Publications on the internet
|©Parliamentary copyright||Prepared 22nd February 2011|
Publications on the internet
Written evidence from the Met Office (AWC 04)
· Winter conditions came early and hard to the UK in 2010– with the average temperature for December in the UK being over 5 degrees colder than normal at minus 1 degrees C. Nationally, this has been the coldest December in a data series starting in 1910 and the whole period was characterised by at least nine major snow events.
· This prolonged period of finely balanced weather conditions provided a real challenge for the Met Office’s forecasting capability. Overall, we performed well not only in forecasting the key hazards but in providing consistent, timely and useful advice to Government, customers, the emergency response community and the public.
However, we did learn some valuable lessons, particularly with respect to further developing the National Severe Weather Warning Service. We are taking these forward in 2011 to ensure that our Public Weather Service remains in step with what users need and expect from a national weather service consistently placed in the top three operational forecasters in the world.
· Accurate regional forecasts on a monthly scale have proven to be useful in mitigation planning and we are committed to developing the cutting edge science employed in monthly and seasonal forecasting so that these forecasts become as relevant and useful as our short term forecasts and longer term climate change predictions. The extent and speed of this development is, of course, dependent on the availability of resources – particularly in supercomputing power to enable modelling to incorporate new science and understanding.
What we did
1. The Met Office is the UK’s National Met Service and as such is funded by Government to provide a range of weather forecast services to enable the public to make informed decisions in their day to day activities. A critical element of this service is our National Severe Weather Warning Service (NSWWS)1, set up to provide advance warning of extreme weather to the public, business community, emergency responders and Government to help protect life, property and infrastructure.. The NSWWS is designed to advise on the potential for disruption across a region but it cannot give specific detail on, for example, a particular road or rail network. The warnings, coming from a single and consistent source, are, however, useful to end users familiar with the local infrastructure to help them mitigate the impacts of severe weather.
2. Climatologically, we define winter as covering the months of December, January and February, though it should be noted that others will naturally apply differing timescales according to their operations, responsibilities and interests. In 2010 winter conditions began early with an intense period of cold weather and some notable snow events towards the end of November. This continued into December with further snowfall and sub-zero temperatures and, until the Christmas period, we experienced only a few days respite from the intense cold around the middle of the month. Nationally, this has been the coldest December in a data series starting in 1910 and the whole period was characterised by at least nine major snow events.
3. Vital as early warnings of severe weather are, rapidly evolving and complex situations require expert and immediate interpretation so that ongoing advice, through direct and full discussion, is provided to end-users. In this way emergency responders and Government can make the best decisions possible in deploying resources to ensure speedy, efficient and targeted response. The Met Office team of PWS Advisers was set up to specifically work alongside the emergency response community to assist both during a severe weather event and in the following recovery period. This is particularly effective when multiple hazards threaten life and infrastructure. We also routinely provide advice based on robust science directly to CCC and COBR.
4. We embedded an experienced forecaster within DfT from 17 to 23 December to offer additional short and medium term contingency planning support during the traditionally busy travel period in the run up to Christmas. The forecaster was able to add value to input to Ministerial briefings and field questions on the spot from officials within DfT and the Secretary of State’s office. Our forecaster also worked closely with Salt Cell during this period and continued to brief the meeting from Exeter after returning to Met Office headquarters.
5. This approach of embedding experts within other Departments and organisations during an emergency has shown great value in the past – with the Institute of Animal Health and DEFRA during the foot and mouth outbreak of 2001, and hosting an EA hydrologist during the floods of 2007, for example. It’s an approach that also works for business as usual operations - for the last few winters, for example, we have had experienced weather forecasters embedded in the Highways Agency’s National Traffic Control Centre (NTCC) supporting their operations from there.
6. Although a seemingly small change, there is no doubt that, whether in emergency situations or supporting business as usual problems, both parties benefit from this type of direct access and we are working with DfT to consider how we may continue this level of support in the future.
As well as operating the NSWWS and generating regional and national 1-5 day forecasts, we provide forecasts out to 30 days to the public. This latter service was established as a direct result of feedback in which we were told that long-range probabilistic forecasts over a wide region are of little use to the public and that a more deterministic forecast on a shorter timescale would be of greater benefit. Our 30 day forecasts did indeed prove useful in accurately highlighting the cold weather from early November.
8. In order to lessen the burden on the UK taxpayer, the Met Office also operates in a highly competitive commercial arena and bids for contracts in the same way as other suppliers of meteorological services. In the context of winter services to the transport sector in England and Wales, we currently provide services to a number of local authorities and commercial aviation operators, London Underground, First Scot Rail , Eurotunnel and to BAA. In December we were asked to provide input to the daily teleconference run by NATS.
