Analysis of sounding derived parameters and application to severe weather events in the Canary Islands

Abstract

Severe weather phenomena have serious consequences in Canary Islands. This archipelago is located in the subtropical Atlantic Ocean, west of North Africa. For this reason, its climatic characteristics differ greatly from those of mainland Spain. The importance of forecasting convective precipitation mainly lies in the damage caused by flooding. Therefore, an adequate knowledge of the thresholds for the convective indices associated with severe thunderstorms in the Canary Islands is crucial for minimizing the damage that these events cause. In this paper, 7021 soundings from the Güimar station (id = 60,018, Tenerife, Spain) during the period 2009–2018 were analysed. Observation data are used to categorize soundings as representative of conditions for no thunder episodes, general thunder, rainfall ≥15 mm/h, rainfall ≥30 mm/h and hail or wind gusts ≥120 km/h. From sounding data, several parameters were computed. For some parameters, the results show remarkable differences between categories. In the studied region, thunderstorms are not expected when CAPE values are close to 0 J/kg and the lapse rate in the 0–3 km layer is below 5 °C/km. On the other hand, heavy rainfall events (rainfall ≥30 mm/h) show the highest median of CAPE, a high median total precipitable water (TPW, close to 30 mm) and the lapse rate decreases with height. Finally, hailstorm events are characterized by High Shear (shear vector magnitude ≥35 kt) and Low CAPE (surface-based CAPE ≤500 J/kg and most unstable parcel CAPE ≤1000 J/kg) environments (HSLC).