Tornado season in Mexico arrives with severe storms and possible twisters

30/04/2021

According to the studies that have been carried out, the tornado season in Mexico extends from the end of March to October, with a higher incidence between May and August. It begins when the seasonal change from winter to spring occurs with the interaction of late frontal systems and moisture flows entering the continental region from the Gulf of Mexico. It also takes into account the passage of tropical or easterly waves, and of course, tropical cyclones.

How does a tornado form? Depending on the type of phenomenon. In the case of a supercell tornado, the formation of mesocyclones must be considered, which require environmental conditions such as mid-level shear and high instability. On the other hand, non-supercell tornadoes are related to convergence lines and surface vorticity, without the need for an organized mesoscale system.

It is important to emphasize that both types of activity have been documented in the north of the country: supercell and non-supercell. This is due to the geographical characteristics and environmental conditions in this area (mainly in the northeast), where EF3 or higher are possible. On the other hand, in the center of the country, only non-supercell tornadoes have occurred.

Severe storms and rains

Heat and drought continue to dominate our country, but the tropospheric circulation is gradually changing as the polar masses meet the tropical masses, resulting in great instability with the formation of heavy rains/storms to bid farewell to April and begin the month of May. A frontal system, an Isolated High-Level Depression (LLD), and tropical moisture will be the main rain generating systems.

Precipitation is already present between Sonora and Chihuahua due to the DANA (cold vortex), while in Coahuila storms were generated by cold front 54, systems that are also associated with wind gusts higher than 60 km/h and a subsequent drop in temperatures. Over the extreme north of Coahuila, the rains have been severe with large hail close to 10 cm, as well as a probable tornado according to radar and some images shared on social networks.

The medium-term forecast models continue to show a tendency for rains to be scattered over most of the country during the course of May, including the western region, supported by the instability of cold fronts, tropical humidity, and some areas of disturbance in the Pacific, to the south of the country. Although not yet observed, the first tropical waves will also be crossing the Atlantic-Caribbean, up to the Yucatan Peninsula in the coming weeks.

Deadly tornadoes

In recent times, there have been deadly tornadoes causing serious damage, such as the one in Ciudad Acuña on May 25, 2015, and the one in Piedras Negras on April 24, 2007, both in the state of Coahuila. Mention may also be made of the Apodaca, Nuevo Leon tornado on May 8, 2020.

Since there are no long-term records of tornadoes, it is not possible to determine whether climate change will cause more tornadoes to form in Mexico in the future, or if their formation will spread to areas where they have not occurred before. Although some studies have suggested that climate change may increase the generation of extreme events, in the case of tornadoes, and in Mexico in particular, there is not enough evidence to support this.

By Mexicanist