Height of PV=1 unit

The development is starting between Ireland and France. The PV anomaly is already well defined. The height of PV=1 unit is found at 550 hPa meaning that stratospheric air has protruded to mid troposphere. Just for comparison: the old dissipating cyclone over Mid-Mediterraean and Central Europe has PV=1 unit at 350 hPa. To understand the concept of PV anomalies you can study the Hoskins theory.

The anomaly moves south with stratospheric air found at 550 hPa. The development is getting more pronounced since the cloud structure already forms a spiral shape.

The positive anomaly is now above the Bay of Biscay. A positive anomaly is found in the cold air behind the cloud spiral and negative anomaly in the warm cloud head. The reason for this distribution is big temperature difference.

Stratospheric air has protruded downward up to 500 hPa. The cyclone has formed and moves eastwards.

The anomaly is weakening. Height of PV=1 unit is now found at 450 hPa.

The anomaly moves to the Mediterranean but the value stays the same. In the region of the cyclone developing in the Mediterranean height of PV=1 unit is 450 hPa.

Again the same distribution we saw before: there is positive anomaly in the cold air behind the cloud spiral and a negative one within the warm cloud head.

The shape of PV=1 height field follows exactly the shape of the cloud structure with a positive anomaly in the cold and negative in the warm air.

The height of PV=1 unit remains at 450 hPa and the whole system moves northeast.

The size of the anomaly gets smaller as the cyclone is dissipating.