DISCUSSION: Hot and humid weather has been the main story for much of Europe this past month thanks in part to a strong area of high pressure parked over the region. Temperatures have been several degrees above average these past few months, and there is no relief in sight. Many of the primary global weather models which meteorologists use are indicating that the heat will last until at least the middle of September. Towards the end of the month, stronger bursts of cooler air from the Arctic are expected to cool down the majority of the continent. Places in Spain and Portugal have surpassed 40°C (104°F) on several occasions this past week, which is much above normal even in the heart of summer. Cities and towns in France, Germany, and Austria broke several daily high temperature records this week as well. The one place that has remained rather cool recently is Southeastern Europe, where a cutoff upper-level low pressure system has stalled above the area. Southern Italy and much of Greece have experienced below average temperatures these past few days.
Since the low pressure system is separated from the jet stream, or the upper-level winds that guide the majority of weather systems across the globe, it has nowhere to go until it catches up with the jet stream again. This could take anywhere from a couple of days to sometimes a week or more. Looking at the weather models it appears that the cut-off low pressure system will persist for the next week, bringing cool air, clouds, and showery weather. As for the rest of Europe, it appears that the heatwave will finally break over the weekend as a powerful cold front makes its way across the continent. However, the cool air will be short lived as it appears summer air is bound to make a comeback shortly following the fronts passage.
The unusually warm air for this time of year is being caused by what is known as an Omega block. In an Omega block, an area of high pressure located in the upper layers of the atmosphere is wedged between two areas of low pressure. Inside an area of high pressure, the air sinks, compresses, and warm which is why the temperatures have been well above average. Omega blocks are typically responsible for intense heatwaves; such as that which unfolded during the deadly European heatwave in 2003.
To learn more about other high-impact weather events from across Europe, be sure to click here!