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Status:
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Finalised Material from: Linus, Fernando, Ervin
Discussed in the following Daily reports:
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http://intra.ecmwf.int/daily/d/dreport/2016/01/28/sc/ |
1. Impact
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On 29 January a severe windstorm swept from northern British Isles to Norway. It was named as Gertrude and in Norway as Tor. The storm managed to break the all-time wind speed measurement record setting a new value of 48.9 m/s at Krakenes lighthouse north of Bergen on the coast. |
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The figure below shows the warnings for this event. Red warnings were issued for the Shetlands and southern half of Norway.
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The series of images below show satellite images every 3rd hour for the event.
The plot below shows 24-hour maximum wind gusts for 29 January 12z to 30 January 12z.
The plot below shows significant wave height from one buoy west of Norway. (from magicseaweed.com)
3. Predictability
3.1 Data assimilation
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To see it more quantitatively the evolution of the forecasts, the values for a box around the strongest windgusts observed as [64.5, -5, 56.5, 9.5] including most of Scotland, the Shetland Islands and SW of Norway. The following values are area averages over this box from the HRES, the ENS-control and the Q0, Q25, Q59, Q75 and Q100 of the ENS. The observation is unknown, but the shortest range forecast's 34-35 m/s looks realistic based on the observed wind gust values. The HRES even up to the 00z run on the 24th looks pretty high, only slightly less windy than the latest run on the 29th. In earlier runs the values started to decrease bit faster. All in all the model was able to get continuously closer to the very high values without any major jumpiness, at least on this larger areal average scale. In terms of difference between the operational and e-suite they look very similar. The only maybe systematic difference I can see is the median of the ENS where the e-suite looks higher than the median of the oper forecasts almost in all runs making it slightly better.
The plots below show the ensemble forecast of waves for 61.2N, 1.1E for the forecast initialised 27 January 00z. O-suite (left) and E-suite (right). The waves area clearly higher in the e-suite during the peak period.
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