Spring swing brings colder weather and snow

We’ve had some very mild conditions this week with welcome sunshine pushing temperatures into the high teens. However, in a classic spring swing, colder weather is on the way as we head into the weekend.

By Saturday, we will see a return of easterly winds which will bring in much colder air from Scandinavia and Eastern Europe. Snow is expected across some eastern parts of the country over the weekend. By the start of next week, most of the UK will see daytime highs in low single figures with some frosty and icy nights.

So how unusual is it to see cold weather and snow in March?

The UK’s weather is very much at the mercy of where our winds come from, and throughout spring we can see sudden swings in the weather conditions. If we look back to last year we had very high temperatures at the end of March as the UK was under the influence of high pressure and light south-easterly winds. This year, this week’s south-easterly winds are now giving way to colder easterlies.

What about snow?

Statistics show that snow is more likely in March than around Christmas. As we know, heat from the sun increases as we head towards summer and this can lead to some interesting weather in March. With more heat from the sun the ground warms up more quickly and gives very unstable air, which can lead to a greater number of showers. Warmer air also holds more moisture so showers can give heavier rainfall. If this combines with cold air we can potentially see some heavy snowfall. However, easterly winds tend to be dry and so substantial snow fall is not expected over the next week.

As always, the Met Office will be working with different agencies to keep Britain on the move, and to keep people safe and well during periods of cold weather. The latest forecasts and warnings can be found online, through our mobile apps and through TV and radio broadcasts.

Cold weather clue in upper atmosphere

During a period of colder than average weather across northern Europe in February this year we issued a blog discussing potential causes – including changes in circulation high up in the atmosphere.

We also discussed these disruptions, known as Sudden Stratospheric Warmings (SSWs), in a news release about advances in predicting these events in our long-range guidance for winters.

SSWs happen when the usual westerly winds in the stratosphere, between 10km and 50km up, are disrupted, break down and even reverse.

This signal can then burrow down to the lower atmosphere over the course of a few days to a few weeks, thereby reducing the westerly winds at lower levels.

Figure illustrates how reversal of winds in the stratosphere ‘burrows’ down to surface level.

For the UK in winter, that means a disruption to the westerly flow that usually brings mild air from the Atlantic and there is a potential to allow easterly winds to take hold, bringing in cold air from the continent.

So SSWs can herald cold weather ahead. However, there are variations in their magnitude – sometimes they are fairly minor, just a ‘wobble’ in the flow of the stratospheric winds, but sometimes they are more pronounced, with a complete reversal of the pattern of winds.

The more significant the SSW, the more likely it is to have an impact at the surface and also the greater the potential impact.

Met Office observation systems have picked up a minor SSW in the stratosphere over the past few days, suggesting that this may have an impact on the UK.

Jeff Knight, a Climate Scientist at the Met Office, said: “Satellite and other observation data show that there is a minor SSW going on and this is one factor amongst many others which could perpetuate the colder than average conditions we have seen recently.

“It could take anything from a few days to a few weeks if it is going to have an impact. However, it’s consistent with the current 30-day outlook from the Met Office which favours colder than average conditions – albeit with a fair amount of uncertainty.”

The Met Office will continue to monitor the situation and, as ever, will keep everyone up to date on any periods of cold weather through our forecasts and warnings.

World COPD Awareness Day – it’s not too late

Today is “World COPD Awareness Day” and is based around the theme of “It’s Not Too Late”. The day is organised by the Global Initiative for Chronic Obstructive Lung Disease (GOLD) to improve awareness and care of chronic obstructive pulmonary disease (COPD) around the world. This positive message was chosen to emphasize the meaningful actions people can take to improve their respiratory health, at any stage before or after a COPD diagnosis.

The theme for this year’s World COPD day strongly reflects the work that the Met Office is doing to develop a health forecast that aims to ease the worsening symptoms that patients suffer from as a direct result of weather conditions and virus levels in the air.

