Tropical Weather Discussion
Issued by NWS
Issued by NWS
594 AXPZ20 KNHC 231015 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1005 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 0600 UTC surface analysis and satellite imagery through 1000 UTC. ...SPECIAL FEATURE... Recently upgraded Tropical Storm John is near 14.4N 98.5W at 23/0900 UTC, moving north-northeast at 3 kt. Estimated minimum central pressure is 1000 mb. Maximum sustained wind speed is 40 kt with gusts to 50 kt. Satellite imagery shows increased very cold cloud tops over the center of the depression and increased banding features coiling around the center of the system. The very deep convection consists of the numerous strong type intensity within 60 nm of the center, and within a wide band from 14N to 17N between 100W and 102W. Numerous moderate to isolated strong convection is seen elsewhere from 11N to 17N between 96W and 102W. The coldest cloud top temperatures are in the range of -75 to -83 degree Celsius. Tropical Storm John is forecast to continue north-northeast or northeastward for the next couple of days. On the forecast track, the center of the this system is forecast to approach the southern coast of Mexico during the next day or two and move inland on Tue or Wed. John is forecast to strengthen over the next day or two, and could become a hurricane before landfall. Through Thu, 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. wells associated with John are forecast to begin to affect the coast of southern Mexico later today, with the potential for dangerous surf and rip currents much of the week. 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 is forecast to continue to gradually develop through the middle of the upcoming week. This scenario, combined with daytime heating and orographic lifting, is expected to generate periods of excessive rainfall over southern Mexico and Central America, as well as the adjacent western Caribbean and eastern Pacific waters between 80W and 95W. This activity 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 from tonight 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 northwest Colombia westward to northern Costa Rica, and to 11N86W to 14N96W. It resumes at 16N102W and continues to low pressure of 1007 mb near 16N110W to 11N124W and to beyond 12N140W. Aside convection related to recently upgraded Tropical Storm John, scattered moderate to isolated strong convection is within 60 nm north of the trough between 86W and 90W. ...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. Moderate seas are north of Punta Eugenia. Light to gentle winds are ongoing along the Gulf of California with slight seas. Moderate to fresh 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 elsewhere. For the forecast, recently upgraded Tropical Storm John is near 14.4N 98.5W, or about 110 nm south of Punta Maldonado, Mexico at 2 AM PDT moving north-northeast at 3 kt. Maximum sustained winds are 40 kt with gusts to 50 kt, and the minimum central pressure is 1000 mb. Tropical Storm John will strengthen some as it moves to near 14.8N 98.2W this afternoon, to near 15.4N 97.6W late tonight with maximum sustained winds 60 kt gusts 75 kt, to near 15.8N 97.2W Tue afternoon, and inland to near 16.0N 97.0W late Tue night and dissipate Wed afternoon. Otherwise, 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. 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. ...OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Moderate to fresh southwest to west winds are south of the monsoon trough and 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 and El Salvador due to an active monsoon trough. Strong winds and rough seas are likely in the regions of strongest convection. For the forecast, moderate to fresh southwest to west winds south of the monsoon trough will be at mostly fresh speeds from tonight through Thu, then at moderate speeds afterward. The monsoonal flow is expected to become very active, and dominate the region through the week. This pattern will generate increasing westerly wind waves moving into the area waters. 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. The gradient between the high pressure and a 1008 mb low just west of the area near 12N142W is supporting fresh winds and seas to 8 ft in decaying south swell from about 11N to 14N and west of 139W. Moderate to fresh trade winds and moderate seas are north of 15N per an overnight ASCAT satellite data passes over that part of the area. 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 105W. 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, environmental conditions only appear marginally favorable for slow development of a trough of low pressure that is located several hundred miles west-southwest of southwestern Mexico as t moves slowly eastward to the south of the coast of Mexico through the middle of this week. $$ Aguirre