The workshop is scheduled for autumn, from 16 to 18 October 2023, and takes the very broad view. Target audience are forecasters (“warners”) and heads of forecasters, researchers and practicioners related to warnings, civil protection authorities, and end users of warnings (especially from critical infrastructure).

The following topics will be covered:

1. The broad multidisciplinary view: risk ethics (philosophy, moral reasoning), human behaviour (psychology) and legal frameworks (just) in the context of the warning process
2. Limitations and new prospects for ingredients-based warning approaches: How should the risk matrix be defined? Can more life be brought to forecasting impacts beyond the marketing term?
3. Communication – dealing with uncertainty: Why is there so little progress in communicating the warning uncertainty, and how can this be improved?
4. Action advice and public education: from understanding to response and action. We are seeking for good practice examples.
5. General and tailored warnings: What are the necessary differences? And how can the gaps between warners, emergency managements and end users be best bridged?
6. From physical ingredients to impact warnings: Are impacts in high-end meteorological events easier to predict and stronger tied to the physical magnitude than in more frequent and modest events?
7. A critical moment in the meteorological sphere: transition from forecasting to nowcasting and the resulting potential sudden jump in probability of extremely rare events. Should there be a stronger focus on the warning means in the “last hour”? When in time and at which probability and intensity threshold should sirens and other “strongly interrupting and potentially also frightening” means of warning be used?
8. Cross-institutional and cross-border communication: What is needed to ensure the flow of relevant information in extremely time-critical and high workload situations?

A detailled invitation can be downloaded here (PDF).

The registration for the 11th European Conference on Severe Storms is open and normal registration fees apply until 7 April. Starting 8 April, late registration fees do apply.

Please register here for on-site participation or online streaming (remote presentations are not foreseen).

General information on the ECSS including the scientific and social programme can be found here.

Online webinar: 20 April 2023, 12:00 to 14:30 UTC
Free of cost. Targeted to forecasters in nowcasting and warning operations.

We present and discuss MTG-related news relevant to forecasters: 

• The current status of the MTG commissioning (Stephan Bojinski, EUMETSAT)
• The ESSL Testbed 2022 in retrospect and lessons learned from expert workshops (Alois Holzer, ESSL)
• Testimonial from a forecaster who participated in the ESSL Testbed 2022
• Interesting cases from 2022 revisited (Tomas Pucik, ESSL) 

Please register for the webinar here:

https://events.teams.microsoft.com/event/517ea179-3349-405b-92ac-1a7cb04faa93@df7e8a07-a3fd-42a8-b745-17aa52648828

This webinar features key 2022 results from the joint ESSL-EUMETSAT activity introducing MTG data to operational weather forecasters in Europe. ESSL trainers describe highlights of severe convective weather cases that were analysed by forecasters during the testbeds in Wiener Neutstadt. Forecasters provide testimonials on their testbed experience and the importance of satellite products in the forecasting process. In addition, the ESSL expert workshops put the spotlight on novel MTG products such as the 0.9um FCI channel to detect low-level moisture, or the Lightning imager. The audience will learn about key take-aways from these workshops, for later use in training on MTG for all users.

The year 2022 was another record-breaking year for hailstorms in Europe. In total, 8224 large hail reports (≥ 2 cm in diameter) were submitted to ESWD. That is 2791 more than in 2021, which was already a record-breaking year. Very large hail (diameter ≥ 5 cm) was reported 1334 times and 18 reports involved giant hail with a diameter ≥ 10 cm. There were 213 days with at least one large hail and 94 days with at least one very large hail report. The period of 20 May to 10 July was particularly active concerning very large hail. Out of 52 days, very large hail was observed on 42 of them.

By far the largest number of reports was submitted for France (2461), followed by Italy (993) and Germany (583). The three days with the most hail reports were 4 June (411 reports), 20 June (385 reports), and 25 May (334 reports). Hail injured 215 people and killed 1. The two most societally impactful events were the Casamassima (Italy) hailstorm on 19 August with 100 injuries and the La Bisbal d’Empordà (Catalonia) hailstorm on 30 August with 67 injuries and one fatality. Hailstorms had a very large economic impact, especially in France, where the insured losses reached 4.8 billion € according to Swiss-Re. While some of the hailstorms produced large hail only for 15 minutes, some lasted for more than 3 hours. The longest-lasting hailstorm occurred on 22 May in France, producing large hail for 5 hours in a hail swath over 300 km long.

