28 February 2004: 00 UTC

The zone of backward inclined crowded isentropes in middle and upper troposphere, in the centre of the cross section, indicates a cold front character. In the satellite image the cloud band of this cold front can be seen west of Corsica and Sardinia. From the cross section it can be seen that cold front character is evident in the upper layers, whereas near the ground the stratification is stable and forward inclined isentropes show warm front character.

Potential Vorticity

There are two positive PV anomalies near the ground - one within the frontal zone and the other in the region of the old, dissipating cyclone. The upper-level values of PV also indicate the presence of two anomalies, although the PV=1 is not lower than 500 hPa.

Vorticity Advection

Two PVA maxima in the lower layers indicate that there are two systems in this cross section, however in the upper troposphere there is only one very strong PVA maximum directly above the ground cold front. The strongest upward motion could therefore be expected in that region.

Temperature advection

Similar to the situation in the previous time steps, there is very pronounced warm advection in the upper layers, whereas in the middle troposphere there are two maxima of cold advection - one in the region of the front, and the other within the old, dissipating cyclone. In this cross-section the frontal character of the zone in the middle of the cross-section is confirmed: there is warm advection in front and cold behind the zone of crowded isentropes, indicating a cold front there.