virga

Fire emergency in Spain: what are the “dry thunderstorms” that caused the bonfires

Spain finds itself in the middle of an emergency for the forest fires: the Spanish Ministry of Interior confirmed the presence of 16 active forest fires in the country, of which 11 classified as an operational situation 2 (i.e. they need the intervention of the central government vehicles), with more than 8,000 people evacuated For safety reasons, 2 dead Because of burns and 4 seriously injured.

For the moment the most affected areas are those of north-westwith the communities of Castile And Leónthe Galicia and the region of Madrid who are finding the greatest damage: the situation is particularly serious to Ourenseabout 100 km from Santiago di Compostela, an area at the moment rather beaten by tourists engaged in the path of Santiago, where the flames have already destroyed at least 7,000 hectares.

According to what reported by Aemet (Agencia Estatel de meteorologíathe state agency of Meteorology), among the reasons for these fires there would also be the so -called “Secchi thunderstorms” associated with the intense heat wave that is affecting a large part of Europe, which have fueled the flames and favored the expansion of the bonfires in different areas that are not very accessible for the firefighters.

What are dry thunderstorms and why they promote forest fires like those in Spain

At this moment Spain is in the midst of a heat wave which, according to Aemet, will continue at least until Monday 18 August, with temperatures that will reach up to 44 ° C in the south and 40 ° C in the north. Because of these high temperatures, the air at low and medium altitudes is very hot and dry And the ideal conditions are created for the so -called “dry thunderstorms”, In which in the face of anhigh electrical activity (i.e. lightning formation) rainfall are very scarce (less than 2.5 millimeters) because the high temperatures and low humidity cause rain drops to evaporate even before touching the ground. It seems an impossible thing, but in reality it is not unusual: it will probably have happened to you too to see the so -called virgaethat is, those “columns” of rainfall hanging from the base of a temporal cloud but do not reach the ground. This happens precisely because rainfall evaporates while it is still in fall.

Example of Virga. Credit: KS0STM, CC By –a 3.0, via Wikimedia Commons

As if that were not enough, dry thunderstorms can produce some even intense descending currentsthat once you arrive on the ground they “spread” in all directions by promoting the propagation of flames and fires.

In short, we have almost absent rain that does not go to wet a soil made already arid by high temperatures, and lightning ready to trigger fires in the arid soil. Literally the “perfect storm” for the formation of forest fires. In this context, heat waves have a triple role: first of all the intense heat creates more Instability in the atmosphere And, therefore, it promotes intense bad weather; Then prepare the conditions of drought and aridity of the soil; and finally the possibilities of formation of dry thunderstorms increase.

The problem is that these dry thunderstorms can cause fire even in the most remote and less accessible areas, making the intervention of the rescuers more difficult. For this, they are the most dangerous thunderstorms in the fire season, precisely because they are able to create the ideal conditions for feeding the bonfires.

AEMET forecasts for fires in Spain

According to the forecasts published by AEMET, the fire situation in Spain is intended for worsen In the next few days: the map below shows the areas at risk of fire today, Wednesday 13 August, with the South and the North-West which are among the most affected areas.

Map-ink-SPAGNA-13-August
Fire alert map in Spain for the day of August 13th. In red the areas where the alert for fire is at the maximum level, in blue where the risk is at a minimum. Credit: Aemet

To have a comparison, these are the forecast For Monday 18 August, When the heat wave should end according to what reported by AEMET: the serious risk of fire is extended to the whole country, excluding a small aerial in the autonomous community of Aragon, in the north-east.

Map-ink-SPAGNA-18-August
Fire alert map in Spain for the day of August 13th. Credit: Aemet

The fire season, therefore, is proving to be particularly violent: according to the program surveys Copernicus Effissince the beginning of the year in Spain they have already burned further 100,000 hectares of land, more than double the hectares destroyed by the flames throughout 2024 (equal to 42,615).

In the meantime, the Spanish Prime Minister Pedro Sánchez He defined the situation as “extremely serious”, asking the population to maximum prudence and confirming the intervention of the emergency teams to tame the flames.