000 AXPZ20 KNHC 180915 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 915 UTC Sun Dec 18 2016 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 0600 UTC surface analysis and satellite imagery through 0900 UTC. ...SPECIAL FEATURES... Gulf of California...Moderate to fresh northwest winds continue to move down the length of the Gulf of California this morning. The winds were following a weakening cold front that has since dissipated over the southern Gulf. The winds will increase substantially over the northern Gulf starting tonight as strong high pressure builds north of the area over the Great Basin. Winds may reach minimal gale force or close to it early Monday morning, with seas building to 12 ft north of Tiburon Island. Winds and seas diminish through early Tuesday as the high pressure weakens and shifts east, leaving areas of 20 to 25 kt winds across the Gulf. This pattern repeats again starting late Wednesday with strong to near gale force winds pushing across the Gulf through early Thursday. Gulf of Tehuantepec...A cold front will move through the entire western Gulf of Mexico today and reach the southwest Gulf of Mexico by the evening hours. Cooler, drier air behind the front will move across the isthmus of Tehuantepec into the Gulf of Tehuantepec Sunday night, with winds reaching gale force before 1200 UTC Monday. A large plume of gale force winds, possibly reaching near storm by Tuesday, will persist into early Wednesday across the Gulf of Tehuantepec. Seas may reach as high as 18 ft by late Tuesday given the strength and persistence of the gales. Winds diminish below gale force with subsiding seas through mid week as the airmass to the north modifies and shifts east. Looking ahead, there is some disagreement among major models concerning the strength of another gale event later in the week. Given this uncertainty, the official forecast shows just below gale force winds but another gale warning may be required in the next several days. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from Colombia near 06N90W to 09N115W. The ITCZ continues from 09N115W to 07N125W to beyond 08N140W. Scattered moderate to strong convection is noted within 90 nm either side of the ITCZ between 118W and 122W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Gale warnings are in effect for the Gulf of Tehuantepec and northern Gulf of California. See Special Features section above for details. Moderate to fresh northerly flow persists in the waters off Baja California today, with 5 to 7 ft seas. Although these winds will diminish through late today across the region, plumes of locally strong gap winds will emerge off the peninsula and cross Sebastian Vizcaino Bay late tonight and early Monday. Similarly another gap wind plume with fresh to locally strong winds will emerge off Baja California Sur near Todos Santos Tuesday with seas building to 7 ft offshore. These winds diminish by late Wednesday. Elsewhere offshore of Mexico, and outside of the Gulf of Tehuantepec and Gulf of California, gentle to moderate breezes and 3 to 5 ft seas will persist. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Fresh to strong northeast winds are expected to pulse across the Gulf of Papagayo and coast of Nicaragua during the overnight and early morning hours through Monday, with the assistance of the nocturnal drainage flow. Seas should build 6-8 ft during the peak of each nights wind. A larger gap wind event appears to be in store for most of zone PMZ113 and southern portions of PMZ111 off El Salvador and Guatemala Monday night into Tuesday morning, as strong trade wind flow in the southwest Caribbean funnels across Central America. Marine guidance indicates fresh to strong winds across the Gulf of Fonseca and the Gulf of Papagayo will extend westward to beyond 92W/93W by Tuesday morning, with seas building up to 10-11 ft west of 90W. Moderate northerly winds are expected across the Gulf of Panama at that time. REMAINDER OF THE AREA... Strong high pressure north of the area will support a broad area of fresh to strong northeast to east winds over much of the region north of 07N and west of 120W by Monday. Farther east, an upper level trough to the west of Baja California will become cut off near 22N125W by Monday night/early Tuesday. This has been supporting a surface trough currently reaching from 09N118W to 15N115W. The trough will become more amplified as it drifts northwest into the ridge through the next couple of days. This will enhance the northeast winds Monday through mid week. Seas will build to 12 to 13 ft from 15N to 25N west of 130W by late Monday into Tuesday with an added component of longer period northwest swell. The upper low will drift west into mid week, with the surface following. The tight gradient between this feature and the high pressure north of the area will maintain fresh to strong northeast winds mainly north of 15N and west of 125W from mid to lake week. $$ CHRISTENSEN