The word DANA is the acronym for an “Isolated Depression at High Levels” that Spanish meteorologists coined in the late 1980s to differentiate it from the more generic and imprecise term “cold drop.” DANA specifically refers to the phenomenon by which a mass of polar air at altitude (between 5,000 and 9,000 meters) separates from the atmospheric flow and can generate strong storms by colliding with warmer and more humid air, generally from the Mediterranean Sea.
“As it is disconnected from the general flow of the west, it evolves independently, with its own life cycle,” explains José Miguel Viñas, meteorologist at Meteored. So much so that sometimes they rotate in the opposite direction of the storms and remain stationary in the same place for hours, which increases their destructive potential.
The expression “cold drop” is widely used in the Mediterranean area to refer to any episode of intense rain in the area, regardless of whether there is a DANA or not. But it is not necessary for there to be a pocket of cold air at altitude for there to be torrential rains, nor does this massive rainfall occur every time there is a DANA.
The term was chosen to honor the memory of the meteorologist Francisco García Dana (1924-1984), who headed the Prediction Center of the National Institute of Meteorology (INM) from 1979 to 1984, the year he died.
The most adverse of the century
The State Meteorological Agency (AEMET) has described the storm experienced last night as “the most adverse cold spell of the century in the Valencian Community” and estimates that its impact and records are “higher than the DANA of September 2019.” “It has been a historic storm, on par with the great Mediterranean storms and among the three most intense of the last century in the Valencian Community,” they add.
Episodes of this type occur when the front remains active in which cold air at height and humid, hot air collide. In the zone of rising warm air, new storm cells grow by convection and in the zone of descending cold air they dissipate. On this border, what is known in meteorology as a “gut front” occurs, which manifests itself in torrential and persistent rains like the ones we have seen on this occasion.
Regarding the question about whether this episode has relationship with climate changewe will have to wait for the attribution studies to be carried out, which will take months, to be able to give an answer. All the above data indicate that the increase in temperature in the Mediterranean, warming and greater atmospheric humidity contribute to producing more extreme episodes like the one we have just experienced.
“The air masses have “background heating,” which contributes to a greater intensification of adverse meteorological phenomena,” indicates José Miguel Viñas. “It was seen with Hurricane Milton and those very extreme squall lines that generated tornadoes in Florida before it made landfall. And with this DANA there have also been no shortage of tornadoes, large hail, convective trains, etc.”
Other previous attribution studies have shown a direct relationship between global warming and extreme episodes like this one, including what is known as a “derecho,” which left a dozen dead in southern and central Europe in August 2022.
#DANA #destructive
