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Eastern North Pacific Tropical Weather Discussion

AXPZ20 KNHC 210947

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1005 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 0600 UTC surface analysis and satellite imagery through 
0945 UTC.


Gulf of Tehuantepec Gale Warning: Strong N winds, and seas of 7 
to 9 ft, currently across the gulf waters will diminish and 
subside through late morning. The associated NE swell has been 
mixing with long-period cross-equatorial swell, with 7 to 9 ft 
seas currently across the waters from roughly 09N to 11N between 
95W and 104W, forecast to subside below 8 ft early this 
afternoon. Strong N winds are expected to resume on Wed 
afternoon, with gale conditions developing quickly on Wed 
evening, with 30 to 40 kt winds by late Wed night, and 
continuing into Thu afternoon. 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.         


The monsoon trough extends W along 10N across the SW Caribbean 
to the Pacific coast of Costa Rica at 09N84W, then dips SW to 
06N98W where scatterometer winds indicate a transition to an 
ITCZ, which continues W-NW to beyond 11N140W. A low level trough 
is analyzed from 09N130W to 15N128W. Isolated moderate to strong 
convection is noted within 45 nm of 06.5N78W, and within 180 nm 
either side of a line from 08N122W to 12N130W to 08N139W.



See Special Features paragraph for Gulf of Tehuantepec Gale 

A NW to SE orientated ridge just beyond 250 nm seaward will 
maintain light NW flow W of the Baja Peninsula through Wed 
morning when a trough will form extending SW from the central 
Baja Peninsula to near 23N116W, and continue through early Fri 
before filling. 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, then subsiding some during the upcoming weekend.

Gulf of California: Moderate NW flow expected this morning, 
becoming a moderate to locally fresh NW breeze tonight, 
returning to moderate NW flow Thu. The pressure gradient will 
further relax, with light and variable winds on Fri through Sun. 


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 
to near gale force southerly winds, currently across the waters 
N of 28N W of 138W, 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, in the form of 8 
to 14 ft seas at 12 to 19 seconds pushes into the NW corner.