000 AXPZ20 KNHC 050916 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1005 UTC Sat May 05 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 0600 UTC surface analysis and satellite imagery through 0915 UTC. ...SPECIAL FEATURE... Gulf of Tehuantepec: Fresh to locally strong northerly winds will gradually increase to strong to near gale force this evening, with these conditions continuing through Sun. The northerly drainage flow is forecast to increase to minimal gale force on Sun evening, with seas building to 12 ft downstream near 15N 95.5W. The pressure gradient will relax on Mon with near gale winds continuing through sunrise on Tue. The gap event should end by late Wed morning. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends west-southwest from the Pacific coast of Colombia at 08N78W to 07N95W to an embedded surface trough analyzed from 04N to 14N along 108W. Scatterometer winds indicate that an ITCZ develops at 08N109W and wiggles west- southwest to beyond 07N140W. Scattered moderate isolated strong convection is observed within 90 nm either side of a line from 03N78W to 08N78W to 04N101W, within 45 nm either side of a line from 12N87W to 15N92W to 10N99W, within 60 nm of 06N110W, within 90 nm of 13N113W, within 45 nm either side of a line from 10N122W to 07N129W to 09N132W and within 60 NM of 17N101W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Refer to special features section for a warning in the Gulf of Tehuantepec. A northwest to southeast ridge just seaward of 250 nm will shift east to a position from 22N116W to 17N104W on Sun where it will meander through the middle of next week. Moderate northwest flow forecast through late this afternoon west of the Baja Peninsula. The pressure gradient will tighten late this afternoon resulting in fresh to locally strong northwest flow between 30N and 32N along Baja Norte through tonight. Mostly fresh northwest flow expected by midday Sun, diminishing to a moderate northwest breeze on Mon, with little change then expected through the middle of next week. Long period northwest swell, in the form of 8 to 9 ft seas, will move south into the waters north of 30N east of 122W on Wed, and propagate as far south as 27N on Thu before beginning to subside from the south. Gulf of California: Moderate northwest flow will continue across the gulf waters north of 30N through this afternoon, and moderate to locally fresh northwest flow will continue across the gulf waters south of 25N through this evening. Then light, mostly southerly flow forecast through the middle of next week except moderate nocturnal drainage flow near gap areas. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Gulf of Papagayo: Moderate to locally fresh nocturnal winds are expected through the middle of next week. Gulf of Panama: Gentle northerly nocturnal flow is forecast through the middle of next week. REMAINDER OF THE AREA... A surface high is centered near 32N127W with a ridge extending southwest to beyond 25N140W. The high will shift southeast today allowing a cold front to reach a position from 32N134W to 29N140W late this afternoon where it will stall. Fresh southerly flow will precede the front across the discussion waters north of 30N through early this morning. The cold front will dissipate by late Sun as a ridge redevelops from 32N129W to 24N140W. Strong southerly flow will develop north of this ridge on Sun ahead of a second cold front that will reach from 32N137W to 28N140W early Mon accompanied by strong southerly flow that will extend south to along 29N. Although the front will stall and wash out from 32N130W to 24N140W by late Tue, large seas of 10 to 15 ft are expected west of the front on Mon, but then quickly subsiding to 6 to 9 ft west of a line from 32N125W to 13N140W on Tue night. Model guidance is hinting that a tropical low will develop near 11N115W during the middle of next week and intensify as it tracks northwest and later north. $$ Nelson