Introduction
In these exercises we will look at a case study of a severe storm using a forecast ensemble. During the course of the exercise, we will explore the scientific rationale for using ensembles, how they are constructed and how ensemble forecasts can be visualised.
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In practise many cases are aggregated in order to evaluate the forecast behaviour of the ensemble. However, it is always useful to complement such assessments with case studies of extreme events, like the one in this exercise, to get a more complete picture of IFS performance and identify weaker aspects that need further exploration. |
Recap
ECMWF operational forecasts consist of:
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| Info |
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To save images during these exercises for discussion later, you can use: | Panel |
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| "Export" button in Metview's display window under the 'File' menu. This will also allow animations to be saved into postscript. |
or | Code Block |
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| language | bash |
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| title | Use the following command to take a 'snapshot' of the screen: |
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| ksnapshot |
Printing. If hardcopy prints are desired please use the printer at the rear of the classroom and only print if necessary. |
St Jude wind-storm key highlights
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| bgColor | white |
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| titleBGColor | lightblue | title | St Jude wind-storm key highlights |
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The case study will look at one of several severe wind-storms that hit Europe in late 2013 (see handout of ECMWF article by Hewson et al, ECMWF Newsletter 139). - On the 28th October 2013 a small, severe wind-storm named St Jude in the UK, hit the UK & north-western Europe.
- A total of 19 people were killed across Europe, 5 in the UK.
- The return period of the event based on wind-gust observations show the 10yr return period was exceeded along the North Sea coast.
- From the 23rd October, the ECMWF forecast predicted a greater than 70% probability of a severe wind event (greater than 60kt, 31m/s, at 1km) over southern England. A signal for the storm was evident from the 21st October.
- On the 24th October, the UK MetOffice issued an amber alert for wind-speed across southern England placing the potential impact in the highest category.
- The cyclone first appeared as a cold front wave, over the Atlantic, late on 25th October.
- It deepened and moved rapidly east then northeast, with the storm centre reaching southern Sweden late afternoon on the 28th.
- The most rapid deepening occurred between 06-12UTC on the 28th when the strongest wind gusts were observed.
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