New study: More (very) large hail in most of Europe

A new study by ESSL, Adam Mickiewicz University, NSSL, and the Freie Universität Berlin, lead-authored by ESSL researcher Francesco Battaglioli, has been published in the AMS Journal of Applied Meteorology and Climatology

In the study, entitled “Modelled Multidecadal Trend of Lightning and (Very) Large Hail in Europe and North America (1950-2021)” they reconstructed the climatology of lightning and (very) large hail in Europe and North America since 1950 using statistical models (AR-CHaMo) trained with about 24 million lightning observations and more than 44000 hail reports.

Left: Mean modeled annual and seasonal number of hours with hail of 5 cm or larger in a 0.25 x 0.25° box.
Right: Change in the annual number of hours with very large hail per decade. Significant trends (p<0.05) are hatched.

They found that, across Europe, large (≥ 2 cm) and very large (≥ 5 cm) hail is most common across northern Italy, south-western France, and eastern Spain. Hail frequency has increased across large parts of Europe. This increase is caused by rising humidity in the lowest layers of the atmosphere.


Left: Mean modeled annual and seasonal number of hours with hail in a 0.25 x 0.25° box.
Right: Change in the annual number of hours with hail per decade. Significant trends (p<0.05) are hatched.

In North America, hail is most common across the U.S. Great Plains. Unlike Europe, the modelled hail frequency has only increased in certain areas, while it decreased in others. Areas with increasing hail include the High Plains of Colorado and Central Canada.

Modelled time series of hail across Northern Italy and Central Oklahoma.

Focusing on two hail-prone areas, northern Italy and central Oklahoma, temporal changes in large hail frequency can be shown using “Hail Stripes”, much like those used to illustrate temperature changes, first by Ed Hawkins. These stripes show that, across northern Italy, very large hail is now 3 times more likely than it was in the 1950s.


Modeled seasonal cycles of large and very large hail for three different periods (1950–73,
1974–97, 1998–2021).

Since 1950, the season in which large hail occurs has lengthened across Northern Italy, especially because of an earlier start in Spring.     

Experimental lightning and hail forecasts, with hail observations overlaid,
based on AR-CHaMo, available at https://stormforecast.eu

The AR-CHaMo models also have important applications in hail forecasting and are used for experimental real-time forecasts available at the website stormforecast.eu. The so-called Convective Available Potential Energy, a parameter often used by forecasters, was shown to be of limited value. Instead, the part of this potential energy released high in the storm cloud at temperatures below -10 °C was found to be a much better predictor for large hail.

This work was funded by the German Ministry of Research and Education (BMBF) within the project CHECC, part of the ClimXtreme Research Programme. Stormforecast.eu has been developed in the Project PreCAST supported by the Austrian Science Fund (FWF) and the European Centre for Medium-Range Weather Forecasts (ECMWF).

Hail record broken again – 19cm hailstone confirmed in Italy

Less than a week after setting a new European record, a hailstone 19 cm in diameter was found in Azzano Decimo, Italy.

Record breaking hailstone in Italy
 © Tornado in Italia – Marilena Tonin

The previous record of 16cm in Carmignano di Brenta from 19 July lasted for only five days. On 24 July 2023 at about 11 PM in the evening, giant hail hit the town of Azzano Decimo, where the record breaking hailstone was found. After a thourough examination of the reports and photos, the specialists of the European Severe Weather Database (ESWD) came to the conclusion, that the diamter of this hailstone can be confirmed as 19 cm.

The new hailstone comes very close to the world record of a hailstone from 23 July 2010 in Vivian, South Dakota, with a diameter of 8 inches (20.3 cm).

The high frequence of hail in Northern Italy is consistent with research results of the European Severe Storms Laboratory (ESSL), showing, that this region has experienced the largest increase in the frequency of large hail, compared to other European regions in the past decades.

200% increase of large hail in Northern Italy since the 1950s
© ESSL / Francesco Battaglioli
Increase of hail events in Europe
© ESSL / Francesco Battaglioli

At the end, ESSL want to thank its local partners, as PreTemp in Italy, and the reporters of hail to their great collaboration and contributions to the European Severe Weather Database (ESWD)!

New European record: 16cm hailstone found in Italy

On 19 July, severe hailstorms affected large parts of Southern Europe. According to the experts of the European Severe Storms Laboratory (ESSL) so-called “giant hail” (hailstones with a diameter of more than 10 cm) was reported 24 times; 2 times in Croatia and 22 times in Italy!

