000 AXPZ20 KNHC 092107 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1851 UTC Tue Jan 9 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 1800 UTC surface analysis and satellite imagery through 2030 UTC. ...SPECIAL FEATURE... Gulf of Tehuantepec Gale Warning: High pressure building southward along the Sierra Madre Oriental behind a cold front over the Isthmus of Tehuantepec is maintaining minimal gale force winds over the Gulf of Tehuantepec. However, the ridge is weakening. This will allow gale force winds to subside by 00Z this evening. Seas of up to 13 ft will subside to below 8 ft by dawn on Wed. Modest winds and seas will then follow through Thu night. Looking ahead, a much stronger Gulf of Tehuantepec gap wind event is slated to commence Fri morning. This event could peak at storm force on Sun, then continue to beyond Tue. This next event is expected to generate a large downstream area of seas greater than 8 ft. 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 10N84W to 05N90W. The intertropical convergence zone continues from 05N90W to 05N94W to 07N108W to 08N130W to beyond 08N140W. Scattered moderate and isolated strong convection is present from 06N to 15N between 123W and 129W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see the Special Feature section above for more details concerning gale force wind event currently in progress over the Gulf of Tehuantepec and the potentially stronger event expected to commence on Fri morning. Weak 1017 mb high pressure currently centered near 21N116W will maintain light winds over the forecast waters in the vicinity of Baja California Sur and Cabo Corrientes tonight. A cold front extending from 30N117W to 25.5N120W to 21N129W will sweep E across NW Baja California Norte this evening, then to the northern Gulf of California tonight. Fresh to locally strong NW winds and NW swell in excess of 8 ft will accompany the front. The swell are arriving in far NW portion of the offshore waters of Baja California Norte. Seas will build to around 13 ft in the far NW waters by dawn on Wed. Strong SW winds are preceding the front and are developing over the far northern portion of the Gulf of California. These strong winds will continue until around midday Wed. Strong gap winds are anticipated as well tonight behind the front over 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 Thu evening before subsiding. Strong high pressure building over the great Basin of the United States could generate strong NW winds over the southern two thirds of the Gulf of California Thu night and Fri. Seas could peak around 8 ft on Fri morning near 26N110.5W. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... A relatively weak pressure gradient over central America is maintaining moderate to fresh gap winds over the Gulf of Papagayo. Strong gap winds are expected redevelop over the Gulf of Papagayo on Sat morning as high pres builds over the western Caribbean in the wake of another strong cold front. Winds over the Gulf of Papagayo could reach near gale force on Sun as high pres continues building SE over the Caribbean. The area of 8 ft seas forecasted to develop to the SW of the Gulf of Papagayo and the Gulf of Fonseca is expected to merge with the area of 8 ft seas S of the Gulf of Tehuantepec on Sun. Elsewhere light to moderate SW winds will persist S of Costa Rica and Panama. Seas will remain generally between 3 and 5 ft. Expect scattered nocturnal showers and thunderstorms south of Panama through Wed night. N winds over the Gulf of Panama could become fresh by Mon morning. REMAINDER OF THE AREA... Intense low pressure making landfall near Los Angeles California is supporting the surface front W of Baja California. Satellite- derived wind data from around 18Z showed minimal gale force winds off the California coast as far S as 32N. The low will move farther inland this evening and allow strong to gale force winds to the lee of the cold front and N of 30N to quickly subside. Corresponding seas in this area will run between 12 and 14 ft through Wed evening. Long period NW swell already generated by NW winds behind the cold front will cause seas to build in excess of 8 ft north of 20N and west of 115W by Thu morning. This area of seas will slowly decay on Fri and Sat. A cold front approaching 30N140W on Sun will generate very large long period NW swell. These swell could cause seas in the vicinity of 30N140W to build to 20 ft by Sun evening. $$ CAM