000 AXPZ20 KNHC 231600 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1605 UTC Sun Dec 23 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 1545 UTC. ...SPECIAL FEATURE... Gulf of Tehuantepec Gale Warning: Near gale northerly winds will increase to minimal gale force this evening, then further increase to 30 to 40 kt tonight with seas building to 15 ft downstream near 15N95W. The associated strong winds will reach as far S as 12N97W on Mon. Winds will diminish to near gale force around sunrise on Tue. Please refer to the latest high seas forecast issued under AWIPS/WMO headers HSFEP2/FZNPN03 for additional information. .INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... A surface trough extends SW off the Pacific coast of Colombia at 05N78W to 06N91W where scatterometer winds indicate an ITCZ develops and continues W-SW to 04N104W, then turns W-NW to 08N130W. then continues W to beyond 07N140W. A surface trough is analyzed just N of the ITCZ from 06N120W to 13N119W with scattered moderate isolated strong convection observed within 120 nm either side of the trough. Scattered moderate isolated strong convection is noted within 120 nm either side of lines from 06N78W to 03N81W and from 06.5N91W to 07N100W. Similar convection is observed within 180 nm either side of a line from 08N125W to 09N138W. ..DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Gulf of Tehuantepec...See special features paragraph above. Gulf of California: Light northerly winds are observed across the northern gulf waters, with moderate northerly flow expected to continue across the southern gulf waters through Mon morning. Winds are forecast to become light and variable on Mon evening, then become southerly on Mon night while increasing to a strong breeze along 30N ahead of a cold front that will move across the northern waters on Tue, followed by near gale force northerly winds. Minimal gale force westerly winds, with 7 to 10 ft seas, is expected along 30N on Tue in advance of a secondary cold front that will sweep SE across the central gulf on Wed, preceded by strong westerlies. A ridge extends from 23N116W to 15N98W with moderate northerly winds W of northern Baja California Peninsula, and light to gentle anticyclonic winds elsewhere around the ridge to the N of the Gulf of Tehuantepec. Long-period NW swell, in the form of 7 to 9 ft seas, will reach 30N120W this evening, with seas of 8 ft or greater propagating S reaching the W shore of the southern Baja Peninsula by mid week. A tightening pressure gradient will increase northerly winds to a strong breeze N of 31N on Mon, with strong to near gale force NW winds forecast N of 27N on Tue night with seas building 12 to 20 ft. Conditions will begin to improve on Wed. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... A thin volcanic ash plume, originating over interior Guatemala, is observed on satellite imagery spreading southwest across the Pacific coast of Guatemala between 13.5N and 14.5N, but may not be sinking to near the surface. Gulf of Papagayo: Minimal gale force conditions have diminished. However, strong to near gale force NE flow is still reaching as far SW as 09N91W. Pulses of strong winds will continue this week. Elsewhere: gentle to moderate winds will prevail, with seas in the 4 to 7 ft range. REMAINDER OF THE AREA... The pressure gradient between high pressure centered near 33N131W and lower pressures present near the ITCZ is producing fresh to strong northeast trades from 09N to 14N W of 137W with seas ranging from 8 to 11 ft. This area of trades and associated seas will expand N and E early this week as this meandering high pressure located N of 30N intensifies. NW swell will continue to E across the area covering the waters n of 06N W of 110W on Mon, then covering the waters N of 08N and W of 115W by early Tue. As this swell begins to diminish midweek, another set of reinforcing NW swell will begin to cross 30N140W. The combination of cross equatorial swell and NE swell associated with the Gulf of Tehuantepec and Gulf of Papagayo winds will result in seas of 8 to 9 ft generally S of 10N between the Galapagos islands and 120W through Mon. Strong to near gale force northerly winds and 10 to 20 ft seas is forecast N of 28N E of 125W on Tue night. $$ Nelson