Medal for Met mathematician

A leading Met Office climate scientist has been awarded the Copernicus Medal, a prestigious international award for pioneering research.

Adam Scaife August 2016

Professor Adam Scaife, Head of Monthly to Decadal Prediction at the Met Office – who is also Professor of applied mathematics at the University of Exeter – was chosen as the winner by the international judging panel for his research into the causes, simulation and prediction of climate variability.

Presented with the medal at a ceremony during the Royal Meteorological Society’s Atmospheric Science Conference, Adam said: “I am truly delighted to receive this award. It is encouraging and humbling to have my work recognised in this way and I want to acknowledge the dedication and hard work of all of my collaborators and everyone in my research group. Together, we have uncovered exciting new results on long-range predictability of the atmosphere.”

Adam’s research group issues climate forecasts on a regular basis and develops long range predictions for adaptation to climate variability and change. He carries out research on climate variability and has published more than 150 peer-reviewed articles on the mechanisms, improved computer modelling and predictability of regional climate. His group recently made an important breakthrough in seasonal forecasting which allows skilful prediction and new applications of long range forecasts for Europe and North America.

The Copernicus Medal is presented annually by an international and interdisciplinary panel. It recognises ingenious and innovative work in the geosciences, planetary and space sciences, and exceptional efforts in international collaboration in scientific research.

 

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The summer so far

As we are all aware this summer has been hot and dry so far and there has been much speculation comparing the season so far to record-breaking summers of the past.

But has it been as hot and dry as we think?

As we reach the midpoint of the meteorological summer (June, July and August) we take a look back at the weather statistics and see how 2018 compares so far.

As a whole, the UK has received just 47 mm of rain so far this summer (1 June – 16 July), making it the driest start to summer in modern records which date back to 1961, closely followed by 2013 with 59 mm of rain. However in 2013 although the first half of summer was very dry an outbreak of thunderstorms and a few very wet days in late July changed things for many leaving the summer of 2013 as a whole the 14th driest on records (dating back to 1910).

So what would happen if the rest of this summer were average? Well if rainfall was average for the next month and a half by the end of August, we would be up to 174 mm, which would just sneak into the top 10 driest summers of all time.

Figures from 1 June 2018 to 16 July 2018 compared against the full summer averages (June-July-August)

Regions max act max anom sun act sun anom precip act precip anom
UK 20.9C 2.4C 385 hrs 76% 47.1mm 19.5%
England 22.5C 2.4C 418 hrs 75% 21.1mm 10.9%
Wales 21.6C 3.1C 419 hrs 80% 29.4mm 10.3%
Scotland 18.4C 2.1C 328 hrs 77% 91.7mm 30.1%
N.I. 20.3C 2.4C 348 hrs 82% 66.0mm 25.9%
N Eng 21.1C 2.3C 397 hrs 78% 40.6mm 17.9%
S Eng 23.2C 2.4C 429 hrs 73% 10.8mm 6.1%
N Scot 17.3C 1.9C 294 hrs 76% 90.5mm 28.8%
E Scot 18.9C 2.1C 335 hrs 75% 71.8mm 28.7%
W Scot 19.4C 2.6C 367 hrs 81% 114.6mm 32.6%

Taking the summer as a whole (June, July and August) across the UK, 1995 is the driest on record (dating back to 1910) with a total rainfall over the full three months of 103 mm.

Rainfall in June was below average across England with only 15 mm, just a quarter of the average rainfall for the month, with the lowest rainfall in the south east, making it the third driest June on record for England (since 1910) and the driest June since 1925.

Paul Hickey, head of water resources, Environment Agency, said: “Over two very dry months, we have seen a rapid decline in reservoir levels in the North West and we support the announcement by United Utilities to manage water supplies by introducing household restrictions.

“Across the rest of England, most groundwater supplies are at healthy levels and water companies have enough water to maintain supplies if resources are managed properly.

“Many rivers around the country have dropped to lower levels than normal for this time of year, which can be damaging to wildlife. We have robust plans in place to respond to these pressures and have stepped up our incident response as well as regulation of those abstracting water to ensure the environment is protected.

“We are meeting with affected groups including farmers to provide practical advice about conserving water and planning for prolonged dry weather. We encourage everyone to use water wisely to conserve supplies and protect the environment.”

Many people’s visions of 1976 are of the drought and stand pipes in the street but it’s important to remember 1976 came after a previous sunny summer of ’75 and also a very dry 12-month period.

