Status: Ongoing analysis Material from: Linus
Discussed in the following Daily reports:
http://intra.ecmwf.int/daily/d/dreport/2013/10/23/sc/
http://intra.ecmwf.int/daily/d/dreport/2013/10/24/sc/
http://intra.ecmwf.int/daily/d/dreport/2013/10/25/sc/
http://intra.ecmwf.int/daily/d/dreport/2013/10/28/sc/
1. Impact
On the 28 October a wind storm hit north-western Europe. In total 14 people were killed across Europe (http://www.bbc.co.uk/news/world-europe-24705734). The main affected countries where France, UK, The Netherlands, Germany, Denmark and Sweden. In Denmark the higher ever wind gust (for Denmark) was measured on Kegnäs on Als (53 m/s).
2. Description of the event
Satellite images from yr.no valid 9,12 and 18 UTC on the 28 October.
2.X Denmark
The figures above show the maximum mean (10 minutes) wind speed (left) and wind gusts (right) for Denmark (from DMI). Here we see that the highest wind speeds occurred in the south.
The figures above shows time-series of the mean wind from Kegnaes Lighthouse in the south-west of Denmark and Drogdens Lighthouse located in the east (a little bit south of Copenhagen). The time-axis is in Central European time. For both stations we see a rapid increase in the wind speeds. The increase happened above 2 hours later in the east than the west.
3. Predictability (including 40r1 E-suite evaluation)
3.1 HRES
The figures below shows forecasts of MSLP valid for 28 Oct 12 UTC and maximum wind gust during the 28 October. The o-suite is plotted in the left column and the e-suite in the right.
The figure above shows forecasts initialised 28 Oct 0 UTC. For southern England, the e-suite has less intense wind gusts than o-suite. For souther Scandinavia, it seems like the band of the highest wind gusts are a little bit to far north for both suites. In the morning on the 28th, SMHI (Swedish met service) issue a red warning for the Gothenburg area but later they had to move the red warning to the Malmo area.
The figure above shows forecasts initialised 27 Oct 0 UTC (+36h).
The figure above shows forecasts initialised 26 Oct 0 UTC (+60h). Here a large area west of England had very high wind gusts, what did not happened. We also see that the cyclone centre is more to the west compared to later runs. Both these results is due to a development of the cyclone too far west.
The figure above shows forecasts initialised 25 Oct 0 UTC (+84h).
3.2 ENS
The sequence of figures above shows the strike probability of cyclone with maximum wind speed (mean) over 60 kt (31 m/s) at 1 km height. The plots are valid for the 28 October (24-hours). The first forecast is from 28 Oct 0 UTC and one day is added for each plot. With longer lead time the feature is delayed (too slow) in the model, but the path of the cyclone seems very consistent up to 6 days before the landfall.
CDF for wind gusts (left) and maximum mean wind speed (right) for Reading valid on the 28 October. Different colour represents different initial times and the o-suite (38r2, solid) and e-suite (40r1, dotted). Comparing different initial times, the forecast from 26 October (green and black), were the most severe. For the forecasts from the 27 October the wind speed was less. This is partly because the development of the cyclone occurred later and therefore had not reached such a deep stage when it passed over Reading. Comparing e-suite and o-suite, we see that the winds (both mean and gusts) are less in the e-suite and o-suite.
3.3 Monthly forecasts
We cannot expect to see a strong signal for extreme cyclones in the monthly forecast. However, we can investigate whether the environment was favourable for windy conditions. The figures above show the weekly MSLP anomaly for the week starting on the 28 October. The first figure shows the forecast from the 28 October (Monday of the verifying week), followed by 24 Oct, 21 Oct, 17 Oct, 14 Oct and 10 Oct. At least for the 5 first forecasts a positive NAO signal (negative MSLP anomaly in the northern Atlantic and positive further south) is present. A positive NAO is usually leading to stronger winds over western Europe.
4. Experience from general performance/other cases
5. Good and bad aspects of the forecasts for the event
6. Additional material