Before the next heat wave, a slow-moving low provides a few moments to breathe deeply. During this time, however, it will rain heavily, especially in the east and in the very south, as ntv meteorologist Björn Alexander says. In the next week, midsummer could already do its farewell round.
ntv: Severe storms were recently reported from southern Europe. Does that threaten us too?
Björn Alexander: The peak wind gusts that we received from the island of Corsica on Thursday, for example, are more than 200 kilometers per hour. This is an extremely violent thunderstorm that raged there. Fortunately, there are no signs that such hurricane situations could occur here. Especially since the storms in the Mediterranean were triggered by another low. With us it is low “Karin”, on the Mediterranean it is low “Diana”. Where “Diana” is the international name for the Mediterranean low.
How is the situation developing in southern Europe? After all, it’s vacation time.
First of all, the situation remains tense, especially in northern Italy. This is where the highest risk of storms comes from devastating gusts of wind, heavy rain and an increased potential for tornadoes. Unfortunately, these are also not good omens for the upcoming late summer and early autumn. With a water temperature of up to 30 degrees, the Mediterranean is sometimes three to five degrees above normal. This threatens to intensify the storm in the right weather conditions.
Why is that?
Because warmer water also means more and more water vapor and thus potential energy. In addition, storms on the Mediterranean are often triggered by cold air intrusions, especially in late summer and autumn. And the greater the temperature difference between the cold air above and the warmer water surface, the more intense the weather phenomena.
Key word: intense weather phenomena. Storms are also coming up in Germany. Where is it worst?
Thunderstorm low “Karin” has now reached us and, in a muggy, warm to hot air mass carousel, ensures that powerful thunderstorms can form. Because the differences in air pressure are very small, slow-moving thunderstorm complexes pose a risk of heavy rain. At the same time, the soil is parched in many places, so that the risk of flooding is significantly increased. Wind gusts and hail cannot be ruled out either.
Which areas are affected?
Unfortunately, due to the weak wind conditions, the details cannot yet be predicted exactly. The focus at night is probably in the east with around 20 to 50 liters of rain per square meter – locally more at peaks. In the direction of the Black Forest and the Alps, more intense thunderstorms are also to be expected locally.
How about Friday?
The focus is likely to be in the southeast. In the regions from the edge of the Alps to around the Bavarian Forest and up to the low mountain ranges – depending on the weather model – rainfall of more than 100 liters per square meter is possible in some cases. Even the east could go back to a similar magnitude in some places.
Otherwise the big rain stays away? Also with regard to the low water level on the Rhine.
That’s the way it is. In the direction of the Black Forest, the rain distribution also affects parts of the Rhine catchment area. Unfortunately, no relaxation is to be expected. The now historic lows will therefore continue to occupy us and unfortunately the resulting supply problems will probably do the same.
Where do these extreme weather situations come from – especially in summer?
The basic problem that brought us the drought in 2018 and now, and which caused many severe summer thunderstorms and heavy rain situations in other years, is the lack of dynamics in our atmosphere. Large weather conditions simply last much longer as a result. This means that hot air masses from southern directions, for example, can continue to advance northwards. For example, look at the current heat up to Scandinavia or hot air bubbles in the direction of the British Isles in July or last year with the blatant records of 50 degrees up to Canada.
What is the reason for this lack of drive in the weather?
The worldwide weather processes are mainly driven by the temperature differences between the polar regions and the regions at the equator. Due to the melting poles, however, these differences are becoming smaller and smaller – especially since the reduction in snow and ice surfaces is even making itself felt on several occasions. The bottom line is that the engine for our weather is slowing down – more stationary weather conditions are only one consequence. The weakening of the Gulf Stream is also related to this, for example.
Can we already make forecasts for September and autumn in terms of rain – is there any relief in sight?
At least the experimental long-term forecasts of the American weather service NOAA continue to give hope for a too wet September and a partly too wet October.
Finally, the prospects for the weekend and the next week. What awaits us?
Last flashes of lightning and heavy showers in the south and south-east on Saturday. Otherwise it is dry and at times sunny with temperatures between 20 and 27 degrees for breathing and airing. And the nights are also becoming much fresher with lows of around 16 to 9 degrees.
How does it look afterwards?
In the Alps and in the north it will be slightly changeable on Sunday. In the rest of the world, however, it stays nicer at 20 to 28 degrees – a similar range as on Monday, by the way, before the summer wants to get going again. On Tuesday at 22 to 32 and on Wednesday and Thursday with mostly 24 to 34 degrees. Only at the end of the week could the heat mark of 30 degrees slowly say goodbye to our latitudes.
