000 AXPZ20 KNHC 261619 CCA TWDEP Tropical Weather Discussion...Corrected NWS National Hurricane Center Miami FL 1605 UTC Tue Dec 26 2017 Corrected Remainder of the Area Section to include mention of mid/upper level trough 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 1545 UTC. ..SPECIAL FEATURES... Gulf of Tehuantepec Gale Warning: High pressure extending southward from Texas to southern Mexico is maintaining minimal gale force winds in the Gulf of Tehuantepec. A scatterometer pass at 0350 UTC last night displayed a small area of 30-35 kt N winds across the Gulf of Tehuantepec N of about 15N. The pressure gradient across southeastern Mexico is weakening, and this will allow for the gale force winds to lower to just below gale force in a short while. N-NE winds are expected to remain in the 20-30 kt range over the Gulf of Tehuantepec during 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. Model guidance indicates that this next episode of gale force winds is likely to possibly continue into next weekend. Seas of 8-9 ft in mainly NE swell will propagate downstream from the gulf to near 10N and 101W by Friday. Refer to the latest high seas forecast issued under AWIPS/WMO headers HSFEP2/FZPN03 for more details. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... A surface trough extends from a 1009 mb low at 06N78W to 06N78W to 07N87W to 06N95W where scatterometer data shows the ITCZ begins and continues to 08N110W to low pressure at 09N117W 1009 mb to 09N126W to 09N131W to 08N140W. Scattered moderate isolated strong convection is noted within 120 nm S of the axis between 112W and 115W. Scattered moderate convection is within 60 nm N of the axis between 117W and 119W. ...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. A relatively static synoptic pattern associated with a nearly stationary subtropical high west of California and a surface ridge extending SE from the high will persist for several days, and gentle to moderate NW-N winds are expected to the W of Mexico through the end of the week. Seas will be generally 4-6 ft in offshore waters, and 2-4 ft in the Gulf of California. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Moderate high pressure 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 early Thursday with seas to 7-9 ft in mixed NE wind waves and SW swell. Mainly gentle winds are expected elsewhere through Thursday, with offshore seas generally in the 4-5 ft range. REMAINDER OF THE AREA... Long-period NW swell is producing peak seas north of 25N and west of 135W around 9 ft. Seas will gradually diminish as the wave train continues propagating southeastward. A surface trough near 117W will slowly move westward over the next couple of days. This in combination with high pressure to its N and NE is expected to result in a tightening of the pressure gradient E of the trough as it nears the area between 120W and 122W from 09N to 15N on Wednesday, and between 121W and 123W from 09N to 15N on Thursday. This tightening of the gradient will induce 20-25 kt winds and seas of 8-10 ft within about 180-210 nm E of the trough. Weak low pressure is likely to form along the trough. A large area of NW swell already present over much of the western and central sections of the area will combine with wind waves created by the trough and low to create seas of 8-9 ft near elsewhere near the trough and the expected low to develop along the trough. A mid to upper level trough extends from a cyclonic circulation located at 22N119W southwestward to 14N123W and to near 06N126W. Upper level dynamics associated with a jet stream branch that stretches from the base of the trough northeastward to 15N115W and to continues northeastward to across central Baja California and to NW Mexico acting on very deep atmospheric moisture that is present to the E of the upper trough and low and that is situated under upper level diffluence has resulted in an increasing area of scattered moderate to strong convection observed from 11N to 16N between 109W-115W. This activity may contain gusty winds, and is expected to persist into tonight and through Wednesday, gradually shifting to the E. $$ Aguirre