583 AXPZ20 KNHC 221601 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1601 UTC Sat Sep 22 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 1200 UTC surface analysis and satellite imagery through 1500 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... A segment of the monsoon trough extends from 10N86W to 11.5N108W to 1009 mb low pressure near 09N123W. Another segment of the monsoon trough reaches from 11.5N130W to 11.5N140W. Scattered moderate to isolated strong convection is ongoing beyond 120 nm off the coast of Mexico from 10N to 15N between 94W and 101W. Scattered moderate convection is ongoing from 07N to 16N between 120W and 130W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Strong gap winds will pulse into the Gulf of Tehuantepec over the next several nights both ahead of and in the wake of the northern extent of a tropical wave that will move across southern Mexico through early next week. A sharp upper trough over the Gulf of Mexico is enhancing leftover convection off southern Mexico and north of the monsoon trough. Major global models are indicating development of broad low pressure south of the Revillagigedo Islands Sunday through Tue, although they still differ on exact location. Looking ahead beyond mid week, the gap pulses through Tehuantepec may support develop of another low pressure off the coast of southern Mexico. The persistence of low pressure south of Tehuantepec may in turn help spur strong mainly overnight gap winds through late week. Farther north, weak ridging will persist across the region north of 20N, maintaining generally moderate NW flow off the coast of Baja California, becoming locally 15 to 20 kt near the coast north of Cabo San Lazaro during the late afternoons. Light to gentle breezes along the Gulf of California will become more southerly by late Sun as high pressure builds over northwest Mexico. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Gulf of Papagayo: Moderate to locally fresh east nocturnal drainage flow expected through Mon night. Light and variable winds are forecast elsewhere N of the monsoon trough which is meandering between 09N and 11N. Moderate southwest flow is forecast S of the monsoon trough through the middle of next week. Moderate to fresh southwest monsoonal flow is expected south of 10N late next week as a surface low begins to develop near 13N95W on Thu, and then tracks northwest of the area on Fri accompanied by thunderstorms. REMAINDER OF THE AREA... A surface trough is analyzed along 130W from 11N to 19N. A recent altimeter satellite pass indicated seas to 8 ft along this trough axis, which could also indicate there are fresh to strong winds on the northern end of the trough, facing ridging to the north. Scattered showers and thunderstorms in this area appear to be weakening through the early morning. A broad ridge continues across the subtropics accompanied by moderate to locally fresh anticyclonic flow south of 23N west of 120W, with strongest winds near the trough. The trough will move west of 140W by early Tue, with ridging building into the deep tropics in its wake, allowing a large areal extent of fresh trade winds. Looking ahead, global models indicate the potential for low pressure to develop along the monsoon trough around 10N130W by Wed, but differ on whether this will deepen much as it move westward through late week. Similarly, a more developed low pressure area farther east will move westward and to the south of the Revillagigedo Islands through mid week. $$ Christensen