000 AXPZ20 KNHC 091517 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1517 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 1200 UTC surface analysis and satellite imagery through 1500 UTC. ...SPECIAL FEATURES... Gulf of California Gale Warning: The pressure gradient between deepening low pressure over the Lower Colorado River Valley and an offshore high pressure ridge will briefly support gap winds to gale force over the northern Gulf of California late tonight. Strong winds will persist over the northern Gulf Fri and Fri night north of 29.5N, then gradually diminish as the ridge west of Baja California breaks down. Otherwise, light to moderate winds will prevail over the central and southern Gulf through this weekend. Please read the latest High Seas Forecast issued by the National Hurricane Center under AWIPS/WMO headers FZPN03 KNHC/HSFEP2 or at website https://www.nhc.noaa.gov/text/MIAHSFEP2.shtml for further details. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... A trough extends from 1010 mb low pres near 10N75W to 09N100W to 07N107W. The ITCZ continues from 07N107W to 05.5N130W to beyond 04N140W. Scattered moderate and isolated strong convection is present within 360 nm south of the trough east of 105W, within 180 nm south of the ITCZ between 116W and 125W, and within 180 nm north of the ITCZ west of 123W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A broad high pressure ridge extends into the region from high pressure centered well north of the area southeast to 32N140W to the Revillagigedo Islands. Moderate to fresh NW winds prevail over the open waters mainly north of 19N, as well as west and southwest of Cabo Corrientes. Elsewhere, generally light to moderate winds are occurring over the southern Mexico offshore waters. Overnight altimeter data showed 4-6 ft seas over the waters off Baja California. While agricultural fires persist over southern Mexico, low level winds are transporting the smoke northward toward the Gulf of Mexico. Therefore, no visibility impacts are expected over the Pacific waters at this time. As described in the Special Features section above, deepening low pressure over Lower Colorado River Valley will briefly support gap winds to gale force over the northern Gulf of California late tonight. Low pressure expected to develop off the coast of southern California on Fri will pull a weak surface trough across the northern waters. This will displace the ridge farther south into the weekend with fresh NW to N winds developing near the entrance to the Gulf of California and the waters west of Cabo Corrientes. Combined seas will build to 6-9 ft in this region as N wind waves mix with longer period S swell. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Agricultural fires continue over Central America, but the low level flow is transporting the smoke northward over the western Caribbean and Gulf of Mexico. Therefore, no visibility impacts are expected over the Pacific waters at this time. Scattered showers and thunderstorms are active south of 10N in the vicinity of the seasonal low pressure trough. Gulf of Papagayo: Weakening high pressure north of the area will allow winds to diminish to gentle speeds over the Gulf of Papagayo through the weekend and into early next week. A significant S to SW Southern Hemisphere swell event will reach the Ecuador offshore waters tonight and spread northward across the region through Sat night. Expect 7-11 ft seas south of the Equator with peak periods around 20 seconds. Seas to 8 ft will approach the southern coast of Panama by Sat. This swell will produce dangerous surf conditions along the coast of Central America and northern South America through the weekend. REMAINDER OF THE AREA... A broad high pressure ridge extends southeast across the northern waters from high pressure centered well north of the area southeast to 32N140W to the Revillagigedo Islands. Moderate to locally fresh trade winds prevail south of the ridge axis. Overnight altimeter data showed seas to 8 ft in a narrow band along 130W roughly from 07N to 11N. The ridge will weaken and be displaced southward Fri into the weekend as low pressure develops off southern California and a trough moves across the northern waters. Large, long period S to SW swell over the far southern waters will steadily propagate northward through this weekend. A recent altimeter pass over the southern waters roughly between 107W and 109W confirmed 8 ft seas already reach to the Equator. Seas will build to 12 ft south of the Equator between 100W and 110W by tonight with 8 ft seas spreading as far north as 09N by Fri night. By Sun, the southerly swell will cover the forecast waters south of 20N and east of 120W with combined seas of 8 ft or greater south of 10N. Seas will subside beginning Mon as the long period swell gradually decays in this region. $$ Reinhart