000 AXPZ20 KNHC 300229 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 0405 UTC Sat Sep 30 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 0215 UTC. ..INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends across Central America to a 1007 MB low pres near 14N95W to another 1007 mb low pres near 12N111W to 10N123W to a third low pres near 12N132W to 11N140W. Most of the convective activity is inland over northern Central America and SE Mexico. Scattered moderate convection is from 06N-09N between 82W-86W. Scattered moderate isolated strong convection is N of 14N between 93W-94.5W. A small cluster of moderate to isolated strong convection is near 11N105W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Fresh to strong gap winds will develop over the Gulf of Tehuantepec tonight as a ridge continues to build across the western Gulf of Mexico and the eastern slopes of the Sierra Madre Mountains. This gap wind event will persist during the upcoming weekend, but the strongest winds are expected to occur during the overnight and early morning hours with the assistance of the nocturnal drainage flow. Seas will build to 6-7 ft through early Monday morning. This gap wind event is forecast to likely persist through the middle of next week. Elsewhere, a ridge will dominate the waters west of the Baja California Peninsula producing gentle to moderate northerly winds and seas of 4-5 ft through Saturday. Northerly swell will propagate into the waters west of Baja California Norte Sunday, building seas to 6-8 ft. Fresh to locally strong S-SW winds are expected over the northern Gulf of California Sunday night through Tuesday as low pressure develops over the area. Seas are forecast to build to 5-6 ft with these winds. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... An active monsoon trough is currently across Central America and adjacent waters. This evening, satellite imagery indicates increasing convection over parts of northern Central America and SE Mexico. The trough will remain close enough to the coast, either inland or just offshore, to produce active convection, primarily during the late afternoon and evening hours, over portions of Central America as well as the adjacent coastal waters during the next few days. Winds will begin to increase south of the monsoon this weekend. Long period SW swell will continue to propagate across the offshore waters with seas of 5-7 ft through the weekend. Looking ahead, a broad area of low pressure developing over Central America will cause monsoonal winds to surge to fresh to strong speeds west of Costa Rica from Sunday night through at least the middle of next week. Seas of 8 ft or higher will affect the waters beyond 200 nm off the coast from Nicaragua to Guatemala. Wave Watch Guidance shows a new SW swell train, with a leading edge period of 20 to 22 seconds reaching the waters between Ecuador and the Galapagos Islands Tuesday night, building seas to 7-8 ft by Wednesday night. REMAINDER OF THE AREA... A ridge extends from 1022 mb high pressure located near 32N137W to the south of the Baja California peninsula. The pressure gradient between the ridge and the monsoon trough is supporting gentle to moderate winds. The high pressure is forecast to remain nearly stationary over the next 24 hours. Looking ahead, northerly swell will propagate into the waters north of 25N between 120W and 130W Sun through Mon night, building seas up to 11 ft along 30N by Monday. This swell event will continue to spread across the N waters on Tuesday, covering mainly the area N of 23N between 120W and 133W. Farther south, cross equatorial southerly swell will propagate across the waters south of 02N between 105W and 135W by Tuesday, with seas building to 8-10 ft. $$ GR