On the 13th June 2020 Balon Widokowy began passenger flights at 10:19 am that were suspended at 12:28 am due to increasing wind speeds making flights unsafe. The balloon was moored properly according to weather forecasts and procedures from the flight manual accepted by European Union Aviation Safety Agency (EASA). Around 6:10 pm a Cummulonimbus thunderstorm cloud type formed over Krakow City accompanied by a weather phenomenon called downburst (microburst), which tornadoes are often misinterpreted as and is very hard to forecast. Extremely strong wind gusts, exceeding 33 m/s, caused strong vertical deviation of the balloon. The balloon’s envelope was cut because of the contact made with nearby street lamp.
None of the many weather forecasting models followed by the balloon crew expected wind gusts stronger than 10-15 m/s, neither the phenomena mentioned above. Weather forecast for Krakow Airport informed about low possibility of thunderstorm clouds occurrence and wind gusts up to 20 m/s.
The wind gust registered on 13.06.2020 (33 m/s – 119 km/h) was the strongest in 8 seasons of the Balon Widokowy’s history in Krakow. The storm lasted only a few minutes.
Photo of the cloud that destroyed the balloon taken by Anna Trojanowska and clip from doppler radar below.
More information: https://en.wikipedia.org/wiki/Downburst