WIREDGOV

There is lots of speculation about the potential for up-and-coming heatwaves, extreme temperatures or drought for this summer. The Met Office Contingency Planners 3-Month Outlook is often cited as a source for some of this conjecture, but can it really be used to tell us what the daily weather has in store for the coming months? 

What does our three-month outlook say? 

There’s always a lot of interest in predictions for the summer – how hot will it be, how much rain will we get? Long-range predictions, including the Contingency Planners 3 Month Outlook, are at the cutting edge of meteorological science but are unlike weather forecasts for specific days. We have to acknowledge that the chaotic nature of our atmosphere means it is not possible to predict the weather on any particular day months ahead. With many variables there are unavoidable limitations to what we can predict, particularly during the summer months when the influence of global weather drivers on the UK is small so confidence in Outlooks at this time of year is lower than, say the winter.  

Long range forecasts assess global weather patterns and their potential to influence the type of weather in the UK over the course of a season, dry, windy, hot etc. Factors in the global climate system act to make some outcomes more likely than others, because of this we can make a prediction, showing a spread of possible outcomes. We present the likelihood of each outcome using a range or percentages. As a result, this type of forecast assesses likelihood and risk, but does not predict specific weather, such as the dates of a potential heatwave or exactly how high temperatures may reach on any given day. 

The Outlook gives the percentage chances of the temperature, rainfall amounts and wind speeds varying from their 3 monthly averages for the UK as a whole. The current Outlook for June, July and August gives a 45% chance of the season will be hot with a 50% chance of it will be near average. Whilst it gives a 65% chance of near average rainfall with a 15% chance of a dry season. 

But what do these figures mean for our weather? 

The elevated risk of a warmer than average summer this year, is consistent with wider global warming trends and the UK’s warming climate, after all, four of the five warmest summers on record for England have occurred since 2003. Nevertheless, looking at the figures you can see a near average summer is also still a possibility.   

Whilst there are no strong signals for rainfall this summer, whatever the outcome, figures for the UK as a whole can hide big regional variations. Therefore, even if rainfall turns out to be near average for the country overall, we could still see some localised impacts from heavy rainfall or regional droughts. 

What is behind the summer predications? 

Even though the influence of global weather drivers on the UK is small during our summer months, there are a few considerations relevant to the current Outlook.  

Firstly, long-range prediction centres around the world are in good agreement in their forecast for northern Europe this summer with signals for high pressure to the north of the UK and low pressure to the south. At this time of year, high pressure is usually associated with warmer-than-average weather.  

With the waters warming in the tropical Pacific Ocean there is consensus an El Niño will develop later this year. However, while fundamentally important globally, the impacts of El Niño on UK summer conditions are modest. 

And finally, there is the global warming trend. The effects of human-induced climate change are already being felt on UK’s summer with temperatures in excess of 40C recorded for the first-time last summer and an increase in the frequency, duration, and intensity of extreme heat events over recent decades. Meanwhile, our Global Annual to Decadal Climate Update, issued with the WMO,  has stated there is a 98% chance that one of next five years will be the warmest year on record for the globe. Like in every year the chance of temperatures reaching 40C in the UK is very low and our forecasts suggest this is still the case for the coming summer. However, with an increased chance of above average temperatures we are likely to see some very hot days this summer with heatwaves and hot weather impacts are possible. 

Why do we produce this type of Outlook? 

The science of long-range forecasting is at the cutting edge of meteorology and the Met Office is leading the way in this area. We continue to demonstrate improvements in this type of forecast, identify sources of predictability and build better prediction systems.  

The 3-Month Outlook is produced for planners in government and business who make risk-based decisions. These users are aware of the complexities of this type of Outlook and include those factors in their decision-making process. It gives a spread of outcomes based on the more probable prevailing weather patterns giving the percentage risk of each occurring and must be used in the right context. The uncertainties are often quite large but enable businesses and governments to take weather related decisions, make choices with more confidence, and help the economy and population make better decisions to stay safe and thrive. 

If you are looking for a clue on what the weather will be like in the coming days or weeks you should check out our 30-day outlook (scroll to the bottom of the homepage) which outlines the general type of weather we’re likely to see in the UK over the next month or our 7 day forecast which gives a daily detailed location based forecast and perhaps take any speculation in the media with a good pinch of salt.