The temperatures so far this summer have also been remarkable.  So far (1 June to 16 July), the average daily maximum temperature across the country is 20.9 °C. The average daily maximum in the hottest summer on record, 1976, was 21.0 °C.  If the rest of the summer is average, 2018 will certainly rank in the top 10 warmest summers on record and if we continue to see above average temperatures, it could well be record breaking.

The Environment Agency, SEPA, Natural Resources Wales and Northern Ireland Environment Agency all have advice on water conservation.

1976 was also the sunniest summer on record with 669 hours. So far we’ve had 385 hours of sunshine on average across the UK this summer, however, statistically there are fewer sunshine hours in the second half of summer as the days are getting shorter. If the rest of the summer was average, we would still be in the top five sunniest summers on record.

It is important to remember we are only half way through the season and a lot can change.

You can find the current forecast for your area using our forecast pages, by following us on Twitter and Facebook, or using our mobile app which is available for iPhone from the App store and for Android from the Google Play store.

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Leaving no stone unturned in hurricane preparedness

With hurricanes developing in the Atlantic Basin, Gavin Iley, Met Office Head of International Crisis Management & Resilience, provides a personal account of how the Met Office works tirelessly to ensure its hurricane advice is ‘useful, useable and used’.

Met Office Operations Centre

With a 24-hour operation, the Met Office Operations Centre can always provide the most up-to-date guidance.

Earlier this year I met a colleague from the meteorological service on one of the islands devastated by Hurricane Maria. They described how they walked to work on the day Maria hit, knowing that the storm was coming and its potential impact. They had left their family behind in the full knowledge that it could be the last time they saw them alive. They had chosen, however, to serve their community, going to work to continue to provide the critical meteorological advice, which could perhaps help save lives. Thankfully, the story for this family had a happy ending. Sadly, others were not so fortunate.

As Hurricane Maria and others tore through the Caribbean last year, my colleagues here at the Met Office worked tirelessly to ensure the UK Government had the most up to date and accurate meteorological information available. This included briefing into emergency meetings chaired by the UK Prime Minister and Foreign Secretary, configuring experimental models to ensure we left no stone unturned in our meteorological analysis, and pulling in additional staff to support our operational teams. Looking back at the response now it was unrelenting and extremely stressful, especially when as a civil servant you’re expected to brief the most senior of UK Government officials. But reflecting on the story above, our stress was of course minor compared to the experiences of Caribbean islands’ residents.

This year the Met Office continues to play a crucial role in the UK Government’s efforts to ensure British Overseas Territories in the Caribbean are supported to be as well prepared for the hurricane season as possible. While we can hope for a quieter season, we’ve re-doubled our efforts, working alongside colleagues in the Foreign and Commonwealth Office, the Department for International Development and the Ministry of Defence (amongst others) to make sure we are ready to respond if and when required.

From a Met Office perspective we have looked at best practice from elsewhere to develop new briefing mechanisms, specifically designed to support the enhanced crisis monitoring and response systems in Government for the 2018 season. These briefings draw on the same world-class information, but are presented in a new easy-to-use format tailored for the needs of emergency planners and responders in Government. These briefings are complemented by the wider expertise available 24 hours a day, 365 days a year from the Met Office.

To quote a term often used by those providing information in the disaster management and response sector, making sure our information and advice is ‘useful, useable & used’ is critical. If we can achieve this for the 2018 hurricane season, then the Met Office, along with our meteorological colleagues in the region, can even better support those at the front end of disaster preparation and response efforts and therefore continue to save lives.

To watch a video on how the UK is preparing for the hurricane season in the Caribbean, please click here.

 

 

 

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An update on a record breaking June

Beach huts at Southwold

The spell of weather at the end of June and into July is without doubt a notable heatwave for the UK

On Monday 2nd July we released our provisional climate statistics for June: an exceptional month resulting in a number of new climate records, including the warmest June on record for Wales and Northern Ireland.

A provisional national high temperature record for Scotland was also set with an observation of 33.2 °C recorded at Motherwell, Strathclyde Park on the afternoon of 28th June. Temperatures in the low 30s were observed at a number of sites in the central belt of Scotland, with 31.9 °C at Glasgow, Bishopton, and 33.0 °C was also recorded in Wales at Porthmadog, Gwynedd. Making it undoubtedly the hottest day of the year so far for the UK. However subsequent information has cast some doubt on the Motherwell measurement for that day, meaning that we will not be able to accept it as an official new record for Scotland, which will remain as 32.9 °C at Greycrook, Scottish Borders from 9th August 2003.

