A borrasca is a Spanish term for a storm or tempest. In meteorology, it refers to a specific low-pressure system that brings unsettled, often severe, weather conditions. The term is internationally recognized in European weather forecasting for powerful systems that impact the continent. This article explores the technical nature, geographical context, and official naming process of these systems.
The Meteorological Definition
A Borrasca is scientifically classified as an extratropical low-pressure system, also called a cyclone. Air rises at the center of these systems, leading to cooling, condensation, and the formation of clouds and precipitation. This upward motion creates a region of lower atmospheric pressure at the surface, drawing in surrounding air and generating wind.
The resulting weather is characterized by strong winds, heavy rainfall, and potential maritime hazards like large waves. The severity depends on cyclogenesis, which is the development or strengthening of the cyclonic circulation.
The most intense Borrascas undergo rapid cyclogenesis, sometimes referred to as “bombogenesis.” This involves a dramatic drop in central pressure, defined as a decrease of 24 millibars or more within 24 hours. This sudden intensification creates a vigorous storm with the potential for destructive winds and widespread severe weather. These systems are driven by the interaction of warm and cold air masses in the mid-latitudes and are a significant feature of winter weather across the Atlantic.
Regional Significance and Usage
While borrasca means “storm” in Spanish, its formal meteorological use is concentrated in Western Europe. This usage is driven by the national weather services of nations bordering the Northeast Atlantic. The term is integrated into European weather warning systems to help communicate risk to the public.
Agencies like AEMET in Spain use borrasca for low-pressure systems meeting specific severity criteria. This contrasts with tropical cyclones like hurricanes or typhoons, which form over warm ocean waters. The Borrasca is extratropical, drawing its energy from temperature contrasts rather than latent heat, making it a distinct storm system.
The term focuses on storms expected to impact the Iberian Peninsula and surrounding areas, including Spain, Portugal, France, and Belgium. Using a single, regionally understood term helps standardize communication across different languages and national boundaries for severe weather events.
How Borrascas Are Named
Not every low-pressure system receives a name; only those expected to cause medium or high impacts on land or sea are officially designated a Borrasca. The naming procedure is a collaborative effort involving the national meteorological services of Spain, Portugal, France, Belgium, and Luxembourg. This group works together to ensure a unified warning system for the region.
A storm is named when it is forecast to trigger an orange or red level weather warning for wind, snow, or rain in any of the participating countries. The names are chosen from a pre-determined alphabetical list created annually, which alternates between male and female names. This practice increases public awareness and improves the coherence of storm-related information across the affected territories.