Major hail events of 2022 formed in a large range of CAPE and shear values. That said, the majority of the events occurred with CAPE exceeding 1000 J/kg and 0-6 km bulk shear exceeding 15 m/s, which is a parameter space where the large hail typically occurs. Some of the giant hail-producing events had a rather unremarkable environment. A good example of such a case is the hailstorm of 1 July over Czechia, which produced hail up to 11 cm in diameter with CAPE around 1000 J/kg and 0-6 km bulk shear well below 20 m/s. Giant hail was produced briefly following the merger of two storms. Hail around 3 cm in diameter was observed pre-merger and no large hail followed the brief period of giant hail production. This shows the importance of storm-scale processes, which can’t be captured by looking at the large-scale environment. 

The biggest hailstorm cases of 2022:

20 May: Several hailstorms impacted northern France and western Germany. The largest hail, 8 cm across, fell in Sedan, France. Most hail damage was produced by a hailstorm that passed the northern suburbs of Koblenz, Germany, damaging roofs, windows, and cars. The largest hail reached 6 cm there.  

22 May: A supercell tracked for more than 300 km across west-central France, impacting the towns of Niort, Poitiers, Chauvigny, and Chateauroux. Supercell produced hail for 5 hours with several peaks of activity, when the hail diameter exceeded 8 cm in diameter. The largest measured hail was 12 cm in diameter, but even larger may have fallen with reports of weight up to 780 g. Chateauroux was hard hit with hailstones up to 9 cm in diameter. 4 people were injured and the hail badly damaged 250 houses and 1000 cars. 

25 May: Several supercells produced long hail swaths over southeastern Austria, Slovenia, northeastern Croatia, and Hungary. The largest hail measured 8 cm in diameter. Severe damage to buildings was reported in Kapela Podravska, Croatia, and Kiskorpád, Hungary.

28 May: South-moving hailstorm produced damage east of Milan. The largest hail reached 7 cm in diameter. A hail up to 8.5 cm in diameter was reported in the Smolan region, Bulgaria, damaging cars, roofs, and agriculture. 

29 May: A woman was injured by very large hail in Italy. Hail up to 7.5 cm in diameter caused significant damage to roofs, cars, and greenhouses in Orizari, Bulgaria.

2 June: Severe hailstorms impacted southeastern Austria, Slovenia, and northern Croatia. Damage to crops, houses, and cars was reported. The maximum hail size reached “only” 5 cm, but hail fell in large quantities and was accompanied by severe winds in many locations with drifts up to 20 cm deep. 

3 June: Hailstorms affected southern France. The largest hail measured 7.5 cm in diameter and the longest hailstreak was 150 km long.

4 June:  Widespread hail damage was reported in central France, particularly in Vichy and surrounding areas. Hail reached up to 10 cm in diameter, severely damaging cars, roofs, and agriculture. 1 person was injured by hail in Vichy.

5 June: Hailstorms impacted eastern France, Switzerland, northwestern Italy, Slovenia, Austria, and Serbia. Hail up to 9.5 cm was reported in Frankolov, Slovenia, and an 11 cm hailstone fell in Kufstein, Austria.

19 June: A long-lived, right-moving supercell produced an almost 350 km long hail swath across France, affecting the outskirts of Orléans. The supercell produced hail for 4 hours. Roofs and cars were damaged along the path of the storm and the largest hail, measuring 8.5 cm, fell in Chambord and Saint Cyr en Val.

20 June: A long-tracked supercell crossed northern Bordeaux and destroyed more than 5000 hectares of agriculture with wind-driven hail in Dordogne. The largest hail diameter reached 7 cm. Serious damage to roofs and cars was reported in some parts of the hail swath. North of Pyrennees, a hailstorm produced giant hail with a maximum estimated hail size of 13 cm in Vic en Bigorre with widespread damage to roofs and cars. Long-lived supercells with hail also affected southern Germany and southeastern Czechia, but hail did not reach 5 cm. 

21 June: Third day of severe hailstorms in France in a row. Wind-driven hail up to 9 cm in diameter impacts regions of Auvergne and Bourgogne, destroying agriculture, roofs, windows, and cars. House facades and sides of cars suffered extensive damage as the hail was blown horizontally in the strong wind. A video showing the combination of severe winds and very large hail can be found here. Another long-lived supercell produced hail up to 8 cm, severely damaging roofs and cars in the region of Morvan. Very large hail also fell in Italy, Slovenia and Serbia. In Serbia, hail up to 7 cm in diameter caused severe damage to agriculture and roofs in the Moravički region.

23 June: Hail and windstorm impacted Podgorica, Montenegro with damage to agriculture and cars. Largest hailstones reached 5.5 cm. Hail up to 8 cm in diameter was observed in Sfélinos, northern Greece.

26 June: Severe hailstorms affected eastern France with hail up to 7 cm in diameter. One of the storms also impacted Strassbourg and its outskirts and many cars were damaged.

27 June: Very large hail up to 8 cm in diameter was reported from southern Germany as two supercells tracked along the northern edge of the Alps. 7 cm hail was reported in western Czechia.

