Official blog of the Met Office news team

Following a minor Sudden Stratospheric Warming (SSW) event in January, the Stratospheric Polar Vortex (SPV) has now recovered. Our forecasts for the coming week also suggest that conditions will become milder. So why does there continue to be speculation that cold weather is on the way for the UK with snow and ice for many?

The latest forecasts are showing that a major SSW is now likely to take place. The recent minor SSW weakened the SPV and it’s now likely to collapse and reverse in the middle of February.

A major SSW often makes the jet stream meander more, which can lead to a large area of blocking high pressure over northern Europe, including the UK. This blocking high pressure can lead to cold, dry weather in the north of Europe, including the UK, with mild, wet and windy conditions more likely for southern areas of the continent. However, this is not always the case and impacts on UK weather can also be benign when an SSW occurs. 

Prof Adam Scaife, Head of Long-Range Forecasting at the Met Office, said: “There is now over 80% chance of a major SSW occurring. Although the impact will become clearer nearer the time, any effect on UK weather is most likely to occur in late February and March.”

Other factors can also impact the UKs weather in winter such as the Madden Julian Oscillation which is now also tracking towards a state that favours a cooler spell in late February.     

In the meantime, it is important to remember that the occurrence of an SSW does not always equate to a ‘Beast from the East’ type scenario even though this happened in 2018. For example, in 2019, there was an SSW but little impact on the weather for the UK and NW Europe.    

The current extended range forecast for mid-February suggests that the most likely scenario is for broadly changeable weather with westerly conditions and influxes of wind and rain at times, particularly in the northwest. Temperatures are likely to be around average through mid-February.  We will be updating forecasts with a close view on late February and early March as the SSW unfolds.

This month we’re exploring the climate theme of ‘water security’. Water Security, as defined by the World Meteorological Organization (WMO), refers to ‘a population’s capacity to safeguard sustainable access to adequate quantities of acceptable quality water.’ 

At the Met Office, we work alongside organisations in the water sector to help support resilience and planning through the provision of weather and climate data and expertise. In this blog post, we’ll explore the link between climate change and water security and learn about some of the work that we have undertaken in this space. 

Climate change and increasing heat drought events 

In November 2022, the WMO published its first State of Global Water Resources report which assessed the effects of climate, environmental and societal change on water resources. At the time, WMO Secretary-General Professor Petteri Taalas said, “The impacts of climate change are often felt through water – more intense and frequent droughts, more extreme flooding, more erratic seasonal rainfall and accelerated melting of glaciers – with cascading effects on economies, ecosystems and all aspects of our daily lives. And yet, there is insufficient understanding of changes in the distribution, quantity, and quality of freshwater resources.” 

As the climate continues to change as a result of greenhouse gas emissions, we are seeing increasingly hot, dry conditions in the UK and globally. 2022 has recently been confirmed as the hottest year on record for the UK with an annual average temperature of over 10°C, and this trend is projected to continue in the future. July 2022 saw the driest month since 1935 for England as a whole, and the driest on record for East Anglia, southeast and southern England, with the UK seeing just 56% of its average rainfall for the month. As a result, drought was declared by the Environment Agency in many parts of the UK in August 2022. 

Impacts of drought on water security

Rising temperatures and increasing instances of drought events could have significant implications for water security. In 2020, the Environment Agency published a National Framework for Water Resources which showed that under the current trajectory, the amount of water available in England could be reduced by 10-15%, with some rivers seeing up to an 80% decrease in water during the summer months.

An Environment Agency spokesperson said: “Our climate is changing; the summer of 2022 demonstrates this. Action must be taken now, to ensure we are ready for managing droughts in the short term. As our National Framework for Water Resources shows, we need to develop new sustainable long-term supplies of water and for people and business to use water wisely to protect our precious water resources. In the short term the Government, Environment Agency, water companies, farmers, environmental and angling groups continue to work together through the National Drought Group to balance water needs and manage impacts if we experience prolonged dry weather again.” 

How can we respond to threats to water security?

Climate change projections indicate that rainfall patterns in the UK will shift, which could present additional water security challenges to regional water providers. It is vital that water companies have access to the latest research, advice and accurate meteorological projections, so that they can effectively manage water supplies in their area. 

The Met Office has been working with water company Anglian Water to support water resource management for the East Anglia region, one of the areas which is projected to be most affected by water scarcity. 

