000 AXPZ20 KNHC 231003 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 728 UTC Mon Jan 23 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 0600 UTC surface analysis and satellite imagery through 0900 UTC. ...SPECIAL FEATURES... High pressure building in behind a vigorous cold front that exiting the eastern Gulf of Mexico is tightening the pressure gradient in the Gulf of Tehuantepec. This will cause winds to increase to gale force by 1200 UTC. The high will slide quickly eastward, and winds will quickly diminish below gale force later this afternoon around 2100 UTC. Please see the latest East Pacific high seas forecast under AWIPS/WMO headers HSFEP2/FZPN03 KNHC for further details. Scatterometer data from 0330Z shows gales to the west of the front north of 29N between 129W and 137W. Have upgraded the forecast for this area accordingly. Altimeter data shows large NW swell continuing to spreading across the waters with seas greater than 12 ft north of 15N. Seas as high as 24 ft are present near 30N. Large long period swell will continue to sweep southeastward with 8 ft seas reaching the equator this afternoon. Global models agree that the gale force winds over the northern waters that are associated with the cold front will abate during the next 12 hours as attendant low pressure to the west of the Oregon coast weakens. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The ITCZ extends from 03N91W to 01N99W to 05N123W to 04N131W to 06N140W. No significant convection. ...DISCUSSION... ...A series of strong cold fronts has generated a large area of unusually large swell. These swell will continue to affect most of the forecast area through Wednesday... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Moderate to fresh west to southwest winds are observed as a cold front enters Baja California Norte. Large long period NW swell of 12 to 20 ft generated by gales behind the front will sweep southeastward into the forecast zones. NW winds north of 27N will become fresh to strong today, then subside. The pressure gradient has tightened off the Jalisco Mexico coast as the front approaches. This will briefly support fresh to strong winds today within 120 nm of the coast. Ridging behind the front will allow fresh to locally strong north winds to spread into the southern Gulf of California to near Cabo Corrientes today. Strong winds sustaining the swell event will diminish by Tuesday as the high weakens, with seas decreasing below 12 ft in the offshore Mexico waters Wednesday night. However, seas of 8 to 10 ft will persist west of 100W through the end of the week. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Light to gentle winds will prevail across most of the region through Tuesday. Seas will generally range between 3 and 5 ft until Tuesday, then build about a foot in response to arriving NW swell. REMAINDER OF THE AREA... Gales behind the cold front entering Baja California are affecting the northern waters. See the special features section for additional details. Forecast models remain in general agreement in developing an area of low pressure over the western waters near 12N134W on Thursday and Thursday night, but are trending smaller with respect to the size of the system. Nevertheless, a large area of fresh to strong winds will be possible in the vicinity of the low from 12N to 26N W of 120W by Friday morning. $$ cam