000 AXPZ20 KNHC 202136 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1929 UTC Thu Oct 20 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 2030 UTC. ...SPECIAL FEATURES... Showers and thunderstorms have increased near a small area of low pressure located near 13N114W. Numerous moderate and isolated strong convection is noted from 11N to 15N between 111W and 115W. The most recent scatterometer pass showed winds of 20-25 kt in association with this system and a well defined cyclonic circulation at the surface. The low has a medium chance of developing into a tropical cyclone as it drifts slowly N over the next several days. A gale warning remains in effect for the Gulf of Tehuantepec. This gap wind event is being initiated by a cold front moving S through the western Gulf of Mexico tonight through Friday night. N winds of 20-25 kt are already surging into the Gulf of Tehuantepec. Winds will reach minimal gale force by Friday morning with seas building to 8-12 ft by Friday afternoon. Model guidance suggests this event will be long lived with winds pulsing to gale force through the end of next week. Expect the strongest winds in conjunction with nocturnal drainage flow during the overnight and early morning hours, particularly between 0600-1200 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 12N103W to 1006 mb low pres near 13N114W to 10N125W to 14N137W to 13N140W. Scattered moderate isolated strong convection is noted from 10N to 17N between 101W and 111W. Similar convection is present from 10N to 13N between 115W and 123W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A ridge extends SE from 32N134W to near the Revillagigedo Islands at 19N113W. Near the ridge axis...gentle to moderate NW to N winds are noted per scatterometer data. The combination of these winds and long period NW swell support seas of 7 to 9 ft W of Baja California Norte, and 5 to 7 ft seas W of Baja California Sur. The ridge will weaken through Friday as a cold front approaches the forecast region. The front is expected to stall and weaken near 30N140W by late Friday. Then, the ridge now in place will be reinforced by high pres in the wake of the front. A new batch of swell of 8 to 9 ft generated N of the front is forecast to arrive offshore Baja California Norte late Saturday into Sunday. Seas will subside once again by Monday night. Winds across the northern part of the Gulf of California N of 30N are 20-25 kt with seas of 4-6 ft. NW winds of 15-20 kt with seas of 4-5 ft are across the central waters, mainly N of 26N. By early Friday morning, expect mainly gentle to moderate winds and seas generally less than 5 ft across the entire Gulf of California or Sea of Cortez. Surface troughing developing over the Baja peninsula will promote a light to gentle winds regime over the Gulf of California S of 28N and gentle to moderate winds for the waters N of 28N Saturday through Monday. Farther S, a gap wind event is producing minimal gale force winds across the Gulf of Tehuantepec. See Special Features section for details. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Light to gentle winds are noted in satellite-derived wind data across the waters between Ecuador and the Galapagos Islands with seas of 5-7 ft in SW swell, except to the lee of the Galapagos Islands. Farther N, mainly gentle to moderate SW winds prevail with an area of moderate to fresh SW winds roughly from 05N-10N between 90W and 105W. Seas in this area are in the 8-9 ft range in SW swell. These marine conditions are forecast to persist during the next few days. An area of disorganized cloudiness and showers has persisted near the coast of Central America. Environmental conditions are forecast to become more favorable for some development of this disturbance over the weekend and early next week while the system moves toward the WNW at about 10 kt. REMAINDER OF THE AREA... The pres gradient between the ridge to the N and lower pres near the monsoon through is generating an area of fresh to locally strong trade winds from 14N to 20N W of 133W with seas of 8-9 ft in mixed NE and NW swell. Winds and seas will continue to diminish across the west-central waters during the next couple of days. Currently, seas of 8-9 ft, primarily in NW swell, dominate the forecast waters N of 26N between 121W and 129W. Seas will gradually subside to less than 8 ft in about 12 hours, but another batch of long period NW swell will reach the NW waters by Friday evening. This swell event will propagate SE to cover the waters W of a line from 30N125W to 25N134W by Saturday evening. $$ cam