000 AXPZ20 KNHC 200317 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 230 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 0000 UTC surface analysis and satellite imagery through 0300 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 09N84W to 1010 mb low pressure near 10N131W to 07N140W. Scattered moderate to strong convection is noted from 05N to 08N between 85W and 95W, from 05N to 10N between 105W and 120W, and within 120 nm either side of monsoon trough between 125W and 140W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... An earlier scatterometer satellite pass indicated localized 20 to 25 kt NW winds off Cabo San Lucas, but generally moderate to fresh NW winds continue off the coast of Baja California persist. Seas are generally 6 to 7 ft except to around 8 ft near and to the S of Cabo San Lucas in a 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 on Sunday. 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. 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 Sun night through Mon. REMAINDER OF THE AREA... A cold front that was moving slowly eastward across the eastern Pacific appears to have stalled then dissipated altogether over hte past several hours. This weakened the subtropical ridge across the area north of 20N, and this in turn has maintained moderate to fresh trade winds farther south into the deep tropics north of the monsoon trough. 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. Trade wind convergence is support scattered moderate convection along the monsoon trough. A weak low pressure area is barely evident along the monsoon trough near 10N131W. This had become elongated earlier in the day along the monsoon trough, but may be starting to reform a little. Winds will increase accordingly on the north side of the low especially as the ridge builds north of the area. Seas are reaching 9 ft in area west of 130W between the monsoon trough and 20N, due the trade winds mixing with longer period SW swell. 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 Sun 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