Mediterranean tropical-like cyclones: Impacts and composite daily means and anomalies of synoptic patterns

In the Mediterranean region, a rapidly rotating storm system characterized by gale winds, severe precipitation, and low pressure center, accompanied with a spiral pattern of thunderstorms, is occasionally observed. These tropical-like cyclones (TLC), known as Medicanes or Mediterranean ‘hurricanes’, have similar characteristics with hurricanes and a significant amount of research has been done in recent years to investigate their atmospheric characteristics and impacts. The Laboratory of Climatology and Atmospheric Environment (LACAE), National and Kapodistrian University of Athens, has established a systematic effort since 2009, to document the impact of severe atmospheric phenomena (e.g. medicanes, cyclones, tornadoes, waterspouts), especially over the eastern Mediterranean region. The objective of this study is to discuss on one hand, the intra annual and inter annual distribution of medicanes along with the composite daily means and anomalies of synoptic conditions and instability indices at the middle and lower troposphere, sea level pressure (SLP) and sea surface temperature (SST) as well, during medicane days, based on the National Centers for Environmental Prediction-National Center for Atmospheric Research (NCEP-NCAR) reanalysis data sets. On the other hand, the geographical distribution of medicane impacts over Mediterranean region with respect to period from 1969 to 2014, is illustrated by utilizing the Geographic Information Systems (GIS). The findings shed light on the high activity of medicanes during autumn and winter with maxima in September, decreasing thereafter with a long tail extending in spring and minimizing in summer. The average number of the selected medicanes is 1.4 ± 1.3 events per year while their inter-annual variability is remarkable, although there is not any statistically significant trend (95% confidence level) within the examined period. We found from the analysis of the composite daily anomalies of the synoptic conditions that medicanes initiate and further develop in Mediterranean regions where cold air intrusions appear in the upper atmosphere associated with warm sea waters. Last but not least, the impacts of medicanes over coastal areas, including infrastructure damage and casualties due to associated strong winds, heavy rainfall, and in rare cases, tornadoes, are well presented, indicating the high concern of such extreme atmospheric phenomena should be given by stake holders towards resilience of the society.