000 AXPZ20 KNHC 282128 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1943 UTC Thu Sep 28 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 1800 UTC surface analysis and satellite imagery through 2100 UTC. ..INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends across the Gulf of Panama from 08N79W to 11N86W to 1007 mb low pressure over the Gulf of Tehunatepec near 15N95W to another 1008 mb low pressure near 13N115W to 11N130W to 10N140W. Scattered moderate isolated strong convection is N of 05N E of 80W. Similar convection is also noted over parts of Panama. Scattered moderate convection can be found N of 14N between 94W and 100W, from 12N to 14N between 110W and 115W, and from 11N to 13N between 121W and 124W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... As previously mentioned...a 1007 mb low pressure is over the Gulf of Tehuantepec near 15N95W supporting scattered moderate convection. This area of low pressure will remain off the coast of southern Mexico, and drift SE through Saturday. Fresh to strong gap winds will develop over the Gulf of Tehuantepec by Fri night as a ridge establishes across the western Gulf of Mexico and the eastern slopes of the Sierra Madre Mountains. 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. In the Gulf of California, expect gentle to moderate NW-N winds and seas of 1-2 ft, except 2-3 ft near the entrance to the Gulf through Saturday. Then, winds will turn light and variable on Sunday. Fresh to locally strong S-SW winds are expected over the northern Gulf of California Sunday night through Tuesday as a low pressure develops there. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... An active monsoon trough is currently reaching the pacific coast of Central America. The trough will remain close enough to the coast, either inland or just offshore, to produce active convection, primarily during the late afternoon and early evening hours, over portions of Central America as well as the adjacent coastal waters during the next few days. Moderate SW to W winds are expected south of the monsoon trough through Friday, with moderate to locally fresh SW to W winds during the upcoming weekend. Long period SW swell will continue to propagate across the offshore waters with seas of 5-7 ft through the weekend. Looking ahead, broad 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. REMAINDER OF THE AREA... A 1008 mb low pressure remains embedded within the monsoon trough near 13N115W. Fresh to strong winds are expected within about 120 nm SW, then S quadrants of the low center over the next 24 hours. By 48 hours, marine guidance indicates increasing winds of 20-25 kt and building seas of 8-9 ft south of the monsoon trough between 104W-120W. The low is forecast to drift eastward along the monsoon trough over the next 48 hours. Elsewhere, a 1021 mb high pressure located near 31N141W extends a ridge across the north waters supporting gentle to moderate winds. 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 early Monday morning. Farther south, cross equatorial southerly swell will propagate across the waters south of 02N between 105W and 135W by Tuesday, with building seas of 8-10 ft. $$ GR