Floods Glossary

Vb weather situation

In a Vb situation, a cyclone transports warm and moist air from the Adriatic region and moves in a northeast direction. Upon reaching low mountain ranges (Bohemian Massif, Erzgebirge, Sudeten, and Beskids), the air is orographically lifted over an extended area. Producing large amounts of rainfall in a Vb situation requires a combination of (1) meridional and cyclonic airflow, (2) high water vapor content, (3) low convective lability, preventing cell formation, and (4) prolonged (~0.5 days and more) flow against orography, relating to a slow movement of the long wave. The long or Rossby wave thereby defines the "Großwetterlage" (general weather situation) in Europe. The Großwetterlage "Troglage Mitteleuropa" (TrM) (trough situation in central Europe) contains the Vb situation as one element. In and north of the Alpine region the Vb weather situation is feared for these extremely high precipitation rates. The most famous (and most devastating) examples for its impact are the floods of the Odra in 1997, the Vistula in 2001, the Elbe in 2002, the floods on the northern ridge of the Alps in 2005 and the Events in Switzerland in 1987, 1993 (Brig) and 2000 (Gondo).

Source: Mudelsee et al., 2004