by late Mon.

INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... 

The monsoon trough extends from NW Colombia near 09N77W across 
Costa Rica to near 11N88W to 07N100W to 10N113W. The ITCZ begins
near 10N121W and extends through 07N136W to beyond 08N140W. 
Scattered moderate isolated strong convection is seen NE of a 
line from 05N77W TO 09N85W to the coast of Costa Rica and Panama.
Scattered moderate isolated strong convection is occurring 
within 120 nm S of the ITCZ between 135W and 140W.

...DISCUSSION...

OFFSHORE WATERS WITHIN 250 NM OF MEXICO...

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

A modest high pressure ridge centered offshore of southern 
California has weakened considerably today and is yielding 
gentle and variable winds with seas of 2 to 4 ft across the 
offshore waters of Baja this morning and are expected to continue
today. Seas will begin to build Fri afternoon in NW swell, and 
peak at 4 to 7 ft at 13 to 15 seconds across the waters W of Baja
Fri night, then subsiding some on 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 Mon night and Tue.

Gulf of California: Recent scatterometer passes indicated that 
winds have become light to locally moderate across the entire
Gulf. This flow will continue through tonight. The pressure 
gradient will relax further, with light and variable winds 
expected Fri through Mon. Strong to near gale force NW flow is 
expected to develop N of 26N on Mon night through Tue night, 
with seas building to 10 to 11 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 tonight, with diurnally driven strong 
pulses through Tue. Seas of 8 ft or greater will propagate SW to 
near 08N92W on Tue.

Light and variable 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 NE flow 
expected N of the Gulf of Papagayo early Mon. Moderate southerly 
winds, and 3 to 6 ft seas, are forecast S of the monsoon trough.

REMAINDER OF THE AREA... 

A stationary front from 30N138.5W TO 28N140W will remain in place
through Fri with a broad surface low developing along the front 
near 30N140W tonight. The low will move NE of the area on Fri 
night with the front then moving SE to extend from 30N135W TO 
25N140W by midday Sat. Scattered moderate to strong convection 
is observed E of the front from 15N TO 23N between 137W and 
142W.

Combined seas of 8 to 14 ft at 14 to 16 seconds is currently 
observed across the discussion waters W of a line from 30N129W TO
20N140W. This long period NW swell will propagate across the 
waters W of a line from 32N121W to 12N140W early Fri before 
beginning to subside and shrink in area to mainly S of 20N and W
of 125W by Sat. 

$$
Cobb