By using novel approaches and new datasets, the Met Office worked alongside Anglian Water to strengthen their understanding of drought risk – both for today and for the future, in a warmer world. This improved understanding enables Anglian Water to enhance their resilience to future drought events. 
 
Dr Joe Osborne is an Industry Consultancy Manager at the Met Office. He said: “As part of this work, the Met Office Industry Consultancy team has developed a statistical model to enhance Anglian Water’s understanding of extreme events. The model is used to generate 1,000 alternative realisations of a 105-year historical period (1914-2018), with daily outputs on a 5km grid over the region. The output validates rainfall and drought behaviour well, providing confidence in the suitability our datasets for future scenario planning.” 

At the Met Office, we provide a range of weather and climate services to help support resilience, efficiency and forward planning for the water sector. This includes investigations into historical instances and future projections of drought, river flow analysis and consultancy around climate change projections. With meteorological expertise and knowledge of the latest advances in water resource planning, our consultants can help the water sector to mitigate the impact of weather and climate, adapt to changes and capitalise on the potential benefits of future weather events (for example, average increases in winter rainfall could improve resilience of supply with the appropriate resource management solutions). 

Geoff Darch, Head of Supply Demand Strategy for Anglian Water concluded: “Understanding the investment decisions that are required to protect our customers against future weather and climate extremes is paramount. We need to make decisions based on robust and defendable science. Undertaking this challenging work with the Met Office means that data-driven investments are made where appropriate, ensuring that we better protect our customers and the environment we serve in the face of an ever-changing climate.”

The indications are that we could see some colder weather next week, but how cold and are we facing another Beast from the East?

It looks like we will start to see a change from the current mild conditions to a colder spell from the middle of next week (w/c 6^th Feb), especially for parts of the south and east of England.

High pressure is expected to build and settle over or near to the south of the UK allowing colder air from continental Europe to cross the country. This high-pressure system will act to block the predominantly wet and windy weather from the Atlantic from crossing the UK, resulting in a spell of dry and more settled weather. The north and west of the UK is more likely to retain milder conditions and stay relatively unsettled.

It is most likely this cold spell will be typical of early February, with some frosty nights and colder days, but with daytime temperatures in mid or low single figures, lowest in the south and east.

However, there is a small chance – around 15% – that we may see an even colder, longer-lasting, and more widespread spell of very cold weather with the possibility of some impacts from wintry weather. This scenario is dependent on just where the high-pressure settles in relation to the UK.

At the moment, it looks we will see a gradual return, within just a few days, to milder conditions as wet and windy weather pushes across the country from the north and west. However, if the colder scenario does develop, the return to milder and unsettled weather could be slower for the south and east of the UK.

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2023 has started with a January of marked contrasts, which has resulted in overall near-average figures for many of the UK’s weather statistics.  

According to provisional Met Office figures, the one relatively consistent visitor was sunshine with England having its second sunniest January on record in a series which goes back to 1919. England had an average of 77.6 hours of sunshine, failing to top the record breaking 80.7 hours seen in January 2022.

The UK also had its third sunniest January on record, with an average of 63.1 hours of sunshine. 

Contrasting temperatures 

The month’s temperature figures were marginally warmer than average, with a period of mild weather at the start of the month followed by a cold spell. Later in the month, temperatures returned nearer to average, albeit with the north of the UK seeing the highest temperatures in the month.  

Dyce, in Aberdeenshire, had January 2023’s highest temperature with 15.8°C on 24 January, though partly thanks to the Foehn effect, it’s not uncommon for Scotland to see the highest temperature recorded in a winter month.  

Drumnadrochit, Inverness-shire, posted the lowest daily minimum temperature of the month, with –10.4°C the lowest temperatures got in January.  

These contrasts helped to bring the UK mean temperature for January to 4.4°C, just 0.4°C above average.

The National Climate Information Centre Manager Dr Mark McCarthy said: “After a record-breaking 2022 for heat in the UK, January has started this year with a near-average month for temperature, which masks a period of cold weather in the middle of the month, as well as some mild weather at the start of the year. 

“The month’s weather has largely been flipping from westerlies with milder air and rain to influxes of northerly air with cold and dry weather, which is not unusual for a UK winter. What this results in is fairly typical January temperature and rainfall statistics when averaged across the whole month.” 

Fluctuating rainfall 

Similarly to the temperature figures, January 2023 saw near average rainfall for the UK with 125.7mm falling, 3% more than average.  

