000 AXPZ20 KNHC 141531 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1605 UTC Wed Dec 14 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 15000 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec...A Gale Warning is in effect for the Gulf of Tehuantepec beginning Thursday evening. Currently, northerly winds in the 20-25 kt range are noted across the Gulf, with seas of 5-6 ft. Winds will further increase to 30 kt tonight, with seas building to 8 ft in and downstream of the Gulf. A cold front moving across the Gulf of Mexico on Thursday will allow northerly winds behind the front to begin to spill through the Isthmus of Tehuantepec into the Gulf of Tehuantepec. Winds across these Pacific waters are forecast to reach minimal gale force Thursday evening through Friday morning. Seas are forecast to build to 10-11 ft with this gap wind event. A stronger cold front could produce a more robust gale wind event beginning on Monday. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends across the Gulf of Panama near 08N79W to 10N90W to 1010 mb low pressure near 09N96W to 07N101W. The ITCZ continues from 07N101W to 08N120W to 11N133W...then resumes W of a trough at 12N136W to beyond 11N140W. Scattered moderate convection is N of 07n E of 81W...including the Gulf of Panama. Scattered moderate and isolated strong convection can be found from 09N to 11N between 117W and 127W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Gulf of Tehuantepec: please, see Special Features section for details. Gentle to moderate northerly winds and seas of 4-5 ft are noted over the offshore waters W of Baja California under the influence of a ridge anchored by a 1020 mb high pressure located near 30N122W. The high pressure will weaken over the next couple of days as a cold front moves across the N waters. The front is forecast to approach northern Baja California on Friday and move into the area...including the northern part of the Gulf of California by Friday night. Expect increasing winds ahead and behind the front. Marine guidance suggests strong southwest to west winds ahead of the front and strong to near-gale force west to northwest winds behind the front over the northern Gulf of California Friday night into Saturday morning. Fresh to strong NW winds will affect the offshore zones N of 25N on Saturday and N of 22N Saturday evening, with seas building as high as 10 ft near 30N. Outside of the Gulf of Tehuantepec area, mainly light to gentle winds prevail south of Cabo Corrientes, with seas of 3-4 ft. These marine conditions will persist over the next couple of days. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... A weak 1010 mb low pressure, currently centered south of Tehuantepec near 09N96W will continue to move westward and away from the offshore waters while opening up into a trough by Thursday. Scattered moderate convection is noted in a band to the N of the low center and within about 60 nm N and W of a line from 13N92W to 12N96W to 10N98W. Similar convection is noted within 120 nm SE quadrant of center. Fresh to strong NE winds and building seas to near 8 ft are expected across the Gulf of Papagayo E of 88W/89W beginning early Thursday morning through Friday morning. A larger event appears to be in store for most of zone PMZ113 on Tuesday morning as strong trade wind flow in the SW Caribbean funnels through the gap. REMAINDER OF THE AREA... A cold front has already reached the NW waters and now extends from 30N138W to 26N140W. Fresh to strong S-SW winds are also observed ahead of the front to a line from 30N133W to 26N136W to 23N140W. Seas of 8-10 ft are seen within this area of winds. The front will continue to move across the N waters, reaching Baja California Norte by Friday night. Winds are forecast to diminish to 20 kt or less ahead of the front by Thursday night, and winds will increase again ahead and behind the front Friday night into Saturday morning as a strong high pressure builds across the forecast waters in the wake of the front. NW swell generated behind the front will cause seas to build to 8-10 feet across the far NW waters tonight into Thursday. by Friday. Seas east of 130W will briefly subside to around 8 ft on Saturday before a round of reinforcing N swell arrives on Sunday. High pressure building N of the area will cause a large area of fresh to strong trades to develop N of the ITCZ from 07N to 25N W of 125W by Tuesday morning. Seas in this area will be in the 8 to 11 foot range. As previously mentioned, a 1020 mb high pressure is centered near 30N122W and extends a ridge across the NE waters. The pressure gradient between the ridge and a surface trough extending from 19N134W to 13N135W is producing an area of fresh to strong E-SE winds from 16N to 19N E of trough to 130W. The trough will weaken in about 24 hours, allowing associated winds and seas to diminish on Thursday. The remnants of the trough will gradually lift northward on Thursday ahead of the aforementioned cold front. Expect increasing trade winds and building seas across the west- central waters during the upcoming weekend as strong high pressure builds N of area. $$ GR