000 AXPZ20 KNHC 280250 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 0405 UTC Tue Nov 28 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 0000 UTC surface analysis and satellite imagery through 0245 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec Gale Warning: A fairly tight pressure gradient is across southern Mexico between high pressure building over central Mexico and the western Gulf of Mexico and low pressure over the eastern Gulf of Mexico and lower pressures in the deep tropics. This is resulting in gap winds through the Gulf of Tehuantepec this evening. An earlier 1622 UTC ASCAT pass showed 25-30 KT within 45 nm either side of a line from 16N95W to 12N97W. These winds are forecast to pulse again to gale force overnight during nocturnal drainage flow. The winds should remain below gale force shortly after 12 UTC Tuesday. Lingering NE swell from the gap wind event with 8 ft or greater seas will reach more than 500 nm offshore of the Gulf of Tehuantepec. Pulses of gap winds to near gale force will persist through mid week, with another round of gale force winds expected Friday night. INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from 09N84W to 07N97W to 10N111W, where it transitions to the intertropical convergence zone and continues to 09N120W to 10N130W to beyond 10N140W. Scattered moderate convection is generally within 120 to 180 NM of the monsoon trough between 91W and 94W and between 103W and 108W and also from 11.5N to 14N between 108W and 122W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... See Special Features paragraph above for information on the Gulf of Tehuantepec Gale Warning. A frontal trough will move across the region from the west through tonight, then dissipate from the northern Gulf of California to the central Baja California peninsula to 23N120W by early Tue. Fresh to strong NW winds are occurring off the coast of Baja California Norte. Fresh NW winds will spread over the northern Gulf of California through the overnight hours. NW swell of 8 to 12 ft will follow the front as well, with the leading edge of 8 ft seas reaching the Revillagigedo Islands by late Wed or Thu. Looking ahead, while this swell group decays below 8 ft from south to north, another reinforcing group of NW swell in excess of 8 ft will propagate into the waters off Baja California Norte by late Thu. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Gulf of Papagayo: A tight pressure gradient between high pressure over northern Central America and lower pressure across the southwest Caribbean will enhance overnight drainage effects and result in pulses of fresh to strong gap winds through the Gulf of Papagayo beginning overnight into Tue morning, and to a lesser extent Tue night into Wed morning. Looking ahead, stronger pulses are likely later in the week. Seas will build to a maximize of around 7 ft each morning near sunrise. Light to gentle N to NE winds, and 3 to 5 ft seas are expected elsewhere through Friday north of the monsoon trough. Moderate southerly winds, and 4 to 6 ft seas, are forecast south of the monsoon trough. Northerly swell generated in the Gulf of Tehuantepec has reached the western part of forecast zone PMZ111 (offshore waters of Guatemala and El Salvador) with seas to 10 or 11 ft overnight, diminishing by early Tue. REMAINDER OF THE AREA... A frontal trough extends from 30N119W to 26N120W will dissipate as it moves east of the area through Tue. Fresh to strong NW winds west of the front are diminishing rapidly as the front weakens, but NW swell of 8 to 14 ft will continue to propagate across the region with the leading edge of 8 ft seas reaching from the central Baja California peninsula to 02N140W by late Tue. Building high pressure to the north will allow fresh to strong NE winds north of 15N and west of 125W Tue night through late in the week. Farther south, recent altimeter satellite data indicated seas near 8 ft, likely in NW swell, S of 10N. This will decay below 8 ft through late tonight as it continues to propagate south and west of the area. $$ Cobb