000 AXPZ20 KNHC 192115 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2105 UTC Thu Apr 19 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 2030 UTC. ...SPECIAL FEATURES... A cold front entering the Gulf of Mexico will usher in high pressure over the northern Gulf of Mexico tonight and Fri. This will tighten the pressure gradient across the Isthmus of Tehuantepec and funnel very strong winds over the Gulf of Tehuantepec. N winds will peak at 40 kt tonight and Fri morning and produce 10 to 14 ft wind-driven seas to as far downstream as 08N100W. Winds will diminish by Saturday afternoon, and seas will subside below 8 ft. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... A surface trough extends from 08N77W to 06N93W. The ITCZ continues from 06N93W to 07N115W to 05N130W to beyond 06N140W. A large area of active convection is associated with the ITCZ. Scattered moderate and isolated strong convection is present within 120 nm of either side of the ITCZ axis between 91W and 113W, and from 04N to 13N between 114W and 132W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Moderate NW to N winds and seas of 5-6 ft are evident in the offshore waters. A cold front is beginning to cross northern Baja California this afternoon. The front will weaken as it moves SSE through Fri. Moderate NW to N winds over the waters W of Baja California will freshen behind the front tonight and Fri as a tight pressure gradient develops between a ridge building in behind the front over the northern waters and lower pressure over the SW United States and NW Mexico. NW swell following the front will cause seas to build along the length of the peninsula. Moderate NW winds over the Gulf of California will strengthen on Fri and become fresh over the northern and central Gulf. Winds will subside over the Gulf Sat and Sun as the high weakens slightly and the area of low pressure moves east. See the special features section for details concerning the gale force winds expected for the Gulf of Tehuantepec tonight through Fri morning. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Gulf of Papagayo: Pulsing strong nocturnal NE to E winds are expected across and downstream of the Gulf of Papagayo through at least Mon night with seas reaching 8 ft. Gulf of Panama: Fresh northerly winds and seas of 6-7 ft are across the Gulf of Panama this afternoon. Winds will become moderate Fri through Sun, with seas generally running between 4-6 ft. Elsewhere, mainly light to gentle winds are expected through Tue as a weak surface trough meanders west of Panama and Colombia. Cross-equatorial swell will mix with residual swell from Papagayo through Fri, and increase seas to 5-7 ft S of 10N. Seas will subside to 3-5 ft by Sun as long period SW swell from the Southern Hemisphere decays. REMAINDER OF THE AREA... High pressure centered northwest of the forecast area has a ridge that extends SE across the northern forecast waters to near the Revillagigedo Islands. The ridge is weakening somewhat this afternoon as a weak cold front crosses the waters, extending from 30N119W to 29N130W. The high will become reinforced by stronger high pressure building in behind the dissipating cold front Fri and Sat. Cross equatorial SW swell moving into the southern forecast waters will dominate the waters S of 10N between 95W and 120W into this evening. Seas will subside to 8 ft or less across most of this area by midday Fri. Another round of SW swell could cause waters near the equator to build to 8 ft or above by early next week. A surface trough will develop along the ITCZ near 125W-130W tonight. The pressure gradient between the trough and high pressure to the north will support fresh to strong NE trades N of the ITCZ to 23N and W of 120W through Saturday. The combination of these winds and NW swell will support combined seas of 8 to 11 ft over these waters into Saturday, expanding N to 30N by Sunday as NW swell propagates into the northern waters. The swell will begin to decay below 8 ft Sunday night before becoming reinforced by another set of NW swell by Monday night. $$ Latto