European Flood Awareness System EFAS Bulletin June – July 2017 Issue 2017(4) EUROPEAN FLOOD AWARENESS SYSTEM: Bimonthly Bulletin – Issue 2017(4) NEWS During June, a high pressure system governed the weather conditions in southern and northwestern Eu- A report from user survey conducted for the web de- rope, which later on influenced southern parts of velopment of EFAS is now available to download from Scandinavia and other northeastern European coun- the EFAS website. If you would to leave further com- tries. Southern and northern parts of Europe were still ments or participate in future surveys, please do not dominated by low pressure systems, which slowly dis- hesitate to contact us at [email protected]. placed the high pressure system over Central Europe. New partners By the end of June, a new low pressure system was We gladly welcome the Hydrometeorological Centre of building up over northwestern Europe, strengthening Russia as new EFAS partner. and moving towards Germany. This weather situation led to heavy rain on 29-30 of June, which caused sur- face flooding in parts of eastern Germany, including RESULTS the capital Berlin and surrounding areas of Branden- burg. In some areas more than 150 mm of rain were Summary of EFAS Flood and Flash Flood Notifications recorded in 24 hours. Several provinces of Poland were also affected by heavy rain, thunderstorms and strong The 6 formal and 15 informal EFAS flood notifications winds. issued in June-July 2017 are summarised in Table 1. The locations of all notifications are shown in Figure 23 and Overall precipitation anomalies displayed drier than Figure 25 in the appendix. normal conditions in Iceland, Scandinavia, Belgium, the Balkan states, parts of eastern Europe, Italy, Portugal 30 Flash flood notifications, summarised in Table 2, as well as central and southern Spain (Figure 11 and were issued from June to July 2017. The locations are Figure 12). However, in Greece, northern Spain and shown in Figure 24 and Figure 26 in the appendix. southern France more rainfall than normal was rec- orded. The wetter conditions corresponded to the Meteorological Situation flooding during this month. The highest accumulated precipitation amounts were observed in the Alps with by EFAS Meteorological Data Collection Centre up to 431.1 mm. The average recorded temperatures ranged from -2.7°C in Iceland to 28°C in the Mediterra- Meteorological situation for June 2017 nean Basin (Figure 15). Recorded temperatures in In the beginning of June two strong low pressure sys- Europe were generally above the average with the ex- tems were located over Scandinavia and the North ception of Russia and Finland (Figure 16). The cold spot Atlantic close to Iceland, moving slowly eastwards. One on the Italian Peninsula is a result of a faulty measure- of these strong low pressure systems caused extreme ment rainfall during the night between 6 and 7 of June in northeastern Scotland, which led to river floods. Edin- Meteorological situation for July 2017 burgh recorded 65.2 mm of rain in 24 hours. On 7 June, In the beginning of July a high pressure system influ- storms and heavy rain also caused flooding in parts of encing southern Europe moved slowly towards central northeastern Serbia resulting in 1 fatality and 42 evac- Europe. In all other European regions low pressure sys- uations. After these events, the low-pressure systems tems dominated, the strongest of which were located weakened resulting in regionally limited high pressure over Scandinavia and Iceland. In mid-July, a high pres- systems. sure system located close to the European Atlantic coast moved towards Central Europe. Meanwhile, low Between 13 and 14 June, one person died and around pressure systems in the rest of Europe led to high pre- 160 were evacuated from the Haute-Loire department cipitation amounts. Between 16 and 18 July, a storm of France after a major storm. Rainfall with up to 123 named “Medusa” caused flash floods in parts of the mm of precipitation in one hour caused flash floods. Greek peninsula of Halkidiki, a popular tourist destina- Furthermore, rivers rose rapidly in the upper basin of tion. On 18 July heavy rainfall in Turkey hit the city of the Loire, e.g. at Chadrac by almost 6 meters. Istanbul and surrounding areas with up to 65 mm per hour resulting in around 150 buildings being damaged. 