000 AXPZ20 KNHC 071542 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1542 UTC Sun Jan 7 2018 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 FEATURE... Gulf of Tehuantepec Gale Warning: Strong high pressure over the western Gulf of Mexico continues to support gale force N-NE winds through the Gulf of Tehuantepec. Winds will subside below gale force today, then fall to moderate speeds by Mon morning as the ridging over the Gulf of Mexico weakens and shifts E. NE swell in excess of 8 ft generated by the persistent strong winds are propagating downstream up to 600 nm to the southwest of the Gulf of Tehuantepec, subsiding below 8 ft through tonight. A cold front over the central Gulf of Mexico Mon night will provoke another gale force gap wind event over the Gulf of Tehuantepec Mon night to Tue night. Please refer to the latest high seas forecast issued under AWIPS/WMO headers HSFEP2/FZPN03 for additional details. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... A surface trough extends from 08N78W to 06N90W. The intertropical convergence zone continues from 06N90W to 10N125W, resuming from 08N135W to beyond 06N140W. Scattered moderate convection is observed from 02N to 07N between 77W and 85W, and from 08N to 11N between 122W and 125W. Scattered moderate convection is also noted form 17N to 20N between 125W and 130W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see Special Features section above for more details about the ongoing gale force wind event in the Gulf of Tehuantepec. Looking ahead, another gale force wind event will start in the Gulf of Tehuantepec Mon night as high pressure builds behind a cold front over the Gulf of Mexico. A cold front will sweep across the region from off Baja California Norte through the northern Gulf of California Tue, before slowing and eventually dissipating over the waters off the southern Gulf of California and southwest of Los Cabos through late week. Fresh NW winds and NW swell in excess of 8 ft will accompany front. The swell will propagate into the offshore waters off Baja California Norte early Tue, with seas building to around 13 ft by Tue night. Strong SW winds will briefly pulse over far northern portion of the Gulf of California later on Tue ahead of the front, with the possibility of strong western gap winds Tue night in the northern Gulf of California south of San Felipe. Looking ahead, the NW swell will gradually decay off Baja California through Wed, but long period swell to 8 ft will reach the Revillagigedo Islands by early Thu before subsiding. Fresh to possibly strong NW winds will follow the front across the central and southern Gulf of California Wed into Thu with seas to 6 ft. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... High pressure north of the Caribbean Sea is weakening and shifting east. The tight gradient over the southwest Caribbean had been supporting strong overnight gap wind pulses. These will diminish, with at most only fresh overnight pulses expected into the Gulf of Papagayo through mid week. Elsewhere moderate SW flow will persist into Costa Rica and Panama, with light northerly flow off the remainder of the coast of Central America. Seas will remain generally 3 to 5 ft. Expect occasional scattered showers and thunderstorms south of Panama mainly at night. REMAINDER OF THE AREA... A sharp upper trough parked along roughly 133W remains the main weather maker, supporting a series of low pressure cells and troughs mainly north of 20N between 125W and 130W. The latest of these is a 1012 mb low pressure area centered near 30N131W, about to move north of the area. An earlier scatterometer satellite pass indicated fresh to strong winds on the northwest quadrant of the low. Concurrent altimeter satellite passes showed seas of 9 to 11 ft, with a likely component of NW swell mixed in. Farther south, a related surface trough is noted from 10N and 20N between 130W and 135W. The same scatterometer pass confirmed fresh to possibly strong SE winds on the east side of this trough. The short term forecast through tonight has these winds across the region diminishing as the upper trough finally starts to dampen out and lift to the northeast. This will be ahead of another mid to upper level disturbance passing eastward to the north of the region through late Mon. An associated cold front will sweep across the waters north of 20N through Tue. This will be accompanied by strong NW winds and seas in excess of 12 ft mainly over the waters north of 28N. Long period NW swell in excess of 8 ft will also propagate across the region north of 20N through mid week, eventually cover the area north of 10N by late week. $$ Christensen