Status:Finalized Material from: Fernando, Linus

 

Discussed in the following Daily reports:

 

Picture

1. Impact

On the 31 March 2015 a strong windstorm hit north-western Europe.the cyclones was named Niklas. At least 9 people were killed by the severe winds.

http://en.wikipedia.org/wiki/Cyclone_Niklas

http://www.bbc.co.uk/news/world-europe-32138213

2. Description of the event

Cyclone Niklas was the third cyclone over the last days in March, associated with a positive phase of NAO. The figures below show short forecasts (12h) of MSLP and precipitation. Niklas passed over northern Germany around 12z on 31 March.

MSLP and precipitation (12h forecasts)
01. 28 March 00z
02. 28 March 12z
03. 29 March 00z
04. 29 March 12z
05. 30 March 00z
06. 30 March 12z
07. 31 March 00z
08. 31 March 12z
09. 1 April 00z
10 .1 April 12z

The plot below show 24-hour maximum winds on the 31 March. Observations of more than 25 m/s in the gusts over land spread from Ireland to Poland.


3. Predictability

  

3.1 Data assimilation

 

3.2 HRES

The plots below show 24-hour maximum wind gusts valid 31 March and MSLP valid at 12z on 31 March.

24-hour max wind gusts 31 March
01. 31 March 00z
02. 30 March 12z
03. 30 March 00z
04. 29 March 12z
05. 29 March 00z
06. 28 March 12z
07. 28 March 00z
08. 27 March 12z
09. 27 March 00z
10. 26 March 12z


3.3 ENS

 

Cyclone feature 1km wind 600 km
01. 31 March 12z
02. 31 March 00z
03. 30 March 12z
04. 30 March 00z
05. 29 March 12z
06. 29 March 00z
07. 28 March 12z
08. 28 March 00z
09. 27 March 12z

The plots below show the cyclone feature plots for maximum wind speed at 1 km height inside a 600 km radius for 31 March 12z.

 

The plots below show the EFI and SOT for winds gusts valid 31 March.

EFI and SOT wind gusts 31 March
01. 31 March 00z
02. 30 March 00z
03. 29 March 00z
04. 28 March 00z
05. 27 March 00z
06. 26 March 00z
07. 25 March 00z

The next plot shows the probabilities of exceeding 10-year return period of maximum wind gusts. The top-left panel shows the verification based on ERA Interim.


As mentioned in Section 2, the windy days in the end of March were associated with a strong positive NAO. The figure below shows the distribution of projections onto the positive NAO regime, averaged over 29-31 March. The strong phase of the NAO was well predicted 6-7 days in advance and all issued forecasts (up to 15 days in advance) was for a positive NAO.




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


6. Additional material