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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

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Sequence is the Met Office surface analysis, with fronts, covering the period when the maximum gusts occurred. It shows the storm to be a small and rather innocuous looking feature! Note also that some of the charts - eg when the low was over Sweden - show a Keyser-Shapiro type structure, with a bent back cold front rather than an occlusion - implying a warm core.

Analyses for MSLP and Eady Index (showing baroclinic zones) from 26 Oct 0 UTC to 28 Oct 12 UTC, every 12 hours. Here we see the baroclinic zone over the Atlantic and a wave in the surface pressure field moving to the east. A rapid development happened after 28 Oct 0 UTC.

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The panels above relate to the mesoscale structure of the storm as it passed over the UK (and beyond). We refer here to the warm conveyor belt (WCB), sting jet (SJ) and cold conveyor belt (CCB). Refer also to fronts on the Met Office analysis charts at the start of this page - the WCB is in the warm sector, the sting jet tends to be near to the tip of the occlusion / bent back front, and the CCB on the western and southern flank of this wraparound front.

The IR sequence shows, perhaps unsurprisingly, all the hallmarks of an extreme extra-tropical cyclone, including evidence of a SJ event. Notably, fingers of cold top cloud continue to emerge forwards from the tip of the cloud head, but evaporate as they descend (the 'smoking gun' effect). This happens first across S England, then on across the N Sea, and finally over S Denmark; thereafter there is more evidence of cold top cloud surrounding the cyclone, as the cold conveyor CCB phase of the maturing cyclone takes over. The cyclone seems to fit the model proposed by Keith Browning in his October 1987 sting jet (QJRMS) paper very well, and also the model of related 'damage swathes' shown on the final panel. As well as the evaporating cloud fingers note the evidence on IR of curved slabs of slantwise upward motion extending NW from the low centre, with dry gap(s) inbetween. A new 'slab' develops at the start of the IR sequence, and relates also to a propogating band of intense rain at the surface - note the narrow band of bright echoes in the northern portion of all the radar sequences. In the SJ conceptual model this equates to one of the dark-shaded arrows on the top panel. The lighter shaded arrows, meanwhile, denoting evaporating descending branches, correspond to the dry gaps on the radar sting jet sequence, two of which are highlighted on the 'Reading max SJ gust' panel. It is expected from modelling studies performed by Pete Clark, that these descending branches will be the source of the main SJ gusts at the surface, and so it proves for this case, at least at the Reading university site, as the traces and radar show. Detailed analysis of the storm of October 30th 2000 has shown a similar correspondance. The temperature trace for Reading shows falling temperatures during the SJ phase, related perhaps to the mini cold fronts shown in the SJ conceptual model, though, perhaps significantly (?), there is a mini plateau at the time of maximum gust, which could conceivably relate to warming during a relatively dry stage of descent. Note also that the SJ conceptual model diagram corresponds to a more mature sting jet; at Reading we are just looking at the very beginning, wherein the tips of the lighter grey arrows (and mini cold fronts) would be much further back relative to the low centre position.

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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 - believed to be attributable to the SJ.


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.

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The figure above shows forecasts initialised 25 Oct 0 UTC (+84h).

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4.2 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.

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