AXPZ20 KNHC 210245

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
245 UTC Mon May 21 2018

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 0330 UTC.


The monsoon trough extends from 11N85W TO 10N130W. The intertropical convergence zone continues from 10N130W to beyond 10N140W. Scattered moderate to strong convection is noted from 06N to 09N between 85W and 90W. Scattered moderate to strong convection also noted from 08N to 11N between 105W and 115W. Scattered moderate convection is from 10N to 12N between 130W and 135W.



Moderate to fresh NW winds continue across the offshore waters of Baja California this evening, and are maintaining seas of 5 to 7 ft across these waters. Generally light to gentle variable winds are noted over the Gulf of California, except for moderate southerly winds across far N portions. Light NW to W winds are noted farther south across the Mexican coastal waters. The main forecast issue ahead will be the onset of long period SW swell moving into the open Pacific waters off Mexico through mid week. Large SW swell in excess of 8 ft will reach waters of southern Mexico by early Mon, and into the open waters off Baja California Mon night and Tue, mixing with NW swell off Baja California Norte. Seas across the region will build to 7-8 ft in this mixed swell by Mon afternoon and spread into the mouth of the Gulf of California early Tue.

In the Gulf of Tehuantepec, light winds will persist into Tue, then moderate to fresh gap winds will pulse briefly as sharp troughing shifts slowly NW across southeast Mexico.


Gulf of Papagayo: Light to gentle winds will dominate the gulf the entire forecast period as weak pressure will prevail across Central America. Seas of 5-8 ft are forecast over the Gulf and nearby waters through mid week due to the strong long period SW swell expected to arrive tonight.

Gulf of Panama: Gentle to moderate S to SW winds are forecast through Wed with seas of 4-6 ft in long period SW swell, building to 5-7 ft on Mon as the swell reaches the coasts of Panama and Colombia.

Elsewhere, gentle to moderate SW winds are expected to the south of the monsoon trough with light to gentle variable winds north of trough as a weak pressure pattern remains over Central America. Seas of 6-7 ft in building long period SW swell west of the Galapagos Islands are expected to propagate northward tonight through late Tue next week, building to 8 to 9 ft to the west and northwest of the Galapagos Islands tonight through Mon night.


A ridge extends from 1028 high pressure centered near 32N141W through the Revillagigedo Islands. The ridge is supporting moderate to fresh trade winds farther south into the deep tropics north of the monsoon trough and ITCZ. Convergence of the moderate to fresh NE trades with light to moderate SW flow on the south side of the monsoon trough is supporting clusters of showers and thunderstorms near the monsoon trough west of 105W. Various recent altimeter satellite passes indicate 4 to 6 ft seas north of 20N where winds are lighter, and 7 to 9 ft seas in the trade wind belt between the monsoon trough as far north as 17N as SW swell has begun to move into the region.

The ridge will build north of 20N through early in the week, enhancing trade winds especially near a developing weak low pressure along the monsoon trough near 10N125W. Various recent altimeter satellite passes continue to show SW swell in excess of 8 ft south of 10N, propagating northward. This will overtake the region east of 130W through Tue. Looking ahead, the upper pattern will amplify by mid week, supporting development of another weak low along the monsoon trough west of 125W.

$$ Christensen