000 AXPZ20 KNHC 010228 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 0405 UTC Sun Oct 1 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 0200 UTC. ..INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends across Central America to 14N94W to 12N110W to 1010 MB low pres near 11N117W to 09N124W to 1009 MB low pres near 11N132W to beyond 10N140W. Scattered moderate convection can be found from 06N to 08N between 84W and 87W, from 12N to 15N between 90W and 96W, from 10N to 14N between 107W and 112W, and from 10N to 12N between 130W and 132W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Fresh gap winds will develop over the Gulf of Tehuantepec during the overnight and early morning hours beginning tonight, and will continue through Tuesday as a ridge persists across the western Gulf of Mexico and the eastern slopes of the Sierra Madre Mountains. Seas will build to 6-7 ft through early Monday morning, and to 7-8 ft by early Tuesday morning. Marine guidance suggests increasing winds and building seas across the Tehuantepec area as an area of low pressure develops a few hundred miles south of the southern coast of Mexico or Guatemala, near the Gulf of Tehuantepec, by the middle of next week. Environmental conditions are expected to be conducive for gradual development of this system while it moves slowly west-northwestward or northwestward. Elsewhere, a ridge dominates the waters west of the Baja California Peninsula producing gentle to moderate northerly winds and seas of 4-5 ft. Northerly swell will propagate into the waters west of Baja California Norte starting Sunday morning, building seas to 8-9 ft through Tuesday. 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 over the northern Gulf 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. 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 are on the increase south of the monsoon trough with seas building seas to 8 ft. Winds and seas are forecast to further increase south of the monsoon trough through at least the middle of next week. As a result, fresh to strong SW to W winds and seas of 10-11 ft will affect the waters beyond 200 nm off the coast from Nicaragua to Guatemala beginning Monday morning. A fresh SW swell train, with a leading edge period of 20 to 22 seconds is forecast to reach the waters between Ecuador and the Galapagos Islands Tuesday night, building seas to 7-8 ft by Wednesday night. REMAINDER OF THE AREA... A 1026 mb high pressure located N of area near 39N131W extends a ridge across the waters N of 20N. The pressure gradient between the ridge and the monsoon trough is supporting moderate to locally fresh NE winds from 18N to 26N W of 130W based on scattermeter data and a few ship observations. The high pressure center is forecast to move SW over the next 24 hours, reaching a position near 35N135W. The pressure gradient between the high and lower pressure inland over the SW of U.S., and NW Mexico will produce N winds of 20-25 kt across the waters N of 28N between 122W and 128W by Sunday evening, and N of 27N between 122W and 130W by Monday evening. These winds combined with northerly swell propagating into the waters north of 24N between 120W and 130W Sun through Mon night, will build seas to near 12 ft along 30N by Monday. 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