Is the general weather situation heading towards late summer?

The clouds are increasing – as is the tendency for showers and thunderstorms – and will ensure a change of weather for the weekend, which could increase the potential for regionally severe thunderstorms. But how sustainable is this change in the weather – is early autumn coming to Germany, or is there late summer?

pSeptember too hot. What has already been indicated in the last few days continues today. The weather will be noticeably more changeable in the coming days and that temperatures decrease with an increased tendency for precipitation to an interval of +18 to +24 degrees and may orientate itself towards the +15 degree mark with prolonged precipitation, but this is a normalization of an excessively high temperature level.

Foggy and warm with severe weather events

If you compare the most recent September days with the long-term average, September has so far been about 4.0 degrees too warm. And yes, yesterday there were peak values ​​of up to +32.3 over Kleve (North Rhine-Westphalia) a hot day over Germany, whereby the values ​​today can reach +30 degrees and more. 2.9 percent of the precipitation target was met. It takes a proper cooldown to mitigate the high level, but it doesn’t get that cold when you look at the area. More on this in the current weather forecast for September.

that Forecast of the American weather model (left) and the average of all control runs (right): A mixed weather situation with low elevations and ups and downs ©

The rain forecast

Still, the showers and Thunder will be described as significant in the coming days. Although these do not occur across the board, they may be concentrated in the west, north, northeast and east of severe weather events worries. There is a tendency for less precipitation over the south, southeast and over the eastern edge of the low mountain range.

On the left the rain forecast for the Europeans, in the middle for the Americans and on the right next to the German: No even distribution of precipitation
On the left the rain forecast for the Europeans, in the middle for the Americans and on the right the German: Not even distribution of precipitation ©

Thesis – Conservation trend with late summer consequences

For a few days now, the Americans have simulated the possibility of an (early) autumn-like weather situation, where temperatures can cool down significantly and aim for +10 degrees during the day and +5 degrees at night. Above the higher mountain country would be after this Weather forecast with the first snowfalls to count on. But the Americans spoke in relation to the control runs with this one Forecast always for the coldest varieties.

Tilt the pattern in the direction that is too hot

Anyone who has been our guest for a long time may know what we are saying.

In times of global warming, the hot varieties are not always predominant, but increasingly so

observation in recent years

What is it about early fall and what about late summer?

And that’s how it works. First, the prediction models calculate optimal conditions for a variant that is too cold. An extreme, so to speak. Then the optimal conditions gradually weaken and eventually the general weather situation changes to the opposite. Too cold becomes too hot – and this phenomenon has been disproportionately common in the past.

You could already be suspicious yesterday. The period from September 12 to 16 shows a high accumulation of significantly too warm varieties in the control runs, which was confirmed again today and should lead to a temperature exceedance of +2 to +4 degrees. A change in the weather in early autumn certainly looks different. But this is still not excluded, but the first – significant – delay with a contradiction weather trend.

What is the reason for this? Very easy. Low western Europe now shifts towards Scandinavia, but weakens in the process. Meanwhile, another low pressure system forms in the Atlantic, and the space between the two low pressure systems is filled by a high pressure system. To put it another way, instead of a low point (north-south), there is a high point in Central Europe (south-north), and that would be the 180-degree turn and late summer can find its way to Germany.

The rainfall performance decreases after September 12 and the temperatures reach +18 to +24 degrees. The achievement of summery +26 degrees could therefore no longer be ruled out.

A low on the left and a low on the right in Europe - in between a late summer to summer high
Forecast according to the US (right) weather model from yesterday and a selected control run: a low on the left and a low on the right for Europe – in between a late summer to summer high over Germany ©

Really late summer? A look at the marginal factors

In order for a late summer weather development to occur at all, no high pressure wedge should project northward into the Atlantic. Instead, an Icelandic low should establish itself, also eroding to the south. Put simply, this is the characteristic of a positive NAO index. And if you look at it, it’s currently negative, but trending positively. And precisely this circumstance one could thwart the early autumn weather.

If you look at the pressure anomalies up to September 15th and compare them to the average of all control runs, the pattern becomes a late summer temperature development approved. A low point approach initialized from Scandinavia cannot be identified. Instead, a mixed weather situation with a southwesterly flow of the air masses.

A trough looks different - a southwesterly flow of the air masses is favored for this
Forecast according to the average of all control runs and the pressure anomalies: A trough looks different – for this a southwesterly flow of the air masses is preferred © |

In a nutshell: too hot for the season

Whether will confirm the thesis of a late summer weather development, remains to be seen. The decision is expected between September 9 and 12, which will show how and whether the high over Germany will hold and thus lead to a maintenance bias.

According to the probability, temperatures of more than +20 degrees are 60 to 80 percent likely on September 15. Values ​​below +15 degrees have a probability of 0 to 10 percent. It’s a message. Looking at September 20, the probability of temperatures above +20 degrees is between 40 and 60 percent and of values ​​below +15 degrees between 0 and 20 percent. This also speaks against an early autumn weather development.

Lots of rain?

The rainfall peaks from September 7 to 10 are notable and then weaken but remain relevant. In combination with the warm air masses, this confirms the thesis of a southwesterly inflow of the air masses. Let’s shake.

Mixed weather conditions in the form of a southwesterly flow of the air masses
Forecast after the average of all control runs: mixed weather conditions in the form of a southwesterly influx of air masses ©
The temperature forecast for the control is running
Day temperature spectrum average temperature
September 12 +17 more
+31 degrees
+20 more
+24 degrees
September 16 +12 more
+27 degrees
+18 more
+20 degrees
September 20 +13 more
+27 degrees
+18 more
+20 degrees
Chart temperatures September 2022
Probability of the September 2022 monitoring runs being too cold, normal, too warm compared to the long-term average (1961 to 1990)

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