000 AXPZ20 KNHC 151540 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1540 UTC Fri Dec 15 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 1500 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec Gale Warning: A cold front moving southward across the western Gulf of Mexico will reach the isthmus of Tehuantepec later today. Cool and dense air will funnel through the Chivela pass into the Gulf of Tehuantepec this evening with winds rapidly ramping up to near gale force and further to gale force later tonight. The front will weaken Saturday, which will diminish winds funneling across the Gulf of Tehuantepec. This will keep this gale force gap wind event brief as winds are expected to diminish below gale force by Sat afternoon. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 09N84W TO 06N98W, where it transitions to the intertropical convergence zone and continues to beyond 10N140W. No significant convection is observed near the monsoon trough or ITCZ, but scattered moderate convection is noted from 15N to 18N between 110W and 115W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Gulf of California: Strong high pressure north of the area over the Great Basin and northern Rockies is supporting fresh to occasionally strong NW winds over the far northern Gulf of California this morning. Fresh winds will gradually spread across the northern half of the Gulf through tonight with seas to 5 ft. A cold front will move into across the northern Gulf Sat, before stalling and dissipating over the central Gulf Sun. Winds over the northern Gulf will shift SW early Sat ahead of the front, as associated low pressure deepens over the lower Colorado River basin. The main issue by Sat night will be the possibility of strong W to NW winds over the northern Gulf as the low pressure shifts eastward into the Sonoran Desert. While the fetch across the northern Gulf will be to limited to develop large seas, mariners should be aware of the possibility of sudden strong winds through low lying areas of Baja California Norte through early Sun. Winds diminish through early next week after the low pressure dissipates. Elsewhere, fresh N to NE gap wind will spill across Baja California Norte into the Bay of Sebastian Vizcaino this afternoon then diminish. A cold front will move through the waters off Baja California Norte through early Sat followed by strong NW winds and seas building to 8 to 12 ft by late Sat. Seas of 8 to 10 ft will cover most of the waters beyond 60 nm of the Baja coast through early next week in NW swell. Elsewhere gentle to moderate winds and 3 to 5 ft will persist along the coast of Mexico outside of the Gulf of Tehuantepec through mid week. Please see Special Features section for more information the Gulf of Tehuantepec gale warning. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Fresh to strong winds across the Gulf of Papagayo are diminishing this morning, but will strengthen again Sat night. Fresh N winds will funnel across the Gulf of Panama through late this morning before diminishing through the weekend. REMAINDER OF THE AREA... Ridging extends from 1033 mb high pressure near 42N138W to the Revillagigedo Islands. The pressure gradient between this area of high pressure and lower pressure in the vicinity of the ITCZ is supporting moderate to fresh winds north of the ITCZ to 20N and west of 120W. Fresh to strong tradewinds are noted on a earlier scatterometer satellite pass north of trough near 140W. Seas associated with a fresh pulse of NW swell are peaking near 13 ft in the area of strong trades W of 135W. Seas will slowly subside as the swell propagates southeast the next few days. A cold front will move into the far northern waters Saturday. This will usher in another set of northerly swell into the area. $$ Christensen