The word DANA is the acronym for “isolated high-level depression” 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 whereby a polar air mass aloft (between 5,000 and 9,000 meters) separates from the atmospheric flow and can generate strong storms by colliding with warmer, more humid air , generally from the Mediterranean Sea.
“As it is disconnected from the general westerly flow, 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, increasing their destructive potential.
The expression “cold drop” is widely used in the Mediterranean basin to designate any episode of intense rain in the area, whether or not there is a DANA. But there doesn’t have to be a pocket of cold air aloft for there to be torrential rains, nor do these massive precipitation events occur every time there is a DANA .
The term was chosen to honor the memory of meteorologist Francisco García Dana (1924-1984), who headed the Forecast Center of the National Institute of Meteorology (INM) from 1979 to 1984, the year of his death.
The worst of the century
The National Meteorological Agency (AEMET) has described the storm that occurred last night as “the most harmful cold wave of the century in the Valencian Community” and considers that its impact and records are “higher than the DANA of September 2019” . “This is a historic storm, comparable to 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 aloft and warm, moist air collide. In the area of rising warm air, new storm cells develop by convection and in the area of descending cold air, they dissipate. On this border occurs what is called in meteorology an “intestinal front”, which manifests itself in torrential and persistent rains like those we saw on this occasion.
Regarding the question of 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 indicates that the increase in temperature in the Mediterranean, warming and increased atmospheric humidity contribute to producing more extreme episodes like the one we have just experienced.
“The air masses have a “background warming”, which contributes to a greater intensification of adverse weather phenomena,” says José Miguel Viñas. “This was seen with Hurricane Milton and these very extreme squall lines that generated tornadoes in Florida before they made landfall. And with this DANA, tornadoes, large hail, convective trains, etc.
Other previous attribution studies have shown a direct relationship between global warming and extreme episodes like this, including a so-called “derecho,” which left a dozen dead in the South and the central Europe in August 2022.
