Ng. Prezerakos et al., ABSOLUTE VORTICITY ADVECTION AND POTENTIAL VORTICITY OF THE FREE TROPOSPHERE AS SYNTHETIC TOOLS FOR THE DIAGNOSIS AND FORECASTING OF CYCLOGENESIS, Atmosphere-ocean, 35(1), 1997, pp. 65-91
The dynamics of a case of cyclogenesis over the central Mediterranean
associated with heavy precipitation, especially over the southeast Aeg
ean Sea, have been investigated on the basis of the analyses of two me
teorological parameters, namely, the isobaric absolute and relative vo
rticity and the isentropic potential vorticity. On the whole, the two
approaches demonstrate the important role of the upper level dynamics
in the initiation of the surface cyclogenesis and seem to identify the
same features: interaction of a region of positive absolute vorticity
advection ahead of a 500 hPa trough with a shallow frontal system, in
the first approach, and an isentropic potential vorticity anomaly at
the upper levels with a low level baroclinic zone in the second approa
ch. Furthermore, the analysis of potential vorticity identified an int
ense low level potential vorticity anomaly, for which there are indica
tions that this is associated with diabatic heating and is important f
or the deepening of the system. This makes potential vorticity analysi
s preferable for forecasters. Special emphasis is given to the upper-l
evel circulation and the vorticity field over the major European regio
n before the surface cyclogenesis commences, since it is considered to
be crucial for the forecasting of the event.