Large-scale atmospheric dynamics and local intense precipitation episodes

Weather extreme events have important consequences in the environmental, social and economic sectors. Numerous efforts have been devoted to identify the large-scale (LSC) climate dynamics connected to them. In this paper we show that the LSC circulation patterns associated with intense precipitation episodes (IPE) over a specific domain can be identified from clustering algorithms. For an extended winter season (from 16th October to 15th April), using daily maps of geopotential height at 500 hPa selected on the basis of precipitation threshold exceedence, we found that over western France, the LSC pattern linked to IPE occurrence displays a strong negative anomaly over Great Britain. This pattern corresponds to the structure observed during the transition from Zonal to Greenland Anticyclone standard weather regimes. It is the least likely transition from the Zonal regime, suggesting potential links between atmospheric dynamics and the occurrence of IPE.