On the evidence of a general whirling action in the Providence Tornado

Abstract

The results of a systematic investigation and recording of tornado and waterspout occurrence in Greece for the 10-year period 2000–2009 are presented. This is the first database developed in Greece in an attempt to collect and record comprehensive information about tornadoes, waterspouts, funnel clouds, dust devils and other whirlwind phenomena. The primary research purpose of this database is to search, diagnose and record tornado and waterspout occurrences and identify their morphological and climatological features. Based on the 10-year data, a mean annual number of 1.1 tornadoes per unit area of 104 km2, is depicted for Greece. The seasonality appears differently for various parts, with winter most active tornado season for western Greece and summer for northern Greece. Spatial distribution showed that tornadoes are more frequent over western Greece and the Ionian coasts with a local maximum over northwest Peloponnese. Waterspouts occur in both the Aegean and the Ionian Sea mostly in summer and autumn, with a peak in September, while a considerable geographical maximum is located over north off the shore of Iraklion, Crete Island. A preliminary estimate of probability of tornado occurrence for each of the 51 Greek prefectures plus the Mount Athos area, showed highest values for Kerkyra Island and Elias prefectures, western Greece. Analysis based on intensities as assessed by damage data, indicated that the majority of tornadoes reached T4 of the T-scale or F2 of the F-scale. Short wave trough is found as the most relevant synoptic circulation pattern to tornadic activity. Thermodynamic and wind parameters showed a wide range of values, suggesting that threat levels should be adjusted for various areas since tornadoes and waterspouts can occur in different environments.