Mexico: Adverse weather conditions forecast across central and southern regions through at least Oct. 1 /update 4

Adverse weather is forecast to continue across much of central and southern Mexico through at least Oct. 1. A combination of meteorological phenomena is expected to generate heavy rainfall and thunderstorms across the affected regions over the coming days. Strong wind gusts, lightning, and hail are possible during storms. Tropical Storm John will weaken into a tropical depression as it tracks along the coasts of Michoacan, Colima, and Jalisco Sept. 27 but will continue to bring heavy rainfall, strong winds, and rough seas to western Mexico through Sept. 28. A cold front over the Gulf of Mexico will bring showers, storms, strong winds, and possible hail to eastern, southeastern, and southern regions over the coming days; strong winds may also generate rough seas in coastal areas. A low-pressure channel over west-central Mexico will bring further showers and storms to central and western regions Sept. 28-30.

Rainfall totals of over 25 cm (10 inches) are forecast over parts of Colima, Guerrero, and Michoacan state on Sept. 27. Rainfall totals of 15-25 cm (6-10 inches) are expected over parts of Chiapas, Oaxaca, and Tabasco Sept. 27-29, Jalisco Sept. 27, and Veracruz Sept. 28-29. Rainfall totals of 2.5-15 cm (1-6 inches) are forecast across much of the rest of the affected area Sept. 27-30. Heavy downpours may trigger flooding in low-lying areas and landslides on unstable slopes across parts of the affected area over the coming days.

Sustained heavy rainfall could trigger flooding in low-lying communities near rivers, streams, and creeks. Urban flooding is also possible in developed areas with easily overwhelmed stormwater drainage systems. Sites downstream from large reservoirs or rivers may be subject to flash flooding after relatively short periods of intense rainfall. Further landslides are possible in hilly or mountainous areas, especially where heavy rain has saturated the soil.

The severe weather could contribute to transport disruptions throughout affected regions. Floodwaters and debris flows may render some bridges, rail networks, or roadways impassable, impacting overland travel in and around affected areas. Ponding on road surfaces could cause hazardous driving conditions on regional highways. Authorities could temporarily close some low-lying routes that become inundated by floodwaters.

Severe weather may also trigger flight delays and cancellations at airports across the affected region. Authorities may temporarily suspend port operations if strong winds trigger hazardous sea conditions, impacting freight and passenger maritime traffic. Flooding could block regional rail lines; freight and passenger train delays and cancellations are likely in areas with heavy rainfall and potential track inundation.