Rain in January generally coincided with the mild air and a dominant westerly regime early in January.  

Wales has seen 25% more rain than average, with 194.7mm falling in the month and England 9% more than average with 90.5mm.  

Northern Ireland and Scotland both saw less rainfall than average, with 95.2mm (83% of average) and 171.5mm (96% of average) respectively.  

Sun shines for January 

January sunshine was in good supply, though not enough to trouble 2022’s record January sunshine figures for England.  

The UK had its third sunniest January on record in a series which dates back to 1919, though much of the UK experienced a sunnier than average month.  

Western and northern areas of Scotland got the least in the way of sunshine, with the Western Isles, a location not prone to January sunshine, having a fairly dull month, though not record-breaking.  

In contrast, Berwickshire was one of a number of counties to see record levels of January sunshine, with many seeing more than 50% more sunshine hours than their averages for the month.  

Dr Mark McCarthy continued: “One notable feature of January’s weather was the sunshine, with plenty of clear spells of weather, though not enough to trouble any national records.  

“The far northwest might feel a little short-changed with sunshine duration, as well as western areas of Northern Ireland thanks to some more persistent cloud and rain moving in off the Atlantic in January.” 

A typical winter so far 

Two months into meteorological winter, the statistics are remarkably near average for rainfall and sunshine so far.  

At this point in the season, you’d expect 68% of winter’s average rainfall and sunshine. At the conclusion of January, both of these are at 69%, though there have been obvious fluctuations, as is normal in a UK winter.  

So far, there has been 236.7mm of rain for the UK in winter, though areas in the south of the UK have generally seen more rain compared to their averages.  

During winter, rainfall and temperature can be closely linked, with wet weather generally linked to mild temperatures when Atlantic weather systems bring milder more unsettled conditions, and dry weather is associated with colder conditions when the UK is under the influence of air from the north or east. 

During the period between 18th December and 15th January, the UK received over 162.6% of average Jan rainfall. During this time Wales received 212.6%. This was certainly a notably wet winter period, but not record breaking, and not as wet as equivalent spells in February 2020 or Jan 2016.   

Winter so far has been slightly cooler than average for the UK with the mean temperature from December and January sitting at 3.6°C, which is 0.5°C cooler than average.

In this latest blog on our January climate theme of health, we explore the links between climate, air quality and our health. This blog has been written by Met Office scientists Steven Turnock, Fiona O’Connor, Paul Agnew and Matthew Hort.

A complicated, interconnected picture

Poor air quality is one of the leading environmental risk factors to human health, with an estimated 4 million annual premature mortalities worldwide and approximately 30,000 annual premature mortalities in the UK attributed to long-term exposure to outdoor air pollutants. Elevated concentrations of certain pollutants can also lead to other environmental impacts, including poor visibility, reduced crop yields and damage to buildings and vegetation. Poor air quality episodes can cover geographic areas from a single city to larger regions, and normally last from days to weeks.

Certain air pollutants (such as ozone (O₃) and fine particulate matter (PM_2.5)) are also ‘radiatively active’, which means they can influence the climate by providing additional warming or cooling. These pollutants are identified as short-lived climate forcers (SLCFs) because they reside in the atmosphere for a short period of time (less than 1 year), meaning their impact on climate is also shorter (within 2 decades) than long-lived greenhouse gases such as carbon-dioxide (CO₂).

Climate change can also influence the concentrations of air pollutants, with warmer temperatures projected to have detrimental impacts on surface air quality across several regions (e.g., South Asia) in the future.  It is also expected to increase the frequency of hot and cold weather events, which may also adversely impact our health. As shown in the graphic below, this leads to a complicated, interconnected picture between health, air quality and climate, where future changes to one can strongly impact the other.

What we are doing to better understand the interactions

Within the Met Office, we undertake research on air quality, both at local scales over days to weeks, and at the global scale for periods of decades up to 100 years into the future.

Scientists in the Met Office Hadley Centre have been working on numerous collaborative initiatives, including the Climate Science for Service Partnership China (CSSP China) project (supported by the UK Government’s Newton Fund), to better understand how climate and air quality interact. A large part of this work contributes to the World Climate Research Programme’s 6^th phase of the Coupled Model Intercomparison Project (CMIP6), which seeks to provide a better understanding of the past, present and future climate.