28 June: 1 person was injured by very large hail in Kastoriá, Greece.

29 June: Widespread large to very large hail was reported in eastern Czechia and southern Poland.

30 June: Very large hail fell in France, Italy, northern Czechia, Poland, and Bosnia-Herzegovina. The largest hail, 8.5 cm across, was reported in Blamont, France.

1 July: Giant hail up to 11 cm in diameter fell in Rovensko pod Troskami, Czechia. Very large hail also fell in eastern Czechia and western Slovakia from two long-lived supercells. Splitting supercells produced hail up to 6 cm in diameter in the Veneto region, Italy. 

5 July: Severe hailstorm impacted southwestern Serbia. Hail up to 7 cm in diameter damaged crops, roofs and cars. 

4 July: Very large hail up to 6 cm in diameter injured 2 in Castel Maggiore.

7 July: Several supercells formed in Veneto, Lombardia, and Emilia-Romagna regions in Italy, each producing very large hail. Widespread damage to cars, windows, and roofs was reported. The largest hail fell in Ostiglia and was estimated to be 9 cm in diameter. 

20 July: Severe hailstorms occurred in Switzerland and eastern France. The most severe storm affected the region of Franche-Comté and the commune of Doubs, where hundreds of roofs, windows, and vehicles were badly damaged. The largest hailstone fell in Le Russey, estimated at 9 cm across. 

27 July: Very large hail was reported from the Abruzzo province in Italy. The largest hail, 9 cm in diameter, fell in Teramo and Ascoli Piceno. Damage to cars, roofs, and windows occurred. 

28 July: Left-moving supercell produced very large hail up to 8 cm in diameter near Lleida, Spain, damaging roofs, cars, windows, and greenhouses.  

13 August: Southward moving supercell produced a long hail swath across Sardegna, a rather rare occurrence on the island. The largest hail was estimated to be 9 cm in diameter and fell in Alà dei Sardi.

17 August: Widespread large to very large hail was reported from southern France. The largest hail fell in Bonnétage, estimated at 8 cm across. In Catalonia, a woman was slightly injured by a 5 cm hailstone. 

18 August: The event known especially for the powerful derecho producing wind gusts exceeding 60 m/s over Corsica also featured a number of damaging hailstorms. In the early morning hours, wind-driven hail injured 22 people in Sestri Levante and Lavagna in Liguria, Italy. Hail damaged cars, windows, and facades of houses. Around noon, a hailstorm struck Menorca with hail up to 7 cm in diameter. In the evening hours, another series of hailstorms impacted Italy, especially the regions of Marche and Tuscany. The largest hail, 11 cm in diameter, fell in Macerata Feltria damaging cars, and roofs and injuring 1 person.

19 August: Giant hail, reaching 10 cm in diameter, was reported from Casamassima, damaging cars, and windows. At least 100 people were lightly injured by hail. Most of the injuries were inflicted by broken glass. The number of injuries ranks as the third highest recorded in the ESWD for large hail events. 

30 August: In the late afternoon, a supercell storm formed over the eastern Pyrenees. The storm moved southeastward and entered the district of Girona in Catalonia, producing a swath of very large hail (≥ 5 cm) between Esponnellá and Tamariu. Multiple reports of hailstones larger than 10 cm in diameter were collected with the largest stones estimated to be 12 cm. Impressive videos of the hailfall can be found here or here. Besides serious damage to roofs and cars, 67 injuries and even one fatality (a 2-month-old baby) resulted in the town of La Bisbal d’Empordà. 28 people had to be taken to the hospital, including one serious head injury. This was the first direct hail fatality in Europe since 1997. Furthermore, the number of injuries ranks as the fourth highest recorded in the ESWD for large hail events.

8 September: Southeastward moving supercell over Lazio, Italy produced a swath of very large hail. The largest hail, 9 cm across, fell in Boville Ernica.

27 September: Serious hail damage to roofs, cars, windows, and greenhouses was reported from Serbia, especially in Pomoravski okrug region. Hail reached up to 6 cm in diameter.

23 October: Intense storm that resulted in a long-tracked tornado in Haute-Normandie, northwestern France also produced very large hail up to 7.5 cm in diameter.

We cordially invite you to submit a contribution to the 11th European Conference on Severe Storms to be held from May 8th to 12th in Bucharest, Romania.

20 January 2023 will be the final deadline for abstract submission.

Please submit your abstract here.

In the late afternoon of 30 August 2022, an extraordinary supercell storm formed over the eastern Pyrenees. The storm quickly started to move to the right of the mean wind as it entered the district of Girona in Catalonia, producing a swath of very large hail (≥ 5 cm) between Esponnellá at 16:50 UTC and Tamariu at 17:34 UTC, after which it moved over the sea.