The Healthy Outlook® service helps patients suffering with COPD stay informed about, and take positive action against any potential adverse cold weather periods that may have an effect on their well-being. It’s not just the patients that benefit either, Healthy Outlook® also gives professionals and patients the opportunity to take action by giving them advance warning of colder weather and circulating infections. Studies have shown that a 20 per cent reduction in hospital admissions can be achieved through the service, which helps patients to stay out of hospital and reduce pressures on GP surgery staff and budgets.

To broaden the reach of our service, Healthy Outlook® is also being trialed in-store in selected major retail pharmacies to give those suffering from COPD a more flexible method of managing their condition. By signing up to the service through the pharmacy retail outlets, patients can benefit from COPD forecast alerts even if their local PCT is not involved. This means that means more people with COPD will be able to get improved access to advice and support.

Katie Russell, Met Office Business Manager for Health, said: “We are excited to be working with the NHS and GPs surgeries again this year, as well as running pilot Healthy Outlook® services in retail pharmacies. The Met Office has been involved in COPD Health forecasting for a number of years and we are thrilled to be able to expand our network of expertise and support this winter.

“We have two major retail pharmacies working with us to broaden the reach of Healthy Outlook® and we are all keen to see how the pilots work across the UK.  The involvement of the Co-operative Pharmacy is proving to be a valuable route for patients to receive the service.”

When patients sign up to the service they will receive a patient pack containing advice and tools that can help them to manage their condition. They will also be alerted to conditions in the environment which are expected to increase the risk of symptoms of COPD becoming worse by an automated telephone call to a number of their choice.

Jane Devenish, Clinical Services Pharmacist at The Co-operative Pharmacy, said: “People with COPD can do a number of things to reduce the risk of their condition flaring up, such as minimising exposure to cold air and making sure they don’t run out of medication. With the alerts that are received through the Healthy Outlook® service people can make sure they are prepared for the periods when the weather takes a turn for the worse.”

What’s in store this winter? Responding to the headlines

It seems that it is the time of year for colourful headlines about an impending big freeze. We had them at this time last year, which prompted our Chief Executive to write an opinion piece in The Times.

Now we have very similar stories again, with the front page of the Daily Express declaring ‘Coldest winter freeze on way’ and warning that temperatures are set to plunge as low as -15C.

There have been other stories elsewhere along similar lines, with some saying that the Met Office is briefing the Government about a cold winter ahead.

So what are the facts behind the headlines?

Some of the stories have taken a cue from parts of our current 30-day forecast. Today’s forecast for 26 November to 10 December reads as follows:

As is usual, there are uncertainties in the forecast for this period, but there are signs that the changeable conditions will continue through the start of this forecast period. There is also a signal for temperatures to be close to or just below the seasonal average. Into December, although there are no strong indications that any particular weather type is going to dominate, on balance colder, drier conditions than at present are favoured, rather than milder, wetter weather, especially across the southern half of the UK.

However, perhaps what the newspapers have failed to pick up on and report to their readers is that there is still a great deal of uncertainty about exactly what weather we will see – as there often is when looking at timescales of over five days ahead.

The science does not exist to make detailed forecasts for temperature and snowfall for the end of this month, let alone for December or even the winter as a whole.

With regards to us ‘briefing the Government on a cold winter’, this is related to our three monthly outlook for contingency planners.

This is a complex product designed to help contingency planners making long-term strategic decisions based on risk exposure. However, it’s not useful for most other people as it doesn’t give one forecast for what’s ahead – rather it outlines potential scenarios and their associated probabilities.

It’s worth noting that while contingency planners use our three month outlook to inform long-term decisions, they make their operational decisions on our five day forecasts and warnings.

These will always provide the best possible guidance on any periods of cold weather, frost or the likelihood of snow, giving detailed local information across the UK.

Ultimately, we’re heading into winter and we expect winter to be colder than the rest of the year – but it’s too early to say exactly what temperatures we can expect or where and when we might see snow.

Healthy Outlook® – helping patients with COPD this winter.

