000 AXPZ20 KNHC 120942 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1005 UTC Sun Nov 12 2017 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... ...A GALE WARNING FOR THE GULF OF TEHUANTEPEC... Gale-force winds continue in the Gulf of Tehuantepec. A high surface ridge along the Sierra Madre Oriental is maintaining a tight pressure gradient across the Isthmus of Tehuantepec. Model guidance suggests that the current synoptic pattern will remain favorable for gale-force N to NE gap wind flow until Wednesday morning. The wind speeds will peak between 35 and 40 kt Sunday night through Mon night. Sea heights will range from 10 feet to 13 feet in the current conditions. Sea heights could build to 16 feet on Tuesday due to the long event duration and sustained wind speeds. The leading edge of the resultant 8 foot seas, propagating away from the source region, is forecast to reach 06N102W early on Wednesday. The wind speeds are forecast to remain at or above gale-force until Wednesday morning. High pressure in the western Gulf of Mexico should weaken and shift eastward on Thursday, allowing the wind speeds in the Gulf of Tehuantepec to subside finally. A 1008 mb surface low is centered near 12N122W. The low pressure centered has become comparatively better defined. Consensus global model guidance indicates that this low center should move WNW to NW through Tuesday. The guidance indicates the pressure gradient between this low and high pressure to the north will create a swath of 20 to 30 kt winds within 240 of the low on Sun, with associated seas building to 9 to 10 feet by Sunday afternoon, then to 14 feet by Monday sunrise, and reaching 17 feet by sunset on Monday. Gradual development of this system is possible before upper-level winds become unfavorable for development by the middle of next week. The chance of formation to develop into a tropical cyclone through 48 hours is high. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough passes through Costa Rica near 09N84W, to 07N92W, to 08N99W, to 07N106W, to a 1008 mb low pressure center that is near 12N122W, to 11N127W, to 12N133W to 11N140W. Precipitation: scattered strong from 06N to 07N between 77W and 78W along the coast of Colombia. Scattered moderate to strong within 300 nm to the north of the monsoon trough between 126W and 130W. scattered moderate to isolated strong within 45 nm to the south of the monsoon trough between 117W and 119W, within 90 nm to the north of the monsoon trough between 123W and 126W, within 60 nm on either side of the line from 13N120W to 14N123W, and within 60 nm on either side of the line from 16N121W to 16N124W to 15N126W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please refer to the Special Features section for information regarding the ongoing Gulf of Tehuantepec gale warning. A ridge will dominate the waters W of Baja California during the next several days. An inverted surface trough will meander along the coast of NW Mexico and in the Gulf of California. Moderate to fresh N to NW winds will prevail across the waters W of Baja California through Tuesday night. The surface pressure gradient W of Baja California will tighten slightly Sun night and Mon as high pressure shifts eastward closer to the coast. Expect fresh to locally strong NW winds N of 25N and E of 119W from early Monday to early Wednesday, with seas building to 8 ft on Wednesday in response to NW swell. Long period NW swell propagating SE across the waters W of Baja California are decaying slowly. This will allow seas W of Baja to subside from between 6 and 9 ft tonight to between 5 and 7 ft on Monday and slowly subside through Sunday. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Light and variable winds, and seas of 4-6 ft, are generally expected N of 09N. Moderate to locally fresh S to SW winds and seas of 5 to 7 ft are forecast S of 09N through Tuesday. It is possible that the sea heights in the Gulf of Panama may build to 8 feet or greater on Tuesday night in response to a surge of monsoonal winds. REMAINDER OF THE AREA... Long period NW swell propagating southeastward is maintaining seas at 8 feet or greater, generally from 10N to 25N W of 113W. Seas in most of this area will subside to less than 8 feet by Mon morning as the swell decays. It is possible that another round of NW swell, generated by a cold front to the N of the discussion area, may reach the NW corner of the discussion area from the early morning hours of Tuesday, during all of Tuesday, and continuing into Friday, from 22N northward from 132W westward. $$ mt