New study could make windstorms easier to predict

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If you were to ask me what meteorologists traditionally thought about windstorms, I’d answer by saying that we haven’t really spent much time thinking about them...Very little attention has been paid to wind itself.
Professor David Schultz
It might be a quarter of a century too late for weatherman Michael Fish, but new research has broadened our understanding of how violent storms develop...

New meteorological research has improved our knowledge of how severe storms develop. The transatlantic study, which has been published in the journal Weather and Forecasting, offers fresh insight into the mechanisms that transform seemingly benign subtropical cyclones into violent windstorms.

The Great Storm of 1987 took the British public – and indeed, its meteorological community – by surprise. Gale-force winds of up to 120mph swept across southern England and northern France resulting in 22 deaths and causing extensive damage to property. The windstorm also succeeded in embarrassing BBC and Met Office weather forecaster Michael Fish, who infamously told viewers not to worry about a rumoured ‘hurricane’. Similarly, in late 2011, ‘Hurricane Bawbag’ – as it was colloquially known – left thousands of Scottish homes without power.

Storms such as these are characterised by sting jets: the most damaging of Europe’s gale-force winds. The team’s observations revealed that as a weather front intensifies, winds steadily rise in a region ahead of the front known as frontogenesis. These winds then start to descend from the frontolysis at the tail end of the front: an area several kilometres above surface level. When conditions are favourable, winds descending at sufficiently rapid speeds can cause sting jets at the surface.

To learn more about the development of these violent windstorms, I spoke to David Schultz, Professor of Synoptic Meteorology at the University of Manchester’s School of Earth, Atmospheric and Environmental Sciences…

Could you begin by explaining more about the types of windstorm that you have been investigating? These aren’t actually hurricanes, are they?
No, they aren’t. These particular storms are known as extratropical cyclones. Essentially, they are low-pressure systems that include cold and warm fronts, and they tend to move through middle latitudes. Systems such as these pass by every day, and most of the time, they’re pretty innocuous: they might cause a few clouds and a bit of rain. Occasionally, however, they result in strong winds that can cause significant damage.

Did your results come as a surprise, or are they broadly in line with what you expected to find?
I think that there was actually a big gap in our knowledge. If you were to ask me what meteorologists traditionally thought about windstorms, I’d answer by saying that we haven’t really spent much time thinking about them. Extratropical cyclones are prolific when it comes to heavy rain and snow. A great deal of research has gone into these phenomena. However, very little attention has been paid to wind itself. Historically, the tendency has been to assume that the stronger the storm, the stronger the winds. Some of our findings, which have not yet been published, suggest that this explanation is incomplete.

My investigation focuses on a specific type of windstorm. Sting jets were first recognised in 1995, although if you go back to the early Norwegian meteorologists operating at the turn of the 20th Century, you will find that they had a very basic understanding of sting jets. Of course, the phenomenon hadn’t been mapped at this point. In 2004, a Met Office scientist discovered that sting jets were present in the Great Storm of 1987, and our research follows up on this finding. We have only just begun work that needs to be done. Even so, encouragingly, my findings are in keeping with those of my peers. Of course, this specific case cannot explain all windstorms. We know that strong winds occur around extratropical cyclones that are not associated with sting jets.

I understand that some of your colleagues had to fly through a developing storm in order to collect data for this study. Could you explain more?
I wasn’t actually onboard that flight. This project is a collaborative effort between meteorologists at the University of Manchester, the University of Leeds, the University of Reading, the University of East Anglia (UEA), University College London (UCL) and some academics in the United States. Sting jets are not very common: they occur perhaps once or twice per winter in the United Kingdom. However, when one of these storms occurred in the north of Scotland, some of my colleagues seized the opportunity and succeeded in getting an aeroplane into the right place to look at it. The footage that you can see in the video (embedded) was shot during one of their flights.

If this information had been available in 1987, do you think that Mr Fish’s blushes might have been spared?
That’s a good question. I have to say that I haven’t conducted any detailed analyses of the computer models that were being used at the time. However, having looked at the maps, I can say that this was a storm that grew very quickly. I would be very surprised if one of today’s models were to miss a storm like that of October 1987. The current generation of computers is sufficiently powerful to capture these types of event. The computers of the late 1980s, on the other hand, probably weren’t powerful enough to run models capable of capturing this sort of windstorm. Knowing whether or not sting jets were likely to occur wouldn’t really have helped Michael Fish, but higher-resolution models might well have done.

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