Alongside our Cold Weather Alert Service this winter, the Met Office is working with the NHS and Primary Care Trusts (PCTs) to help keep people well at times of severe cold weather with our specially produced Healthy Outlook® service. The service helps patients suffering with Chronic Obstructive Pulmonary Disease (COPD) stay informed about any potential adverse cold weather periods that may have an effect on their well-being. Healthy Outlook® also gives professionals and patients the opportunity to take action by giving them advance warning of colder weather and circulating infections.

COPD is the term used to describe a number of conditions, including chronic bronchitis and emphysema, where people have difficulty breathing because of long-term damage to their lungs. Poor weather conditions, such as extreme cold in winter can exacerbate COPD symptoms and contribute to breathing difficulties which often leads to a spell in hospital for the patient. There are around 30,000 COPD-related deaths each year in the UK and it is the second highest cause of emergency hospital admissions.

Katie Russell, Met Office Business Manager for Health, said: “We are excited to be working with the NHS and GPs surgeries again this year. The Met Office has been involved in COPD Health forecasting for a number of years and feedback from patients shows that 82% found Healthy Outlook® helped them manage their COPD better during periods of cold weather.”

This winter, Healthy Outlook® is also being trialled in-store in selected retail pharmacies to give those suffering from COPD a more flexible method of managing their condition. By signing up to the service through the retail outlets, patients can benefit from COPD forecast alerts even if their local PCT is not involved.

As with the standard service, patients will receive a pack containing advice and tools that can help them to manage their condition.  An automated telephone call to a number of their choice will also alert them to conditions in the environment which are expected to increase the risk of symptoms of COPD becoming worse.

The latest information about the weather and warnings can be found on the Met Office website, iPhone and Android apps and on twitter. Further information on Healthy Outlook can be found on the Met Office’s Cold weather and health web pages.

Met Office in the Media: 29 October 2012

Today there a couple of news stories (one in the Express and another in the Daily Star) which refer to the ‘Met Office winter forecast’, but they create a slightly misleading picture.

They seem to be based on our three-month outlook for contingency planners, a product which is updated each month and is available to view on our website. There are a couple of points to mention here.

Firstly the current three-month outlook covers November to January, so does not cover a full winter period. Meteorologically speaking, winter runs from December to February – so a full look at winter won’t be available until towards the end of next month.

The second point is that the three-month outlook is designed for contingency planners – those people making longer-term strategic resourcing decisions based on their preferred exposure to risk. It’s a complex product which shows the range of probabilities for temperatures and precipitation for the whole of the UK over the three-month period.

It is not, therefore, the sort of forecast that the public find useful when making decisions, such as deciding when to go on holiday.

Specifically looking at the current three-month outlook for both temperature and precipitation, both clearly state there are currently relatively few large-scale influences and, therefore, there is low confidence in the forecast.

While the Met Office is a world leader in longer-range forecasting and we continue to make improvements in this area, it is still a developing area of meteorology.

As ever, our highly accurate five-day forecasts and weather warnings provide the best possible advice and detail on what weather to expect in the UK. These can be used alongside our 30-day outlook, which gives a more general view of the weather ahead over a longer-timescale.

When does Autumn start? Defining seasons

Seasons are fundamental to how we understand the UK climate and the environment around us, but how do we define when they start and end?

In meteorological terms, it’s fairly simple – each season is a three month period. So, Summer is June, July and August; Autumn is September, October and November, and so on.

Of course, this is fairly arbitrary, but provides a consistent basis for the Met Office, as the holder of the UK’s national weather and climate records, to calculate long term averages and provide seasonal climate summaries from year to year.

Mike Kendon, of the Met Office National Climate Information Centre, said: “Defining seasons in this way means we can compare weather from one season or year to the next. It also has the advantage that each season is roughly the same length, neatly dividing the year into four quarters.

“Looking at longer timescales, our recently updated 30-year averages can show us how ‘normal’ seasons are changing over time, giving us clues about trends in the UK’s climate.”

