000 AXPZ20 KNHC 090249 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 154 UTC Thu May 9 2019 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 0230 UTC. ...SPECIAL FEATURES... A cold front will approach the northern Gulf of California Fri morning. SW gap winds will develop ahead of the front Thu evening along 30N, then winds will increase to minimal gale force late Thu night, then subside below gale force on Fri. Strong winds will linger over the northern Gulf of California Fri near 30N, then gradually decrease over the northern Gulf as the ridge west of Baja California breaks down. Otherwise, light to moderate N to NW winds will prevail over the central and southern Gulf during the next several days, with daytime heating leading to onshore seabreezes along much of the coastline of mainland Mexico. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... A trough extends from 08N78W to 07N105W. The ITCZ extends from 07N105W to beyond 04N140W. Scattered moderate/isolated strong convection is noted from 06N to 10N between 79W and 87W while scattered moderate convection is south of 10N between 123W and 140W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A broad ridge extends southeast into the region from a 1034 mb high pressure well north of the area near 47N136W southeastward across the basin. This is supporting moderate to fresh NW winds over open waters mainly north of 20N, with generally light to moderate NW farther south. Recent altimeter data indicated seas are generally 4 to 6 ft in open waters off Mexico. Land-based observations along with visible satellite imagery indicate smoke and haze are persisting over southern Mexico, impacting adjacent Pacific offshore waters. Based on these observations, visibility over the offshore waters may be as low as 3 to 5 nm south of Cabo Corrientes. Looking ahead, a cold front will move through Baja California and the northern Gulf of California late Thu into Fri. As described in the Special Features section above, deepening low pressure over lower Colorado River valley will support gap winds to gale-force over the northern Gulf of California by early Fri as the front moves through. The front and low pressure will dissipate through Sat, but a broader low pressure area will persist off Baja California Norte through Sun. This will displace ridging farther south to along 20N. Long period SW swell will move into open waters starting Thu. Areas of smoke and haze persist south of Cabo Corrientes. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Fires over Central America continue to produce smoke across the region and may occasionally reduce visibilities off the coast of Guatemala and El Salvador. Based on various observations on land, visibility may be limited to 3 to 5 nm due to smoke. Scattered showers and thunderstorms are active south of 10N, where the resident seasonal trough has set up. Active thunderstorms are also ongoing off the coast of Colombia reaching the adjacent coastal waters. Recent altimeter satellite passes show seas of 3 to 5 ft in this area. For the forecast, weakening high pressure north of the area will allow the fresh NE to E winds over the Gulf of Papagayo to diminish tonight. A significant S to SW swell event will move into the Ecuador offshore waters on Thu and spread northward across the region Thu night through Sat night. Expect seas of 7 to 10 ft with periods near 20 seconds. This swell will produce dangerous surf conditions along the coast of Central America and northern South America through the end of this week, and could produce areas of significant beach erosion and minor coastal flooding. Areas of smoke will persist at least in the short term, reducing visibility over the offshore waters of Guatemala and El Salvador. REMAINDER OF THE AREA... A broad ridge extends southeast into the region from a 1034 mb high pressure well north of the area near 47N136W southeastward to the Revillagigedo Islands. Convergence of moderate trade winds south of the ridge is supporting scattered showers south of 10N between 123W and 140W. A mid to upper level low pressure area near 32N135W will shift southeastward and open into a short amplitude mid to upper level trough along 125W by late Thu enhancing convection. The ridge will weaken and shift southward to along 20N through late Thu as a trough or front pivots across the waters off Baja California. This will allow trade wind flow to diminish through at least Sat, with a related decrease in showers and thunderstorms along the ITCZ west of 120W. Looking ahead, a significant S to SW swell event will arrive in the far southern waters tonight and steadily propagate northward through the end of the week and into the weekend. Seas will build to 12 ft south of the Equator between 95W and 110W on Thu with 8 ft seas spreading as far north as 08N by Fri night. Most of the waters S of 20N and E of 125W will have combined seas of 8 ft or greater by early next week. $$ ERA