Status:Ongoing analysis Material from: Linus, Mohamed
Discussed in the following Daily reports:
http://intra.ecmwf.int/daily/d/dreport/2015/01/02/sc/
http://intra.ecmwf.int/daily/d/dreport/2015/01/06/sc/
http://intra.ecmwf.int/daily/d/dreport/2015/01/07/sc/
http://intra.ecmwf.int/daily/d/dreport/2015/01/08/sc/
http://intra.ecmwf.int/daily/d/dreport/2015/01/09/sc/
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1. Impact
On 9-10 January 3 severe storm hit north-western Europe. The first hit Scotland early on Friday 9 January with wind gusts up to (? mph) and later Denmark and Germany. The second one (named Nina in Norway) hit the Norwegian west coast on Saturday 10 January with hurricane force on 5stations ( http://artikkel.yr.no/sa-sint-var-nina-1.12143639) and a maximum mean wind of 37 m/s on Eigerøya. A third cyclone formed (named Egon in Sweden) in lee southern Norway and caused hurricane wind gusts in southern Sweden and heavy snowfall further north. The wind also led to elevated sea-levels along the Norwegian and Swedish coasts.
The evalution below is both for the Friday 9 January and Saturday 10 January.
2. Description of the event
The plots below show observed 24-hour maximum wind gusts for 9, 10 and 11 January. For the 9 January the worst affected areas were Scotland together with Denmark and Germany. On 10 January the strongest winds occurred along the Norwegian west coast. Sweden was also hit by strong wind gusts late on the 10th. On 111 January the strongest gusts were found around the Baltic sea.
Observed maximum 24-hour wind gusts
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The plots below show satellite images from yr.no every third hour. In the image sequence one can follow the development of the three cyclones.
Satellite images (every 3rd hour) |
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The cyclones formed in connection to a strong baroclinic zone. The plots below shows the analyses of z500 and t850 every 12th hour.
z500 and t850 analysis |
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The plot below show the jet steam and MSLP (in polar projection) for the same analyses as above.
200 hPa wind and MSLP analysis
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The plots below show 12-hour forecasts of MSLP and precipitation.
MSLP and precip 12-hour fc
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3. Predictability
3.1 Data assimilation
3.2 HRES
Friday
The plots below show the 24-hour maximum wind gusts from HRES valid for 9 January.
14-hour max wind gusts Friday
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Saturday
The plots below show the 24-hour maximum wind gusts from HRES valid for 10 January.
14-hour max wind gusts Saturday
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3.3 ENS
Cyclone feature 1km wind 600 km Friday 00z
The plots below show the cyclone feature plots for maximum wind speed at 1 km height inside a 600 km radius for 9 January 00z.
1 km wind 600 km Friday
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Cyclone feature 1km wind 600 km Saturday 12z
The plots below show the cyclone feature plots for maximum wind speed at 1 km height inside a 600 km radius for 10 January 12z.
1 km wind 600 km Saturday
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EFI Friday
The plots below show EFI and SOT for wind gusts valid 9 January.
EFI wind gusts Friday
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EFI Saturday
The plots below show EFI and SOT for wind gusts valid 10 January.
EFI wind gusts Saturday
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CDF for maximum wind gusts
CDF for Bergen, Norway valid 10 January (observed 37.7 m/s in town)
CDF for Vaxjo, Sweden valid 10 January (observed 29 m/s)
Return period forecasts
The plots below shows probabilistic forecasts and verification of a binary event defined as exceeding 2-year return period for 24-hour maximum wind gusts.
First plot: 8 January 06z - 9 January 06z. Second plot: 9 January 06z - 10 January 06z.
Regime forecasts
The plot below shows a 2-d plot of projections into regime 1 (NAO+) and regime 2 (Scandinavian blocking), where each plot represents an analysis at 00z and the last point (lower right) the the 11 January. On 9-10 January the projection was very strong on positive NAO.
The plot below shows the ensemble forecast of projection to regime 1 where the x-axis represents the initial time of the forecast. Forecast from 1 January and onwards had a strong positive NAO signal, especially from the 4 January and onwards.
3.4 Monthly forecasts
3.5 Comparison with other centres
The plot below shows forecasts from different centres for probability for >25 m/s 10-metre mean wind from 6-hourly data, valid 10 January. The data are from the TIGGE archive.
Prob ws>25 m/s ECMWF Friday
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Prob ws>25 m/s NCEP Friday
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Prob ws>25 m/s UKMO Friday
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Prob ws>25 m/s DMI-HIRLAM Friday
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The plots below are the same as above but for 10 January.
Prob ws>25 m/s ECMWF Saturday
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Prob ws>25 m/s NCEP Saturday
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Prob ws>25 m/s UKMO Saturday
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Prob ws>25 m/s DMI Saturday
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4. Experience from general performance/other cases
5. Good and bad aspects of the forecasts for the event
- Early signal for transition to strong positive NAO
- Good predictability for the Friday storm over Scotland
- More problems for Saturday storms