Astronomical definitions of seasons also exist – using the Earth’s position relative to the Sun as the cue for separating one season from another via equinoxes and solstices.

So the Summer begins around the Summer Solstice, when daylight hours are at their longest (around 21 June), and ends around the Equinox, when days and nights are of equal length (around 21 September, on 22 September this year). Thus astronomical Autumn begins, continuing until the Winter Solstice, when daylight hours are at their shortest (around 21 December), and so on. Astronomical seasons therefore are about three weeks behind the meteorological ones.

One thing both methods have in common is that the dates are fixed by the calendar and don’t take into account what is actually happening in nature, which is after all how most of us understand the notion of seasons.

So comes the third method, which is based on phenology – the process of noting the signs of change in plant and animal behaviour.

In this distinction, Autumn may be deemed to have arrived at the first tinting of oak or beech trees, the appearance of ripe sloes or elderberries and the arrival of winter migrant birds such as redwings and fieldfares. Winter begins when native deciduous trees are bare, and so on.

For more than a decade The Woodland Trust has been using observations from thousands of members of the public to build a phenological record for the UK, called Nature’s Calendar. This builds on records going back over much longer periods of time.

It aims to give a comprehensive view of how nature defines the seasons in a record which takes into account how weather in individual years or longer term changes to climate may affect natural signs from one year to the next. As such it is a more fluid, natural definition of our seasons.

Dr Kate Lewthwaite, project manager for Nature’s Calendar for the Woodland Trust, said: “Taken individually the observations of what’s going on in nature provide only anecdotal evidence, but taken as a whole and analysed with temperature data, they offer a powerful insight into local and national impacts of environmental and climatic change.

“For example, our data shows that, on average, native trees are producing ripe fruit 18 days earlier than a decade ago, with a potential consequence being that animals’ food reserves could become depleted earlier in the winter. In contrast, leaf fall, indicating the end of the growing season, is often much later nowadays than in the past.”

Ultimately, however you choose to define them, it is weather and climate which govern the perception of the passing of seasons for plants and animals, including us humans.

So, like our weather, the exact timing of when we ‘feel’ one season is over and a new one has begun will always be liable to change. Whereas, in contrast, the meteorological seasons always remain fixed by calendar month.

Between the Met Office’s climate records and our forecasts up to a month ahead, you can stay up-to-date with what’s going on with the UK’s weather and climate.

How often does it snow in May?

Reports of snow showers in parts of the UK over the past 24 hours and the prospect of more on high ground tonight may seem a little out of context at this time of year, but is it unusual?

Snowfall at this time of year isn’t an annual event, so it’s not completely normal, but it’s fair to say it’s not completely unusual either. We last saw snow in May all the way back in… 2011, just last year, and we also saw more snow in 2010.

If we look back through the records dating back to 1910, the snowiest May on record was most likely in 1979 when 342 weather observation sites reported snow on 2 May.

This snowy spell lasted through the whole of the first week of that month. The light snow showers we’ve seen this May seem slight in comparison.

Besides these wintry showers, much has been made in the media of the ‘cold spell’ which is ‘gripping’ the UK this month and the rather unsettled weather we’ve had.

While many people associate May with the start of summer weather, it can actually be a month of very mixed and variable conditions – with wide contrasts possible.

This is borne out by the piece of old weather lore:

 

Ne’er cast a clout,

Until May is out.

 

While this rhyme is a bit ambiguous and open to interpretation, one view is that this means don’t throw out your winter clothing (from clout – which means thread or cloth) until May is over – presumably because you can expect virtually any type of weather at this time of year.

So, unsettled and cool weather – even with snow or frosts – isn’t out of context in May despite perceptions that it’s typically a warm and sunny time of year.

This week really sums that up. We are expecting some night-time minimums which are below average – isolated areas in Scotland and northern England could get down to freezing or just below.

During the day, however, temperatures in places could get to 15C or above in parts of southern England – and it may even feel quite warm when the Sun is out, particularly in spots sheltered from the wind.