How we did
9. The Met Office faced enormous challenges during November and December, especially when required to forecast at the limit of our capability for a prolonged period of finely balanced conditions: to provide accurate forecasts, particularly of snow amounts and pinpointing where this would fall; to consistently communicate the key hazards to all audiences – from Government and emergency planners and responders, to the public - across the widest range of media possible. Especially important was the timescale of our warnings – the emergency response community typically require 1-2 days lead time for effective mitigation planning,
10. In assessing our performance during the severe weather, we wanted to take not just a quantitative approach but to look at the quality of our warnings and services with respect to relevance and usefulness. We set out to collate evidence in terms of: did we forecast what happened, did we communicate this effectively and did our forecasts and warnings add value to the end user?
11. The combination of a more traditional empirical verification of forecasts and warnings, feedback from customers and a public survey gave good evidence that we performed very well in accuracy of forecasts, consistency, clarity of information and advice and in providing the warnings on useful timescales. We also learned some good lessons which we intend to take forward to inform a review of the NSWWS.
12. We provided the Cabinet Office with a routine update to the rolling 3 month long range forecast and a specific update on the chances of early onset weather conditions on 25 October. At this point we highlighted an increased risk of a cold and early start to winter conditions and from then we provided Cabinet Office and DfT with our Chief Forecaster daily briefings. These were also shared with BAA from late November. At the beginning of November our website gave the first indications to the public of the onset of a cold spell from the end of that month.
13. The first of the advisories issued under the NSWWS went out on 22 November. Over the entire period we issued three Emergency Flash, or Red, warnings alongside numerous warnings and advisories on a daily basis for both snow and ice. Our entire team of Public Weather Service Advisors were mobilised and worked closely with local authorities and the emergency response community. Regular briefings were supplied to Minsters and Officials and key customers and stakeholders. A key element in the feedback we received is the fact that the forecasts provided to customers, the warnings disseminated through the NSWWS to the public and the emergency response community, and the 30 day outlooks are all generated from a single source and are backed up by authoritative and consistent advice.
14. Feedback from responders and public surveys indicate that we were successful in the clarity and relevance of our messages. In surveys conducted this winter through the Central Office of Information (COI) by GFK, over 90% of the general public who said they received Met Office warnings found them both useful and accurate.
15. We were also able to maintain a heavily trafficked web and mobile platform during the period which saw 145 million page views in December from nearly 13 million visitors. Our own weather desk took over 16,000 calls in the month before Christmas – an answer rate of over 95%.
16. Although evidence shows we performed well in modelling and applying expert interpretation to produce accurate forecasts for a sustained period over the entire UK, and our communication of these hazards was good – we are committed to using the experience to ensure our services develop in line with user requirements:
17. We are working with DfT to consolidate and build on the embedded forecaster service we provided during this period of severe weather to ensure a robust service is in place to support any future emergencies.
18. Seasonal forecasting in the UK, although still in its infancy, already provides a useful planning tool to Government and to those sectors who are experienced in routinely managing risk based on a probability of outcomes. We are committed to building on the encouraging successes evidenced in some areas of the world, notably in forecasting the hurricane season and in climate vulnerable areas such as Africa, in developing this cutting edge science so that these forecasts become as relevant and useful as our short term forecasts and longer term climate change predictions.
19. The extent and speed of this development is of course dependent on the availability of resources – particularly in supercomputing power to enable modelling to incorporate new science and understanding.
20. We have provided, through the Government’s Chief Science Advisor, Professor John Beddington, an initial assessment of the likelihood of severe winters in the next 20-30 years. We are now working closely with leading scientists in academia across the UK to expand on this research in order to provide a fuller and more comprehensive assessment.
21. We are planning further development to the NSWWS. The current method of providing colour coded states at differing lead times was introduced shortly after the floods of 2007. They have proved themselves to be much more comprehensive for end users and provide a valuable planning tool for emergency planners and responders as they can monitor increasing or decreasing risk over a longer lead time.
22. However, these warnings still focus on what weather is coming, where and when. During December 2010, we became acutely aware of the need for warnings in a complex and finely balanced situation, as this was, to be expressed more in terms of impacts – i.e. to close the gap a user may have between us highlighting a risk of extreme weather and them understanding how that will affect their lives/planning/response etc. Throughout this period, warnings reflected impacts as much as possible and in particular media broadcasts highlighted the expected impacts. We intend to take this forward during 2011, thereby ensuring that our Public Weather Service remains in step with what users need and expect from a national met service consistently placed in the top three operational forecasters in the world.
