000 AXPZ20 KNHC 261602 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1414 UTC Sun Nov 26 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 1200 UTC surface analysis and satellite imagery through 1530 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec Gale Warning: A tight pressure gradient will set up across southern Mexico between a building high pressure over the western Gulf of Mexico and relatively lower pressure over the deep tropics. This will result in strong gap winds in the Gulf of Tehuantepec beginning early this morning, enhanced by local drainage effects. Winds will reach gale force by this afternoon, with seas building to 12 ft. The gales will further increase to 40 kt by tonight into early Mon morning, with seas building to 17 ft downstream. Swell from the gap wind event with 8 ft or greater will reach more than 500 nm offshore of the Gulf of Tehuantepec by late Mon. The high pressure weakens and shifts east Tue, allowing gale force winds to diminish. Another round of gale force winds is expected Wed and Thu. INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from 09N84W to 08N110W, where it transitions to the intertropical convergence zone and continues through 11N140W. Scattered moderate convection is noted from 10N to 15N between 105W and 125W. Scattered moderate to isolated strong convection is noted from 08N to 12N west of 135W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... See Special Features paragraph above for information on the Gulf of Tehuantepec Gale Warning. A 1019 mb high pressure centered near 26N125W will maintain gentle to moderate breezes and slight seas into Monday, ahead of a cold front approaching the area from the west. The front will cross the offshore areas off Baja California Mon and the northern Gulf of California Tue. NW winds will increase to fresh to strong off Baja California Norte in the wake of the front Mon and Mon night. Seas will build to 8 to 12 ft in NW swell, with 8 ft swell reaching as far south as the Revillagigedo Islands by Tue night. Fresh to strong NW flow will also follow the front in the northern Gulf of California Mon night into Tue with seas building 4 to 6 ft. Winds will diminish Tue into Wed as the front stalls and dissipates, but seas in excess of 8 ft will persist in open waters through late week as another round of reinforcing swell moves into the region. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Gulf of Papagayo: Expect a typical nocturnal maximum of around 25 kt across the region through early Tue morning, diminishing to 15-20 kt by mid afternoon. Seas will maximize to around 7 ft each morning near sunrise, and will likely build locally to 8 ft early Monday morning, with a more extensive area of 8 ft seas expected Tue morning. Moderate to locally fresh NE winds are expected across the Gulf of Fonseca each night through Tue. Light to gentle N to NE winds, and 3 to 5 ft seas are expected elsewhere through early Mon to the N of the monsoon trough which has been meandering between 09N and 11N. Moderate southerly winds, and 4 to 6 ft seas, are forecast S of the monsoon trough. Northerly swell generated in the Gulf of Tehuantepec will reach the western part of forecast zone PMZ111 (offshore waters of Guatemala and El Salvador) building seas up to 11 or 12 ft late tonight through Mon night. REMAINDER OF THE AREA... A cold front is over the NW waters and extends from 30N130W to 19N140W. Recent ship observations and an earlier ASCAT pass indicated fresh to strong NW winds in the wake of the front. The ship observation along with an altimeter satellite pass farther upstream indicated seas of 8 to 12 ft west of the front. An area of 8 to 10 ft seas in NW swell persists S of 14N W of 125W. These seas will propagate southward across the equator while decaying through early Mon, just ahead of the reinforcing NW swell currently entering the forecast area. $$ Christensen