000 AXPZ20 KNHC 031541 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1541 UTC Sun Dec 3 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 1200 UTC surface analysis and satellite imagery through 1500 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... A trough axis extends from northern Colombia near 08N77W to low pressure near 06N79W. The monsoon trough extends from the low to 08N85W to 06N100W to 07N105W. The intertropical convergence zone axis then continues to low pressure near 10N113W to 07N120W to 08N130W to 12N140W. Scattered moderate and isolated strong convection is within an area bounded by 09N122W to 14N113W to 14N107W to 09N108W to 07N120W to 09N122W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Gulf of California: Strong high pressure will build well N of the area, over the U.S. Great Basin and northern Rockies through the early part of the week. This will support strong northerly winds over the northern Gulf of California by early Mon, spreading into the central Gulf Mon night and early Tue, and the southern Gulf Tue night into Wed, with seas up to 9 ft. Winds may reach to at least near gale force over the northern Gulf Mon night and Tue, with strong easterly gap winds penetrating across areas in Baja California Norte into the Bay of San Sebastian. A local diagnostic tool indicates the potential for gale force winds as do SREF model 34-kt probabilities. The winds will diminish slightly Wed, but will increase again late in the week as reinforcing high pressure builds N of the region. Gulf of Tehuantepec: Higher pressure N of the area continue to support fresh to strong gap winds through the Gulf of Tehuantepec. Associated seas including shorter period swell generated from the strong gap winds reach 200 to 300 nm downstream of the Gulf of Tehuantepec, mixed with longer period NW swell. The high pressure weakens through tonight, allowing for the plume of stronger winds to shrink. Even so, winds will continue to pulse, mainly at night, to fresh to strong through Thu morning, possibly increasing to gale force by Thu night as a cold front pushes across the western Gulf of Mexico and through southern Mexico. Looking ahead, strong high pressure builds N of the area behind the front, supporting a persistent strong gale event across the Gulf of Tehuantepec through late in the week. Elsewhere off the Pacific coast of Mexico, weak high pressure is maintaining gentle to moderate breezes across the region. Long period 7 to 10 ft swell is propagating across all open waters, except within 150 nm of the coast south of Los Cabos. The swell will gradually decay to less than 8 ft across all offshore waters by Tue. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Gulf of Papagayo: An earlier scatterometer pass indicated fresh to strong winds feeding out from the Gulf of Papagayo. These winds may diminish slightly today, but will increase again during tonight. Seas downstream from the Gulf will build to 6 to 8 ft during the time of peak winds, subsiding slightly each afternoon and evening. Elsewhere, light to gentle N to NE winds are expected N of the monsoon trough, and mainly moderate S to SW winds are expected to the S of the monsoon trough. Seas are in the 4 to 6 ft range, but are expected to build to 5 to 7 ft in a SW swell to the S of the monsoon trough beginning this afternoon and into Mon. REMAINDER OF THE AREA... An earlier scatterometer pass showed fresh to strong winds NE of a weakening cold front which wraps around a 1011 mb low W of the area near 28N142W through 30N140W to 21N140W. The low will move S-SW remaining W of the discussion area through the early part of the week, with fresh to strong winds persisting over the NW corner of the discussion waters. Meanwhile, a trough is analyzed to the S from 21N135W to 14N140W. This trough will remain nearly stationary or drift northward through early week resulting in a tight pressure gradient and winds increasing to fresh to strong on the N side of it. A 1010 mb low pressure area is embedded in the ITCZ near 10N113W with fresh to strong winds on the NE side. The low will dissipate and become an open trough between 24 and 36 hours, with associated winds diminishing to 20 kt or less by early Tue. Otherwise, NW swell greater than 8 ft covers almost the entire discussion waters beyond 250 nm offshore of Central and South America. These seas will gradually decay through the early part of the week. $$ Lewitsky