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Status:Ongoing analysis Material from: Linus

 

Discussed in the following Daily reports:


Picture

1. Impact

On the 14 March strong wind and precipitation hit northern Scandinavia together wind precipitation. The station Stora Sjofallet in Sweden measured 36 m/s in mean wind. After the storm, a ski resort in the area had a major avalanche.


2. Description of the event

The figures above show the 24-hour maximum wind speed (left) and wind gusts (right) for the 14 February. The Stora Sjofallet station is the purple and black dots respectively in the figures.

3. Predictability

  

3.1 Data assimilation

 

3.2 HRES

HRES 24-hour wind gusts and MSLP
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The figures above show example of wind gusts forecast for 1, 2 and 3 days before the event. Also the three day forecast was good for the event.

10-meter wind speed and wind gusts for Stora Sjofallet (67.5N, 18.2E) for forecasts (red) and observations (red). Forecast initialised is14 March. For the Friday (14 March) the forecast had wind speeds around 5 m/s but the observed was >35 m/s. However, the wind gusts were in the better forecast with a peak on 38 m/s but missed the observed maximum. Except the maximum, the wind gusts forecast were very good.

The figure above show the forecast from 14 March 00UTC (same as above) but for Ritsem (57.7N, 17.5E). Here the maximum wind speed on the Friday was 10 m/s.The mean wind was therefore ok while the wind gusts here were clearly overestimated.

Ritsem is located along the same long-narrow lake as Stora Sjofallet. However, the gap between the mountain ridges is very narrow at the site of Stora Sjofallet, and the station is well-known for the channelling effect of the wind.

3.3 ENS


The CDF is for wind speed (left) and wind gusts (right) for Stora Sjofallet, valid on the 14 March. Here we see that the wind was extreme for the area.

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

  • The synoptic forcing of the event was well forecast 2-3 days before the event.
  • For Stora Sjofallet, the mean wind was far too low but the wind gusts were ok
  • For Ritsem, the mean wind was not very strong, as in the forecast, but the wind gusts were too high.
  • Is this an effect of sub-grid variability or a more general mountain problem?


6. Additional material

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