193 AXPZ20 KNHC 201538 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1537 UTC Thu Sep 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 1200 UTC surface analysis and satellite imagery through 1500 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 09N84W to low pressure near 09N87W 1006 mb, to 12N100W to 10N117W. Another segment of the monsoon trough continues from 1009 mb low pressure near 15N123W to 09N140W. Scattered moderate convection from 11N to 15N between 97W and 102W, and from 07N to 12N between 110W and 113W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... The remnant low of of Tropical Depression Nineteen-E well inland over the Mexican state of Sonora, near 28.5N110W. Fresh onshore winds continue to support showers and thunderstorms over the mountains, with the heaviest activity currently ongoing in the northern portions of Sinaloa, between Culiacan and Los Mochis. Life-threatening flash floods and landslides are possible through the afternoon. For the marine areas over the southern Gulf of California, a recent altimeter pass indicated seas have subsided since yesterday, with seas 2 to 4 ft. Elsewhere north of 20N, moderate to fresh NW winds persist off the Pacific coast of Baja California, funneling between the coastline and 1026 mb high pressure well northwest of the area. A satellite altimeter pass from 11 UTC showed seas approaching 8 ft north likely due to NW swell entering the discussion area north of 29N and west of 116W. While this is expected to decay below 8 ft today leaving mainly 5 to 7 ft seas, the NW swell and local wind waves will interact with southerly swell off the coast Baja California over the next several days. Farther south, strong winds into the Gulf of Tehuantepec are diminishing. These were evident in an evening scatterometer satellite pass. The winds are the result of a fairly tight gradient due to enhanced troughing over the southwest Gulf of Mexico. A weaker and short-lived pulse of strong winds is possible tonight in the Gulf of Tehuantepec. Looking ahead, another strong pulse of gap winds is possible late Sat into early Sun ahead of a tropical wave moving through Central America and southern Mexico. Looking further ahead, there is growing consensus among major models of weak low pressure forming by late Mon into early Tue around 240 nm southwest of Manzanillo and 240 NM southeast of Socorro Island. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Fresh offshore nocturnal winds will pulse across the Gulf of Papagayo the next several nights. Cross-equatorial SW swell reaching the Central American coast will slowly subside this weekend. The monsoon trough will meander near 10N the next few days. Looking ahead, an increase in moist southwest flow is advertised by the major global models by early next week, possibly culminating in a Central American gyre pattern by mid week. This may bring increase showers and thunderstorms to the Pacific waters off Central America by early next week, and possibly increased winds and seas thereafter. REMAINDER OF THE AREA... An elongated surface trough extends from roughly Clarion Island to 1009 mb low pressure near 15N123W. Surface ridging prevails over the waters NW of the trough axis. Moderate to locally fresh trades are north of the trough west of 120W, supporting seas to 8 ft from 14N-19N W of 130W. These seas will subside during the next 2 days as the pressure gradient weakens. $$ Christensen