When the cold drop was renamed DANA

He dramatic weather episode that devastates the Spanish Mediterranean coast is a Isolated High Level Depression, DANAa term officially adopted by the Spanish Meteorological Agency (AEMET) since the mid-80s of the last century, although The media would continue to call these sudden and violent phenomena “cold drop”a term wildcard which is not entirely accurate.

Already in 2004, the veteran physicist Francisco Martin Leon explained in an article for the AEMET [consúltelo íntegro al final de este texto] that when one referred to a cold drop it was not necessarily due to depression at high levels: “In Spanish terminology we have explicitly added the concept of ‘high levels’ to differentiate them from other types of depressions or isolated lows, such as, for example, those of thermal origin that occur in the peninsula during the warm months in lower layers” , he pointed out in the aforementioned article.

Martín León describes the DANA phenomenon in an entertaining and understandable way. This originates from a excessive polar jet stream ripplea band of strong winds, up to 180 km/h, flowing from west to east at a maximum altitude of about 9,000 meters and surrounding the Earth.

“When the jet, originally rectilinear, intensifies, it undulates and has a very marked north-south component, a process of isolation and strangulation of part of this intense circulation can be generated,” he explains. “These circulations are isolated from the general circulation, they move away from the areas of origin and become closed on themselves”he adds. This is when a DANA can form.

A predicted catastrophe

In this message published by the AEMET on Saturday, October 26, that is, three days before the catastrophic floods occurred in the province of Valencia and other nearby places, you can see perfectly how the evolution of this depression could be foreseen which, together with the temperature and humidity of the Mediterranean, has punished large areas of eastern Spain with torrential and persistent rains, and has caused dozens of deaths who knows if many of them are avoidable.

The definition of DANA (which in English is cut off low or detached or isolated low) is, therefore, “a closed depression in height that has been isolated and completely separated from the circulation associated with the jet, and that moves independently of such flow, sometimes becoming stationary or even retrograde (its movement is, in these cases, in an east-west direction)”.

Fortunately, there is less and less talk about cold drop — a term that he mentioned for the first time the meteorologist Manuel Ledesma Jimeno and popularized the “first weather man” on TVE, Mariano Medina— and more from DANA when this atmospheric phenomenon happens, so concrete and perfectly described by science. All you have to do is compare both terms in Google Trends to verify its adoption in recent years.

As a curiosity, the Spanish acronym DANA was chosen in tribute to the meteorologist Francisco García Dana (1924-1984), who headed the Prediction Center of the National Institute of Meteorology (INM) from 1979 until his death in 1984.