BAD WEATHER CAUSED BY A DANA

Bad weather caused by a DANA brings heavy rainfall, flooding, and stormy winds to the region where it passes.

In recent years, southern Spain has increasingly faced intense rains and storms that cause significant damage. One of the primary causes of this extreme weather is a meteorological phenomenon known as a DANA, which stands for Depresión Aislada en Niveles Altos in Spanish, which roughly translates to “Isolated Depression at High Altitude.” A DANA often leads to unpredictable and intense weather conditions, ranging from heavy rain and fierce winds to flooding and landslides.

What is a DANA?

A DANA refers to a cold air mass that detaches at high altitudes in the atmosphere from typical air currents. Unlike usual weather systems, this cold air layer is not carried along by the prevailing westerly winds but remains in place over a specific area—often over the western Mediterranean. Under certain conditions, this can lead to prolonged rain showers and stormy weather.

A DANA forms when a cold air mass from the north comes into contact with warmer, humid air, often present over the Mediterranean region. Due to this temperature difference, the warm, humid air rises quickly, condenses, and creates heavy rain and thunderstorms. In extreme cases, a DANA can lead to flooding and significant damage to infrastructure and agricultural areas.

Formation and development

A DANA usually forms in autumn or early spring, when temperature differences between atmospheric layers are at their peak. Additionally, the Mediterranean climate still brings relatively warm sea temperatures during this period, creating a greenhouse effect that fuels extreme weather, particularly in southern Spanish regions like Andalusia, Murcia, and Valencia.

The process begins when a polar jet stream carrying cold air from northern regions splits. One branch remains to the north, while the other heads south, forming a cold air bubble over the Mediterranean area. This cold air bubble then detaches and remains at a high altitude, resulting in the formation of a DANA.

Effects of a DANA on the weather

Once formed, a DANA can linger over an area for several days or even up to a week, bringing large amounts of rain, thunderstorms, and strong winds. Heavy rains frequently cause flooding and mudslides, especially in low-lying areas and valleys. The impact of this rainfall can be severe, with residents evacuated, damage to homes and infrastructure, and agricultural losses.

Southern Spain is particularly vulnerable to the effects of a DANA. The dry climate in this region means that the soil absorbs water less effectively, causing faster flooding. Rivers and canals often cannot handle the sudden downpours, leading to a rapid rise in water levels and subsequent flooding. For example, in 2019, a DANA caused severe flooding in the Murcia region, requiring the evacuation of thousands of people and resulting in millions of euros in damage.

Is a DANA becoming more frequent?

The frequency and intensity of DANAs appear to be increasing, potentially due to climate change. Rising sea and ocean temperatures globally allow the air above to absorb more moisture, which results in more precipitation when it encounters a cold air mass like a DANA.

Additionally, climate change has increased the frequency of extreme weather events worldwide. This means that situations like a DANA are likely to occur more often and become more intense. With more energy available in the atmosphere, the development of intense thunderstorms, prolonged rainfall, and extreme winds associated with a DANA becomes more probable.

Can a DANA occur in the Canary Islands?

Bad weather caused by a DANA in the Canarian Islands can also occur in Tenerife and the other the Canary Islands, although the phenomenon is less frequent and typically less intense than on the Spanish mainland. This is because the Canary Islands are geographically farther from the Mediterranean region, where the warm, humid air combined with cold fronts creates favorable conditions for a DANA to form.

However, the islands are not completely immune to extreme weather conditions. When a cold air mass from the north meets the subtropical climate of the Canary Islands, this can lead to heavy rainfall and stormy conditions. Due to the islands’ lower annual rainfall and dry, rocky landscapes in many areas, heavy rains can more quickly cause flooding and mudslides. This happened, for instance, in 2005, 2010, and in 2020, when heavy rains led to flooding in parts of Tenerife, Gran Canaria, and La Palma.

Weather Alerts

As sea temperatures continue to rise due to climate change, the likelihood of heavy rains and intense storms in the Canary Islands also increases. As a result, it is becoming more important for the islands to adapt their infrastructure, such as drainage and warning systems, to better manage the impacts of such extreme weather. The government activates weather alerts whenever a DANA approaches the Canary archipelago.

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