THE STATUS OF ATMOSPHERIC INSTABILITY INDICES ASSOCIATED WITH HAIL EVENTS THROUGHOUT MOLDOVA

Abstract

The lower pressure of water vapor of the outer eastern and south-eastern Carpathians, as well as in Dobrogea, determines within these areas an average annual number of days of under 2 days. In sheltered areas from Bârlad Plateau the average multi-annual value decreases even below 0,5 days. Hail events that affect the territory of Moldova are, in most cases, caused by thunderstorms during May and June (frequency of over 60 %). We had analysed in the present paper a representative number of statistical severe convective events causing hailstorms and material damage between 1990-2013 period. Values of atmospheric instability indices have been analyzed for these episodes as CAPE (Convective available potential energy), SWEAT (severe weather threat), Li (lifted index), KI (K index), TT (total totals) to evaluate their medium range forecast under the hail production conditions. These indicators measure the degree of atmospheric instability providing information about possible occurrence of clouds with large vertical extent. The most powerful correlations have been recorded in the case of parameter LI, for which the daily mean value was used. The status of these indices is assessed for both the days with hail, but also on previous intervals with hail to assess their capacity to forecast this extreme weather phenomenon