Status:Ongoing analysis Material from: Linus, Tim, Thomas H.,..
1. Impact
On 12-17 September a low-pressure system named Boris caused record-breaking rainfall in Central Europe. It led to severe flooding in e.g Austria, Czech Republic, Slovakia and Poland and also caused fatalities in Romania.
ECMWF In Focus article about the event:
https://en.wikipedia.org/wiki/2024_Central_European_floods
https://www.bbc.co.uk/news/articles/c5yjjqyv84eo
2. Description of the event
The evaluation of the rainfall will focus on 72-hour rainfall on 13 September 00UTC - 16 September 00UTC in Vienna, Austria (48.2N, 16.4E). Some diagnostics will also be for Ostrava in Czech Rep. (49.9N, 18.1E)
The plots below show analyses of MSLP and 6 hour rainfall from 11 September 00UTC to 16 September 00UTC, every 12th hour.
The plots below show analyses of T850 and z500 from 10 September to 16 September.
For Vienna, 7 stations was found nearby (3-day accumulation):
stnid,latitude,longitude,stnid,elevation,value_0,count
11082,48.04,16.28,11082,212.0,131.1,3
11040,48.12,16.42,11040,200.0,113.4,3
11036,48.12,16.58,11036,183.0,129.7,3
11034,48.2,16.37,11034,177.0,217.6,3
11037,48.2,16.56,11037,153.0,166.6,3
11035,48.25,16.36,11035,209.0,176.9,3
11090,48.26,16.43,11090,162.0,176.1,3
Below are a list of new 5-day records of precipitation in Austria:
3. Predictability
3.1 Data assimilation
3.2 HRES
The plots below show 72-hour precipitation in observations (first plot, to be added), concatenated short forecasts (second plot) and the INCA analysis from Austria (shifted 6 hours).
The plots below show 72-hour precipitation in ENS control forecasts with different lead times.
The plots below show 72-hour precipitation in DestinE 4.4km with different lead times.
The plots below show 72-hour precipitation in AIFS with different lead times.
The plots below show 72-hour precipitation in AIFS0-ENS member 1 with different lead times.
3.3 ENS
The plots below shows EFI for 3-day precipitation (13-15 September).
The plot below shows the forecast evolution plot for 72-hour precipitation for Vienna (split in two figures to fit all forecast types).
Observation - green hourglass
Analysis - green dot
ENS control–red
ENS - blue box-and-whisker
AIFS - cyan dot
Desint4.4km - evergreen dot
AIFS-ENS - grey box-and-whisker
cy49r1 ENS - purple box-and-whisker
Model climate – cyan box-and-whisker
Ensemble mean as black diamonds. Triangle marks the maximum in the model climate based on 1800 forecasts.
The plot below shows the same as above but for Ostrava.
The plot below shows the evolution plot for 3-day precipitation in a large box (48-51N, 14-18E, see attached observation plot below).
The plots below show hit (green), misses (purple) and false alarms (cyan) of predicting precipitation above the 99th percentile of model climate, based on the ensemble median.
The plots below show the same as above but for AIFS-ENS.
3.4 Monthly forecasts
The plots below show forecasts of weekly precipitation anomalies for 9-15 September.
3.5 Comparison with other centres
4. Experience from general performance/other cases
- The ensemble gradually picked up the signal and was above 99th percentile for Vienna 7 days before the event (6 September).
- Determininstic AIFS showed a very early signal, while AIFS-ENS showed a similar development of the signal as IFS-ENS (and underestimated the maximum intensity)
5. Good and bad aspects of the forecasts for the event