Shear and Curvature Vorticity at 300 hPa

The distribution of the vorticity is at this stage governed by the jet stream. The zeroline of shear vorticity (brown) shows the location of the jet axis. On the left-hand side of the axis (looking windwards) there is a maximum of positive (cyclonic) vorticity, whereas on the right-hand side there is a maximum of negative (anticyclonic) vorticity. Curvature vorticity is at this stage strongest in the Bay of Biscay, whereas the shear vorticity maximum is more to the north, along the jet axis. In the region where development is taking place both vorticity components have positive maximum.

Curvature is getting much stronger and the cyclone develops into a spiral form. Notice how the shear vorticity maximum turns west over south France.

Both vorticity components have maxima very near to the developed cyclone.

At this stage development in the Mediterranean takes over. There is a strong maximum of cyclonic shear vorticity in the region near the Baleares.

Six hours later the maximum of curvature vorticity also comes closer. The cloud band in the Mediterranean forms a spiral.

Curvature vorticity shows a typical distribution for a cyclone. Both shear and curvature vorticity have their maxima directly below the cloud head.

The curvature vorticity in the cloud head gets more anticyclonic, due to the warm advection and the small ridge forming there. Shear vorticity is still the strongest below the cloud head, along the jet axis.