000 AXPZ20 KNHC 231610 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1605 UTC Mon Sep 23 2024 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 1200 UTC surface analysis and satellite imagery through 1530 UTC. ...SPECIAL FEATURE... Tropical Storm John is centered near 14.8N 98.5W at 23/1500 UTC, moving north at 3 kt. Estimated minimum central pressure is 992 mb. Maximum sustained wind speed is 60 kt with gusts to 75 kt. Tropical storm force winds are occurring within 30 NM of the center, except within 40 NM of the center in the NE quadrant. Seas 12 ft or greater are occurring within 45 NM in the northern semicircle, and within 75 NM in the southern semicircle, with peak seas of 15 ft. Scattered strong convection is occurring within 150 NM in the east semicircle of the center, and within 250 NM in the west semicircle. Rapid strengthening is forecast, and John is expected to become a hurricane by this afternoon, with additional strengthening expected before the center reaches the coast of southern Mexico. John will move to near 15.2N 98.3W this evening, move to 15.7N 97.9W Tue morning, inland to 16.0N 97.6W Tue evening, move inland and weaken to a tropical storm near 16.2N 97.4W Wed morning, and dissipate Wed evening. Through Thursday, John is expected to produce 6 to 12 inches of rain with isolated totals around 15 inches across the coastal areas of Chiapas. In areas along and near the Oaxaca coast to southeast Guerrero, between 10 and 20 inches of rain with isolated totals near 30 inches can be expected through Thursday. This heavy rainfall will likely cause significant and possibly catastrophic, life-threatening flash flooding and mudslides to the Mexican States of Chiapas, Oaxaca, and southeast Guerrero, particularly in areas near the coast. A dangerous storm surge is expected to produce significant coastal flooding near and to the east of where the center makes landfall. Near the coast, the surge will be accompanied by large and destructive waves. Please see local statements for more information. 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 John NHC Forecast/Advisory and Public Advisory at www.hurricanes.gov for more details. A Central American Gyre will generate periods of excessive rainfall over southern Mexico and Central America this week, as well as the adjacent western Caribbean and eastern Pacific waters between 80W and 95W. This scenario, combined with daytime heating and orographic lifting, could produce dangerous flash flooding and mudslides across the area. Furthermore, strong to near gale force winds, rough seas and thunderstorms are forecast to affect the offshore waters between Costa Rica and El Salvador through the end of the week. Please follow the forecasts from your local weather offices for more detailed information. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from 15N111W to 12N140W. Aside convection related to Tropical Storm John, scattered moderate convection is occurring from 08N to 11N between 127W and 136W. ...OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please refer to the Special Features section above for information on both Tropical Storm John and on the developing Central American Gyre (CAG). A broad surface ridge extends southeastward to just west of the Baja California offshore waters. The related gradient is allowing for generally gentle to moderate northwest winds to exist over the Baja California offshore waters, with locally fresh winds and moderate seas north of Punta Eugenia. Light to gentle winds are ongoing along the Gulf of California with slight seas. Fresh to strong winds are noted in the vicinity of Tropical Storm John, with seas to 10 ft. Otherwise, light to gentle winds and slight to moderate seas are occurring elsewhere. For the forecast, away from Tropical Storm John, high pressure will remain in place through mid-week. Gentle to moderate northwest winds will continue over the Baja California offshore waters through Wed night, with moderate to fresh winds occurring Thu into the weekend. Light to gentle winds will continue over the Gulf of California through the period, with occasional instances of gentle to moderate winds in the central section. Looking ahead, a trough of low pressure located several hundred miles west-southwest of southwestern Mexico is producing limited shower and thunderstorm activity. Environmental conditions only appear marginally favorable for gradual development of this system while it moves slowly eastward to the south of the coast of Mexico through the middle of this week. ...OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Moderate to fresh southwest to west winds are occurring across the offshore waters from Colombia to Costa Rica along with moderate seas. Gentle to moderate winds and slight to moderate seas prevail elsewhere. Scattered showers and thunderstorms are over the offshore waters between northern Costa Rica through western Panama. Strong winds and rough seas are likely in the regions of strongest convection. For the forecast, moderate to fresh southwest to west winds will continue through Wed morning, becoming moderate speeds Wed afternoon through the end of the week. Increasing westerly wind waves are likely in the wake of Tropical Storm John, moving into the waters off of Guatemala today, expanding farther east toward El Salvador on Tue, and toward Nicaragua Wed. Periods of very active weather are also expected over most of the Central America offshore waters through at least mid week. ...REMAINDER OF THE AREA... High pressure is generally present north of about 15N and west of 115W. Moderate to fresh trade winds and moderate seas are north of 15N and west of 135W. An area of fresh to strong winds and seas of 8 to 9 ft prevails near the monsoon trough from 08N to 15N between 98W and 108W. Gentle to moderate trade winds along with moderate seas are noted elsewhere north of the monsoon trough. For the forecast, southwest monsoonal winds will continue to become well established through the next couple of days as the monsoon trough lifts slowly northward. Looking ahead, a trough of low pressure located several hundred miles west-southwest of southwestern Mexico is producing limited shower and thunderstorm activity. Environmental conditions only appear marginally favorable for gradual development of this system while it moves slowly eastward to the south of the coast of Mexico through the middle of this week. $$ ADAMS