EUMeTrain: Cold front over middle Europe

Meteorological Physical Background

The following phyisical theories can be used to describe forming and development of the wave within the front:
  1. Cyclogenesis according to the classical polar front theory
  2. Cyclogenesis in connection with the left exit and the right entrance region of a jet streak
  3. The Hoskins theory based on PV and PV anomaly
In this case study there were two wave developments analysed and for both of them the mentioned theories can be applied in the following way:
Ad1. Cyclogenesis according to the classical polar front theory

This theory can be applied for the both waves. In the beginning there is a classical cold front and due to the suitable conditions a occlusion developed from the cold front cloud band. The cold air moves south-eastward and warm air moves north-westward and this circulation is superimposed on the eastward-moving front. During this circulation a strengthening of the low pressure area occurs and further development of a new cyclone can be observed.

Ad2. Cyclogenesis in connection with the left exit and the right entrance region of a jet streak

For both waves this theory has an important role. Cloud bulges of both waves are developing in the left exit region of a jet streak.

Ad3. The Hoskins theory based on PV and PV anomaly

The downward protruded dry air which overruns a low level baroclinic zone has a very important role in both wave development. This can be seen in WV images, in relevant model fields like potential vorticity (PV) and in vertical cross sections (especialy for the second wave development).