000 AXPZ20 KNHC 180930 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1005 UTC Fri Aug 18 2023 Tropical Weather Discussion for the eastern Pacific Ocean from 03.4S to 30N, east of 120W including the Gulf of California, and from the Equator to 30N, between 120W and 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... Hilary is a large and powerful category 4 hurricane on the Saffir-Simpson Hurricane Wind Scale. It is is centered near 17.2N 110.8W at 18/0900 UTC, moving west-northwest at 11 kt. Estimated minimum central pressure is 942 mb. Maximum sustained wind speed is 125 kt with gusts to 150 kt. Numerous moderate to strong convection is present within 90 nm of center. Bands of moderate to scattered strong convection are noted from 12N to 19N between 107W and 114W. The 12 ft seas radii continues to expand. It extends outward within 210 nm W semicircle, 360 nm NE quadrant and 330 nm SE quadrant, with maximum seas to 40 ft. Meanwhile, the elsewhere 8 to 12 ft seas cover the area roughly from 07N to 23N between 100W and 115W, including the waters near Cabo Corriente, between Las Marias Islands and Los Cabos as well as the entrance of the Gulf of California, and the southern part of the Gulf to about 24N. On the forecast track, a turn toward the northwest and north- northwest is expected today and tonight, followed by a faster motion toward the north Saturday night and Sunday. The center of Hilary will move close to the west coast of the Baja California peninsula over the weekend and reach southern California by Sunday night. Fluctuations in intensity are likely over the next day or so. Weakening is expected to begin by Saturday, but Hilary will still be a hurricane when it approaches the west coast of the Baja California peninsula Saturday night and Sunday. Hilary is expected to weaken to a tropical storm by Sunday afternoon before it reaches southern California. Hilary is forecast to produce rainfall amounts of 3 to 6 inches, with isolated maximum amounts up to 10 inches, across portions of the Baja California Peninsula through Sunday night. Flash flooding, locally significant, will be possible. Heavy rainfall in association with Hilary is also expected to impact the Southwestern United States through next Wednesday, peaking on Sunday and Monday. A storm surge could produce coastal flooding along the western Baja California peninsula of Mexico near where the center passes the coast in areas of onshore winds, or east of the center if Hilary makes landfall. The surge will be accompanied by large and destructive waves. Large swells generated by Hilary will affect portions of the coast of southwestern Mexico and the Baja California peninsula over the next few days. These swells are likely to cause life-threatening surf and rip current conditions. Please consult products from your local weather office. Interests elsewhere on the Baja California peninsula and along the coast of northwestern mainland Mexico and the southwestern United States coastline should closely monitor the progress of Hilary. Please read the latest HIGH SEAS FORECAST issued by the National Hurricane Center at website - https://www.nhc.noaa.gov/text/MIAHSFEP2.shtml and the latest Hilary NHC Forecast/Advisory and Public Advisory at www.hurricanes.gov for more details. ...TROPICAL WAVES... A tropical wave is along 94W from 04N northward to across the Gulf of Tehunatepec. It is moving westward around 10 kt. Scattered moderate to isolated strong convection is from 04N to 10N between 90W and 100W. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from southern Costa Rica near 09N83W to 08N90W to 11N100w. It resumes SW of Hurricane Hilary from near 12N118W to 09N138W. The ITCZ extends from 09N138W to beyond 08N140W. Scattered moderate to isolated strong convection is seen from 08N to 11N between 109W and 125W. ...OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see the Special Features section for information on powerful Hurricane Hilary. Outside of Hurricane Hilary, a ridge dominates the offshore forecast waters of Baja California N of Cabo San Lazaro while the outer cyclonic circulation of Hilary is approaching the waters between Las Maria Islands and Los Cabos. The associated pressure gradient is allowing for gentle to moderate NW to N winds N of Cabo San Lazaro. Seas are 4 to 6 ft within these winds. In the Gulf of California, gentle to moderate southerly winds prevail, except in the southern part of the Gulf where moderate to fresh winds are noted per scatterometer data. Sea heights are already on increase near the entrance to the Gulf of California as seas generated by Major Hurricane Hilary continues to spread in all directions. Moderate to fresh north winds and seas to about 7 ft are in the Tehuantepec region. For the forecast, Hilary will move to 18.3N 112.0W this afternoon, 20.2N 113.2W Sat morning, 22.4N 114.0W Sat afternoon, 25.3N 114.7W Sun morning, 28.7N 115.6W Sun afternoon, and move inland and weaken to a tropical storm near 32.9N 116.7W Mon morning. Hilary will weaken to a remnant low near 43.6N 117.3W early Tue. Very rough seas and tropical storm conditions are expected in the Gulf of California this upcoming weekend. Fresh to strong N winds are forecast in the Gulf of Tehuantepec at night through Sun night. Looking ahead, a broad area of low pressure could form offshore of the coast of southern Mexico early next week. Some gradual development of this system is possible thereafter while it moves slowly toward the west-northwest or northwest, generally parallel to the coast of southern and southwestern Mexico. This system has a low chance of tropical cyclone development over the next 48 hours and 7 days. ...OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Moderate to fresh northeast to east winds are in the Papagayo region and downwind to about 89W. Seas are 5 to 7 ft with these winds. Gentle to moderate winds and seas in the 4 to 6 ft range prevail elsewhere across the Central and South America forecast waters, with the exception of 1 to 3 ft seas in the Gulf of Panama, and 3-4 ft just offshore Colombia. For the forecast, moderate to fresh winds will prevail in the Papagayo region through Sat night, then mainly gentle to moderate winds and moderate seas in SW swell are forecast. Fresh SW to W winds and building seas to 8 or 9 ft are expected across the offshore waters from northern Costa Rica to western Panama Sun night through Tue night. This could be associated with a developing low pressure along the monsoon trough. Elsewhere across the offshore forecast waters of Central and South America, gentle to moderate winds and moderate seas are expected through the early next week. ...REMAINDER OF THE AREA... The remnant low of former tropical cyclone Fernanda is near 16N135.5W with a pressure of 1006 mb. Fresh to strong winds are still noted within 180 nm N and 60 nm S semicircles of center with seas of 9 to 12 ft. This system is forecast to cross 140W by Fri night. A ridge dominates most of the waters N of 20N and W of 120W. Numerous showers and thunderstorms are noted along the W coast of mainland Mexico between Mazatlan and Huatabampo. The pressure gradient between the ridge and the remnant low pressure supports an area of moderate to fresh winds from 19N to 23N between 130W and 140W. Light to gentle winds are noted elsewhere under the influence of the ridge. Moderate to fresh winds are south of the monsoon trough roughly between 103W-122W due to the large circulation of Hilary. Elsewhere, seas are generally 4 to 7 ft in mixed swell. $$ GR