Record breaking hailstone found in Carmignano di Brenta (Italy)
© Tornado in Italia – Floriana

In Croatia, the largest hailstone was found in Ribnik, estimated to be 13 cm in diameter. In Italy, the largest hailstone fell in Carmignano di Brenta. The specialists of the European Severe Weather Database (ESWD) estimate the size of this hailstone to be 16 cm in diameter, based on photos.

“According to our information, this would be the largest recorded hailstone in Europe”, says Thilo Kühne, Quality Control Manager of the European Severe Weather Database. “The previous record was a 15 cm hailstone from 20 June 2016 in Sânandrei, Romania”.

Besides enormous economic damage, the hail caused 109 injuries on that day alone, according to the European Severe Weather Database.

Hail reports 20 July 2023
© ESSL / ESWD

ESSL obtaining its data from a large European network of weather entusthiasts and cooperating weather services. The Italian cases, including the new record braking hailstone, were reported by PreTemp, which collaborates closely with ESSL.

The experts of ESSL and the European Severe Weather Database urge all people sending photos to the weather services or our data base, or posting hail pictures on social media, to use a ruler, coin or other reference objects next to the hailstones when making a picture. This makes it easier to estimate the exact size of hailstones.

ESSL supports civil defense exercise

ESSL was asked by the City of Wiener Neustadt to support a major civil defense exercise for the city and surrounding districts. On July 5th, shortly before the start of the exercise, ESSL Director of Operations Alois Holzer gave a lecture on tornado basics as a prelude for the management team of around 40 officials. The tornado scenario of the exercise concerns urban areas.

Kick-off presentation at civil defense exercise for City of Wiener Neustadt and surroundings on 5 July 2023

Already 10 years ago, ESSL provided the tornado scenario for a similar civil defense exercise. The recent talk gave the participating entities insight into the impacts of violent tornadoes. Part of the presentation was the case of 24 June 2021 over Czechia, when 6 persons died and hundreds were injured in an F4 tornado. Even more people were killed in the historical tornado event of the year 1916, when 34 persons died in another F4 tornado that struck the northern neighborhoods of Wiener Neustadt.

From left to right: Markus Biffl (Head of City Administration Wiener Neustadt), Alois M. Holzer (ESSL Director of Operations), Doris Hailzl (Head civil protection department and main organizer of exercise). Background: situation room for civil defense emergencies.

ESSL welcomes Météo-France as a new Full Institutional Member

In June 2023, Méteo-France has become a member of the European Severe Storms Laboratory. This means that they have joined the present 25 Institutional Members of ESSL: public or non-profit organizations in Europe active in the realm of weather and climate forecasting or related fields. The ESSL Team extends a warm welcome to Météo-France, which will now have full access to the European Severe Weather Database to support its activities. In addition, full ESSL members have a vote in ESSL’s General Assembly and benefit from reduced participation rates in ESSL activities. ESSL is looking forward to the cooperation with Météo-France.

Mayor of Wiener Neustadt and Lower Austria Science Officer Visit ESSL

On the occasion of the first EUMETSAT-ESSL Testbed in 2023, the mayor of the city of Wiener Neustadt, Klaus Schneeberger, and the head of the governmental science department of the Federal State of Lower Austria, Martina Höllbacher, paid a visit to ESSL this week.

From left to right: Alois M. Holzer (Director of Operations, ESSL); Martina Höllbacher (Head of Science, Federal State of Lower Austria); Klaus Schneeberger (Mayor, City of Wiener Neustadt)

ESSL staff informed the officials on the anticipated advances in connection with the new satellite generation (EUMETSAT MTG). Our guests have been impressed by the variety of impactful activities the small ESSL team has undertaken over the past years, as documented by scientific posters and by the growing list of events, ranging from testbeds and seminars to expert workshops.

The official visit took place on 8 June 2023. The next day, a science journalist from the Austrian Broadcasting Corporation (ORF) visited our ESSL Research and Training Centre to interview participants and prepare a report on the EUMETSAT-ESSL Testbed and its importance for operational meteorologists in Europe. This week, participants from 15 different countries are taking part, from Ireland to Turkey, and from Portugal to Finland.

IF-Scale draft published for public commenting

ESSL and collaborators drafted a document on the “International Fujita Scale” (IF-Scale). It defines a new method to rate tornado and wind damage and was presented at the European Conference on Severe Storms in Bucharest, Romania, earlier this month.

The document is open for commenting until 31 May 2023. ESSL plans to implement the new scale in the European Severe Weather Database by 1 July 2023.

More information on the IF-Scale draft you can find here.

First ESSL Expert Workshop on Severe Weather Warnings: from Expectations via Physical Ingredients to Impact-based Warnings and Beyond

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).

ECSS: Registration open and programme published

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.

ESSL-EUMETSAT annual forecaster event

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.