000 AXPZ20 KNHC 201539 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1247 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 1200 UTC surface analysis and satellite imagery through 1500 UTC. ...SPECIAL FEATURES... Showers and thunderstorms have increased near a small area of low pressure located near 13N114W. 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. A cluster of moderate to isolated strong convection is within about 75 nm E semicircle of low center. Although upper-level winds are only marginally conducive, this system has the potential to become a tropical depression over the next couple of days before upper- level winds become unfavorable for development. The low is expected to drift northward over the next several days. Latest tropical weather outlook gives this system a medium change of tropical cyclone formation. A gale warning remains in effect for the Gulf of Tehuantepec. This gap wind event will be associated with a cold front moving S through the western Gulf of Mexico tonight through Friday night. N winds of 25-30 kt will begin to surge into the Tehuantepec area this morning. Winds are forecast to continue increasing to 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 to gale force lasting until early Sun, and strong to near gale force winds persisting through the end of next week. Expect the strongest winds during the overnight and early morning hours, particularly between 0600-1200 UTC, with the assistance of the nocturnal drainage flow. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 13N106W to 1006 mb low pressure near 13N114W to 11N123W to 13N135W to 13N140W. Scattered moderate isolated strong convection is noted from 10N to 13N between 107W and 112W. Similar convection is from 10N to 13N between 114W and 121W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A ridge dominates the waters W of the Baja California peninsula. Under the influence of this system...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 6 to 8 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 reinforcing 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. Winds across the northern part of the Gulf of California north 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. Winds are forecast to briefly increase to 20-25 kt across the central waters this evening. By early Friday morning, expect mainly gentle to moderate winds and seas generally under 5 ft across the entire Gulf of California or Sea of Cortez. Farther south, a gap wind event with minimal gale force winds, is expected to begin across the Gulf of Tehuantepec late tonight into Friday morning. 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 per an earlier Ascat pass across the waters between Ecuador and the Galapagos Islands with seas of 5-7 ft in SW swell, except in the lee of the Galapagos Islands. Farther N, mainly gentle to moderate southwesterly flow prevail with an area of moderate to fresh SW winds roughly from 06N-10N 90W and 103W. Seas in this area are in the 8-9 ft range in SW swell. These marine conditions are forecast to prevail over the next few days. Disorganized cloudiness and showers near the coast of Central America are associated with a surface trough. Environmental conditions are forecast to become more favorable for some development of this disturbance over the weekend while the system moves toward the west-northwest 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 21N W of 125W with seas of 8-11 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 25N between 118W and 130W. Seas will gradually subside to less than 8 ft in about 24 hours, but another set of long period NW swell will reach the NW waters by late Friday. This swell event will propagate SE covering the waters NW of a line from 30N125W to 23N140W by early Saturday morning. $$ GR