The dry storm, the dangerous phenomenon that can cause fires

BarcelonaForest fires are common in our Mediterranean climate during the summer months. But in recent years, the number of fires, along with their spread and virulence, have increased due to global warming and the effects of the climate crisis. Eighty percent of fires are caused by humans, whether they are deliberately set or caused by accidents or negligence. But when the cause is natural, there is a term of particular concern: the dry storm.

This is a meteorological phenomenon that is especially dangerous for forests when the risk of forest fires is high. A dry storm is characterized by the fact that it hardly has any associated precipitation. And, if it rains at all, most of this water ends up evaporating before reaching the ground. However, despite the absence of rain, the storm is accompanied by lightning and strong winds, and that is what makes it very dangerous.

A storm that doesn't soak the ground in summer but does generate electrical discharges in a dry, heated territory is a real threat to forests, especially in a climate like the Mediterranean, characterized by hot, dry summers. Therefore, a lightning strike in these circumstances can generate and spread forest fires in a matter of moments. as has happened in recent days in some parts of the Iberian Peninsula. And also this Tuesday in Alins, Lleida, where there was a small fire caused by lightning in a wooded area.

In addition to lightning, the strong, hot gusts of wind that occur during a dry storm facilitate the rapid spread of a fire, which can quickly cause a blaze to spread out of control.

A phenomenon of this nature occurs in conditions of dry, warm air with little humidity in the lower and middle layers of the atmosphere. These factors are increasingly common and intense in summer, as heat waves or episodes of extreme heat become more frequent and persistent year after year.

The climate crisis makes extreme events like this more likely and dangerous, but also makes forests more vulnerable. A fatal combination that increases the risk of forest fires and a violent sixth-generation fire. In the event of a dry storm, it is important to take shelter in safe, enclosed spaces to avoid lightning strikes, since the lack of rain can create a false sense of security.

The latent rays, the silent start of a fire

Lightning is one of the main causes of naturally occurring forest fires, but it doesn't always start a fire immediately. Sometimes it strikes a tree, and the effects of the discharge are stored inside the trunk, where a slow combustion process progresses due to the low oxygen content. This is known as latent lightning, a phenomenon that can cause a fire hours or even three days after the storm.

Detecting lightning is very difficult, as it doesn't generate any prior smoke column and is not visible to the naked eye. No one expects it, and this element of surprise and silence makes it especially dangerous, because when weather conditions worsen and the ground dries out, fire can burst from the trunk and start a fire. Latent lightning can occur in a dry thunderstorm or in a storm accompanied by precipitation.