000 AXPZ20 KNHC 100326 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 0405 UTC Sun Dec 10 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 0000 UTC surface analysis and satellite imagery through 0300 UTC. ...SPECIAL FEATURES...Updated Gulf of Tehuantepec Storm Warning: A very tight pressure gradient across the Isthmus of Tehuantepec will support storm force winds of 40-55 kt across the Gulf of Tehuantepec through late Sun morning, and then again Sun night into Mon morning. The latest scatterometer pass provided observations of 35-45 kt winds roughly within 60 nm of a line from 16N95W to 14N96W. Seas are quite large, in the 14-20 ft range within the area of 35-45 kt winds, and are forecast to build up to 22 or 23 ft on Sun with the storm force winds. This will be an impressive blast of storm force winds given the favorable synoptic set-up with a strong cold front over the NW Caribbean, and a high pressure of 1031 mb centered over NE Mexico, extending a ridge across the eastern slopes of the Sierra Madre Mountains. A large area of gale force winds of 30-40 kt is forecast to be elsewhere of the storm force winds, with fresh to strong NE-E winds extending downwind to beyond 100W. Seas 8 ft or greater are expected to propagate well away from the Gulf to near 105W on Sunday, and farther W to near 110W on Monday. Gale conditions are forecast to continue into early next week while gradually tapering off, however, marine impacts with respect to resultant very large seas will affect waters to the S and SW of the Tehuantepec well into next week. Gulf of Papagayo Gale Warning: Strong high pressure building N of the area as describe above with the Gulf of Tehuantepec warning will induce a strong gap wind event across the Gulf of Papagayo beginning tonight into early Sunday morning, at which time NE winds are forecast to reach minimal gale force of 30-35 kt. N-NE winds of 20-30 kt are expected elsewhere downstream from the gale force winds over an area defined from 07N-11N between 85W-88W early on Sunday morning, and from 06N-10N between 86W- 90W early on Monday with sea heights to 9 ft in NE swell derived from the gale force winds. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The Monsoon Trough extends from 11N86W to 07N100W to 10N120W to 09N134W. The ITCZ axis continues from 09N134W to beyond 09N140W. Scattered moderate convection is from 07N to 10N between 95W and 100W. Similar convection is from 08N to 12N between 120W and 131W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Gulf of Tehuantepec: Please see Special Features section above for details. High pressure over the Great Basin will continue to support fresh to strong northerly winds over the northern Gulf of California through Sunday. N-NE winds funneling through the Baja California peninsula into the Pacific waters have diminished 15-20 kt, with seas subsiding below 8 ft off the coast of Baja California through tonight. Elsewhere gentle to moderate winds and 4-6 ft seas will persist through next week. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Gulf of Papagayo: Please, see Special Features section above for details. Strong high pressure building across northern central America will induce a strong Papagayo gap wind event tonight, reaching minimal gale force Sunday morning, and again Mon morning. Large NE swell from a Tehuantepec gap wind event will spread across the offshore waters of Guatemala and El Salvador tonight through Mon. Localized gap pulses of strong NE winds are possible off the coast of El Salvador and Guatemala, including Gulf of Fonseca beginning early on Sunday. REMAINDER OF THE AREA... Long period NW swell has spread across the forecast waters covering roughly the area to the W of a line from 30N125W to 20N112W to 04N130W to 02N140W. A cold front has just crossed into the far NW part of the area, but it is starting to weaken. This front will dissipate by early on Sunday, however, a stronger cold front will be approaching the NW corner at the same. The pressure gradient between it and high pressure over the northern is expected to develop strong S to SW winds N of 28N W of 135W along with waveheights in the range of 9-14 ft in NW swell. The front is forecast to reacg a position from 30N135W to 25N140W by Sun night while weakening. Seas of 12-14 ft in NW swell will follow the front. These conditions will continue into Monday, then gradually decay through the middle part of next week. Yet another set of NW swell is forecast by wave model guidance to approach the far NW portion by that time. $$ GR