000 AXPZ20 KNHC 130344 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 344 UTC Tue Mar 13 2018 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 0300 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec Gale Warning: Strong high pressure is building over the western Gulf of Mexico behind a cold front, with associated cooler and drier air pushing through the Chivela Pass into the Gulf of Tehuantepec. Reports from Salina Cruz on the southern end of the Tehuantepec isthmus is showing strong northerly winds, hinting near gale to minimal gale conditions farther shore over the Gulf of Tehuantepec. The gale winds will persist through late Wed, then diminish below gale force as the high pressure north of the area weakens and shifts east. Seas will reach as high as 16 ft late Mon night into early Tue before subsiding to below 8 ft by late Thu. Please see the latest Pacific Ocean High Seas Forecast product under AWIPS/WMO headers HSFEP2/FZPN03 KNHC, for more details. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... A surface trough axis extends from 09N83W to 03N100W where it transitions to the intertropical convergence zone and continues to 02N120W then to 05N140W. Scattered moderate convection is noted within 90 nm north of the surface trough between 93W and 100W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see the Special Features section for information on the Gulf of Tehuantepec developing gale event. 1019 mb high pressure centered near 28N121W is maintaining generally moderate northwesterly winds across the region, except for moderate to fresh winds off the coast of Baja California Sur from Cabo San Lazaro to Punta Eugenia. Seas are 5 to 7 ft off the coast of Baja California and 3 to 5 ft in the Gulf of California. Winds and seas will diminish through Tue night into early Wed as the high pressure shifts eastward and weakens ahead of a cold front approaching from the west. The front will push across Baja California Norte and the northern Gulf of California by late Wed. Strong westerly gap winds are possible over northern Baja California into the Gulf of California Wed night, then diminish as the front moves farther south and weakens. Long period northwest swell in excess of 8 ft will move into the waters off Baja California starting Wed following the front. The swell will propagate to the waters of Baja California Sur by late Thu before decaying below 8 ft. Winds and seas will continue to diminish into Fri as high pressure builds over the region. Looking ahead, SW winds will increase and another round of NW will move into the region ahead of another cold front moving west across the region. Strong westerly gap winds are again possible into the northern Gulf of California Fri night into Sat as the front moves through the region. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Over Gulf of Papagayo, high pressure ridging over the Caribbean will cause moderate to fresh winds to pulse over the Gulf of Papagayo through Tue. Winds will increase back to fresh to strong early Tue night and through Fri night as the pressure gradient re- strengthens in response to high pressure building southeastward over the Caribbean from the Gulf of Mexico. Over the Gulf of Panama, gentle to moderate winds will prevail through mid week, increasing to moderate to fresh thereafter. Seas are expected to run between 4 and 6 ft as moderate cross- equatorial SW swell propagates through these waters, building the seas 5 to 7 ft Thu and Fri as the winds also increase. Elsewhere, expect gentle to moderate winds and 4 to 6 ft seas to prevail, except seas of 8 to 11 ft in northerly swells generated from a gale force gap wind event in the Gulf of Tehuantepec, which will propagate into the Guatemala offshore waters tonight through Tue night. REMAINDER OF THE AREA... A cold front reaching from 30N130W to 22N140W will shift eastward across the waters north of 20N through Mon night into early Tue. A few showers and thunderstorms are active along the front currently north of 24N. An earlier scatterometer pass indicated strong westerly winds behind this front mainly north of 29N, but this may be diminishing as deep low pressure north of the region supporting these strong winds lifts farther to the northeast. Related NW swell is propagating into the region behind the front, with seas in excess of 8 ft reaching as high as 15 ft. These seas will subside somewhat through Mon, but swell in excess of 8 ft will encompass most of the region west of 120W through mid week. Farther south, an earlier group of long period northwest swell mixed with shorter period trade wind waves are creating combined sea heights to 8 ft from 07N to 10N between 125W and 130W, although the extent of this area in excess of 8 ft is decreasing rapidly as the swell decays and the trade winds diminish. $$ Christensen