000 AXPZ20 KNHC 160229 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 0405 UTC Thu Mar 16 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 0000 UTC surface analysis and satellite imagery through 0200 UTC. ...SPECIAL FEATURES... GULF OF TEHUANTEPEC GALE WARNING: Persisting ridge along the Mexico coastal plains continues to maintain a tight pressure gradient into the Gulf of Tehuantepec. This is supporting gale force winds of 30-40 kt through the Gulf of Tehuantepec, with fresh to strong northerly winds extending downwind to near 12N98W. Minimal gale force winds are expected across the Tehuantepec region through Monday with winds likely increasing to 40 KT during the overnight and early morning hours with the assistance of the nocturnal drainage flow. Northerly swell generated by this gap wind event will propagate southward and mix with long-period southwest swell from the southern hemisphere, and NE swell generated in the Papagayo gap wind region, resulting in combined seas of 8 ft or greater covering the waters from 05N to 12N between 90W and 104W by Friday morning. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... During March and April of each year, a double ITCZ is usually present in the southern hemisphere of the eastern Pacific basin. Based on this weather pattern, no monsoon trough is currently present east of 140W. Only a weak trough is analyzed from 06N86W to 04N93W while an active ITCZ is noted south of the Equator. Then, the ITCZ in the northern hemisphere extends from 06N118W to 05N30W to 03N140W. Isolated moderate convection is near the the eastern end of trough axis from 03N to 07N between 84W and 87W. Scattered moderate convection is within 180 nm north of the ITCZ axis between 118W and 123W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... See the Special Features section for information on the Gulf of Tehuantepec gale warning. A 1023 mb high pressure center is located near 29N132W and extends a ridge SE to near the Revillagigedo Islands. Gentle to locally moderate NW winds and seas generally under 5 ft are noted across these waters under the influence of the ridge. Gentle and variable winds and seas of 2 ft or less are inside the Gulf of California. These general marine conditions will persist through the rest of the work week. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Fresh to strong NE-E winds are expected across and downwind of the Gulf of Papagayo, particularly during the overnight and early morning hours through the remainder of the week and into the upcoming weekend. Seas will build to 8-9 ft during the strongest winds. Winds will reach 25-30 kt Thursday night through Friday night. Building high pressure across the NW Caribbean and Gulf of Mexico is forecast to induce a strong gap wind event across the Gulfs of Papagayo and Fonseca late Thursday night into early Friday morning. Fresh to strong northerly winds are also forecast across the Gulf of Panama and downwind to about 04N-05N at night. Seas will build to 5-7 ft in this area, including offshore of the Azuero Peninsula. These weather conditions will likely persist through Friday night. Otherwise, light to gentle winds and combined seas of 3-5 ft are expected to continue through the week and into the upcoming weekend. REMAINDER OF THE AREA... A 1023 mb surface high centered near 29N132W will remain nearly stationary over the next 24 hours. A frontal boundary is now clipping the far NW corner of the area, and will lift back NW tonight as another cold front approaches from the west. Fresh to strong southerly flow is expected ahead of the second front Thursday night into early Friday, with the front entering the forecast region early Friday afternoon. This front will reach from 30N136W to beyond 26N140W Friday night, and from 30N132W to 25N140W on Saturday, then stall late Saturday into Sunday. Seas to 8 ft are expected on either side of the front over the forecast waters. A second push of cold air will move the front to a position from 30N130W to 22N140W by early Monday morning with a secondary front extending from 30N135W to 27N140W. Otherwise, mainly moderate to locally fresh trades will persist elsewhere across the open tropical Pacific waters. Combined seas will be in the 5-7 ft range, but will build to 8-9 ft along and south of 10N roughly between 90W-110W Thursday night through late Saturday as fresh swells generated by central American gap wind events propagate westward. $$ GR