Exciting weather trend – cut-off process decides between late summer and autumn weather

DThe disturbance is expanding into Germany with its unstable layered air masses and will initially cause some showers and thunderstorms over the south and southwest and by the middle of the week also over the west and north – some of them heavy and regionally severe (thunderstorm radar || warning report). Temperatures will mostly still be in the summer range at +22 to +27 degrees, but will drop to +20 degrees near showers and may make mid-summer temperatures of +35 degrees possible over the eastern parts of the country.

Uncertainties in the second half of the week – persistent storm-like rain?
In most forecast models, the disturbance pulse will expand over the Alps in the second half of the week and pump warm, humid air northwards from the Mediterranean region. The decisive factor now will be how far the precipitation fields can spill over to the north – over the Alps. Changes are to be expected here in the coming hours, but at the current stage, further precipitation – some of it severe – is to be expected, particularly over the Alpine region, as well as over Baden-Württemberg and Bavaria, up to and including Saturday. Further north, the clouds will clear and sunny September days can be expected. With persistent rain, hardly more than +20 degrees can be expected, while over the north it can remain summery to mid-summer hot with up to +28 degrees and over the east with up to +34 degrees. If you want to know more – Weather September 2024

Weather forecast according to the European weather model: The tendency to maintain the situation, no autumn weather

As already indicated yesterday, there will be further corrections in the forecast models. Yesterday, both the Americans and the Europeans had rejected a tendency to maintain the situation and suggested that a reactive polar vortex would lead to the breakthrough of autumn over Germany, Switzerland and Austria. However, these were adventurous Calculations that were collected today.

High pressure system regenerates
A tendency to persist is when a large-scale weather situation can be briefly disturbed but can then quickly renew itself. The weather over Germany was dominated by a high, while this week the disruptive impulse is making its way to Central Europe. But before it can establish itself and spread further south over Central Europe, a wedge of the Azores high is already moving in and will settle directly over Germany between September 9th and 10th.

Late summer weather
And so the weather development that we have been describing in our summary for days is coming about. No extremes, but the gradual transition from midsummer to late summer. After the nighttime fog clears, the high ensures an increasing amount of sunshine and a decreasing amount of precipitation. Temperatures reach +20 to +25 degrees in a low-gradient and low-wind environment and can even allow summery values ​​of up to +27 degrees in the eastern parts of the country.

Weather trend according to the American weather model: No autumn weather – high pressure weather!

But the Americans also don’t want to know much about yesterday’s autumn forecast. This was completely rejected. But the structure of the tendency to maintain the weather also shows weaknesses, which could force the coming general weather situation to change.

High pressure zone is coming, but shows weaknesses
The disturbance impulse will also be displaced between 9 and 10 September by a wedge of the Azores high moving towards Central Europe and, with a decrease in precipitation activity, the sun will prevail over a wide area.

Late summer weather trend
However, the high does not manage to stabilize itself over Central Europe to the extent that one could speak of a sustained stable weather development. Rather, the high is surrounded by further disturbances and so a latently increased tendency for showers and thunderstorms cannot be ruled out. Overall, however, from 10 to 18 September in the Weather forecast Americans expect high pressure to dominate the weather. Temperatures will reach their lowest point for the time being on September 8th at +15 to +20 degrees and locally up to +12 degrees, and will then settle into a late summer range at +20 to +25 degrees and at times up to +27 degrees. If there are showers and thunderstorms, it can temporarily cool down to +16 degrees.

In a nutshell: the extension of midsummer or the brutal breakthrough of autumn?

The question still remains today. The details of the cut-off process (the formation of vortices in a low-pressure area) are still unknown, although they are of crucial importance for the further development of the general weather situation. For the moment, at least, the forecast models have made a new correction and favor the tendency for the disturbance to remain, in which the disturbance is a passing disturbance and the high pressure zone can subsequently build up again over Central Europe.

What weather is likely:
The control runs remained Stubborn and only a reduced number of them calculate the breakthrough of the disturbance in the second half of the week. This is more clearly shown when comparing the forecast of the forecast models with the control runs. Both show by far the coldest and wettest development in the period from 5 to 9 September. The control runs themselves calculate a temperature spectrum which, with an average of +4 to +7 degrees, could be significantly to considerably too warm compared to the long-term climate average from 1961 and 1990. We’ll have to wait and see!

At the beginning of the second decade of September, the temperature spectrum of the control runs decreases to an anomaly of +1 to +3 degrees, but remains too warm for the time of year.

Rain forecast:
The rain forecast also says wait and see. There will probably be moderately increased precipitation activity over the south and west, as well as over the northwest, from September 3rd to 5th, which will collapse towards the northeast and east. There are also weak to slightly increased precipitation signals. A sustained stable weather development looks different – but so does classic autumn weather. Rather, today the Weather trend of the past few days: the transition from midsummer to late summer with the first signs of early autumn. Let’s see.