Analysis of synoptic conditions for tornadic days over western Greece

Abstract

Abstract.Tornadoes have been reported in Greece during the last few decades and recent studies have given evidence that western Greece is an area vulnerable to tornadoes, waterspouts and funnel clouds In this study, the composite means and anomalies of synoptic conditions for tornadic events (tornadoes, waterspouts and funnel clouds) over western Greece are analyzed and discussed.The daily composite means of synoptic conditions were based on the National Centers for Environmental PredictionNational Center for Atmospheric Research (NCEP-NCAR) reanalysis data sets, for the period 12 August 1953 to 31 December 2012. The daily composite anomalies were calculated with respect to 30 years of climatological study of the synoptic conditions. The analysis was carried out in terms of seasonal and monthly variability of composite means and anomalies of synoptic conditions for specific isobaric levels of 500, 700, 850, 925 hPa and the sea level pressure (SLP). In addition, an analysis and discussion about the dynamic lifted index from NCEP-NCAR reanalysis data sets is presented.The daily composite mean analysis of 500 hPa revealed a trough line across the northern Adriatic Sea and central Italy, associated with a SW upper-air stream over western Greece. The maximum composite anomalies were depicted at the isobaric level of 500 hPa during autumn, spring and summer, against winter when the anomaly appeared at 925 hPa isobaric level. In addition, 48 % of tornado events during the autumn season occurred in pre-frontal weather conditions (cold fronts) and 27 % developed after the passage of the cold front. Furthermore, the main difference in synoptic patterns between tornado and waterspout days along western Greece during the autumn season is the maximum daily composite anomaly over the Gulf of Taranto.

Analysis of waterspout environmental conditions and of parent‐storm behaviour based on satellite data over the southern Aegean Sea of Greece

“…Sioutas () found that the short‐wave trough pattern is the most common synoptic pattern on waterspout days, followed by the closed low pattern. However, research by Nastos and Matsangouras (, ) and Matsangouras et al () over different geographical areas of Greece showed that waterspouts and tornadoes in Greece are reported for a variety of different synoptic conditions. Thus, an objective synoptic classification based on regional clustering of the waterspout and tornado events is necessary in order to interpret synoptic conditions that favour waterspout and tornado development over a specific geographical area.…”

“…Our findings of prevailing northwesterly winds at 500 hPa are in agreement with Matsangouras et al (), who showed that a very broad trough at 500 hPa was located over the Aegean Sea, resulting in W–NW upper air flow over Crete on autumn waterspout days during the period covering 1 September 1948–31 December 2012. However, the occurrence of northwesterly winds that favoured waterspout activity during the autumn season, at middle and lower levels of the troposphere over the southern Aegean Sea, differs from the SW upper and lower air flow that favours waterspout activity over western Greece (Nastos and Matsangouras, ). Northwesterly winds in autumn at 850 and 925 hPa are consistent with a shallow, cyclonic circulation over the SE Aegean Sea.…”

Condições atmosféricas de grande escala associadas a três eventos de tornados ocorridos no Estado do Rio Grande do Sul, Brasil (Large scale atmospheric conditions associated with three tornado events occurred in Rio Grande do Sul State, Brazil)

“…Na literatura, diversos estudos têm sido realizados a fim de compreender e identificar o ambiente em que tempestades geradoras de tornados se desenvolvem. Alguns estudos mostram que tornados podem se formar no setor quente de sistemas frontais (Nastos;Matsangouras, 2014;Wrona;Avotniece, 2015;Tochimoto;Niino, 2016). Nestes estudos, os autores observaram características semelhantes nas condições atmosféricas de grande escala nas quais as formações tornádicas analisadas ocorreram.…”

Waterspout cloud top detection using MSG SEVIRI infrared brightness temperature over the northern Ionian Sea, Greece

“…Keul et al (2009), Sioutas and Keul (2007), and Matsangouras et al (2014b) presented a spatial and temporal analysis of waterspout thermodynamic characteristics over the Ionian, and the Aegean Sea. Moreover, specific synoptic types favouring waterspout formation over the northern Ionian Sea were classified by Matsangouras et al (2013), and an analysis of composite synoptic conditions relating to tornado and waterspout formation over western Greece was carried out by Matsangouras (2012, 2014). Based on the abovementioned tornado database, a systematic scientific research project is in progress at LACAE, analyzing significant tornado case studies, numerical simulations, and investigating the contribution of Greek complex topography in tornadogenesis (e.g.…”