000 AXPZ20 KNHC 180920 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1005 UTC Wed Apr 18 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 0900 UTC. ...SPECIAL FEATURES... A gale warning is now in effect for the Gulf of Tehuantepec, with northerly winds expected to reach minimal gale force in about 48 hours. High pressure building over the northern Gulf of Mexico Thu night is expected to tighten the gradient across the Isthmus of Tehuantepec and induce very strong winds funneling into the Gulf of Tehuantepec through Fri morning, producing 8 to 12 ft wind-driven seas downstream to about 14N. Model guidance indicates this will be a brief high wind event, with winds diminishing to 10-15 kt by Sat afternoon. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... A surface trough extends from 08N78W to 08N87W to 07N91W. The ITCZ stretches from 07N91W to 09N110W to 07N118W to 05N125W to 07N140W. Widespread active convection is associated with the ITCZ, with scattered moderate isolated strong convection indicated from 05N to 10N between 94W and 107W, as well as from 05N to 14N between 107W and 129W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A cold front will reach northern Baja California on Thu, then weaken as it moves S-SE through Fri. Moderate NW to N winds will dominate the waters W of Baja California the next two days, then freshen behind the front Thu night and Fri as a tight pressure gradient develops between a ridge over northern waters and lower pressure in the SW CONUS and NW Mexico. NW winds in the Gulf of California will become gentle to moderate through Fri. Seas will gradually subside today, with seas falling to 5-7 ft by tonight. See special features section for details about gale force winds expected in Gulf of Tehuantepec Thu night and Fri morning. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Gulf of Papagayo: Pulsing nocturnal NE-E winds are expected across and downstream of the Gulf of Papagayo through Fri. Gulf of Panama: Fresh northerly winds are expected across the Gulf of Panama through tonight, with seas of 4-6 ft. Elsewhere, light to gentle winds are expected through Sun, with a weak surface through meandering west of Panama along 06N-08N. Seas in the 3 to 5 ft range will continue over most of the area. Cross equatorial SW swell will mix with residual swell from Papgayo today through Fri, and raise seas to 5-7 ft S of 10N. REMAINDER OF THE AREA... High pressure located north of the forecast area extends a broad ridge across the northern forecast waters. The ridge will weaken some during the next 24-48 hours, and then will be reinforcing by a stronger high pressure by late Thu behind a cold front. NW swell continues to propagate SE through the forecast waters, with max seas of 8-9 ft. This swell is mixing with NE swell generated previously from the Tehuantepec area. 7 ft or greater seas cover most of the area W of 100W this morning. Cross equatorial SW swell moving into southern forecast waters will dominate the waters S of 04N between 95W and 120W today. Seas are forecast to subside to 8 ft or less across most of the area W of 120W by late tonight. $$ Mundell