Our scientists have been analysing what the different future climate and air pollutant pathways mean for SLCFs and their impact on both climate and air quality. Our research shows that significant reductions in all air pollutants are beneficial to climate, air quality and human health, whereas there are some negative impacts on air quality and health across regions such as Africa if there are not future reductions in air pollutants. Therefore, it is important to consider the impact on air quality and health from future changes in these SLCFs.

Methane is another important SLCF. It is the second most important greenhouse gas after carbon-dioxide, albeit shorter lived in the atmosphere, and it contributes to poor air quality globally by forming ozone in the lower atmosphere. Efforts to control atmospheric methane may help to reduce the near-term future rate of warming, along with substantial reductions in surface ozone – providing clear climate and air quality benefits.

A pledge agreed at the 2021 United Nations Climate Change conference (COP26) to reduce global methane emissions from human activity by 30% from 2020 levels by 2030, has the potential to deliver benefits to climate, air quality and human health. Analysis from the United Nations Environment Programme’s Global Methane Assessment suggests that the 30% emissions’ reductions could result in 0.3°C of avoided warming over the next two decades.

Corresponding decreases in surface ozone could reduce premature deaths from poor air quality by over a quarter of a million and prevent more than half a million visits to accident and emergency departments from asthma globally every year. Using new methane modelling capability, the Met Office is working with partners in the UK academic community to quantify these outcomes. We will also assess how changes in emissions other than methane may affect the climate, air quality and health impacts.

Our local air quality forecasts

The Met Office produces a 5-day forecast of the Daily Air Quality Index (DAQI) for the UK. The DAQI is a representation of pollutant concentrations time-averaged throughout the day and gives an indication of overall air quality. The forecast is provided to Defra, as the government department responsible for air quality in the UK, for display on their website, and the data is also used in the Met Office weather app. The air quality forecast is made by combining a computer model for atmospheric chemistry and aerosols with recent observations from the Automatic Urban and Rural Network (AURN) of air pollution monitors. The observations are also used to check the accuracy of the forecast, as illustrated below.

Improving the understanding of air quality and health

The Met Office is involved in several research and development projects to improve our air quality forecast, and to further understand the links between air quality and human health. A core activity is the development of a new modelling framework which will permit an improved forecast resolution.

Another research topic, funded by the Clean Air Programme and delivered by the Met Office, concerns the production of a UK air quality ‘re-analysis’. This will use past observations and a modern computer model to provide estimates of hourly pollutant concentrations from 2003 to the present day for the whole of the UK. When compared alongside health records of the UK population, this new dataset has the potential to provide insight and improved understanding of the impacts of poor air quality on human health across different regions and following episodes of elevated pollution levels.

The future of air pollution and health

Poor air quality continues to be an important environmental issue, posing a considerable threat to our health both in the UK and around the world. The future direction of travel, in terms of human-induced emissions, could either worsen or improve this situation and have unintended consequences for climate. The Met Office is at the forefront of research that looks at improving our understanding of the interaction between health, air quality and climate. This will help us to make better predictions of air quality across a wide range of spatial (local to global) and temporal (days to decades) scales, enabling us to help people make better decisions to stay safe and thrive.

You may have heard speculation about a Sudden Stratospheric Warming (SSW) and that a ‘Beast from the East’ is on the way with freezing conditions and widespread snow.

Is there any truth behind the headlines and what can we say about the weather for the coming month?

Well, a sudden stratospheric warming is underway, but only a minor one. The warming is expected to peak towards the end of January. The strong westerly winds high over the Arctic, called the stratospheric polar vortex, have weakened and the vortex is partially collapsing. However, the polar vortex has been unusually strong so far this year and although there has been a minor SSW, the winds are expected to rebound quickly, recovering to speeds around normal for the time of year.

It can take a week or more for any impacts from an SSW to work its way down through the atmosphere and to have any influence on the weather in the UK. However,  not all SSWs lead to cold weather and widespread snow for the UK, for example, the SSW in February 2018 led to the ‘beast from the east’ whereas the SSW in January 2019 had no significant impact for the UK weather, in fact, it stayed mild for the rest of the winter.

Forecasts at present show only minor impacts are expected and that other factors, such as La Nina and the Madden Julian Oscillation are also likely to influence our weather over the next few weeks. Our predominant weather is expected to come from the west with wet and windy periods. The unsettled conditions are expected to impact the north and west of the UK at the start of February as frontal systems push south across the country, weakening as they go with parts of the south remaining largely dry. Temperatures will stay around average for many.

