000 AXPZ20 KNHC 282158 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2034 UTC Wed Feb 28 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 2100 UTC. ..SPECIAL FEATURES... Gulf of Tehuantepec Gale Warning...Marine guidance continues to suggest an increase in winds and seas across the Tehuantepec region beginning on Thu night. A that time, expect N winds of 25-30 kt and building seas to 8 ft. Winds will further increase to minimal gale force on early Fri morning through Fri night, with seas building to 11 or 12 ft. This gap wind event will be associated with a cold front moving across the western Gulf of Mexico followed by strong northerly winds. Northerly winds of 25-30 are expected Sat and Sat night. Please refer to the East Pacific High Seas Forecast under AWIPS/WMO headers HSFEP2/FZPN03 KNHC for more details. A gale warning has been issued with the 1800 UTC forecast package. The Fuego Volcano inland over Southern Guatemala near at 14.5N 90.9W continues to produce frequent volcanic ash puffs. The volcanic ash plume is moving to approximately 90 nm WNW of the summit, reaching a very small area of the forecast waters N of 14.5N between 92W and 92.5W. The volcanic ash may reach to the surface limiting visibilities. Mariners should exercise caution. If mariners encounter volcanic ash, they are encouraged to report the observation to the National Weather Service by calling 305-229-4425. Please refer to the East Pacific High Seas Forecast under AWIPS/WMO headers HSFEP2/FZPN03 KNHC for more details on the ashfall advisory. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... A surface trough extends from 06N87W TO 02N96W. The ITCZ continues from 02N96W to 03N120W to 06N140W. No significant convection. Another trough is noted S of the Equator and extends from 03S91W to 01S100W. During March and April of each year, a doble ITCZ is usually present in the Southern Hemisphere in the Eastern Pacific basin. Based on this weather pattern, no monsoon trough is currently present. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Pacific waters W of the Baja Peninsula: A ridge dominates the offshore waters producing moderate to fresh winds based on scatterometer data. Seas are in the 8-12 ft range in NW swell. Winds and seas will begin to gradually diminish tonight. Then, expect seas to less than 8 ft by late Thu into Fri morning. Another cold front will reach 30N120W on Fri night with another round of NW swell following the front driving seas back up to 8 to 12 ft N of 23N W of 115W late on Sat. Seas of 8-10 ft will dominate the waters N of 20N W of 112W on Sun. Gulf of Tehuantepec: Please, see Special Features section for details. Gulf of California: The most recent ASCAT pass showed fresh to locally strong NW to N winds across the Gulf of California from 25N to 28N. A weakening cold front crosses the area, and extends from 27N110W TO 24N112W. This front will dissipate this evening. Fresh to strong NW-N winds will persist mainly across the southern Gulf of California tonight into Thu morning, with these conditions spreading S reaching Las Marias Islands and Cabo Corriente. Seas are forecast to build to 8 ft near Cabo Corrientes. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Gulf of Papagayo: Fresh to locally strong NE winds will continue to pulse through and downstream of the Gulf of Papagayo through the upcoming weekend, with seas building to 8 ft. Gulf of Panama: Moderate to fresh winds are expected through the forecast period. Elsewhere, gentle to moderate offshore flow will prevail N of 07.5N while light to gentle SW winds are forecast S of 07.5N. REMAINDER OF THE AREA... High pressure of 1034 mb located near 32N147W extends a ridge SE across the forecast waters roughly from 30N140W to beyond the Revillagigedo Islands. The pressure gradient between the high and lower pressure in the vicinity of the ITCZ is supporting mostly strong NE trades, and 8 to 13 ft seas, across the tropical waters W of a 115W. The aerial extent of the trades will slightly diminish over the next 24-48 hours as the high pressure moves westward, and new cold front reaches the northern forecast waters. Recent scatterometer data confirmed the presence of the strong trades while altimeter data show seas of up to 13 ft within the area of the trade winds. Sea heights of 8 to 13 ft in mixed NE and NW swell are forecast to subside on Thu, but mainly across the waters N of 20N. Another set of long period NW swell will follow a cold front forecast to reach the north waters early on Fri. This swell event will propagate S across the waters N of 23N W of 118W on Sat. $$ GR