The case described here deals with several interesting phenomena. The main investigation is related to convection within the cold front. The other processes followed here are convergence at the leading edge of the front and convection within an cut off low over the Atlantic west of Portugal.
The following theories can describe convection within and in front of the cold front:
During the case a series of convective developments within the cold front (vigorous V-shapes) and some MCSs on the leading edge are observed. This type of process follows closely the course of classical development described here in the above theory. The MCSs develop on both days at the leading edge of the front which can be followed by satellite loops and numerical model fields.
Situation typical for the thickness ridge, ahead of the cold front, is confirmed by the analysis of 500 hPa geopotential field and the Equivalent Thickness. The moist warm air is advected from the south or south-east which, together with the drier and colder air in the upper levels, leads to potentially unstable stratification of the troposphere. The MCSs develop ahead of the front, during the 3rd October.
In this case study the Cut-Off plays an important role in the convection over Spain during the events of this case. This persistent cyclone is well seen in the upper layers of the tropopshere. Its clear cyclonic rotation transport warm humid air towards Spain. On the WV boundaries of this cyclone as well as in the core at a later stage also some cells develop. Towards the end of the case study these cells have wandered into Spain.
The enhancement of convection by PV is followed as the wave is forming within the front over Morocco. The maximum of PV shows the penetration of stratospheric air into the troposphere, at the rear of the frontal cloudiness. In all the satellite images small CBs are seen developing on these WV boundaries.