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Eastern North Pacific Tropical Weather Discussion



000
AXPZ20 KNHC 211611
TWDEP 

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1605 UTC Tue Nov 21 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 
1500 UTC.

...SPECIAL FEATURE...

Gulf of Tehuantepec Gale Warning: Nocturnal northerly drainage 
flow across the Gulf region is gradually diminishing this 
morning, with winds beginning to fall below 25 kt and seas 5 to 7 
ft. Winds are expected to diminish to 15 kt or less with seas 3-
6 ft by early afternoon. Gale force Nly winds are expected to 
develop rapidly Wed afternoon, as a cold front moves quickly 
southward across Mexico and the western Gulf of Mexico. Light 
winds across the Tehuantepec region Wed morning and afternoon 
with quickly increase to 20-25 kt by mid-afternoon and then 
blast 30-40 kt by late afternoon into the evening hours, and 
continue through Thu morning. Minimal gale conditions will then 
persist through Fri morning. Expect max seas of 16 ft near 
14.5N95.5W late Thu. The resultant NE swell will propagate SW, 
mixing with long-period cross equatorial swell, with seas 8 ft 
or higher across the waters well downstream of the Gulf of 
Tehuantepec, roughly within 120 nm of line from 12N97W to 
07N100W early Fri before beginning to subside.         

INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... 

The eastern Pacific monsoonal circulation has weakened in recent 
days with the monsoon trough currently extending from the semi-
permanent low pressure near 10.5N74W across Panama on to 06N94W. 
the ITCZ then begins from 06N94W TO 06.5N116W TO 12N129W TO low 
pres near 10.5N138W 1012 MB. Widely scattered moderate 
convection continues along the Colombian coastal waters from 03N 
to 06N east of 80.5W. Scattered moderate to strong convection is 
noted W of a line from 08N140W TO 13N132W TO 16.5N140W.

...DISCUSSION...

OFFSHORE WATERS WITHIN 250 NM OF MEXICO...

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

A weak NW to SE orientated ridge extends across the waters just 
beyond 250 nm seaward of the Baja Peninsula and will maintain 
light to moderate NW winds across the offshore waters N of 20N 
through Wed morning. A weak trough is expected to form extending 
SW from the central Baja Peninsula to near 23N116W, and continue 
through early Fri before filling. This will occur as the ridge 
shifts slightly NW and act to weaken weaken winds through the 
week, with light to gentle winds prevailing.  Expect seas in the 
3 to 4 ft range through Thu, building to 4 to 7 ft across the 
waters N of 25N late in the week.

Gulf of California: Moderate NW winds this morning will increase 
late this afternoon due to daytime heating, reaching around 20 
kt through central portions late this afternoon then gradually 
subsiding overnight. Seas are expected to peak at around 5-7 ft 
through central portions early tonight. The pressure gradient 
will relax thu and Fri, with light and variable winds expected 
through Sun. 

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

Gulf of Papagayo: Light drainage flow expected during the 
overnight hours through Thu, with fresh to locally strong 
nocturnal drainage beginning on Thu night and continuing through 
the upcoming weekend.

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, while moderate to locally fresh 
southerly winds, and 3 to 6 ft seas, are forecast S of the 
monsoon trough through the upcoming weekend.  

REMAINDER OF THE AREA... A NE to SW aligned ridge will meander 
from 32N125W to beyond 18N140W for the next several days. Strong 
southerly winds, currently across the waters N of 26N W of 136W, 
will diminish to 20 kt or less on Wed as the ridge weakens 
allowing a cold front to reach 32N140W on Wed. The cold front 
will stall from 32N137W to 23N140W on Thu. Seas of 11 to 16 ft W 
of the front on Wed will subside to 9 to 11 ft on Thu night. The 
associated long period NW swell, in the form of 8 to 11 ft seas 
at 12 to 15 seconds, will propagate E across the discussion 
waters W of 120W through late week, and subside over the 
upcoming weekend as another round of swell produces 8 to 14 ft 
seas at 12 to 19 seconds pushing into the NW corner.

$$
Stripling