Black storm warnings in Mexico, Digi Mart USA News: The National Meteorological Service (SMN) forecast very heavy rain in eight Mexican states for Friday, November 6, leading some media outlets to use the term “black storm.” However, the label comes from the warning system used in Hong Kong, where it represents the highest level of alert for intense rainfall, according to the Hong Kong Observatory.
In Mexico, the term “black storm” is not part of the official definitions of the SMN and is used informally to describe heavy precipitation exceeding 70 millimeters [mm] of accumulated water. Such rainfall can increase the likelihood of flooding, waterlogging, river overflow and landslides.
The storm and intense rain warning system, used in several countries and regions of Asia including China, Japan and Taiwan, has three levels: amber, red and black. The black level represents the highest degree of warning for severe precipitation.
The Hong Kong Observatory noted that red and black signals alert the public to “heavy rain that could cause serious flooding on roads and traffic congestion.” The intense rain warning was first introduced in April 1967, together with the thunderstorm warning, by the Royal Observatory of Hong Kong, following three storms in 1966 that claimed 86 lives.
The SMN forecast very heavy rain of 50 to 75 millimeters for Friday in areas of Sonora, Chihuahua, Nuevo León, San Luis Potosí, Hidalgo, Puebla, Tamaulipas and Veracruz, due to various weather systems affecting the country. Heavy rain of 25 to 50 millimeters is also expected in Querétaro, Guerrero, Oaxaca and Chiapas, while showers are forecast for Mexico City, the State of Mexico, Tlaxcala, Morelos, Guanajuato, Michoacán and other states.
The precipitation could be accompanied by electrical discharges and hail, in addition to causing waterlogging and flooding.
These conditions are related to cold front number 4, reinforced by a mass of cold air, as well as low-pressure troughs and other atmospheric phenomena. The agency also anticipated a drop in temperature in northern and northeastern Mexico, with minimums of down to -5 degrees Celsius in mountain areas of Baja California, Chihuahua and Durango.
