AXPZ20 KNHC 230322

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
0405 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 0000 UTC surface analysis and satellite imagery through 0315 UTC.


Gulf of Tehuantepec Gale Warning: Gale force NW to N winds were indicated earlier today southward across the Gulf of Mexico W of 95W behind a cold front now pushing through the Isthmus of Tehuantepec. NWP model and gridded marine forecast data suggests Gale force northerly winds are sweeping through the Chivelas Pass and into the Gulf of Tehuantepec. These winds are forecast to peak at 35 to 45 kt later tonight into early Thu. Gale force winds will spread farther downstream of the coast to about 13N, and seas building to 16-17 ft, with winds then diminishing slightly 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. Looking ahead, Strong N winds are forecast to resume again on Sat evening with Gale conditions from sunrise Sun and continuing through sunrise on Tue.


The monsoon trough extends from low pres near 11N76W 1010 MB across Panama to 10N90W to 10N102W, then transitions to ITCZ near 10N102W and continues through 10N115W to 08N130W to 09N140W. Scattered moderate convection was across far eastern portion of the basin from 07N to the coast of Panama between 80W and 84W. Scattered moderate to strong convection was noted within 60 NM of a line from 20N135W to 18N136W.



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

A NW to SE orientated ridge axis extends from a 1020 MB high near 29N128W through 18N110W, or about 250 nm seaward of the Pacific coast of Mexico. This ridge will only be interrupted by a weak surface trough extending S from the central Baja Peninsula to near 20N112W, and is expected to persist through Fri night before filling. Expect 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.

Gulf of California: Moderate to locally fresh NW flow prevails across across all but southern portions of the gulf this evening as high pressure is building across N Mexico behind a cold front. Winds will diminish slightly tonight 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 late Mon night, with gale conditions possible on Tue afternoon with seas building to 10-11 ft across the long fetch waters.


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.


A NE to SW aligned ridge will meander from 29N128W to 25N134W for the next several days. SW winds currently across the waters N of 30N W of 135W have moderated in advance of a cold front has entered the far NW portion of the area. This front is expected to move to near 30N138W to 27N140W and stall through Fri as elongated low pressure develops along the front.

The front will usher in long period NW swell into the far NW corner of the area tonight and Thu with seas building to 9 to 15 FT at 14 to 16 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 11 ft seas at 12 to 17 seconds in the wake of the front.

$$ Cobb