Unprecedented Weather Event in Mexico City
Mexico City, known for its warm and sunny climate, experienced a rare and intense snowfall in January 1967. This unusual weather event was the result of a combination of atmospheric factors that created the perfect conditions for snow to fall in the city and surrounding areas.
The snowfall occurred on the morning of January 11, 1967, catching residents off guard and prompting them to take immediate action to protect themselves and their property. The snowfall was not limited to Mexico City, as other cities in the north of the country, such as Monterrey, Chihuahua, and Zacatecas, also experienced significant snow accumulations.
Atmospheric Conditions Leading Up to the Snowfall
The 1960s were marked by significant climate variability, influenced by the Arctic Oscillation (AO). In late 1966, the AO entered a negative phase, leading to lower pressure in the Arctic and a more undulating jet stream. This allowed cold polar air to penetrate further into the middle latitudes, including Mexico.
The AO index reached minimum values in mid-December 1966, weakening the jet stream and allowing cold air to enter North America. An isolated upper-level depression (DANA) formed in northwestern Mexico in early January 1967, which, combined with the undulating jet stream and polar air mass, created a low-pressure system that intensified precipitation and generated ideal conditions for snow formation.
Key Factors Contributing to the Snowfall
The snowfall of 1967 was the result of a combination of global climate patterns, including the Arctic Oscillation (AO) and the El Niño phenomenon. The negative phase of the AO weakened the jet stream, allowing cold air masses to move to lower latitudes and creating an environment conducive to snowfall.
The formation of DANA in northwest Mexico was a key factor in the snowfall, as it created a low-pressure system that intensified precipitation and generated ideal conditions for snow formation. The combination of these factors led to a favorable scenario for the formation of snowfall, which ultimately resulted in the historic snowfall of 1967.
The Snowfall at Its Maximum Intensity
The snowfall of 1967 was the result of the interaction of several systems, including the High Level Isolated Depression (DANA) in the northwest, a cold front advancing from the north, and a powerful mass of polar-arctic air. The snowfall began in the northern states of Mexico on January 8, 1967, and quickly spread to the south and center of the country.
Cities such as Zacatecas, Aguascalientes, Monterrey, and San Luis Potosí experienced heavy snowfall, with accumulations up to a meter thick in some areas. On January 11, 1967, the snowfall reached the Valley of Mexico, covering Mexico City and neighboring states with a white blanket.