A climatology of instability indices derived from Friuli Venezia Giulia soundings, using three different methods

In the previous work, “Evaluating the sounding instability with the Lifted Parcel Theory” (hereafter ESI also published in this issue), we described a program which implements the Lifted Parcel Theory in three different ways. In this work, we build a climatology of the sounding-derived instability indices based on 5050 different soundings, made in Udine (WMO code 16044) from April to September 1995–2001. Every 6 h, we associate a sounding with the presence of cloud-to-ground lightning strikes and also with a continuous variable, CALCA6h, built using lightning strikes number, rain and wind gust, measured in the plain of our region. For each of the about 30 indices, we studied the skill score for forecasting the presence of thunderstorms and the linear cross-correlation for forecasting the thunderstorm “intensity”. We also introduce the use of some relatively new indices: the maximum buoyancy, the cloud precipitable water, the mean horizontal vapour flux and the standard deviation of the sounding vertical velocity. Finally, we discuss which indices and which of the three methods are the best in our region for forecasting convective events.