000 AXPZ20 KNHC 071528 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1528 UTC Fri Oct 7 2016 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. ...SPECIAL FEATURES... Gulf of Tehuantepec Gale Warning...the pressure gradient will tighten due to high pressure building to the north over eastern Mexico and the Gulf of Mexico. This will allow fresh gap winds today which along with overnight drainage effects will increase to strong tonight. The gradient will tighten even more through Saturday with minimal gale force winds expected Saturday night. A cold front will move across the Gulf of Mexico later this weekend which will allow dense, cooler, and drier air to push into the Gulf of Tehuantepec, increasing the winds to 30 to 40 kt Sunday night. Gap winds will diminish slightly thereafter as the airmass to the north modifies and shifts east. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from 09N79W to 07N84W to 09N91W, then resumes from 12N100W to 14N116W to 11N126W to 12N135W to 11N140W. Scattered moderate and isolated strong convection is within 240 nm southwest of a line from 08N78W to 10N87W, from 09N to 11N between 93W and 99W, from 13N to 17N between 103W and 105W, within 240 nm southwest of a line from 10N110W to 16N117W, and from 11N to 13N between 117W and 134W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A sub-tropical ridge axis extends from northwest to southeast across the Pacific waters to the Revillagigedo Islands. Strong northerly winds off the coast of California to the north of the region is supporting a surge of northerly swell as far south as 26N between 119W and 127W, impacting the offshore zones off of Baja California Norte. This swell is expected to decay to less than 8 ft later today, although swell of 5 to 7 ft will persist through Saturday. Otherwise, gentle to moderate northwest to north flow is observed elsewhere across the open Pacific waters west of 110W. The pressure gradient will relax late through today, with the northwest flow diminishing to 5 to 10 kt, and associated seas forecast at 3 to 6 ft everywhere west of 105W by late today. Little change then expected through next Tuesday. Moderate to occasionally fresh northwest winds expected across the Gulf of California north of 30N through early Saturday with seas building to 5 ft. Winds will diminish to a gentle northwest flow by late Saturday and persisting through early next week. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Light to gentle westerly winds are expected through tonight north of the monsoon trough which is meandering east to west along about 11N, while moderate southwest flow is expected south of the monsoon trough through the upcoming weekend. Winds will become light and variable across the waters north of 11N on Saturday, with little change except moderate easterly flow possible across the Gulf of Papagayo on Sunday night. Combined seas of 3 to 6 ft, primarily in long-period southwest swell, is expected across the offshore waters later in the period from the early to middle part of next week. Fresh trade wind flow is likely between 10N and 15N between the low pressure areas, and the mostly stationary ridge to the north early next week. REMAINDER OF THE AREA... High pressure at 1021 mb centered north of the area near 35N133W will shift southeastward through the next couple of days, ahead of a cold front moving toward the region by early next week. Areas of moderate to fresh trade winds persist north of the monsoon trough to near 20N, with seas of 5 to 7 ft. Global models are in good agreement showing a series of weak low pressure areas forming along the monsoon trough. Although the model depictions differ somewhat in precise locations, there is some general agreement of low pressure forming between 115W and 125W through late Saturday, and there is a moderate chance of tropical cyclone development with this low early next week as it tracks westward along the monsoon trough west of 125W. At any rate, it is plausible there will be areas of 20 to 25 kt winds and seas to 8 ft near this migratory low pressure area. $$ LEWITSKY