Abstract:

An attempt is made to investigate the role of the jet streaks upstream an upper tropospheric diffluent trough in its evolution. A proof of the relationship that controls the rate of change of the mean absolute vorticity in the region of the diffluent trough is provided. It is demonstrated that for certain value of the rate of the increasing mean regional vorticity, a cut-off low can develop in the upper troposphere, which is likely to trigger the initiation of surface cyclogenesis, under favourable lower tropospheric conditions. Therefore, it seems that this approach offers to the operational meteorologists a simple tool to evaluate the numerical weather prediction of a cyclonic development in southern Europe and to decide for its uncritical accept or rejection when the initial atmospheric conditions in northwest Europe are similar to those described above. This diagnostic tool is then applied to the case of cyclogenesis that occurred on the 29th January 1994 in Greece, in order to demonstrate its practical significance.

Notes:

cited By (since 1996)5

Website