000 AXPZ20 KNHC 150858 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 858 UTC Thu Feb 15 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 0830 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec Gale Warning: High pressure ridging southward across eastern Mexico and the adjacent waters, to the east of the Sierra Madre Oriental range, is supporting gale force winds offshore and across the Gulf of Tehuantepec. The gale force winds will diminish this afternoon as the ridging weakens, with a round of strong to near gale force winds Thu night, and then fresh to strong winds pulsing each night thereafter. Gulf of Papagayo Gale Warning: Offshore northeast winds will pulse to minimal gale force in the offshore Gulf of Papagayo waters through early Fri, with a brief lull during the afternoon hours. A surrounding area of fresh to strong winds, including near the Gulf of Fonseca will also persist. Downstream seas will build to 8-11 ft during the strongest winds through tonight. Pulsing fresh to near gale force winds are then expected each night thereafter through the weekend. Ashfall Advisory: The Fuego Volcano at 14.5N 90.9W over S Guatemala is erupting. A plume of volcanic ash may reach to the surface through this evening N of 14N and E of 93W. Low level visibilities may be reduced to 1 nm. 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 both gale warnings and the ashfall advisory. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... A surface trough extends from 08N83W to 05N100W to 05N111W. The ITCZ axis continues from 05N111W to 06N119W, then resumes from 09N130W to 06N140W. No significant convection is noted. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see the Special Features section above for more details on the gale warning in the Gulf of Tehuantepec, and on an ashfall advisory near the far southeast coast of Mexico. Light and variable winds and seas of 2 ft or less this morning across the Gulf of California will become northerly while increasing to moderate to locally fresh through Fri as the pressure gradient tightens. The gradient will then weaken this weekend allowing for conditions to once again improve. Looking ahead, a cold front will approach southern California and Baja California Norte by the end of the weekend, with southwest flow ahead of it increasing to 20-30 kt in the far northern Gulf into next Mon. Fresh northwest swell of 6-8 ft will also propagate into the open Pacific waters of Baja California Norte. Elsewhere across the open Pacific offshore waters of Mexico, light to moderate winds will prevail through the next several days, except pulsing to fresh offshore of Cabo Corrientes Fri night through Sun. Seas will mainly be 4-6 ft in mixed southwest and northwest swell. Scattered showers associated with an inverted trough southwest of the area will continue to move to the northeast across the waters north of 20N ahead of a deep associated mid to upper level trough. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Please see the Special Features section above for more details on the gale warning in the Gulf of Papagayo, and on an ashfall advisory near the coast of Guatemala north of 14N. For the Gulf of Panama, fresh to near gale force northerly winds are peaking with seas up to 10 ft, however, fresh to strong northerly flow will still persist through Fri morning before diminishing Fri afternoon. Elsewhere, gentle to moderate offshore flow will prevail north of 09N, and light to gentle south-southwest winds will generally prevail south of 09N. REMAINDER OF THE AREA... Low pressure at 1012 mb is near 16N124W with a surface trough extending from 27N117W to the low to 12N124W. Associated scattered moderate convection is within an area bounded by 24N115W to 17N117W to 11N115W to 13N123W to 23N122W to 30N116W to 24N115W. This convection is streaming off to the northeast ahead of a deep mid to upper level trough which extends from 32N125W to 20N124W to 08N110W, and around a large upper level anticyclone positioned over central Mexico near 23.5N101.5W. A tight pressure gradient between the low and troughing and high pressure well northwest of the area is supporting fresh to strong northeast winds from 18N to 24N within 300 nm northwest of the trough, where seas are also 8-10 ft. The pressure gradient is also supporting fresh trades elsewhere west of these features to 140W with seas 8 to 9 ft in mixed southeast and northwest swell. The low is forecast to dissipate by 24 hours, however the pressure gradient will remain tight as the high pressure northwest of the area builds. Fresh to strong trades will expand and cover the waters north 16N west of 120W by 24 hours. The gradient will then gradually weaken through the upcoming weekend allowing for the trades to diminish along with any residual seas of 8 ft or greater. $$ Lewitsky