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block patternThe current wave of bad weather in Europe and Italy is linked to blocked circulation Normally, atmospheric currents in the mid-latitudes flow from west to east, driven by the jet stream. This high-altitude flow regulates the weather in much of Europe. Occasionally, this pattern gets stuck for several days. creating a reverse circulation.
Reverse circulation describes those blockage situations in which anticyclones move northwards, for example towards Scandinavia and alter the normal trend of the currents at high altitude. This anticyclone blocks the normal Atlantic flow from west to east, which is forced to divide: one part rises towards the north, while the other moves towards North Africa. This exchange between high and low pressure generates winds at high altitude from east to west in central Europe.
This type of circulation, altered, thus transports cooler air towards the Mediterranean.where it collides with moist, energetic air, creating unstable and disturbed conditions. Meanwhile, Northern Europe experiences more stable and mild conditions due to the presence of the anticyclone.
circulation reversed with the anticyclone over ScandinaviaThis phenomenon, which is completely normal but temporary, is linked to Rossby waves.. These waves separate cold polar air from warm tropical air and influence the weather. When Rossby waves grow too large and “break”, high pressures move further north, causing the circulation to reverse.
These slowly evolving configurations can cause extreme events simultaneously in several parts of the Northern Hemisphere. In addition to Europe, the eastern United States is also experiencing heavy rainfall due to these patterns. In winter, the reversed circulation can lead to severe cold spells in Europe.