Mexico's Tornado Threat Revealed

It was believed that tornadoes did not exist in Mexico, but the professor of the College of Geography of the Faculty of Philosophy and Letters of the UNAM, María Asunción Avendaño García, jointly created the first database on the subject, through which it is confirmed that from 2000 to 2023, 773 occurred, that is, an average of 61 per year. By 2024, there would be approximately 50.

The geographer and teacher in anthropology, together with her teacher Jesús Manuel Macías Medrano, researcher at the Center for Research and Higher Studies in Social Anthropology, prepared the document called Tornados México, which reports the presence of these phenomena in regions such as Michoacán, Hidalgo, Tlaxcala, Coahuila and Mexico City.

“A tornado is defined as a column of air that rotates violently in contact with the Earth's surface, below a cumuliform cloud (an isolated cloud with a horizontal base with vertical development and that takes the form of cotton mountains), and often (but not always) visible as a funnel,” he explained.

At the UNAM Geography Institute, he gave the conference “Tornadoes in Mexico,” as part of the Geography Forum. Academic Talks first semester, in which he specified that, depending on their origin, they can be classified into two types:

Supercell tornadoes, which are created by a severe, long-lasting storm whose wind is rotating, known as a mesocyclone or supercell. And non-supercell or non-mesocyclone tornadoes, which are generally less severe and mostly form under cumulus congestus clouds.

To measure them, there are the Fujita Pearson scales, which consider the categories weak, strong and violent, as well as mild, moderate, significant, severe, devastating and incredible. Likewise, the Improved Fujita, which also offers details of the indicators of damage to houses, facilities and buildings.

“In Mexico, supercell and non-supercell tornadoes have occurred, although the latter are more common, which can be seen with the naked eye as a snake or viper that goes from the ground to the atmosphere,” he said.

Avendaño García documented that pre-Hispanic communities in our country and current peasant groups identify these phenomena, depending on their intensity and region, as air or water snakes; water vipers, hail or air; cloud tails; waterspouts and waterspouts.

“The term viper comes from the morphology of the meteorological phenomenon, which is usually similar to the silhouette of a viper/terrestrial snake. Hence, the name, whose diameter varies between the base of the cloud and the surface of the earth,” he said.

The results

Avendaño García explained that the information base is organized taking as a reference the Storm Prediction Center -located in Norman, Oklahoma, and part of the National Meteorological Service of the National Oceanic and Atmospheric Administration-, in addition to studies in Japan carried out in 1997 by Niino, Fujitani and Watanabe.

In its initial results it is revealed that 2015 is the year (between 2000 and 2023) in which they occurred the most, with 98; while in 2016 there were 74 and in 2021 a total of 61. In contrast, in 2001 there were only two; 2002, six; and 2003, seven.

In 23 years the most frequent months were May, 134; July, 126; and August, 105. In winter there were fewer, since in December there were only 10; in November, 13; and 18 in January.

As for the federal entities, the largest number occurred in the State of Mexico (75), Veracruz (70) and Chihuahua (63); the states with low occurrence are: Aguascalientes (3), Baja California (3) and Durango (4).

Although there is no information in 27 percent of the cases, 57 percent of the tornadoes occurred in the afternoon, 10 percent in the morning and five percent at night, Avendaño García added.

The intensity of these phenomena is estimated by the so-called Fujita Scale or Enhanced Fujita Scale. Most of the tornadoes that occur in Mexico have been EF0 and EF1, weak non-mesocyclonic tornadoes. The deadliest mesocyclonic tornadoes have been seen in Coahuila.

“We have recorded tornadoes with EF3 and EF2 scales, such as the one in Piedras Negras, which was a supercell or mesocyclonic tornado-genesis, categorized in the range of the Enhanced Fujita scale of EF3 (by the North American meteorologists who reviewed the damage in their territory, and by us). The deaths were because the affected people were outside their homes, in an open area.

The one in the Zócalo of Mexico City, June 1, 2012, based on the same Enhanced Fujita scale, was categorized by us as a weak EF2 tornado, not a mesocyclonic one. It did not cause fatalities, but several injuries and material damage.

On the morning of Monday, May 25, 2015, a tornado was observed in the western area of ​​Ciudad Acuña, Coahuila, which damaged infrastructure, homes, in addition to a balance of 290 injuries and 14 deaths. Categorized in the range of the Enhanced Fujita Scale of EF3.

The specialist explained that to estimate the intensity, there is a methodology called "Enhanced Fujita Scale Protocol", which is carried out after the tornado. So far, four of 773 (occurred between 2000 and 2023) have had formal categorization:

Piedras Negras (2007), Coahuila; Zócalo, Mexico City (2012); San Cristóbal de Las Casas, Chiapas (2014); and Ciudad Acuña, Coahuila (2015).

"It should be noted that we face a methodological absence in the registration of damages, we must go to field work to have the different damage indicators and thus establish the intensity category of the tornado. Most of our records do not gather sufficient elements of damage to categorize all tornadoes," she concluded.