Bizkaia Gipuzkoa

Fig 1. Basque Araba A study of severe storms in Basque Country: country location. r d t h e 3 June 2018 case Figure 2. SLP, 850hPa Geop-isoterm, 500h Pa Geop- Figure 3. Metoffice analysis isoterm maps from 12 UTC 03/06/2018 and 00 UTC for 00 UTC on 03/06/2018 J o s e b a E g a ñ a 1 , 2 a n d Santiago Gaztelumendi 1 , 2 04/06/2018 (top to down and left to right). and 04/06/2018 (left to right).

1- TECNALIA, Energy and Environment division. Meteorology Area. Parque tecnológico de Álava. Araba, Basque Country. 2- Basque Meteorology Agency (EUSKALMET). Parque tecnológico de Álava, Miñano, Araba, Basque Country. Abstract In this study we analyze a strong thunderstorm case that cantabric area. At surface level, low pressures are also occurs in the Basque Country during 3rd June 2018. After a prevailing in the northwest. An instability line first and an mostly sunny morning, during evening heavy showers affect occluded front later, associated with that depression, affect Figure 4. 12:00 and 18:00 UTC MSG VIS12 many areas in the territory. About 4:00 pm, rain intensity our territory promoting severe storms. images for 03/06/2018 (left to right). increases, with ten minutes precipitation over 10 mm, The event is characterized by very heavy showers, causing many incidents and the intervention of fire brigade punctually torrential (> 60mm / 1h), in the inland regions of and police in numerous municipalities. the Basque Cantabrian slope; that cause local floods, In this work, different aspects of this event are analyzed at landslides and problems in roads in different affected synoptical, mesoescale and local level, using all available villages. During the afternoon, very active convective nuclei information, including automatic weather station mesonet, are formed affecting different points such as Antzuola, MSG and Radar information provided by Basque Bergara, Amurrio and Atxondo. It is worth noting the local Meteorology Agency (Euskalmet). nature and limited extension of these storms, whereas in In height, a cut-off low is located in the northwest of the some location the precipitation was torrential in places just Iberian Peninsula, generating instability in all the peninsular a few kilometers much smaller precipitation quantities are observed. Results and Discussion General Environment Aixola and Eitzaga respectively (22.3 and 28.8 l/m2 in one hour) (see figure 6, 7 and table 1). In fact and considering 70 During this episode, Basque Country (BC) area (see figure the PAC 1h radar product (high resolution radar adjusted 1) is affected by a cut-off low located at the north-west of with automatic weather stations) accumulated rain could Iberian peninsula with temperatures around -22ºC, at reach 60-80 l/m2 in one hour at some points in that area 60 surface a low pressure center is located at same place with (see figure 7). Figure 5. 13:22, 14:12 and a slightly movement to the south-east (see figure 2). 16:12 UTC Kapildui Radar Two hours later, storms developed outside BC borders with 50 Associated with this low pressure configuration a instability SW-NE movement reached the area of Amurrio, Orozko Max 2-15km with lighting line and a occluded front crosses the peninsular cantabric and Llodio, another of the most affected areas during the products (top to down). slope affecting our territory (see figure 3). 40 episode, with convective developments up to 12-13 km Figure 7. 14:00 and 14:30 Local Environment high (see figure 5). In the Areta (Orozko) station 13.9 l/m2 hourly accumulated and 15.4 l/m2 were registered in two consecutive ten- 30 precipitation estimation from The morning of Sunday, day 3, was generally sunny and minutes rain observations, in just 30 minutes 35 l/m2 (38.8 radars and rain-gauges the maximum temperatures reached 26-29 ºC in points of l/m2 in one hour) (see table 1). At same time, another very observation (top to down). the interior of the Cantabrian slope, especially in Gipuzkoa. developed stormy spot left significant accumulations in the 20 About 2:00 pm the first storms began to form within the BC High Deba, specifically in Bergara and Antzuola were Figure 6. AWS precipitation (see figure 4). Some convective nuclei were also developed kriging map for 10 min, 1 hour maximum hourly accumulated precipitation around 40-50 10 at South of BC with a movement from SSW to NNE (see l/m2 are plausible according to the PAC 1h product (see and daily precipitation (top to figure 4 and 5). figure 7). In same area, in an automatic rain gauge located dBZ down). for managing purposes on the Deskarga highway civil Surface Data works (sited in Antzuola), 60.7 l/m2 were registered in one At 4:00 p.m. local time, the first very intense showers hour and 45.1 l/m2 in just 30 minutes (see table 1). All the occurred, with ten minutes precipitation above 10 l/m2 (see thunderstorms that occurred were accompanied by a large figure 6 and 7). Particularly In Saratxo, 13.2 l/m2 were electrical device with more than 3000 strokes. accumulated in 10 minutes and 23.5 l/m2 in one hour (see Table 1. Precipitation registered in Subsequently, the storms were moving on one side to the some AWS. table 1) as a consequence of the local development of a north of Bizkaia through Bilbao while losing strength. On Precip Time Precip Time Precip very active storm cell. On the other hand, another very the other hand, they spread through Gipuzkoa leaving active Thunderstorm developed and affected the AWS 10 min. UTC 1h UTC 24h strong showers in Berastegi at 7:10 p.m. local time (10 l/m2 (mm) (mm) (mm) Duranguesado area (Atxondo, Elorrio and Abadiño), in 10 minutes and 28.2 l/m2 in one hour). Then they were Antzuola 19.4 14:30 60.7 14:00 68.3 leaving ten-minutes rain intensities of 11.1 and 13.2 l/m2 in deactivated as they moved north and northeast. Areta 15.4 14:30 38.8 15:00 41 Eitzaga 13.2 14:30 31.3 15:00 37.8 Gardea 11 14:20 29.3 14:50 31.4 Impact analysis Berastegi 10 16:30 28.2 17:10 30.1 The precipitation amounts in very short time periods caused In Llodio and Amurrio there were large accumulations of Saratxo 13.2 14:00 23.5 14:40 25.2 Aixola 11.1 14:30 22.3 15:10 34.8 considerable and widespread material damage in the areas water in the streets and punctual river flood that affected Figure 8. Some pictures of the impact of heavy rainfall in different municipalities of the Basque Eskas 7.7 13:20 19.3 13:50 21.4 affected by the storms. vehicles and commercial premises (see figure 8) Country and a map with their location. Orozko 8.7 14:20 17.7 14:30 24.5 Numerous homes, garages and commercial premises were In Abadiño and Atxondo some homes and commercial affected by water, that also accumulates on roads causing premises was affected and road cuts are produced. The Abadiño Abadiño Atxondo retentions and total closures, at some locations due also by river overflows in some location and the water reached landslides or falling trees (see figure 8). some houses, garages and municipal facilities (see fig 8). Heavy rain, rapid accumulation of water and local floods In different neighborhoods of Bergara there were various leave considerable damage in various locations. In Bizkaia, damages in parked cars that were covered by water, as well the most affected populations were Atxondo, Elorrio and as the dragging of containers. In Antzuola, there were Abadiño, in Álava, Amurrio, Llodio and Orozko, and in significant damages in public facilities such as the Llodio Gipuzkoa Bergara and Antzuola. During the afternoon there ambulatory or the library, as well as traffic interruptions and Atxondo were many incidents in various municipalities, which forced road closures due to standing water on the road. In the Fire Department and the Police (Ertzaintza) to act. Eskoriatza the road is cut by landslides (see figure 8). Remarks and Conclusions In spite of the local nature and limited extension of the after this type of episodes needs higher spatial resolution. storms that affect our territory during 3rd June 2018, The use of combined radar-rain gauge seems to be Antxuola Antxuola precipitation was torrential causing local pluvial floods, essential. In our case a estimation of surface reflectivity with landslides and problems in roads. rain gauge registered data is combined and interpolated Not surprisingly, due to the limited extend of the convective using KED (kriging with external derivative) techniques are Bergara nuclei that affect the studied area, quite different available. Amurrio precipitation quantities are observed in places just a few Temporal resolution is also a key question, although in the kilometers distance one from another. Basque AWS network data are available each 10 minutes Although the Basque country network of automatic weather interval, quite good temporal resolution comparing with Antxuola stations has more than 100 data collection points other AWSl networks. A system to increase this temporal widespread in the territory, with an average density of one resolution down to a minute is planned to be implemented station every 10 km, correct characterization during and operationally in Euskalmet. Acknowledgements References ° Aranda J.A., Morais A., 2006: The new weather-radar of the Basque ICEAWS, Malaga feb 2003. meteorology agency (Euskalmet): site selection, construction andinstallation. ° Gaztelumendi S., Egaña J., Gelpi I.R., Otxoa de Alda K., Maruri M., The authors would like to thank the Emergencies and Meteorology Directorate (Security Department - Basque 4th European Conference on Radar in Meteorology and Hydrology, Barcelona Hernandez R., 2006: The new radar of Basque meteorology (Spain). Agency:Configuration and some considerations for its operative use. 4th Government) for operational service financial support and public provision of data. We also would like to thank all our ° Egaña J., Gaztelumendi S, Mugerza I, Gelpi I.R. 2005:Synoptic patterns European Conference on Radar in Meteorology and Hydrology, Barcelona associated to very heavy precipitation events in the Basque Country. 5th (Spain). colleagues from TECNALIA and EUSKALMET for their daily effort in promoting valuable services for the Basque EMS. Utrech(Netherlands). ° Gaztelumendi, S. Gelpi IR, Egaña, J Otxoa de Alda 2007 Mesoscale ° Egaña, J.; Gaztelumendi, S.; Gelpi, I.R.; Otxoa de Alda, K. 2007. A preliminary numerical weather prediction in Basque Country Area: present and future. , community. analysis of summer severe storms in the Basque Country area: synoptic EMS7 & ECAM8, 1-5 Octubre 2007, Madrid characteristics”. ECSS 2007. Fourth European Conference on Severe Storms. ° Gaztelumendi S., Otxoa de Alda K., Egaña J., Gelpi I.R.,Pierna D., Carreño Trieste (Italy). 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Palma de Mallorca, (Spain) 03 - 07 October 2011. ° Gelpi, IR Gaztelumendi, S Egaña,Otxoa de Alda 2007 A preliminary ° Gaztelumendi S, Otxoa de Alda K. Hernandez R. 2003 Some aspects on the mesoscale analysis system for the Basque Country: Description and some operative use of the automatic stations network of the basque country III results. , EMS7 & ECAM8, 1-5 Octubre 2007, Madrid..

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