000 AXPZ20 KNHC 281535 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1530 UTC Thu Dec 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 1200 UTC surface analysis and satellite imagery through 1500 UTC. ..SPECIAL FEATURES... Gulf of Tehuantepec Gale Warning: A tight pressure gradient related to strong ridging over eastern Mexico and the western Gulf of Mexico will continue to support gales into the Gulf of Tehuantepec through late Fri night. Seas will build as high as 14 ft in the main area of gales in the Gulf of Tehuantepec, with related swell to 8 ft reaching as far as 700 nm to the WSW of the Gulf of Tehuantepec, mixed with longer period NW swell. Winds and seas diminish Sat as the high pressure north of the area weakens. Refer to the latest high seas forecast issued under AWIPS/WMO headers HSFEP2/FZPN03 for more details. Looking ahead, another stronger front will move through the Gulf of Mexico late Sun and early Mon, delivering strong gales or even storm force winds through the Gulf of Tehuantepec by Mon night into Tue morning. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... A surface trough axis extends from 05N77W to 07N90W to 06N108W, where it transitions to the intertropical convergence zone and continues west to a 1012 mb low pressure area centered near 10N125W, then farther west to beyond 07N140W. Scattered convection is noted from 10N to 15N between 110W and 120W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please refer to the special features section above for details of a Gulf of Tehuantepec Gale event. A fairly tranquil synoptic pattern associated with a nearly stationary subtropical high west of California and a surface ridge extending SE from the high will persist for several days. This will maintain gentle to moderate NW to N winds off Mexico through the weekend. Seas will be in the general range of 4-6 ft over the offshore waters and 2-4 ft in the Gulf of California. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... A moderate high pressure gradient in the western Caribbean will continue to support pulsing fresh to strong NE winds from 09N to 11N east of 90W, including Gulf of Papagayo, through Mon night with seas to 7-9 ft primarily from NE wind waves. Mainly gentle winds are expected elsewhere through the weekend, with offshore seas generally 4-5 ft. REMAINDER OF THE AREA... Long-period NW swell is producing 8-9 ft seas from 15N to 25N west of 125W. Seas will continue to gradually diminish today as the peak swell continues moving southeastward. Divergence aloft southeast of an upper trough along 120W along with convergence of fresh trade winds in the lower levels are supporting the scattered showers and thunderstorms from 10N to 15N between 110W and 120W. A related surface trough and weak low along the intertropical convergence zone near 10N125W will drift westward over the next 48 hours then dissipate. The gradient between the trough and high pressure over northern waters will increase trade winds sufficiently to build seas to 8-9 ft in mixed NW swell and wind waves. $$ Christensen