Annex A: breakdown of the major snow events, with comments on our warnings for each
Annex B: chart showing the comparison of December 2010 across a national series from 1910
Annex C: background paper exploring the causes behind the severe weather experienced not just in the UK but globally in 2010, written by our Chief Scientist and freely available on our website
Annex A: Summary of snow events and warnings
Annex B: UK mean temperature for December
Annex C: The cold end to 2010 - a global perspective
It certainly seems to have been a year of headline making weather. In the summer of 2010 many meteorologists were asking what could be the causes behind the Russian heatwave and the floods in Pakistan and China. At the end of the year it was the UK’s turn with many areas experiencing heavy snowfalls and very low temperatures; while on the other side of the world eastern Australia saw flooding of "biblical proportions". But as with the summer’s extreme weather conditions, the early winter’s snow and ice in the UK and the extreme flooding in Australia are just as much a part of the natural variability of our climate. In the UK, although this winter’s weather is very unusual - especially after a run of mild winters in the last 20 years or so - it is not unprecedented.
Last summer, the jet stream - the current of air in the upper troposphere that circles the northern hemisphere and guides our weather systems - was very disturbed with large amplitude troughs and ridges moving warm air northwards and cold air south. This winter we have seen similar large disturbances in the position of the jet stream and some very large temperature anomalies as a result. There have been persistent signals of substantially above normal temperatures over Greenland and Chukot and of below normal temperatures over Canada, into Florida, and over central Russia and Western Europe.
Surface temperature anomalies (0C) for December 2010 (from International Research Institute).
So what is driving the formation of these large amplitude troughs and ridges? Since the autumn, the global circulation has been in the grip of arguably the strongest La Niña event for over a century. La Niña, the cold counterpart of El Niño, brings colder water to the surface of the tropical east and central Pacific and confines the warmest ocean waters to the West Pacific. The direct consequences for tropical rainfall patterns have been profound.
Global rain and snow anomalies for December 2010 (from International Research Institute).
We also know there is a link between La Niña and colder winters over Western Europe (including for us, here in the UK) as it can produce a negative North Atlantic Oscillation (NAO) pressure pattern. The effect of this is to shift the Atlantic jet stream southwards with higher pressure building over Greenland. This means that in La Niña years our weather is more likely, although not always, to come from the colder and drier north and east as it has in 2010, rather than the milder and wetter south and west. However, the intensity and persistence of the blocking weather pattern experienced in late 2010 was quite exceptional, so it is very likely that other factors will have contributed.
Diagrams showing the atmospheric circulation patterns associated with positive and negative modes of the North Atlantic Oscillation (NAO) along with the related sea surface temperature patterns. The time series (right) of the recorded NAO index (red positive, blue negative) showing large variability and the tendency over recent years for negative phases. (http://www.cpc.ncep.noaa.gov/products/precip/CWlink/pna/nao.shtml).
One such additional influence could be the strength of the negative phase of the NAO [or the pressure difference between the Azores and the Norwegian Sea]. We know that there is considerable variability in the NAO and that on longer timescales of up to a decade or more variations in ocean temperatures influence the weather to either positive or negative NAO patterns. At the moment, ocean temperature anomalies show a ‘warm-cold-warm’ sea surface temperature distribution from north to south across the Atlantic Ocean. This pattern has been in place for some time and it is one that encourages a negative phase of the NAO, and a blocked pattern in our weather
Other factors that may be influencing our weather include the declining extent and thickness of Arctic sea-ice and variations in the radiation from the Sun. These factors are very much at the cutting edge of our research, but there is increasing evidence that both may have contributed to the negative North Atlantic Oscillation pattern that we have experienced this winter and last winter.
What is clear from our analysis is that the cold early winter we have just experienced and the other recent extreme events around the world such as the Queensland and Sri Lankan flooding can be explained by the natural variations in our climate, especially La Niña. Our climate always has varied and will continue to vary naturally. Furthermore the range of that natural variability is much greater than the longer-term warming we have seen over the last 150 years or so. So we should not be surprised to experience cold winters; nor do a few cold winters signal the end of global warming.
2010 has just been confirmed as one of the warmest years on record, and even though our planet is warming, lots of other factors come into play to determine what our weather will be like at a regional and local level from one year to the next. Broad scale influences on our winter weather include atmospheric pressure systems that define where our weather comes from, Arctic sea-ice conditions, Atlantic Ocean sea surface temperatures, El Niño and La Niña in the tropical Pacific, and variations in the sun’s output.
Our understanding of some of these aspects is still immature and some are not well represented in contemporary climate models. This means that on decadal timescales it is difficult to predict the likelihood of severe winter weather conditions going forward. That being said the accuracy of our weather forecasts has never been better. As our understanding grows of the range of possible drivers for our climate and we develop improved climate models so that we can predict further ahead, so we hope to provide confident, robust and actionable advice to the government and the public in the future at longer time scales.
 Significant improvements were introduced to the NSWWS following the 2007 flood events to provide better clarity and longer lead times for getting information to end users. The warnings issued under the NSWWS fall into three categories: Advisories, issued daily as routine and showing our changing confidence in the potential for extreme weather; Early Warnings, issued when confidence reaches 60% and the Flash Warning which is issued at a confidence level of 80%.
|©Parliamentary copyright||Prepared 22nd February 2011|