Upper-tropospheric downstream development leading to surface cyclogenesis in the central Mediterranean

In this study an attempt is made to investigate the upper-tropospheric down stream development over north-west Europe, which leads to surface cyclogene sis in the central Mediterranean. A case study is analysed to demonstrate t hat the upper-tropospheric downstream development could be closely related to the upper-tropospheric frontogenesis that appears upon the north-eastern flank of a blocking high. The frontogenesis is characterised by a jet stre ak within a strongly baroclinic zone and a tropopause folding associated wi th cold stratospheric air intrusion into the troposphere. According to this interpretation, the eddy ageostrophic divergence of eddy geopotential flux es (dispersion and spreading of eddy kinetic energy), other than friction d issipation and barotropic conversion to the mean flow, is mainly responsibl e for the loss of Kinetic energy from a decaying depression of synoptic sca le that has passed the mature stage. This dispersed eddy Kinetic energy acc umulates in the vicinity of the aforementioned jet streak where it is trans ferred downstream and further triggers the generation or rejuvenation of a new disturbance.