000 AXPZ20 KNHC 290301 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 0224 UTC Thu Dec 29 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 0000 UTC surface analysis and satellite imagery through 0245 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec Gale Warning...The pressure gradient between a surface ridge over the Gulf of Mexico and lower pressures within the Monsoon Trough over the eastern Pacific is supporting gale force winds over the Gulf of Tehuantepec. This synoptic setup will prevail through Thursday supporting these winds. By Thursday night, the high pressure will strengthen north of the area behind a cold front moving through the Gulf of Mexico. This will bring a slight increase to the gale-force winds by Thursday night into Friday morning. A progressive pattern will see this area of high pressure shift rapidly into the southwestern Atlantic waters Friday night into Saturday. Winds over the Gulf of Mexico will veer and winds funneling into the Gulf of Tehuantepec will decrease. This will bring an end to the latest gale force gap wind event in the Gulf of Tehuantepec on Saturday. Please see the latest National Hurricane Center High Seas Forecast product under AWIPS/WMO headers MIAHSFEP2/FZPN03 KNHC for further details. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The Monsoon Trough extends from 09N84W to 06N97W. The ITCZ extends from 06N97W to 13N121W to 09N140W. Scattered moderate convection was noted within 100 nm on either side of the ITCZ between 125W and 140W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see the special features for details on the Gulf of Tehuantepec gale-force gap wind event. The pressure gradient between a high pressure west of the Baja California and lower pressures over western Mexico is supporting fresh to strong northwest winds over the southern portion of the Gulf of California. The gradient will weaken through the next 24 hours and winds will diminish. Elsewhere, winds will remain 20 kt or less, with seas below 8 ft through the end of the week. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Winds will pulse over the Gulf of Papagayo the next several nights, peaking to near 25 kt during the overnight hours as the gap winds are enhanced by nocturnally induced drainage flow. Winds will decrease to 20 kt during the late afternoon and early evening hours. Elsewhere, winds will remain 20 kt or less, with seas below 8 ft through the end of the week. REMAINDER OF THE AREA... A surface trough extends from 29N125W to 22N130W. The pressure gradient between 1027 mb high pressure centered north of the area near 40N129W and the trough is supporting fresh to strong northerly winds mainly northwest of the trough's axis. Northwest swell is propagating across the northern waters with seas in the 8 to 11 ft range. Northwesterly swell is mixing with northeasterly generated wind waves to produce seas greater than 8 ft over much of the forecast waters north of 07N and west of 115W. The trough will prevail across the northern portion of the basin the next two days before dissipating. The area of high pressure will weaken through the next 48 to 72 hours. This will help decrease winds and seas over the forecast area. Winds are expected to diminish below advisory criteria Thursday, while the areal extent of seas 8 ft or greater will continue to decrease through the weekend. A frontal boundary will approach the far northwest waters by Friday where it will stall. The front will usher in another set of long period northwesterly swell into the area. Seas associated to this swell will peak near 11 ft on Friday. $$ NATIONAL HURRICANE CENTER