ECSS2019 Conference Photo

Taken in the poster area during today’s morning coffee break, the official ECSS2019 Conference Photo is now available for download here:

ECSS2019 Conference Photo (photographer: Thomas Schreiner, ESSL. CC license: BY-SA)

It also has been published on the ECSS webage.

Frequency rise of future European thunderstorm hazards

Researchers at the European Severe Storms Laboratory (ESSL), Munich Re, the Ludwig-Maximilians University Munich (LMU) and the German Aerospace Centre (DLR) could show that damaging convective weather events including lightning, hail and severe wind gusts are likely to become more common across Europe until the end of this century. An increase in convective instability as a result of rising humidity near the earth’s surface was identified as main reason for the increase in hazard frequency.

They applied a set of additive logistic regression models (AR-CHaMo) to an ensemble of 14 regional climate simulations to predict the frequency of severe thunderstorms and its associated hazards in Europe under projected anthropogenic climate conditions.

Simulated annual 6-hourly periods with (a), (b) and (c) hail ≥ 2cm (d), (e) and (f) wind (g), (h) and (i) with hail ≥ 5 cm. The first column (a, d and g) represent the historical period (1971-2000) while the second and third column show the percent change at the end of the century (2071-2100) for the (b, e and h) RCP4.5 and (c, f and i) RCP8.5 scenarios. Trends are called (very) robust where the change is larger than (twice) the initial standard deviation of the model ensemble. (Very) robust changes are indicated by (large) black dots in (b, c, e, f, h and i). Areas where models already diverge greatly for the historical period are displayed in gray in (a, d and g). From Rädler et al. (2019).

They projected a slight decrease in thunderstorm occurrence in southwestern and southeastern Europe, but an increase in the probability of severe weather. Large hail (≥ 2 cm) is projected to become 40%-80% more likely across central Europe in the RCP8.5 scenario by the end of the 21st century (Figure c ) while very large hail is projected to become more likely across most of Europe, with a doubling possible in parts of central and northeastern Europe (Figure i).  As a consequence of the rising hazard probabilities, risk models will need to be adapted and public warnings and precautionary measures should be issued as storms approach.

More information on this study can be found in this open access article: 
Anja T. Rädler, P.H. Groenemeijer, E. Faust, R. Sausen and T. Púčik, 2019: Frequency of severe thunderstorms across Europe expected to increase in the 21st century due to rising instability, npj Climate and Atmospheric Science, DOI:10.1038/s41612-019-0083-7

Giant hail in Europe

Yesterday, 11 June 2019, multiple severe storms occurred over parts of Central Europe. Several of these storms were prolific hail producers and two of them even produced hailstones reaching a diameter of 10 cm or more, which we call giant hail. Such large hail was reported from Gorzów Wielkopolski-Ustronie and Wojcieszyce in western Poland with the largest stone measuring 12 cm. This makes it the biggest oficially measured hailstone in this country according to our partner Skywarn Polska.

Giant hail also occurred in Stari Trg ob Kolpi, southern Slovenia, and Brod Moravice, northern Croatia, with maximum reported hail diameter of 11 cm. This hailstorm actually tracked very close to the path of another giant hail producing storm last year that struck Crnomelj, Slovenia, with hail up to 12 cm in diameter.

With these events ocurring, one might wonder how rare such large hail actually is in Europe. Before 11 June 2019, giant hail was reported 91 times in the European Severe Weather Database ( across many different regions in Europe (see figure below) and 42 times since the founding of ESSL on 1 January 2006. Giant hail comprises on only about 0.38% of all large hail reports (minimum diameter 2 cm) submitted to the database. Such hail can cause very serious damage, injuries and occasionally be fatal to humans and animals.

Very large and giant hail reports across Europe based on the European Severe Weather Database (

Have we observed even larger hail sizes in the past over Europe? The answer is actually yes: The largest reported hail sizes in recent years are 15 cm on 20 June 2016 in Sânandrei in western Romania and 14.1 cm on 6 August 2013 in Undingen in southwestern Germany.

New study shows: severe thunderstorms more frequent if Europe warms and moistens

A new study led by ESSL researcher Dr. Tomáš Púčik shows how climate change will affect weather conditions responsible for severe thunderstorms. In the study, which has appeared in the Journal of Climate, no fewer that 14 regional climate models were studied. Because climate models are still too coarse to simulate convective storms directly, the researchers looked how often the three necessary ingredients for severe storms occur: unstable conditions, a strong change of wind with height, and a mechanism to trigger the storms.

The climate models predict that strongly unstable situations will occur more frequently, because the water vapour content in the lowest air layers will increase. At the same time, the wind shear, a factor important for the development of well-organized supercells, will not change much. As a result, severe convective storms are forecast to occur more frequently, with the strongest increases scenario with higher greenhouse gas emissions.

The increase is not geographically uniform and considerable uncertainty remains about the future changes in severe convective storm frequency over southwestern and southern Europe, due to a drying in the summer season.

The full open-access article can be downloaded here:

Tomáš Púčik, Pieter Groenemeijer, Anja T. Rädler, Lars Tijssen, Grigory Nikulin, Andreas F. Prein, Erik van Meijgaard, Rowan Fealy, Daniela Jacob, and Claas Teichmann, 2017: Future Changes in European Severe Convection Environments in a Regional Climate Model Ensemble, J. Climate, in press.

Present annual number of 6-hourly periods with high instability, strong wind shear and precipitation in the period 1971-2000 (a) and the changes expected in two future periods according to a scenario of moderate climate change (rcp4.5, b. and c.) and strong climate change (rcp8.5, d. and e.).

ESSL Testbed 2017 active

The ESSL Testbed 2017 welcomes all participants of this years’ edition.

We are proud to present an interesting selection of leading-edge forecasting and warning tools and we are thankful to all participating partners. New this year are for example a number of products from the EUMETSAT Nowcasting SAF.

You can follow our daily activities in the ESSL Testbed Blog or in our online sessions during the testbed period:

Tue – Thu at 9 UTC: Online severe weather briefings and daily expert lecture.
Fri at 9 UTC: Severe weather online briefing only.

At the online meeting times you can join us here in WebEX with the session number “953 698 353” and the password “testbed”. This service is kindly provided by EUMETCAL.

ECSS abstract submission extended

Upon request of many colleagues the deadline for the ECSS abstract submission was extended to 10 April 2017. This will be a final deadline.

Decisions on travel support grants and acceptance or rejection of conference contributions will be communicated by the ECSS scientific programme committee in the second half of May.