There will also be some rainfall this week, but many places will see sunny and dry spells too.

So, don’t throw away your summer wear yet – nor your winter woolies.

 

A tale of two halves for February and winter

As February and winter draw to a close, early statistics show that both have been stories of two halves.

We often talk about why you can’t pre-judge a month or a season at its half-way stage, and the latest figures perfectly illustrate why that’s the case.

The mean temperature for the first half of February was very low as cold weather gripped the UK – particularly in England where temperatures were 4 °C colder than the long term (1971-2000) average.

If you’d projected those figures out to the end of the month you would have expected one of the coldest Februarys on record.

However, the second half of the month (figures go up 26 February) has seen some exceptionally mild weather to balance things out and we have ended up with a rather average month for overall UK mean temperature which so far, was just 0.1 °C above average.

This story of two halves can be seen in the maps below, with the blue colours denoting lower than average temperatures in the half-month figures on the left, and the more balanced situation by the end of the month on the right.

Winter, which meteorologically speaking runs from December to February, has been a fairly similar story – but in reverse.

A mild December and first half of January meant we had a very mild first half of the season, which led to some media headlines mooting one of the mildest winters on record.

However, the last few days of January and the first half of February were colder than average, bringing the overall temperature for the season down.

With a couple of days still to go, the early statistics show the UK’s mean temperature for winter is 0.7 C above average, making this a mild winter – comparable with several other mild winters in the last decade.

One common theme between this February and winter as a whole is dry weather – particularly for the south and east of the UK.

February was particularly dry, with the UK having seen just 62% of the normal amount of rainfall we’d expect for the whole month by the 26th. With a few days left, this is unlikely to change by much.

England was the driest country, having so far seen just 43% of the rainfall we’d expect for the month and Wales not far behind at 49%.

Winter has also been dry overall in England, with just 82% of the rainfall expected for the season and Wales has seen 89%. This is slightly balanced out in the statistics by Scotland being wetter than normal over the season, seeing 116% of its normal rainfall.

The relative lack of rainfall for February and the season as a whole can be seen in the two maps below, with the brown colours denoting drier than average weather for the month on the left and for the season on the right.

Coldest temperatures of winter so far

Last night and today have seen some of the lowest temperatures of the winter so far.

Official observations show Holbeach in Lincolnshire dropped to -15.6 °C overnight, beating the previous coldest temperature of this winter of -12.4 °C at South Newington in Oxfordshire overnight on 3-4 February.

Today has seen also the lowest day-time maximum temperature for the UK so far this winter, with Coningsby in Lincolnshire only getting up to -5.3 °C. The previous record for this winter was -2.8 °C, set at Cassley in Scotland on 15 January.

It’s worth noting that some even lower temperatures have been quoted in the media. However, these are not official Met Office observations.

Our official observation sites conform to rigorous standards set by the World Meteorological Organization (WMO). This includes observation equipment undergoing regular checks and calibration, as well as meeting requirements about the location of the observation site to ensure readings aren’t affected by other factors.

This doesn’t mean readings from non-official sites are wrong, just that they cannot be officially recognised because they are not part of our WMO-approved network.

The reason last night and today have seen these low temperatures comes down to a combination of factors. Cold air from the east is still flooding over parts of the UK. Snow is also still lying in some places, and this can keep temperatures down by acting like an ice pack – as well as reflecting back energy from the Sun. Clear skies and light winds have also played a part, as these factors mean heat can radiate away into the sky.

Looking ahead, tonight is expected to be cold, although it is unlikely to be quite as cold as last night. As we move through next week, temperatures are expected to move closer to or even slightly above average. You can stay up to date with the latest outlook with our forecasts and warnings.

 

Coldest overnight temperatures for 10-11 February

-15.6 °C Holbeach, Lincolnshire

-15.5 °C Cavendish, Suffolk

-15.3 °C Cambridge, Cambridgeshire

-15.2 °C Wainfleet, Lincolnshire

-14.6 °C Santon Downham, Suffolk