How do we verify records

Dr Mark McCarthy is the head of the Met Office’s National Climate Information Centre. He said: “At the Met Office we manage a network of weather observing sites across the UK. This network is comprised of approximately 259 automatic weather stations managed by Met Office and a further 160 manual climate stations maintained in collaboration with partner organisations and volunteer observers. We have previously written about how our temperature records are measured and verified.

“At first review the Motherwell record appeared plausible given the wider conditions on the day and was therefore reported as such. However for all new records we undertake further careful investigation to ensure that the measurement is robust. This investigation includes statistical analysis of the station data, evaluation against neighbouring sites, and in some cases an additional site visit to check for unexpected issues with the instrument enclosure or equipment to ensure the measurement meets our required standards.”

Why has it been rejected?

Unfortunately in this particular instance we have evidence that a stationary vehicle with its engine running was parked too close to the observing enclosure and the Stevenson screen housing the thermometers during the afternoon of 28th June. Although the measurement appears plausible given the weather conditions that day we cannot rule-out the potential for contamination of the measurement by this non-weather-related factor.

The Met Office works closely with collaborating organisations who host or manage weather stations on our behalf. The observing site at Motherwell makes a very valuable contribution to our observing network, and the rejection of this particular record does not detract from that or from the hard work of those making the observations. We will continue to work closely with our partners at the site, and across our network, to maintain a high-quality climate-observing network for the nation.

What does this mean for the June heatwave?

The spell of weather at the end of June and into July is without doubt a notable heatwave for the UK, and particularly for Scotland and Wales, with some very high temperatures on 28th June. The rejection of the Motherwell observation for that day does not detract from that. More detail about June and other statistics can be found on our climate pages

 

 

 

 

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A warm and dry June so far

As we reach the mid-point in June, statistics for the UK as a whole show that the weather has been warm and dry for many with temperatures over 1 degree above average so far and rainfall just 33% of the whole month’s average total. This follows on from what was, for many, a dry and warm May.

june max temp

Max temperature for June 2018 so far compared to monthly average

However, the UK-wide statistics hide some regional variations, with Central, Southern and South East England having had just 2mm of rainfall (1 to 16 June) – 5% of the June average, while western Scotland has had 55mm (1 to 16 June) – 51% of the June average.

Some of the driest counties in southern areas of the UK include Essex, which has only received 1.4 mm of rainfall, 3% of the month’s average, Dorset, which has had 1.2mm of rain, 2% of the month’s average, and Buckinghamshire, which has had 2.1mm of rain, 4% of the month’s average.  Without further rainfall this month, some southern counties could see one of the driest Junes on record.

Conversely, Western Scotland has seen above average rainfall with Argyllshire having received 76mm so far this month – 64% of the June average, Dumfriesshire has received 57mm – 66% of the June average, and Stirlingshire has received 62mm – 67% of the June average.

june rainfall anomoly

Rainfall for June 2018 so far compared to monthly average

While temperatures overall this month so far have been above average there have also been some regional differences, with the east side of the country generally being nearer average, for example Lincolnshire and Kent are so far just 0.4 °C above the average maximum. However, the west side of the UK has seen higher temperatures with areas such as Cornwall and Cardiganshire being 2 °C above the average maximum so far this month.

Looking back at the rainfall figures for spring it was north-western areas that were the driest, with only around half the season’s average, the reverse of rainfall amounts so far this month. It was however a rather wet spring in most eastern, central and southern areas, with rainfall 50% above normal in the wettest places.

The latest figures from UK water companies show that following the spring rainfall the water resources outlook remains healthy for the summer particularly in the south and east, a significant transformation from the situation at the start of 2018.

The Environment Agency is continuing to urge us all to think carefully about our water consumption saying the average person in England uses 140 litres per day. They published a recent report examining water resources.

Paul Hickey, Environment Agency Deputy Director of water resources said:

“At the start of June for most areas of England, the river flows, groundwater levels and soils were normal for the time of year. This followed the rain in early spring, which helped groundwaters in the south east to recover from previously low levels. During dry spells, it is not unusual for some rivers and lakes in faster responding catchments to drop quickly, but they tend to recover quickly when the rain returns. The Environment Agency continues to work with water companies, businesses and farmers to provide advice, helping to balance the needs of water users and minimise impacts on the environment of any dry weather.”

As we look at the rest of June, the forecast shows high pressure building across the south of the UK later this week with indications this will last into next week as well – meaning dry settled conditions for the south. Further north, the weather looks more unsettled with a chance of rain or showers.

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Will summer be a washout or a scorcher?