Multiple reports of hailstones larger than 10 cm in diameter were collected with the largest stones estimated to be 12 cm. Based on some videos, the hail fall was relatively dense for stones of that size. The impacts of the storm were high: Besides serious damage to roofs and cars, 67 injuries and even one fatality resulted in the town of La Bisbal d’Empordà. 28 people had to be taken to the hospital, including one serious head injury. Based on our study on hail impacts across Europe, this was the first direct hail fatality in Europe since 1997. Furthermore, the number of injuries ranks as the third highest recorded in the ESWD for large hail events.

Given the societal and economic impact of this hailstorm and the fact that the giant hail has already been reported 18 times in Europe this year, we look at the predictability of this particular event from the perspective of the large-scale, pre-convective environment addressing these two questions:

1. How likely was the convective initiation?
2. How likely were the initiated storms to produce giant hail?

Limiting ourselves to the large-scale environment we do not address two important sources of data: high-resolution convection-allowing models and nowcasting data, such as products based on radar

How likely was the convective initiation?

With an abundance of low-level moisture along the coastline and steep mid-tropospheric lapse rates advected from the interior of Iberia, high convective available potential energy (CAPE) was present to support the development of severe thunderstorms. 

With this potential being present, the most important question was if a trigger strong enough to set this energy free would be available in this environment. The synoptic-scale lift was forecast only over extreme northeastern Spain and in the upper troposphere near 300 hPa, but not at lower levels. With the absence of fronts or other large-scale air-mass boundaries, the mesoscale lift had to come from an upslope flow of maritime air against the high terrain.

Convective initiation across Spain was complicated by a substantial amount of convective inhibition (CIN), negative energy to be overcome before a storm can form, especially over the southern part of Iberia. Near the eastern coastline, CIN rapidly increased from the mountains towards the coastline, restricting the ability of the storms to tap into the moisture- and CAPE-rich air mass. The largest area of relatively low CIN (< 50 J/kg) existed over far northeast Iberia, where the supercell formed. 

Combining the lowest CIN and the presence of at least some synoptic-scale lift over far northeast Spain, with hindsight it is possible to pinpoint this area as one with the highest probability of storm formation. Severe hailstorms are often isolated cells, rather than storms which are embedded in a larger convective system. On the 30 of August, the absence of widespread mesoscale lift and the presence of some CIN in the environment probably helped to limit the number of storms that formed to the one storm that produced the giant hail.

While it is easy to retrospectively explain the isolated nature of the storms on this day, beforehand it was not possible to state with certainty what will be the exact track of the storms or whether there will be three or no storms at all.

How likely were the storms to produce giant hail?

The supercell moved into the environment that has been found to be very conducive to severe weather, featuring high CAPE and strong vertical wind shear. Considering the model-simulated Skew-T and the surface observations from the area (temperature of 29, dewpoint of 23°C, and 5 m/s SSE wind), very large hail production was supported by:

1. High values of CAPE (MLCAPE ≈ 4000 J/kg) with large amounts of CAPE found in the temperature zone < -10°C
2. Vertical wind shear supportive of supercells. Very large hail occurs almost exclusively with this type of convection. Furthermore, strong shear resulted in a strong inflow into the storm. Based on the simulated hodograph, observed surface wind and observed storm motion, the surface inflow into the storm was almost 20 m/s. Strong inflow supports wide updrafts and wide updrafts lead to long hail embryo residence times in the favorable growth zone.
3. Unidirectional vertical wind shear (i.e. straight hodograph). Straight hodographs have been found to be more conducive to large hail growth than curved hodographs. 

Both low-level shear and storm-relative helicity were quite weak in this case. Unlike for tornadoes, high values of these parameters are not necessary for very large or even giant hail.

Supercell also profited from being the only storm around with no disruption to its inflow and updraft. Its deviant motion to the right was also more pronounced than anticipated by the Bunker’s ID method, suggesting the presence of a strong mesocyclone.

Was it possible to make a confident forecast of the storm producing hail reaching 10 cm? Such a forecast would be useful, as 10+ cm hailstones have a higher probability of causing both damage and injuries compared to 5+ cm hailstones. However, hail diameter doesn’t linearly increase with increasing CAPE and shear. For example, increasing CAPE may even limit the large hail production beyond some point. There are likely other factors that influence the trajectory of hail embryos through the updraft and their residence time in a zone of abundant super-cooled water droplets. Some of these are covered in a lecture by Matthew Kumjian. Testing these factors against a large sample of very large or giant hail cases will perhaps bring us even closer to confident forecasts of such devastating hailstorms.

In conclusion, the combination of very favorable large-scale conditions for hail with isolated convective initiation resulted in a perfect scenario for a damaging hailstorm. Such knowledge provided a good chance to correctly nowcast the event once the storm entered a supercell stage.