000 AXPZ20 KNHC 082153 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2210 UTC Sat Oct 8 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 1800 UTC surface analysis and satellite imagery through 2100 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec Gale Warning...High pressure building southward over eastern Mexico and the Gulf of Mexico will tighten the pressure gradient across the Isthmus of Tehuantepec over the next several days. This will allow the strong northerly gap winds to combine with nocturnal drainage effects to result in strong to gale force winds over the next few days. Gap winds across the region have diminished to around 25 kt late this afternoon. However, the pressure gradient will tighten further tonight with minimal gale force winds expected tonight through late morning on Sunday. A cold front will move across the southwest Gulf of Mexico later Sunday 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 late Monday, as the airmass to the north modifies and shifts east. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from low pres near 09N71W to 11N85W to 13N99W to low pres near 11.5N117.5W to 11N130W to 11.5N140W. Scattered moderate to strong convection is occurring within 150 nm N and 270 nm S of the trough between 81W and 116w, and within 90 nm N and 180 nm S of the trough between 116W and 128W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A weak sub-tropical ridge axis extends from northwest to southeast across the Pacific waters to just NW of the Revillagigedo Islands. Fresh to strong northerly winds off the coast of California to the north of the region had supported a surge of northerly swell of 5 to 7 ft across the waters offshore of Baja California. The swell is expected to subside to 4 to 6 ft through the next 12 to 24 hours. Light to gentle northerly breezes will persist across the region north and west of Cabo Corrientes, including the Gulf of California, through the next several days on the western periphery of the weak ridge. Meanwhile, light to moderate east to southeast winds are expected across the waters between the Gulf of Tehuantepec and Cabo Corrientes through at least Sunday. 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 north to south along about 10N to 11N, while moderate southwest flow is expected south of the monsoon trough through the next several days. Winds will become light and variable across the waters north of 11N through the remainder of today, 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 broad, weak and transient low pressure areas, and the mostly stationary ridge to the north and northwest early next week. REMAINDER OF THE AREA... High pressure of 1018mb centered north of the area near 34N132W will shift southeastward through the next couple of days, ahead of a cold front moving into the forecast area in the next 24 to 36 hours. 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 broad, weak, and transient 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 consolidating between 115W and 120W late Sunday through early Monday, and there is a high chance of tropical cyclone development with this low during the next 5 days as it tracks slowly and generally westward along the monsoon trough west of 120W. Expect winds of 20 to 25 kt with seas of 7 to 9 ft in the southeast semicircle of the low within the next 24 to 48 hours. $$ Stripling