000 AXPZ20 KNHC 020305 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 305 UTC Tue Jan 2 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 0200 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec Gale Warning: A strong and long duration gale event has begun over the Gulf of Tehuantepec as strong high pressure building behind a cold front is moving across the Gulf of Mexico helping to tighten the pressure gradient over the region. Gale force winds are expected to persist for much of the week, peaking near 45 kt late tonight and again early Thu. Seas are building to 14 ft this evening and will peak near 18 ft Tue morning and again on Thu morning. Swell associated with this event will push downstream of the Gulf of Tehuantepec, with seas 8 ft or greater reaching as far south as 05N and west to 108W by midweek. Refer to the latest high seas forecast issued under AWIPS/WMO headers HSFEP2/FZPN03 for more details. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... A surface trough extends from 07N78W to 06N90W to 05N99W. The intertropical convergence zone continues from 05N99W to 12N125W to beyond 08N140W. Scattered moderate to isolated strong convection was noted from 09N to 18N between 117W and 129W. Scattered moderate convection was observed within 150 nm of the ITCZ between 129W and 139W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see special features section above for more details about the gale force gap wind event in the Gulf of Tehuantepec. Relatively tranquil marine conditions will persist through the week with light to gentle winds prevailing across the forecast waters. Seas in the range of 3 to 5 ft will continue in the offshore waters, while seas in the 1 to 3 ft range will prevail in the Gulf of California. NW swell of 6 to 8 ft will propagate into the waters off Baja California Norte later in the week. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... NE winds will pulse to fresh to strong in the Gulf of Papagayo through the middle of the week. Winds will further increase to near gale force Thursday as high pressure builds north of the area. 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. Swell up to 11 ft from the Gulf of Tehuantepec gale event may reach the far western waters offshore Guatemala through the week. REMAINDER OF THE AREA... A 1006 mb low pressure is centered near 28N136W under a sharp upper trough. An occluded front wraps around the NW semicircle of the low, while a cold front extends from 30N133W to 25N131W to 17N136W. Scattered showers and isolated thunderstorms are within 90 nm E of the front N of 26N, and within 150 nm of the center of the low. A scatterometer pass at 1918 UTC earlier this afternoon confirmed fresh to strong NW to N winds west of the low, N of 25N over our area E of 140W. Seas are likely 11 to 14 ft under this area of winds, with a broader area of 8 to 11 ft NW swell west of the cold front. The low and associated fronts will weaken as the low lifts NE the next 24 hours, with winds decreasing below 20 kt by Tue afternoon. The NW swell will continue to propagate SE through Tue night, with seas 8 ft or greater reaching as far S as 15N and as far east as 125W Wed morning. The swell will persist over this region into the latter part of the week. A surface trough that extends from 24N125W to 19N126W is supporting a tight pressure gradient between itself and high pressure to the NE. As measured by a 1738 UTC scatterometer, SE winds of 20 to 25 kt were occurring over the northern portion and just NE of the trough axis. This trough and associated winds are weakening, with winds likely dropping at or below 20 kt as of this evening. The interaction of this surface trough, and a deep moisture plume on the eastern side of a sharp upper trough to the west is supporting scattered moderate and isolated strong convection from 18N to 24N between 117W and 127W. Elsewhere mainly gentle to moderate winds and 5 to 7 ft seas will prevail through midweek. The only exception will be NE swell associated with a Gulf of Tehuantepec gale event that will reach as far as 108W by midweek. $$ Latto