000 AXPZ20 KNHC 180339 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 0405 UTC Wed Jan 18 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 0000 UTC surface analysis and satellite imagery through 0230 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... A meandering trough extends from 06N76W TO 03N100W. The ITCZ extends from 03N100W TO 07N122W TO beyond 06.5N140W. Scattered moderate isolated strong convection is located within 270 nm N of the ITCZ between 112W and 130W. Scattered to locally numerous strong convection is occurring from 11.5N to 18N between 110W and 121W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Satellite imagery shows a dissipating frontal trough across the Pacific offshore waters west of Baja California extending from 23N113W to 27N120W and has become nearly stationary. A supporting upper level trough extends from a deep layered cut off low across SW New Mexico border SW to beyond 19N130W. An upper level jetstream is moving through the base of this trough and into central Mexico, and transporting an upper level cloud and moisture plume. Strong low level convergence is occurring in a broad zone about 200 nm wide from offshore of Cabo Corrientes near 20N107W to near 13N122W. Scattered to numerous convection described above is occurring within this zone and being enhanced by the jetstream energy aloft, with lighter elevated convection likely moving NE and inland across western Mexico between Manzanillo and Mazatlan and continuing NE across the Sierra Madres. Gentle to moderate mainly northwest winds prevail off the coast of Baja California and in the Gulf of California. Light to gentle northerly winds prevail south and east of Acapulco. Seas across the area are running 5-6 ft west of Baja California, 1-3 ft in the Gulf of California, and 3-5 ft elsewhere. Global models indicate a cold front will move into the waters off Baja California Norte Thursday, then become diffuse ahead of a much stronger cold front that will quickly move in across Baja California and the Gulf of California Friday and Saturday. The second front will be accompanied by fresh to strong winds and large northwest swell. This swell is expected to build seas to 12-19 ft over the waters off Baja California Norte Saturday, and 8-13 ft seas off Baja California Sur. This will produce hazardous marine conditions to mariners navigating the nearshore and coastal waters, and very dangerous surf conditions along the coasts and beaches. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Moderate northwest winds this afternoon will pulse to 25 kt late tonight through Wednesday morning, and then again briefly late Wednesday night across the Gulf of Papagayo and downwind to about 89W. Winds area then expected to diminish by Thursday night. Light to gentle variable winds are expected there Friday. Light to gentle easterly winds will prevail elsewhere through Saturday. Seas will be generally 3-5 ft in the forecast waters. REMAINDER OF THE AREA... 1024 mb high pressure centered near 28N134W extends a ridge southeast to the Revillagigedo Islands. The gradient between this high and lower pressure associated with the Itch is supporting an area of fresh to strong northeast trade winds from 10N TO 15N W OF 130W, with 9-11 ft seas. Fresh trades are found elsewhere from 11N TO 14N BETWEEN 119W AND 130W, with seas 8-10 ft in mixed northwest swell and northeast wind waves. The zone of strongest trade winds will decrease in coverage and shift westward during the next couple of days. Fresh trades will remain from 07N to 20N west of 122W, with 8-10 ft seas in mixed northeast waves and northwest swell. As mentioned above, a very active jet stream branch is rounding the base of the deep layered trough across northwest Mexico. The upper trough will move eastward during the next couple of days as high pressure aloft builds eastward behind the previously mentioned cold fronts, with associated moisture and weather shifting eastward with it. Looking ahead, northwest swell with seas to 8-12 ft associated with a cold front moving eastward across the waters north of 25N Wednesday and Thursday will be followed by a second front expected to sweep southeastward into northern waters Thursday night and Friday. Wave model guidance shows large northwest swell will propagate southeastward into the waters north of 20N behind the second front, with seas building to 15-20 ft in the far northern waters east of 130W late Friday into Saturday. $$ Stripling