10 March 2006, 12 UTC

The isentropes show a downward inclined crowding zone, which extends through the whole troposphere.Closed circles in the lower troposphere discover that the area is highly unstable, especially at the windward side of the Apennine peaks.

Temperature advection

Temperature advection field reveals warm advection ahead of the frontal zone and cold advection within and behind the crowding zone of the isentropes, a distribution typical for the Cold Front in Cold Advection. Another maximum of warm advection, connected to tropopause folding, can be observed in the upper levels.

Relative humidity

There is moist air (relative humidity > 50%) in front of the crowding zone of the isentropes and dry air behind it. The dry air is located behind the frontal zone which corresponds to the fact that in that region dry stratospheric air has protruded downward. High values of the relative humidity, higher then 90 %, are found in the upper troposphere and they have a backward inclination from the lower to the higher levels of the troposphere which is common to the Ana Cold Front. Another maximum is in the lower parts of the troposphere, connected to the upward motion due to the orography.

Potential Vorticity

Potential vorticity shows an anomaly protruding down into the troposphere at  the rear of the zone of the highest gradient of the isentropes. This lowering of the so-called dynamical tropopause is revealing the initial stage of cyclogenetic processes. The tropopause height sinks below 350 hPa.

Omega

Omega field shows negative values (upward motion) situated in the crowding zone in the upper levels which is connected with upward motions in the warm air at the leading edge of the front. Behind the crowding zone there are positive values of omega due to the sinking of dry and cold air.

Another interesting feature to notice in this VCS is the distribution of the omega field in the lower parts, within the crowding zone, where one can see the distribution of omega that corresponds to the vertical motion in the windward and lee sides of the mountain.

Vorticity Advection

Positive values of vorticity advection are located within the crowding zone in the higher levels, indicating the position of the jet.