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Tropical Weather Discussion

Tropical Weather Discussion NWS National Hurricane Center Miami FL 2115 UTC Sun Oct 22 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 1800 UTC surface analysis and satellite imagery through 2100 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec Gale Warning: High pressure building southward across eastern Mexico in the wake of a cold front will help tighten the pressure gradient over the area. In response to the tighter pressure gradient, fresh to strong northerly flow will funnel through the Chivela pass into the Gulf of Tehuantepec starting tonight. Winds will further increase to gale force by early Monday morning as the cold front moves through the western Gulf of Mexico. Winds may even approach minimal storm force by early Wednesday, with seas building to up to 18 to 20 ft by midweek. The gale force winds are likely to persist into early Thursday morning before diminishing to fresh to strong for the remainder of Thursday, then to 20 kt or less by Friday. ...TROPICAL WAVES... The axis of a tropical wave is along 103W from 08N to 15N moving W at around 10 kt. Scattered moderate and isolated strong convection is noted from 06N to 10N between 98W and 104W. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from 11N84W to 08N100W to 09N115W to 08N125W. The intertropical convergence zone axis extends from 08N125W to 09N140W. Scattered moderate and isolated strong convection is from 08N to 12N between 120W and 125W, and also from 06N to 12N W of 134W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see the special features section above for information on a developing gale event in the Gulf of Tehuantepec. Recent altimeter satellite passes indicated seas of 8 to 14 ft over much of the area offshore of Baja California with the highest seas measured N of Cabo San Lazaro. Concurrent scatterometer satellite passes indicated that winds have diminished to moderate levels. The swell is forecast to decay to less than 12 ft through this evening, then subside further to less than 8 ft off Baja California Sur and within 200 nm of the coast of Baja California Norte through late Monday. Looking ahead, gentle breezes associated with a weak pressure pattern along with slight to moderate seas will prevail by late week. High pressure over the Great Basin region of the western United States has strengthened winds over the Gulf of California. Fresh to strong winds are expected to continue through Tuesday, before diminishing as the area of high pressure shifts eastward and the pressure gradient weakens. Winds will be the strongest tonight through Monday when seas will peak around 8 ft. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Gentle to moderate winds will prevail over the forecast area through early Monday, increasing to moderate to fresh S of the monsoon trough by Monday afternoon. NW swell originating from the Gulf of Tehuantepec will propagate into the offshore waters of Guatemala and El Salvador by the middle of the week. REMAINDER OF THE AREA... A set of large NW swell with seas near 12 ft will continue to propagate SE while gradually subsiding. A new reinforcing set of NW swell will arrive at 30N140W on Monday, however peak seas will be less than the previous set. Seas will then subside, to less than 8 ft, by mid week with tranquil marine conditions expected by the end of the week.