000 AXPZ20 KNHC 281507 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1226 UTC Wed Dec 28 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 Gale Warning...The pressure gradient between high pressure over eastern Mexico and low pressure within the monsoon trough over the eastern north Pacific is supporting gale force winds over the Gulf of Tehuantepec. This synoptic setup will prevail today and Thursday supporting the gale force winds. Thursday night 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 over the Gulf of Mexico 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 latest National Hurricane Center high seas forecast MIAHSFEP2/FZPN03 KNHC for further details. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 09N84W to 06N91W to 06N99W. The ITCZ extends from 06N99W to 12N120W to 09N130W to 07N140W. Scattered moderate isolated strong convection was noted within 210 nm north of the ITCZ between 108W and 116W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see special features for more on the Gulf of Tehuantepec gale-force gap wind event. The pressure gradient between a ridge of high pressure west of the Baja California peninsula and a trough of low pressure over western Mexico is supporting fresh to strong northwest winds over the southern portion of the Gulf of California. The troughing will weaken at weeks end and winds will diminish below advisory criteria Friday. 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 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 28N126W to 25N125W to 22N123W. The pressure gradient between 1031 mb high pressure centered north of the area near 36N137W and the trough is supporting fresh to strong winds north and west of the trough. Northwest swell is propagating across the northern waters with seas in the 8 to 12 ft range. The pressure gradient between the area of high pressure discussed above and lower pressure in the vicinity of the ITCZ is supporting fresh to strong trades over the waters west of 125W and north of the ITCZ. Northwesterly swell is mixing with northeasterly generated wind waves to produce seas greater than 8 ft over much of the forecast waters north of 05N and west of 125W. 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 week. 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 cold front will move into the far northwest waters 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 10 ft on Friday. $$ AL