000 AXPZ20 KNHC 272138 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2205 UTC Mon Nov 27 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 1800 UTC surface analysis and satellite imagery through 2130 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec Gale Warning: A 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, along with relatively lower pressure over the deep tropics. This is resulting in gap winds of minimal gale force through the Gulf of Tehuantepec this afternoon. An earlier 1622 UTC ASCAT pass showed 25-30 KT within 45 nm either side of a line from 16N95W to 12N97W. These winds may briefly diminish below gale force this evening as the high pressure weakens with one more pulse of gale force winds expected overnight. Swell from the gap wind event with 8 ft or greater 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 07N95W to 09N112W, where it transitions to the intertropical convergence zone and continues to 08N127W to beyond 10N140W. Scattered moderate convection is generally within 90 to 120 NM either side of the monsoon trough between 91W and 107W and also from 11N to 14N between 110W 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 weakening cold front will move across the region from the west through tonight, then stall and dissipate from the northern Gulf of California to the central Baja California peninsula to 23N120W late tonight or early Tue. Fresh to strong NW winds will follow the front this afternoon off the coast of Baja California Norte, then later this evening into the overnight hours over the northern Gulf of California. The winds will diminish through tonight, but 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 tonight 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 through tonight, diminishing by early Tue. REMAINDER OF THE AREA... A weakening cold front extends from 30N119W to 23N130W will begin dissipating as it moves east of the area through Tue. Fresh to strong NE 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 09N140W 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