Storm tracks and cyclone development using the theoretical concept of the Dynamic State Index (DSI)

The Dynamic State Index (DSI) basing on the Energy-Vorticity Theory is able to detect all non-stationary and diabatic processes in the atmosphere. It is shown for the first time that the index is practicable for diagnostic analysis of the synoptic scale, in particular on pressure levels, using the ERA-40 reanalysis data set from the European Centre for Medium-Range Weather Forecasts (ECMWF). To verify the practical value of the DSI as a parameter diagnosing atmospheric developments, the index is applied to the synoptic scale. In a global view two different north hemispheric winters and particularly two case studies concerning the winter storm ‘Lothar’ and hurricane ‘Andrew’ are presented. For analysing the storm structures, both DSI on pressure levels and three-dimensional views of DSI isosurfaces are utilized. The results of this study document that the magnitude of the index expresses the intensification and decaying of the observed vortices. Thereby, it draws conclusions from the steering mechanism of ‘Lothar’ and ‘Andrew’ by virtue of their different DSI structures. A main result for practical weather forecasts is the early visibility of cyclones in the DSI field compared to the pressure field. Furthermore, storm tracks and their intensity can be visualized using the index.