000 AXPZ20 KNHC 302204 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2205 UTC Sat Dec 30 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 2300 UTC. ..SPECIAL FEATURES... Gale Warning: A deep layer low pressure system, that is to the NW of the area, has been moving slowly northward during the last few days. A cold front, that currently is crossing 140W north of 22N, is associated with the deep layer low pressure system. The front will weaken today as it moves more to the east, and then it will dissipate tonight. A second and stronger cold front will enter the NW corner of the region right after the first front dissipates. Strong to minimal gale force winds will follow the second front Sun night into Mon as high pressure builds behind the front along with a push of cooler air. Gale-force winds will be limited to the waters that are to the N of 28N between 135W and 140W. The wind speeds will diminish to less than gale-force through late Mon, as the low pressure moves more to the east and weakens, and the cold front modifies as it continues eastward. Very rough to high seas can be expected in the area of gale-force winds, building as high as 22 ft late Sun and early Mon. This will be due in part to the gale-force winds, and in part to NW swell that will be entering the area. The large seas will subside to 8 to 10 ft through mid week. Please read the latest high seas forecast issued under AWIPS/WMO headers HSFEP2/FZPN03 for more details. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... A surface trough is along 09N83W 07N90W 06N93W 06N97W. The ITCZ continues from 06N97W to 08N110W to 11N124W, and from 08N133W beyond 09N140W. Precipitation: widely scattered moderate to isolated strong rainshowers are from 04N to 09N from 84W eastward, and from 05N to 15N between 97W and 123W. Isolated mdoerate to locally strong rainshowers are within 300 nm to the W of the line through 30N130W, to 24N132W, and 10N137W. This precipitation is to the east of the cold front, that passes through 30N135W to 25N138W to 21N140W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... In the Gulf of Tehuantepec, winds finally have diminished to less than gale-force, as high pressure that is to the north of the area weakens, and the winds veer more easterly. Strong gap winds will pulse again tonight due to overnight drainage flow, with seas briefly reaching 8 ft. A strong cold front will push into the Gulf of Mexico late Sunday, reaching the Bay of Campeche Monday. Strong high pressure in its wake is expected to induce the next gale-force gap wind event in the Gulf of Tehuantepec. This next gale-force gap winds event has the potential to be a strong and long-lasting event, persisting for much of the next week. Elsewhere, tranquil marine conditions are expected with light to gentle winds prevailing over the forecast waters. Seas in the range of 3 to 5 ft will continue over the offshore waters, while seas in the 1 to 3 ft range will prevail in the Gulf of California. A sharp upper trough is supporting widespread cloudiness and maybe a few showers across Baja California Sur and adjacent waters. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... NE winds will pulse to fresh to strong over the Gulf of Papagayo through the middle of next week. Light to gentle NE to E winds will prevail elsewhere N of 09N, with gentle to moderate S to SW winds expected S of 09N. REMAINDER OF THE AREA... Please read the SPECIAL FEATURES section, for more on the gale warning in the northwest waters, and the associated swell. A pair of surface troughs persist from roughly 10N to 15N between 120W and 130W. Earlier scatterometer passes indicate winds of 20 to 25 kt between the troughs and 1022 mb high pressure centered north of the area. Concurrent altimeter satellite passes indicate seas to 8 ft in the areas of strong winds. A surface trough will persist and shift northward through Tue ahead of advancing front, supported by a broad mid to upper trough slowly moving into the area from the west and persisting over the region west of 130W through at least mid week. Strong winds and seas to 8 ft are expected with the associated surface trough by Tue as it moves northward along 125W from 20N to 25N. Long period northwest swell in excess of 8 ft will cover most of the area north of 10N and west of 125W through mid week. $$ mt