000 AXPZ20 KNHC 182205 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2205 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 1800 UTC surface analysis and satellite imagery through 2145 UTC. ...SPECIAL FEATURES... Hilary remains an impressive major and powerful Category 4 hurricane on the Saffir-Simpson Hurricane Wind Scale. It is centered near 18.7N 112.2W at 18/2100 UTC, moving northwest at 10 kt. Estimated minimum central pressure is 948 mb. Maximum sustained wind speed is 115 kt with gusts to 140 kt. Satellite imagery clearly shows the eye of Hilary, about 15 nm in diameter. Numerous strong convection is tightly coiled around the eye, within 150 nm in the SE quadrant, 90 nm in the NE and SW quadrants and within 60 nm of the eye in the NW quadrant. Numerous moderate to strong convection is elsewhere from 15N to 21N between 108W-115W. A rather wide outer rain band consists of numerous moderate to strong convection within 45 nm of a line from 17N108W to 14N112W to 12N115W. The 12 ft seas radii continues to expand. It has expanded outward to within 330 nm of the center of Hilary in the NE quadrant, 360 nm in the SE quadrant, 300 nm in the SW quadrant and 270 nm in the NW quadrant, with maximum seas to 43 ft. Meanwhile, the elsewhere 8-12 ft seas cover the area roughly from 08N to 26N east of 121W, 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 25N. On the forecast track, a turn toward the northwest and north- northwest is expected tonight, followed by a faster motion toward the north Sat night and Sun. The center of Hilary will move close to the west coast of the Baja California peninsula over the weekend and reach southern California by Sun night. Fluctuations in intensity are likely through tonight. Weakening is expected to begin by Sat, but Hilary will still be a hurricane when it approaches the west coast of the Baja California peninsula Sat night and Sun. Hilary is expected to weaken to a tropical storm by late Sun 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 southern California and southern Nevada. Dangerous to locally catastrophic flooding will be possible. Elsewhere across portions of the Western United States, rainfall totals of 1 to 3 inches are expected. A dangerous storm surge is likely to 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 the Baja California peninsula, and south California 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 in southwestern United States should 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 95W from 03N to 17N. It is moving westward around 10 kt. Numerous moderate to isolated strong convection is seen from 10N to 14N between the wave and 89W. Scattered moderate to isolated strong convection is within 30 nm of the wave from 04N to 06N. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from low pressure that along the coast of northwest Colombia to central Costa Rica, then to 10N85W to 08N95W to 09N105W. It resumes well to the southwest of Hurricane Hilary at 11N121W and continues to 09N134W to beyond 07N140W. Scattered moderate to isolated strong convection is seen from 05N to 08N between 82W-92W. Scattered moderate convection is from 04N to 06N between 96W-100W, also within 120 nm south of the trough between 124W-128W and within 60 nm south of the trough between 128W-136W. ...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 northwest to north winds N of Cabo San Lazaro. Seas are 4-6 ft within these winds. In the Gulf of California, fresh southeast to south winds are present, except for stronger winds of fresh to strong speeds on the outer periphery Hilary are now juts south and southwest of the southern tip of Baja California as noted in a recent ASCAT data pass. Wave heights continue to 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 is forecast to maintain intensity as it moves to near 20.3N 113.2W late tonight, then begin to gradually weaken as it turns to the north-northwest as it nears 22.6N 114.1W Sat afternoon, near 25.6N 115.0W late Sat night with maximum winds 85 kt gusts 105 kt, to near 29.4N 116.1W early Sun afternoon with maximum sustained winds 65 kt gusts 80 kt, then move inland and weaken to a tropical storm near 34.1N 117.3W late Sun night and to a post- tropical cyclone well north of the area by early Mon afternoon before dissipating on 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. 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 5-7 ft with these winds. Gentle to moderate winds and seas in the 4-6 ft range prevail elsewhere across the Central and South America forecast waters, with the exception of 1-3 ft seas in the Gulf of Panama, and 3-4 ft just offshore Colombia. For the forecast, fresh to strong northeast to east winds are expected in the Papagayo region tonight, then winds mainly at fresh speeds are expected afterward. Moderate seas in southwest swell are forecast for this same region. Fresh southwest to west winds and building seas are expected across the offshore waters from northern Costa Rica to western Panama Sun night through Tue night, most probably related to low pressure that may form 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 period. ...REMAINDER OF THE AREA... The remnant low of former tropical cyclone Fernanda is analyzed near 16N138W with a pressure of 1008 mb. Fresh to strong winds are still noted within 180 nm N and 60 nm S semicircles of its center. A recent ASCAT pass nicely depicted these winds. Seas are 8-12 ft with these winds. The low is forecast to cross just to the west of 141W late tonight, and associated conditions will shift west of 140W by early Fri afternoon. A ridge dominates most of the waters N of 20N and W of 120W. The pressure gradient outside Hilary and the remnant low remains rather weak allowing for generally light to gentle northeast to east trade winds. Moderate to fresh winds are south of the monsoon trough roughly between 104W-121W due to the large circulation of Hilary. Elsewhere, seas are generally 4-7 ft in mixed swell. $$ Aguirre