The Met Office has recently released its contingency planners’ outlook covering the period for June, July and August, with some sources suggesting this is predicting a summer heatwave.

But what does this early look at what might be in store for the summer actually say?

This summer, long-range weather systems show a slight increase in the chance of high pressure patterns across the UK and with this we see an increase in the chance of above-average temperatures. The point about the seasonal outlook, however, is that it gives us the more likely trends within the coming season.  As a result, below-average temperatures, although less likely, remain a realistic possibility.  A summer in which temperatures are more frequently slightly above average is the most likely scenario at this stage, but the fact that warmer and cooler outcomes than this are possible is a feature of the kind of information we are dealing with in long-range forecasting .

The outlook also gives an increase in the likelihood of drier-than-average conditions.  The summer period is one of the driest times of year across the UK; with rainfall coming in short, occasionally intense, showery rain affecting some places but leaving nearby locations dry. On balance, below-average rainfall is more likely than above-average rainfall.

Jeff Knight, manager of modelling of climate variability at the Met Office, said: “Our long term outlook for the summer suggests a greater chance that temperatures will be above average, than below average. However, our outlook certainly doesn’t imply a 3-month heatwave. As always with our climate there are likely to be large day-to-day and week-to-week variations the period. This is an outlook for the general themes over the summer and does not give detailed guidance on events like heatwaves.”

Perception of good weather is often more dependent on rainfall amounts than temperature. For example, even though the UK had a run of ‘poor’ summers between 2007 and 2012, half of these summers had temperatures above the long-term average. The long-range outlook is primarily aimed at giving government departments and agencies a forward view of potential weather hazards in the months ahead. As such, it is a risk assessment rather than a more traditional type of forecast of what the weather is going to be. Using evidence from global weather observations and computer forecast systems, we can estimate the chances of different types of UK weather and how they could be modified in the coming months.

When you look back at the average mean temperature for the UK  both 2017 and 2016 saw temperatures above the 13 C long-term average, with 14.5 C and 13.9 C respectively, and for summer as a whole the mean temperature was 14.7 C in 2017 and 14.9 C in 2016, both also above the long-term summer average of 14.4 C

You can find the current forecast on our website or mobile App or follow us on Twitter or Facebook, and as always our forecasts from one day to one month ahead can be relied upon to provide the best guidance on what to expect whatever weather patterns emerge.

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Met Office temperature records – what do we monitor and how far do they go back?

May saw more than its normal share of fine sunny days and notably high temperatures, reaching a peak of 28.7 Celsius at Northolt on 7th May to coincide with the early May bank holiday. That was just one place on one day. To get a broader picture we also look at the average temperatures across the whole month and all of the UK. The average daily maximum temperature in May was 17.2 Celsius. The persistent sun and warmth meant that this was the highest average maximum temperature on record for May.

But what does “highest maximum temperature for May” mean and how is it calculated? What types of temperature do we monitor, and how do they differ?

Daily Max Temp May

Average of daily maximum temperatures for May.  Setting a new record high for the national series.

 

Maximum, Minimum and Mean temperatures

All our standard temperature observations are made from the UK’s weather station network. Modern automated technology means we can actually track changes in temperature minute-by-minute. It hasn’t always been this way though, and historically it was not very practical to manually record the weather every minute of every day. Thankfully, British scientist James Six invented a maximum-minimum thermometer in the late 18th Century that could record the highest and lowest temperature recorded over a period of time. This invention allowed early weather observers to summarise the temperature of the day based on these two extremes, and the average of the maximum and minimum is widely used as an estimate of the mean temperature. This practice continues to this day, providing the UK with some very long records of the highs and lows of temperature across the country.

Daily Min Temp May

Average of daily minimum temperatures for May.  Ranked joint 10th warmest in the national series.

Station Records

The Met Office has routinely provided summaries of the monthly average of the maximum, minimum and mean temperature for the weather stations located throughout the UK since 1884. For a few stations we hold records going back much further. These station records provide an accurate picture of the month-to-month and year-to-year variations in temperature at particular locations. Our present-day observing network is comprised of over 400 stations.

Weather Observation network

Map showing the present-day weather observation network of automatic (blue) and manual (red) stations.

Find a selection of our historic station series here.

Central England Temperature records

The Central England Temperature (CET) series is the remarkable achievement of the scientist Gordon Manley. In the mid 20th Century Gordon Manley undertook painstaking research to uncover old weather records and diaries stretching back to the mid 17th Century and from these created the Central England Temperature series, providing an estimate of the monthly mean temperature of a region broadly representative of central England.

