Status: Finalised Material from: Ivan, Linus
1. Impact
This vigorous low-pressure system brought destructive winds over Central-European countries on 29 October. Maximum wind gusts exceeded widely 25 m/s, peaking 35-40 m/s over Germany, Czech Republic, Slovakia, Austria, Hungary and Poland. At least four people were reported dead in accidents related to this violent storm named Herwart. Herwart caused a lot of damage and disruption to transport and power supply in central Europe. Prague and Berlin were among the most affected large metropolitan areas. The strongest winds occurred from morning hours of 29th through the whole day. A huge number of severe weather reports were gathered in the European Severe Weather database (ESWD).
2. Description of the event
The animation below shows the ECMWF analysis of MSLP and Air mass RGB, every 6 hours from 18Z on 28 to 18Z on 29 October 2017 showing the development of the storm Herwart.
The plot below shows the track of the cyclone in a short-range forecast.
The plot below shows the 24-hour observed maximum wind gusts from 29 October.
3. Predictability
3.1 Data assimilation
3.2 HRES
The plots below show 24-hour maximum wind gusts for 29 October and MSLP valid 12z on the same day from HRES forecasts with different initial times.
3.3 ENS
The plots below show the EFI and SOT for 24-hour maximum wind gusts on 29 October from different initial dates.
A large number of damages were reported in Berlin metropolitan area with wind gusts exceeding 30 m/s. For this area the EFI reached the maximum possible value of 100% in the short-range which means that all the ensemble members gave values for the wind gusts exceeding the model climate maxima. Quantitatively, the maximum 24-hour wind gusts peaked between 26 and 29 m/s in the ENS for the location corresponding to Berlin.
3.4 Monthly forecasts
3.5 Comparison with other centres
4. Experience from general performance/other cases
5. Good and bad aspects of the forecasts for the event
- Good guidance about a week in advance for strong wind gusts