000 AXPZ20 KNHC 270228 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 0147 UTC Wed Dec 27 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 0200 UTC. ..SPECIAL FEATURES... Gulf of Tehuantepec Gale Warning: An 8 mb pressure gradient from higher pressures over the central Gulf of Mexico to lower pressures in the Gulf of Tehuantepec are likely inducing near gale N-NE winds in the Gulf of Tehuantepec, though no observations have been available in the last few hours. N-NE winds are expected to remain in the 25-30 kt range through Wednesday night before pulsing back up to minimal gale force early on Thursday as another southward surge of high pressure takes place along the eastern slopes of the Sierra Madre mountains to southeastern Mexico. A blend of the GFS and ECWMF deterministic models indicates that this next episode of gale force winds is likely to possibly continue into Saturday before weakening on Sunday. Peak seas should reach about 13 ft early on Friday. An extension of seas of at least 8 ft may reach to 12N100W through a combination of wind waves and NW swell coming across the basin. Refer to the latest high seas forecast issued under AWIPS/WMO headers HSFEP2/FZPN03 for more details. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... A trough axis extends from 05N77W to 06N94W. The ITCZ axis extends from 06N94W to 10N114W to beyond 07N140W. Scattered moderate convection is located within an area bounded by 10N101W to 10N112W to 09N120W to 06N118W to 07N103W to 08N100W to 10N101W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please refer to the special features section above for details on a soon to end Gulf of Tehuantepec Gale event. Aside from the Gulf of Tehuantepec event described above, winds should be fresh breeze or weaker and seas less than 8 ft for the remainder of the Mexican Offshore Waters through Sunday night. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Moderate high pressure gradient in the western Caribbean will continue to support fresh to strong NE winds from 09N to 11N east of 90W, including the Gulf of Papagayo, through Sunday night with seas to 7-9 ft in mixed NE wind waves. The remainder of these Offshore Waters has fresh breeze or weaker winds and seas less than 8 ft through Sunday night. REMAINDER OF THE AREA... A long-period NW swell is producing peak seas centered near 20N130W of around 10 ft. These are propagating southeastward and slowly diminishing. A new pulse of long-period NW swell of about the same wave height is beginning to push through the northwestern corner of our area and it too will spread southeastward over the next few days while gradually diminishing. On Friday and Saturday the E tradewinds in the vicinity of 15N120W will reach fresh to strong breeze as the pressure gradient tightens between a trough along the ITCZ and high pressure to the north. An E swell generated by these tradewinds will contributed toward combined seas of 8 to 10 ft near the vicinity of 15N125W on Friday and Saturday. A mid to upper level trough extends from a cyclonic circulation located at 22N119W southwestward to 10N125W. This is helping to support scattered moderate and isolated strong convection over a large area centered at 15N110W. This upper trough will continue to promote deep convection during the next couple of days in the same general location. $$ Landsea