000 AXPZ20 KNHC 100908 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 908 UTC Mon Oct 10 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 0600 UTC surface analysis and satellite imagery through 0900 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec Gale Warning...High pressure building southward over eastern Mexico and the western 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 currently spilling across the Gulf of Tehuantepec this morning to combine with nocturnal drainage effects to result in gale force into Tuesday morning. Winds will diminish slightly on Tuesday as the high pressure north of the area weakens and shifts east. Strong to near gale force winds will persist through mid week, with strongest winds during the overnight hours. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 10N85W to low pressure near 10N94W to complex low pressure near 12.5N117W to low pressure near 10N126W to 09N132W to beyond 11N140W. Scattered moderate to isolated strong convection is occurring within 120 nm either side of the monsoon trough between 100W and 108W. Scattered moderate to strong convection is ongoing within 210 nm north of the axis between 110W and 120W, and within 120 nm south of the axis between 120W and 125W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A weak sub-tropical ridge axis extends from northwest to southeast across the Pacific waters near the southern tip of Baja California Sur. Light to gentle northerly breezes will persist across the region north of 20N through Tuesday, including the Gulf of California on the eastern periphery of the weak ridge. Winds off the coast of the Baja California peninsula will increase to 15 to 20 kt by mid week north of Cabo San Lazaro between high pressure to the northwest and troughing over northwest Mexico. Elsewhere light to gentle breezes and 3 to 5 ft seas will persist. A few showers and thunderstorms are possible off the coast between the Gulf of Tehuantepec and Cabo Corrientes, mainly at night. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Moderate southwest winds persist from 05N to the monsoon trough which is meandering east to west along roughly 10N to 11N, with light to gentle southwest breezes farther south toward the Galapagos Islands. Seas are 4 to 6 ft south of the monsoon trough largely in long period southwest swell. Little change is expected through late this week. Farther north, a cluster of strong thunderstorms is noted off the southern coast of Guatemala this morning, with scattered showers and a few thunderstorms elsewhere off Central America to the coast of western Panama. A 1009 mb low pressure area along the monsoon trough around 250 nm of the Guatemala coast near 10N94W will support moderate to fresh easterly flow off the Guatemala and El Salvador coasts beyond 150 nm through late today with 6 to 8 ft seas. The low pressure will also enhance easterly flow through the Gulf of Papagayo and within 150 of the Nicaragua coast. Winds and seas will gradually diminish through late Tuesday as the low pressure area moves farther west and the gradient relaxes. REMAINDER OF THE AREA... High pressure of 1017 mb centered near 27N131W will slightly north 30N130W tonight shift northward today ahead of a weakening cold front approaching from the west. The front will stall and start to dissipate from 30N135W to 24N140W by Tuesday. Areas of moderate to fresh trade winds persist north of the monsoon trough to near 20N, with seas of 5 to 7 ft. Increasingly favorable conditions aloft are allowing a series of weak low pressure areas to form along the monsoon trough. A complex low pressure is developing along the monsoon trough between 115W and 120W. Two distinct low pressure areas are noted near 12N114W and 12N119W respectively, both with an estimated pressure of 1008 mb. Bands of strong convection are becoming a little better organized to the north and south of these low pressure areas, and it is likely they will merge into a single area of low pressure late today or tonight. An ASCAT pass from 06 UTC indicated fresh to strong winds within 270 nm to the north of these low pressure areas. Seas are 8 to 9 ft within 120 nm of the mean center, with another area of 8 ft seas noted in an earlier altimeter pass near 12N110W, likely enhanced by southwest swell. There remains a high chance of tropical cyclone development related to this complex low after 48 hours as upper shear relaxes. Global models remain in generally good agreement showing a northwestward movement through mid week. Low pressure developing off Guatemala remains a second area of interest over the next several days, and is expected to continue to develop as it moves westward, crossing 120W by Wednesday night accompanied by strong winds and seas 8 to 9 ft within 120 nm in the northern semicircle of the low pressure. Looking ahead, a large area of long period northwest swell is expected to move into the region by mid week, with 8 to 12 ft seas covering the discussion area north of 15N and west of 125W by late Thursday. $$ CHRISTENSEN