000 AXPZ20 KNHC 161527 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1605 UTC Fri Dec 16 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 1200 UTC surface analysis and satellite imagery through 1500 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec...A Gale Warning is in effect for the Gulf of Tehuantepec through late this morning. An earlier ASCAT pass indicated 20 to 30 kt winds were ongoing, and this will likely increase to minimal gale force later in the morning, with seas building to 9 to 10 ft. Winds will then diminish gradually throughout the early afternoon, reach around 20 kt only across the immediate Gulf of Tehuantepec this evening, and then less than 15 kt by Saturday morning. A stronger cold front over the weekend could produce a more significant northerly gale wind event beginning on Monday. Currently, marine guidance suggests northerly winds of 35-45 kt and building seas of 14-16 ft by Monday evening with the next gale force gap wind event. Gulf of California...A cold front approaching the region from the west is forecast to reach northern Baja California this evening and move eastward across the region, including the northern part of the Gulf of California by tonight. Expect strong westerly winds north of 29N over the far northern Gulf by this evening ahead of the front, then veering to the northwest and briefly increasing to minimal gale force tonight into early morning on Saturday as the front moves east of the area. Strong northwest to north winds will then spread southward across the Gulf of California Sat and Sat night as the front moves southeastward through the region. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from a 1010 mb low pressure near 06N78W to 07N85W to 05N95W to 07N100W. The ITCZ axis continues from 07N100W to 1011 mb low pressure near 09N107W to 07N120W to 09N130W to beyond 08N140W. A trough extends from low center near 09N107W to 15N106W. Scattered moderate isolated strong convection is from 04N to 07.5N E of 80W. Similar convection is from 09N to 15N between 105W and 110W, and from 08N to 10N between 125W and 130W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Gale warnings are in effect for the Gulf of Tehuantepec and Gulf of California. See Special Features section above for details. Gentle to moderate northerly winds and seas of 3-4 ft continue over the offshore waters west of Baja California this morning, under the influence of a weakening ridge extending eastward from a 1018 mb high pressure centered near 24N125W. The high pressure will dissipate later today ahead of a cold front expected to move across the N waters from west to east through Saturday. This will bring fresh to strong NW flow to the waters off Baja California Norte by early Saturday with 8 to 10 ft behind the front, with fresh NW winds and 5 to 8 ft seas off Baja California Sur. These winds and seas will diminish late Saturday through Sunday as high pressure builds eastward behind the front. Elsewhere off Mexico, 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 across the Gulf of Papagayo during the overnight and early morning hours with the assistance of the nocturnal drainage flow through Monday. 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 extending westward to beyond 92W/93W by Tuesday morning, with seas building up to 10-11 ft W of 90W. Moderate northerly winds are expected across the Gulf of Panama at that time. REMAINDER OF THE AREA... A cold front extends from 30N126W TO 28N130W TO 27N140W. The cold front will continue to move east across the N waters through Saturday. This will keep the subtropical ridge fairly weak, with moderate to locally fresh trade wind flow in the deep tropics. The trade winds will increase across the west-central waters this upcoming weekend as strong high pressure builds north of the area behind the front. Trade winds in the 20 to 25 kt range are anticipated from 11N to 17N W OF 130W Saturday morning, and from 08N to 13N W OF 135W, and from 13N to 18N W OF 130W Sunday morning. Fresh to strong NE-E winds are forecast to blow across most of the waters N of 07N W of 130W and N of 16N W of 123W by Sunday night. These marine conditions are expected to persist on Monday, with winds likely increasing to 30 kt and seas building to 11-12 ft across the west-central waters. As previously mentioned, a weak 1011 mb surface low is centered along the monsoon trough near 09N107W, with a surface trough extending north to 15N106W. Fresh easterly winds are noted per scatterometer data within about 150 nm NE quadrant of the low center. The low will dissipate through Saturday as it drifts west along the monsoon trough/ITCZ, with the trough persisting a couple of more days, reaching near 120W by Sunday night. While the low pressure and trough will have little impact on winds and seas in their vicinity as they weaken further, scattered showers and a few thunderstorm are expected to persist near the trough axis through at least Saturday. $$ GR