Ng. Prezerakos et Ha. Flocas, THE ROLE OF A DEVELOPING UPPER DIFFLUENT TROUGH IN SURFACE CYCLOGENESIS OVER CENTRAL MEDITERRANEAN, Meteorologische Zeitschrift, 6(3), 1997, pp. 108-119
An attempt is made to investigate the role of the jet streaks upstream
an upper tropospheric diffluent trough in its evolution. A proof of t
he relationship that controls the rate of change of the mean absolute
vorticity in the region of the diffluent trough is provided. It is dem
onstrated that for certain value of the rate of the increasing mean re
gional vorticity, a cut-off low can develop in the upper troposphere,
which is likely to trigger the initiation of surface cyclogenesis, und
er favourable lower tropospheric conditions. Therefore, it seems that
this approach offers to the operational meteorologists a simple tool t
o evaluate the numerical weather prediction of a cyclonic development
in southern Europe and to decide for its uncritical accept or rejectio
n when the initial atmospheric conditions in northwest Europe are simi
lar to those described above. This diagnostic tool is then applied to
the case of cyclogenesis that occurred on the 29(th) January 1994 in G
reece, in order to demonstrate its practical significance.