Status:Ongoing analysis Material from: Linus

1. Impact

On 21 September the windstorm Knud affected the countries around the North Sea and Sweden.

2. Description of the event

The series of plots below show satellite images from yr.no starting from 00UTC on 21 September to 00UTC on 22 September.

3. Predictability

3.1 Data assimilation

3.2 HRES

The plot below show observed 24-hour wind gusts (first plot) valid for 21 September and HRES forecasts for 24-hour maximum wind gusts (shade) and MSLP valid 21 September 12UTC (contour). The signal in EFI became much stronger between 17 September 00UTC and 12UTC and was relatively consistent after that.

3.3 ENS

The plots below shows EFI and SOT for wind gusts valid 21 September. The signal in EFI became much stronger between 17 September 00UTC (Monday) and 18 September 00UTC (Tuesday) forecasts, in similarity with HRES.

The plots below show cyclone feature maps for 1 km maximum wind within 300 km radius, valid for 21 September 12UTC.

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 strong signal for the event appeared 4 days in advance
  

6. Additional material