Changeable weather is likely to continue through to the second half of the month bringing rainfall, heavy at times, again to the north and west. The south and east are expected to see some drier and brighter periods with some lighter rain. A brief spell of more settled conditions is possible in the middle of the period, bringing a greater risk of overnight frost and freezing fog, especially under clear skies with light winds. Temperatures are expected to be generally at or slightly above average, although a brief colder spell remains possible.

The Met Office will continue to monitor the situation and, as ever, keep up to date on our forecast pages and warnings pages and by following us on Twitter and Facebook. Our app is available for iPhone from the App store and for Android from the Google Play store.

Not so long ago, we might have looked forward to a heatwave, particularly here in the UK – a chance to enjoy the sunshine and balmy evenings.  Heatwaves, however, can cause a range of health problems. If you cannot find somewhere cool or off-load the excess heat from your body it can be very serious indeed and the extreme heat seen in recent years, such as the July 2022 heatwave, has resulted in a significant number of excess deaths.  

Keeping cool is particularly problematic when the heat is ‘humid’. This is when the air contains lots of water vapour. High humidity makes it very hard for sweat to evaporate from our bodies which means that we cannot cool down. For people working outside or in overheating buildings, especially where the work is physically demanding, humid heat is a big problem. The world is getting warmer, and many places are also seeing increases in water vapour and the resulting humidity. 

Researching exposure to high humidity and dry heat events 

The distinction between humid heat and dry heat is a relatively new area of research. What we do know is that dry heat events can be much ‘hotter’ than humid heat events, and at present appear to be more lethal, or at least high temperature shows a stronger relationship with mortality than high humidity. However, humidity plays an important role in health and ‘productivity’. People ‘feel’ worse when the humidity is high and cannot maintain physical activity at the same level. This could mean slower progress in construction, lower yields for manual food harvesting or fewer completed tasks within a factory, which have economic as well as health impacts. 

Climate change and heat health is the focus of some of the research being undertaken by the Weather and Climate Science for Services Partnership (WCSSP) programme, supported by the UK Government’s Newton Fund. A CSSP China project has been developing a global dataset of extreme wet bulb temperature (T_w) and air temperature (T) – HadISDH.extremes – that enables us to study the current level of exposure of regions to both high humidity heat events and dry heat events and measure the rate at which such events have increased in severity and frequency over the last 50 years. Wet bulb temperature is a common way of measuring humidity, is less complex than other measures of heat, and provides a critical threshold of 35°C beyond which the human body cannot survive for long. This is because human skin temperature is around 35°C. If the wet bulb temperature and skin temperature are both 35°C, sweating no longer works because the air next to the skin cannot hold any additional water and the body cannot cool down. In reality, even physically fit people struggle to undertake normal light activity when the wet bulb temperature gets within a few degrees of this threshold.  

The HadISDH.extremes dataset allows us to identify those regions already experiencing very high wet bulb temperatures. Figure 1 shows that 31°C has already been reached several times over much of the tropics. This new dataset also allows us to investigate the two different types of events explicitly and explore what might be termed ‘stealth heat events’ where the air temperature might not be excessively high, but the wet bulb temperature is high enough to affect health and productivity. 

Further global research 

Other WCSSP programme research is also focused on heat health including:  

• Researching which weather patterns bring humid heat over China, a region where high humidity heat is commonplace already because the hottest season also tends to be the wettest. Climate change will make this worse;  
• Producing a global gridded dataset of ‘sector specific’ indices related to temperature such as ‘Heating Degree Days’, a ‘Warm Spell Duration Index’ and ‘Excess Heat Factor’;  
• Using satellite Land Surface Temperature to produce an interactive high resolution gridded dataset of temperature indices and urban hot spots; 
• Quantifying the current and future population exposed to high heat over Brazil, for present day and for a range of potential futures depending on future greenhouse gas emissions. This data has also been used globally; 
• Exploring the predictability of heatwaves and their corresponding impact on population relating to weather patterns over South Africa; 
• Investigating levels of solar and infrared radiation on people from surrounding building layout and fabric, which can significantly affect the heat impact in warm weather; and 
• Assessing the contribution of human-induced climate change to heatwaves and specific heat events, including how much more likely they become.

As our climate continues to change, research into health impacts will be critical to enable appropriate adaptation measures to be put in place. And by reducing emissions, we can minimise the worst impacts of climate change.