Training Module on Upper-Level Lows

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• Case Study: Floods in Central Europe 2021
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• Early Phase: 10 - 12 July 2021
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• 13 July 2021
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• 14 July 2021
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• Final Phase: 15 - 18 July 2021
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• The Impact of Upper-Level Low Bernd on Germany and Austria

Early Phase: 10 - 12 July 2021

A low-pressure system formed over the Atlantic on 10 July and moved quickly over the British Isles and France by 12 July. Bernd's low-pressure core formed north of the polar front, which extended far south over Spain, forming a large upper-level trough (see Figure 1). At this stage Bernd already shows more characteristics of an upper-level low than a classical low-pressure system. A high-pressure zone at mean sea level is found below the core of the ULL. Related to this, a weaker surface low can be found northeast of the ULL.

Figure 1: Airmass RGB from 12 July 2021 at 15:00 UTC. Cyan lines indicate the geopotential height at 500 hPa, black lines indicate the mean sea level pressure.