000 AXPZ20 KNHC 182205 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1913 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 1800 UTC surface analysis and satellite imagery through 2145 UTC. ...SPECIAL FEATURES... A gale warning is now in effect for the Gulf of Tehuantepec. A cold front entering the Gulf of Mexico will usher in high pressure over the northern Gulf of Mexico Thu night 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 minimal gale force Thu night and Fri morning and produce 8 to 15 ft wind-driven seas as far downstream as 10N100W. Winds will taper to fresh speeds by Sat afternoon as seas subside below 8 ft. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... A surface trough extends from 07N77W to 04N82W to 07N90W. The ITCZ continues from 07N90W to 08N108W to 04N124W to 07N134W to beyond 07N140W. An expansive area of active convection is associated with the trough and ITCZ. Scattered moderate and isolated strong convection is present along and up to 90 NM N of the trough and ITCZ axis from 80W to 98W and within an area bounded by 10N99W to 06N101W to 03N121W to 14N119W to 13N107W to 10N99W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Moderate NW to N winds and seas of 6 to 8 ft in NW swell are evident in the offshore waters. Seas will subside below 8 ft tonight as the swell disperse. A cold front will reach northern Baja California around midday Thu, then weaken as it moves SSE through Fri. Moderate NW to N winds over the waters W of Baja California will freshen behind the front Thu night and Fri as a tight pressure gradient develops between the ridge building in behind the front over the northern waters and lower pressure over the SW CONUS and NW Mexico. NW swell following the front will cause seas to build above 8 ft along the length of the peninsula. Moderate NW winds over the Gulf of California will strengthen on Fri and become fresh to locally strong over the central Gulf. Winds will subside over the Gulf Sat and Sun as the high weakens slightly and the area of low pres fills. See the special features section for details concerning the gale force winds expected for the 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 strong nocturnal NE to E winds are expected across and downstream of the Gulf of Papagayo through Sun night. Gulf of Panama: Fresh northerly winds and seas of 6 to 8 ft are expected across the Gulf of Panama through Thu. Winds will become moderate Fri through Sun, with seas generally running between 4 and 6 ft. Elsewhere, light to gentle winds are expected through Mon as a weak surface through meanders west of Colombia. Seas will subside from between 5 and 7 ft to between 3 and 5 ft by Sun as long period SW swell from the Southern Hemisphere decay. The cross equatorial SW swell will mix with residual swell from Papagayo today through Fri, and raise seas to 5-7 ft S of 10N. REMAINDER OF THE AREA... High pressure centered northwest of the forecast area ridges SE across the northern forecast waters to near the Revillagigedo Islands. The ridge will weaken some during the next 24-48 hours, but then be reinforced by stronger high pressure building in behind a dissipating cold front Fri and Sat. Cross equatorial SW swell moving into southern forecast waters will dominate the waters S of 10N between 95W and 120W today. Seas are forecast to subside to 8 ft or less across most of the area W of 120W by midday Fri. Another round of SW swell could cause waters near the equator to build to 8 ft or above early next week. $$ CAM