Fig. 1-2: Marine heat wave off the Northwest Coast of Africa/Southwest Coast of Europe and Western Mediterranean Sea shifts westward.
Discussion: During late winter to mid-spring emergence of a marine heat wave (MHW) off the Northwest Coast of Africa to the western Mediterranean Sea triggered high-pressure aloft intensifying Northwest Africa and Southwest Europe drought. The MHW has expanded while shifting westward during the past 2 weeks (Fig. 1). The departure of the MHW from the western Mediterranean Sea has caused dramatic cooling (Fig. 2). The latent heat released to the atmosphere by this cooling SSTA pattern was immense and propelled a historic rainstorm this week across Northern Italy to Croatia, Bosnia, and Slovenia. Days of rainstorms created “apocalyptic” flood, landslides, and evacuations for the listed countries according to a PBS Newshour Report. During the past week an immense area of low pressure forming in the Western Mediterranean Sea (Fig. 3) in response to the westward shifting high-pressure zone over the MHW pattern triggered rainfall amount >10 in. above normal for the 4-day period of May 12-15 in Southern Europe (Fig. 4). The Extreme rain in Italy wiped-out the previously MHW-driven drought extending to 2022.
Fig. 3-4: Europe upper air pattern of the past week or so and the attendant anomalous rainfall.