This is a common phenomenon in the affected areas.
The devastating floods that hit Spain have already left more than 60 dead and the number could increase. The tragic situation was caused by a DANA which is the acronym for Isolated Depression at High Levelsit is an atmospheric phenomenon that was popularly called cold drop, especially in the Mediterranean area.
A DANA is a low-pressure system at high levels of the atmosphere, which has completely separated from the zonal flow aloft. These isolated depressions at high levels are found, in the northern hemisphere, to the south of the flow established at height.
How a DANA is formed
DANA is formed from polar jeta current of very intense winds of between 150 and 300 km/h, which circulates in the upper part of the atmosphere (at 9,000 meters of altitude). Its journey revolves around North Pole and of West to East (of North America to Europe and Russia).
This phenomenon, as it moves, produces meanders: undulations lasting between 7 and 10 days, which are drivers of storms, anticyclones and DANA. Unlike a common stormmoving eastward, a DANA can remain stationary for several days.
What climate authorities say about DANA
The DANA can “move opposite to the zonal flow of the west (what is called retrogression),” they say from Spanish State Meteorological Agency (AEMET). “Not always when there is a DANA in the upper layers of the atmosphere, the consequences are abundant rainfall, with floods and floods,” says the AEMET meteorologist. Delia Gutierrez to The World.
Gutiérrez also adds that “DANA are a relatively frequent structure in our latitudes and, luckily, most of them do not become so newsworthy”. As he explains, a DANA always entails instabilitybut precipitation is recorded only when there is enough humidityconvergences of wind or orographic obstacles that facilitate the ascent.
Source: Ambito
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