Identification of the Synoptic Causes of Torrential Rainfall Events in the Canary Islands (1950–2020)

Abstract

This work identifies and analyses, from a synoptic point of view, episodes of torrential rainfall (equal to or greater than 200 mm in a single day) that occurred in the Canary Islands between 1950 and 2020. For this purpose, all daily rainfall series available in different databases were used, with a final selection, after applying various filters for the detection of errors, of 88 days on which 200 mm was exceeded. Subsequently, the isobaric configurations at the surface and at 500 hPa were analysed by applying the following two classification methods: the automatic one of Jenkinson and Collinson (1977) and the subjective one of Jorge Olcina (1994). Most of the selected days (63.4%) corresponded to high-altitude isolated depressions (known by their initials in Spanish as DANAs), as well as troughs showing the advection of polar air of different origins (36.5%). According to the Jenkinson and Collinson classification, half of the days were classified as cyclonic or hybrid cyclonic and 37.5% as pure advective or directional (37.5%), with five days classified as undetermined. On only one day, 23 November 1954, was a tropical disturbance observed, with cloud fronts moving from the south of the Canary Islands along the west coast of Africa.