000 AXPZ20 KNHC 152145 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2205 UTC Sat Jun 15 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 1800 UTC surface analysis and satellite imagery through 2130 UTC. ...SPECIAL FEATURES... Central America and southern Mexico Heavy Rainfall Event: A broad area of low pressure has developed over northern Central America and southern Mexico. This weather pattern, known as a Central American Gyre (CAG), enhances moist SW flow off the Pacific and into the coastal terrain of Central America and southern Mexico. This moist flow can persist for several days, resulting in life- threatening conditions that include flooding and mudslides. Numerous heavy showers and thunderstorms have been ongoing for hours today along the coast of Guatemala and the Mexican state of Chiapas, and these conditions are indicative of a CAG. The pattern is expected to persist through at least the middle of next week across northern Central America and southern Mexico, with the threat to life and property increasing as the event persists. The main areas impacted by the heavy rainfall will be northwest Nicaragua, southwest Honduras northwest Nicaragua, and coastal sections of Honduras, El Salvador, Guatemala, and the Mexican state of Chiapas. Farther south, the moist southwest flow was also causing persistent heavy rainfall across Costa Rica and Panama, although this will be diminishing Sun as the focus shifts northward to northern Central America. Again, the persistence of the moist pattern and strong onshore flow will create very hazardous conditions to the region and could be life-threatening. Please refer to your local meteorological office bulletins for more detailed information. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough is well to the north of its normal position across the southwest Caribbean and into Nicaragua, Honduras, and Guatemala due the development of the Central American Gyre. It extends over the eastern Pacific 14N95W to 06N125W. The ITCZ extends from 06N125W to beyond 08N140W. Scattered moderate convection from 06N to 08N between 77W and 87W. Numerous moderate to isolated strong from 12N to 15N between 91W and 95W. Scattered to moderate convection is noted from 10N to 12N between 95W and 105W. ...OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Refer to the section above for details on the Central American Gyre. A large cluster of showers and thunderstorms is active off Chiapas in southern Mexico, associated with a broad area of low pressure over the region known as the Central American Gyre. These thunderstorms are probably causing widespread lightning, gusty winds and locally rough seas off Chiapas. Meanwhile, moderate NE to E winds are starting to gradually increase over this area as the gyre develops further. Farther north, recent scatterometer satellite passes indicate fresh to strong NW winds approaching the waters just west of Guadalupe Island off Baja California Norte. Concurrent altimeter satellite data indicate combined seas are 8 ft in this area, primarily due to NW swell. These winds and seas are influenced by their portion between 1030 mb high pressure near 35N140W and lower pressure over the lower Colorado River valley. This pattern is also support gale force northerly winds farther north off southern California, accounting for the large swell entering the water off Baja California. Mostly gentle to moderate breezes and slight to moderate seas persist elsewhere. For the forecast, fresh to locally strong winds and rough seas will persist off Baja California Norte through Mon, primarily beyond 120 nm offshore. Large swell of 8 to 12 ft will move into the waters off Baja California today, and persist mainly north of Cabo San Lazaro into mid week before subsiding. Meanwhile, off southern Mexico, expect fresh SW winds and building seas starting tonight off Chiapas as a broad area of low pressure, continues to develop over southern Mexico and northern Central America. Winds and seas will increase further off Chiapas and Oaxaca through the early part of the week as the gyre intensifies and persists. ...OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... With the monsoon trough displaced farther north than usual, this is bringing fresh winds across the Colombia and Panama offshore waters with seas 7 to 8 ft, with the maximum seas noted off the southern Azuero Peninsula of Panama. Across the rest of the Central American offshore waters, winds are moderate to fresh with 6 to 8 ft seas. Strong thunderstorms continue to impact mainly northern Central America off Guatemala, bringing heavy rain and frequent lightning. These storms could cause hazardous marine conditions. In the Ecuador and Galapagos Island offshore waters, winds are gentle to moderate. Seas are 6 to 8 ft within S swell. For the forecast, the broad area of low pressure known as a Central American Gyre will cause an increase in winds, rough seas and widespread showers and thunderstorms across much of offshore waters through mid week. Fresh to strong winds and rough seas in the Gulf of Panama will diminish by early Sun, as the focus of strong SW winds and rough seas shifts farther north from Nicaragua to Guatemala. Farther south, seas to 8 ft in S swell will continue around the Galapagos Islands through Tue. ...REMAINDER OF THE AREA... Broad ridging dominates the waters north of the ITCZ and monsoon trough, anchored by a 1030 mb high pressure near 35N140W. Moderate to fresh winds prevail across waters north of the monsoon trough and west of 115W with seas 6 to 9 ft. East of 115W, gentle to moderate winds are noted south of the monsoon trough to 05N. Seas are 5 to 7 ft across the rest of the Pacific waters. For the forecast, strengthening high pressure centered NW of the area will dominate waters west of 120W into the weekend. Fresh to strong winds from the California Channel Islands southward are likely to dip south of 30N at times through early next week. Seas will build to 8 to 12 ft by Sun night into Mon, mainly north of 20N between 120W and 130W. SW flow south of the monsoon trough is forecast to continue tonight between 90W and 115W, supporting seas of 6 to 8 ft. Similar winds and seas are likely to return there by the end of the weekend into early next week. Thunderstorms will persist near the monsoon trough and east of 110W or so through the next couple of days. Seas to 8 ft will hover around 03S near the Galapagos Islands through the weekend. $$ Christensen