d. Europe: Cold winter, wet summer

Most of Europe recorded substantially below-average precipitation early in the year (Fig. 53c), followed by substantially above-average rainfall during the summer months (Figs. 53b, c ). During January, the abnormally dry conditions were accompanied by excessive cold from England to Poland. This cold was linked to a high-latitude blocking pattern across the North Atlantic and Scandinavia, along with significantly diminished onshore flow throughout the region. During February much milder temperatures and very heavy precipitation returned to northern Europe, in association with a temporary reprieve from blocking activity and a return to strong onshore flow across the region.

The May-August period featured well above-normal rainfall throughout Europe (Fig. 53b), much of which fell as a series of strong extratropical disturbances embedded within a very active low-latitude westerly flow affected the region (see section 5, Fig. 72). The largest totals during the period (exceeding 400 mm) were observed across central Europe, the Czech Republic and Poland (Fig. 53a). Totals also averaged 250-350 mm across western Europe and exceeded 200 mm over western Scandinavia.

The most substantial rainfall occurred in July, when regional totals averaged 200%-450% of normal over the eastern half of the Czech Republic, most of central and southern Poland and portions of central Austria (Fig. 54). These excessive rains led to the "flood of the century" in the Czech Republic, and to significant flooding of the Oder River in Poland and eastern Germany. These floods resulted in more than 100 deaths and forced evacuations of more than 150,000 people.

The floods resulted from two periods of very heavy rainfall: 4-7 July and 18-21 July. The first period featured excessive rainfall totals which in some areas were 2-3 times higher than the normal July total. This heavy rainfall was linked to a large-amplitude cyclonic disturbance located immediately downstream of a blocking anticyclone (Fig. 55a ).

This first period of heavy rainfall initiated flooding throughout the northern portions of the Oder River. However, the flood waters had not yet crested along the lower Oder River when, only two weeks later, another period of extremely heavy rainfall occurred. The resulting floods devastated thousands of homes, and destroyed many dikes along the rivers' edge. Also during this period, excessive rains fell in the mountainous areas of Poland and the Czech Republic, with totals in many places reaching more than four times the normal monthly mean. This heavy rainfall was also linked to a very strong upper-level trough amplification and cyclogenesis in the region immediately downstream of a blocking anticyclone (Fig. 55b).

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