000 AXPZ20 KNHC 210930 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1005 UTC Mon Aug 21 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... Post-Tropical Cyclone Hilary is centered near 38.3N 117.9W at 21/0900 UTC, moving north at 25 kt. Estimated minimum central pressure is 1004 mb. Maximum sustained wind speed is 30 kt with gusts to 40 kt. Hilary will continue to move inland over the western U.S. this afternoon, and dissipate Tue morning. Winds and seas are diminishing off Baja California Norte and the Gulf of California this morning as Hilary continues to move farther north and weakens. 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... An Atlantic tropical wave along 91W extends southward across Guatemala to the Pacific waters N of 08N. Scattered moderate convection is within 60 nm of the wave axis north of 09N. A tropical wave is relocated to around 105W, north of 04N and moving westward at 15 kt. No significant convection is evident near this tropical wave. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from 09N84W to 06N101W to 15N115W to beyond 08N140W. Scattered moderate convection is noted from 06N to 09N between 80W and 100W. ...OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see the Special Features section for information on Tropical Storm Hilary, now weakening well north of the area. A recent scatterometer pass confirmed fresh to strong northerly gap winds across the Gulf of Tehuantepec. Seas are likely reaching6 to 8 ft in the within 120 nm of the coast in the the plume of gap winds. Farther north, winds and seas are diminishing north of 20N as the impacts of Hilary fade. Gentle to moderate winds are noted elsewhere over Mexican offshore waters. For the forecast, the northerly gap winds will continue to pulse mainly at night across the Gulf of Tehuantepec through Fri. Looking ahead, another area of low pressure may develop off southern Mexico through mid- week. Any tropical development of this system, if any, should be slow to occur while it moves slowly toward the northwest or north- northwest, possibly supporting fresh winds and rough seas off western Oaxaca and Guerrero by Fri. ...OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Earlier scatterometer satellite data confirmed fresh gap winds across Papagayo. Farther south, fresh SW winds are active south of the monsoon trough, with 4 to 6 ft seas. Slight seas are noted elsewhere. Convection is increasing along and south of the monsoon trough, from the Gulf of Panama to off the Nicoya peninsula of Costa Rica. For the forecast, moderate to fresh E winds will pulse at night across the Gulf of Papagayo region, with fresh to strong pulses thereafter through Thu. Fresh SW monsoon winds will persist over offshore waters of Costa Rica and western Panama with 6 to 8 ft seas into mid week as broad low pressure develops along the monsoon trough. The low and associated winds and seas will lift northward into Nicaragua offshore waters Wed and Thu then diminish. ...REMAINDER OF THE AREA... A 04 UTC scatterometer satellite pass showed fresh southerly winds south of the monsoon trough between 90W and 100W. A concurrent altimeter shows that combined seas in these waters are 6-8 ft. Recent altimeter data also confirms 8 to 10 ft seas north of 25N between 120W and 135W in mixed swell in part from Hilary. Elsewhere in the basin, a weak pressure pattern prevails W of Hilary, sustaining moderate or weaker and moderate seas. For the forecast, SW winds will continue to increase south of the monsoon trough and east of 120W through midweek. High pressure will weaken modestly west of 120W through mid-week and bring a return to moderate NE trade winds south of 20N. $$ Christensen