The Heavy Precipitation Event of May–june 2013 in the Upper Danube and Elbe Basins

SEPTEMBER 2014 AMERICAN METEOROLOGICAL SOCIETY | precipitation amount is only the 18th highest of the analogue time series, showing that even if the atmospheric conditions were favorable to wet conditions over Southern Europe, they do not fully explain the exceptional character of the precipitation anomaly. We conjecture that a potential amplifying cause could be that the oceanic air masses carried by regimes of westerly winds were moister than usual due to warmer SSTs in the Northeast Atlantic (between 0.5 and 1.5 K above normal). We performed an additional analysis by searching circulation analogues among the years of warm Northeast Atlantic SST (i.e., above the 1971–2000 average). The mean monthly European precipitation amounts reconstructed from such “filtered” analogues exceed those of “regular” analogues, picked over 1948–2012 (not shown). Although this is not a definite proof, this pleads in favor of this mechanism. Conclusions. Our analysis suggests that the high precipitation amounts were mainly caused by the cyclonic conditions (NAO– and Atlantic Ridge) that prevailed during the late winter (February and March) over the North Atlantic. Such conditions brought moist air over Southern Europe. This conclusion is drawn from the significant correlations over Europe between the observed and the analogue precipitation, deduced from the North Atlantic atmospheric circulation. The extreme precipitation amounts, not fully explained by the atmospheric circulation, are conjectured to be due to a warmer Northeast Atlantic with more moist air (Trigo et al. 2013). The trend in winter precipitation over Southern Europe is negative but not statistically significant. The frequency of cyclonic regimes over Scandinavia (NAO– and Atlantic Ridge) has also slightly decreased, albeit not significantly (not shown).