2 EUROPEAN FLOOD AWARENESS SYSTEM: Bimonthly Bulletin – Issue 2017(4) On the same day, thunderstorms caused torrential For the month of July, the 90% quantile value was sur- rain, large hailstorms and flash floods in southern Eng- passed by stations on many of the European rivers land. Major flash flooding, with up to 100 mm of (Figure 21) for central (Danube, Rhine, Elbe, Möll), precipitation in 24 hours, occurred in the coastal village northern (Byaelva, Storelva, Masi, Halselva, Tana, Kem- of Coverack in Cornwall. ijoki Näätämö, Torne and Paatsjoki), Eastern (Dnieper) and southern Europe (Po, Ebro, Guadalquivir). Later in the month, the low pressure systems over most parts of Europe weakened with the exception of Out of the 813 stations for which warning levels were northern Europe. One of these low pressure systems available, for both water level and discharge values located over Iceland was strengthening and led to river alike, 44 exceeded the minimum warning level pro- floods in parts of northern Germany on 26 July due to vided at least 1 day during the month of June (Figure heavy rainfall. The worst flooding occurred in the 20). This mostly occurred for stations in Norway (24 mountainous Harz region with up to 117 mm of rain in stations) and for stations that are situated along the 24 hours on 25 July. At least four rivers reached record catchments of the Danube, Rhine, Po, Minho, Elbe, highs in the adjacent state of Lower Saxony. Ume, and Vistula. The rivers Tisza (Danube) and Sec- chia, Chero, Recchio, Riglio (Po) have surpassed the The accumulated precipitation sums indicated a maxi- minimum alert level for a period of over 15 days. mum of 605 mm in the Alps regions (Figure 13). Monthly accumulated precipitation values above 50 In July, 34 stations exceeded the lowest warning value mm were recorded in most European countries, except provided (Figure 22). This occurred for stations that are in parts of southern Europe (Figure 14). During this situated along the catchments of the Danube (22 sta- month, around 50 mm rain fell in Central Spain result- tions), Rhine, Po, Dnieper, Storelva, Satelva and Kalix. ing in positive precipitation anomalies. Especially in The rivers Tisza, Riglio and Secchia surpassed the mini- Greece, England and Germany more rainfall than nor- mum alert level for over 15 days. mal was measured which correlated with the flood events mentioned above. The average recorded tem- peratures ranged from 0.7°C to 29.8°C in southern Europe and parts of eastern European regions (Figure 17). In Scandinavia and northern Europe it was mostly colder than normal (Figure 18, the warm spot visible in Central Sweden is the result of a locational error). Tem- peratures were generally above the average in the rest of Europe with the exception of Portugal. Hydrological situation By EFAS Hydrological Data Collection Centre During June the observed daily average discharge val- ues for the gauging stations of the Po basin (Italy) have surpassed the 90% quantile value, these are mainly tor- rential streams (Baganza, Taro, Parma, Crostolo and Secchia, Figure 19). This same threshold has also been exceeded by some stations present along the catch- ments of the Drammen, Lakselva, Marsvik, Gjerstad, Karpelva and Glomma in Norway, by stations from Mediterranean basins in Spain (Guadiaro and Guadal- horce), in Sweden (River Högvadsån), in Ukraine (River Vistula) and by stations from England (rivers Gwash and Welland). 3 EUROPEAN FLOOD AWARENESS SYSTEM: Bimonthly Bulletin – Issue 2017(4) Verification The map shown in Figure 2 displays the CRPSS at 3 days lead-time. The corresponding maps for 5 and 10 days Figure 1 shows the EFAS headline score, the Continu- lead-time are shown Figure 3 and Figure 4. These maps ous Ranked Probability Skill Score (CRPSS) for one lead- indicate that across much of Europe for forecasts are time, for the June to July period across the EFAS do- more skilful than persistence at all lead times. Regions main for catchments larger than 2000km2. The shown in blue are those where EFAS forecasts are more reference score is the persistence forecast. A CRPSS of skilful than persistence, with darker shading indicating 1 indicates perfect skill, 0 indicates that the perfor- better performance. mance is equal to that of the reference, and any value It can be seen from Figure 4 that the 10-day lead-time <0 (shown in red on the maps) indicates the skill is CRPSS has higher skill for some rivers in the Eastern worse than persistence. borders of the current EFAS domain. With the new cal- ibration that follows the eastwards extension, this is likely to be improved. Figure 1. EFAS CRPSS at lead-time 1 day for the June-July 2017 Figure 3. EFAS CRPSS at lead-time 5 days the June-July 2017 pe- period, for catchments >2000km2. The reference score is per- riod, for catchments >2000km2. The reference score is sistence. persistence. Figure 2. EFAS CRPSS at lead-time 3 days the June-July 2017 pe- Figure 4. EFAS CRPSS at lead-time 10 days the June-July 2017 riod, for catchments >2000km2. The reference score is period, for catchments >2000km2. The reference score is per- persistence. sistence. 4 EUROPEAN FLOOD AWARENESS SYSTEM: Bimonthly Bulletin – Issue 2017(4) FEATURES 22 answers were received from the 28 countries repre- sented at the meeting.