000 AXPZ20 KNHC 200928 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 930 UTC Sun May 20 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 0600 UTC surface analysis and satellite imagery through 0900 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 08N84W to 1010 mb low pressure near 10N131W to 09N135W. The intertropical convergence zone continues from 09N135W to beyond 08N140W. Scattered moderate convection is noted from 04N to 09N between 90W and 95W, from 07N to 12N between 110W and 115W, and within 120 nm north of monsoon trough between 120W and 135W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A scatterometer satellite pass from around 05 UTC indicated localized 20 to 25 kt NW winds continuing off Cabo San Lucas. Generally moderate to fresh NW winds continue elsewhere off the coast of Baja California. Seas are generally 6 to 7 ft except to around 8 ft near and to the south of Cabo San Lucas due to a combination of the slightly stronger NW winds and a component of SW swell. Generally light to gentle variable winds are noted over the Gulf of California, with slightly stronger westerly gap winds near low level areas over the peninsula. Light NW to W winds are noted farther south off the Mexican coast. The main forecast issue ahead will be the onset of long period SW swell in excess of 8 ft moving into the open Pacific waters off Mexico late today. Large SW swell 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. In the Gulf of Tehuantepec, light winds will persist into Tue, then moderate to fresh gap winds will pulse briefly as sharp troughing moves through southeast Mexico. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... 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 strong long period SW swell. 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 8 to 9 ft tonight through Mon. REMAINDER OF THE AREA... A ridge extends from 1026 high pressure centered near 31N145W through the Revillagigedo Islands. The ridge is supporting moderate to fresh trade winds farther south into the deep tropics north of the monsoon trough. Weak 1010 mb low pressure is reforming along the monsoon trough near 10N131W. 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 120W. 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 20N with an added component of SW swell. The ridge will build north of 20N through early in the week, enhancing trade winds especially near the low pressure. A new round of SW swell in excess of 8 ft is noted south of 05N, propagating northward. This will overtake the region mainly east of 130W late today 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