000 AXPZ20 KNHC 262155 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2128 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 1800 UTC surface analysis and satellite imagery through 2145 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec Gale Warning: A tight pressure gradient has become established across southern Mexico between a building high pressure over the western Gulf of Mexico and relatively lower pressure over the deep tropics. The strong gap northerly winds in the Gulf of Tehuantepec from this morning are increasing to gale force early this afternoon, with seas building to the range of 9 to 12 ft. The winds will further increase to 40 kt by tonight and into early on Monday 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 on Monday. The high pressure will weaken and shift eastward Tuesday, 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 isolated strong convection is within 60 nm N and 30 nm S of the W of 137W. Scattered moderate convection is within 60 nm N of the axis between 92W and 94W, and also within 60 nm of the axis between 95W and 97W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... See Special Features paragraph above for information on the Gulf of Tehuantepec Gale Warning. A 1020 mb high pressure centered near 27N126W 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 Monday and the northern Gulf of California on Tuesday. NW winds will increase to fresh to strong off Baja California Norte in the wake of the front Monday and Monday 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 Monday night into Tuesday, with seas building 4 to 6 ft. Winds will diminish Tuesday into Wednesday 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 Tuesday. 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 Monday night. REMAINDER OF THE AREA... A cold front is analyzed from near 32N126W to near 25N131W where it becomes a stationary from to near 20N138W. Recent ship observations and an ASCAT pass from earlier in the afternoon 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 Monday, just ahead of the reinforcing NW swell currently entering the forecast area. $$ Aguirre