The paper identifies mechanisms that potentially inhibit convection at a time when extreme values of selected atmospheric instability indices are recorded. The study involved six indices (LI, SI, CAPE, KI, SWEAT, TTI). Data sources involved records from three Polish data stations collecting upper air soundings and covered the period 2005-2014. Additional data were obtained from SYNOP codes on present and past weather and reportson severe meteorological phenomena from the European Severe Weather Database. The methodology adopted allowed the selection of 26 cases where no convective phenomena were observed despite extreme atmospheric instability. A detailed analysis demonstrated that the occurrence of isothermal or inversion layers in the lower and middle troposphere were the most frequent mechanisms inhibiting the vertical air movement. Convection was also inhibited when the area was free from the influence of atmospheric fronts, convergence zones, low pressure troughs or when high altitudes of LCL occurred.
Angelika Palarz, Department of Climatology Jagiellonian University Gronostajowa 7, 30-387 Kraków: Poland
Daniel Celiński-Mysław, Department of Climatology Jagiellonian University Gronostajowa 7, 30-387 Kraków: Poland