19 November 2004: 06 UTC

Isentropes
The isentropes of the equivalent potential temperature (ThetaE) show a cold-front-inclined crowding zone. The distribtion is typical for a low-level cloud head and its associated frontal cloud band. The surface front (50°N) is indicated by the crowded and inclined isentropes near the surface. This structure of the isentropes indicates instability in this area.

Isotachs
According to the conceptual model of a rapid cyclogenesis the maximum of wind speed is found in the upper tropospheric region of the frontal cloud band. A secondary maximum might be found on the poleward side of the cloud head. In the area of the cold front high wind speeds reach down to lower levels of the troposhere.

Vorticity Advection
The field of vorticity advection shows a PVA maximum at upper levels within the area of the cloud head and is connected to the left exit region of the jet streak. PVA reaches unusually far to the other side of the dry tongue into the gradient zone of the cold front. However, a pronounced maximum of NVA is found near the surface in the area of the dry slot. NVA in all layers of the atmosphere exists south of the Alps.

Temperature Advection
The field of temperature advection shows a very distinct situation. A strong and broad maximum of CA is clearly associated with the area of cloud dissolution. One minimum of temperature advection with very low values coincides quite well with the surface front. A second minimum at upper levels of the dry slot, indicating the strong influence of cold advection in the entire development is remarkable, as well as the large distance between the surface front and the zeroline of temperature advection. Cold Advection reaches very far to the South..

Vertical Motion
The distribution of omega also indicates the surface cold front at 50° N. A small but pronounced minimum can be found close to the surface, indicating upward motion at lower levels.

Relative Humidity
The distribution of relative humidity is used to show dry air in the area of the dry intrusion. It can be nicely seen that dry upper-level air is associated with the broad area of cloud dissolution. High values of relative humidity can be observed in all layers of the cloud head as well as in lower levels of the frontal area. Due to the cloud dissolution in the upper troposhere by the strong influence of dry air advection, the IR image shows the surface front cloudiness in a greyish tone, indicating lower clouds with warmer cloud tops.