The deadly floods that have killed at least 95 people in Spain were caused by a catastrophic weather phenomenon in which cold and warm air meet to form heavy rain clouds, a pattern believed to occur more frequently due to climate change.

The phenomenon is known locally as Danaa Spanish acronym for isolated high-altitude trough, and unlike common storms or gales, can form independently of polar or subtropical air masses.

When cold air blows over warm Mediterranean waters, it causes warmer air to rise quickly and form dense, water-filled clouds that can stay in the same area for hours, increasing their destructive potential.

The phenomenon sometimes causes heavy hail and tornadoes as seen this week, forecasters say.

Eastern and southern Spain are particularly sensitive to the phenomenon due to their location between the Atlantic Ocean and the Mediterranean. Warm, moist air masses and cold masses meet in an area where mountains favor the formation of storm clouds and precipitation.

This week’s DANA was one of the three most intense such storms in the past century in the Valencia region, said Ruben del Campo, a spokesman for the national weather service Aemet.

“The predictions were in line with what happened. But in an area between Utiel and Civa in the province of Valencia, rainfall exceeded 300 liters per square meter. In this region, storm systems were constantly forming and re-forming,” he explained.

While experts say it will take time to analyze all the data to determine whether this particular DANA was caused by climate change, most agree that rising temperatures in the Mediterranean and warmer, wetter atmospheric conditions are helping to create more frequent extreme events .

“We can’t say anything for sure, except that in the context of climate change, these types of events will be more frequent and more intense,” said Spanish meteorologist and researcher Dr. Ernesto Rodríguez Camino.

Before the term DANA was coined in the early 2000s, any heavy fall rainfall typical of the Mediterranean climate was popularly called “gota fria” (cold drop) in Spain and parts of France. The term is still widely used colloquially.

Its origins date back to 1886 when German scientists introduced the concept of “kaltlufttropfen”, or cold air drop, to describe turbulence at high altitude but with no apparent surface reflection.

Aemet says the concept of cold drops is outdated and defines DANA as a high-altitude closed trough that has become isolated and separated from an associated airstream. Aemet says that DANAs sometimes stand still or even move backwards, from east to west.