This work was continued by the Met Office to maintain a Central England Temperature record to this day, providing monthly mean temperature from 1659, daily mean temperatures from 1772, and separate maximum and minimum temperatures from 1878. The different start dates reflect the historical availability of the different types of observations.

The current CET series is, for historical consistency, comprised of observations from just three weather stations, forming a triangle encompassing roughly Lancashire, London and Bristol. This dataset is the longest of its kind in the world, and is an invaluable resource for investigating variations in our climate across several centuries.

However, the CET does not cover the whole of the UK or take full advantage of the complete network of several hundred weather stations currently monitoring weather across the whole country.  The CET series is available here.

National records

For most of the 20th and 21st Century we have had hundreds of observing stations across the UK recording maximum, minimum and mean temperatures. We could take a simple average of all of these observations to estimate a national average temperature. However, the precise number and distribution of stations across the country has changed over time, so a simple average is not the best way to estimate the national record. Instead we take a slightly more sophisticated approach. All available observations from a given date or month are interpolated to a uniform grid of points 5km by 5km covering all land areas of the UK. This gridding method also accounts for factors such as terrain height (mountain tops are cooler on average than lowlands), coasts (the sea can keep coastal areas cooler by day and warmer by night), and cities (the urban heat island effect means large cities are warmer than their rural surroundings). An average value is then calculated from the resulting grid of points. This approach provides the best estimate we have of national records.

There are currently sufficient temperature data on our computer archives for this gridding method back to 1910, providing over 100 years of national records for the UK, Scotland, England, Wales and Northern Ireland. So these records provide our official UK national climate series – the records that you will see quoted when the Met Office releases statistics.

The national and regional series from 1910 available to download here.

 

So what is the best measure of temperature for monitoring climate?

The answer is all of the above. The different types of data provide complementary information, all of which are routinely used to monitor UK climate and are published through the Met Office website each month.

Each of the maximum, minimum and mean temperature are all important in their own right for monitoring our climate and its extremes, and have all been observed for well over 100 years.

The national series derived from our gridded datasets from 1910 provide the most reliable estimates of UK-wide temperature, being based on all available station data. The CET series provide an invaluable and much longer climate series, providing a perspective of our climate for over 350 years. It is however based on a much more limited set of locations and stations. None of these records would be possible without the existence of high quality and long running historical station series. These station records provide observations for the site they are located in, but they are the firm foundations of our weather and climate observation heritage.

 

 

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Cyclone Mekunu closes in on Oman

In the two months prior to the onset of the Indian monsoon in early June, cyclones occasionally form in the North Indian Ocean. This year so far has seen the formation of two cyclones in the region – Sagar and Mekunu.

Cyclonic Storm Sagar formed in the entrance to the Gulf of Aden just over a week ago and unusually tracked along the length of the Gulf before eventually making landfall over Somalia, bringing heavy rain and flooding to northwestern parts of the country and neighbouring Djibouti.

No sooner had Sagar dissipated, another cyclonic storm developed and was named Mekunu. This cyclone formed some distance offshore in the Arabian Sea and has had several days to gather strength. Mekunu is now classified as a Very Severe Cyclonic Storm and is equivalent to a Category 2 hurricane. Mekunu is currently expected to make landfall close to the city of Salalah in southern Oman overnight Friday into Saturday UK time. Winds near 100 mph and 250-500 mm rain are possible, which is likely to cause damage to buildings and flash flooding. This region has an annual average rainfall of just 100-150 mm.

Cyclone Mekunu over the Arabian Sea on 24 May 2018

 

 

Cyclones of the strength of Mekunu have made landfall over the Arabian Peninsula in the recent past. In 2015 Cyclone Chapala brought flash flooding as it came ashore over Yemen. Cyclone Phet brought strong winds and heavy rain to northern Oman when it made landfall in 2010. The strongest cyclone on record to make landfall over the Arabian Peninsula was Gonu in 2007. This cyclone hit the far northeastern tip of Oman with winds in excess of 100 mph.

Mekunu will be making landfall over the central part of the Arabian Peninsula close to the border between Oman and Yemen. The historical record reveals that strong cyclones over this part of the peninsula are relatively rare. The most recent strong cyclones to make landfall close to the city of Salalah occurred in 1963 and 1959. The former produced over 200 mm rain and caused severe sandstorms. The latter caused flooding and severe damage to buildings.

Further Information

Official warnings for the latest tropical cyclones in the North Indian are issued by the India Meteorological Department. The Met Office routinely supplies predictions of cyclone tracks from its global forecast model to regional meteorological centres worldwide, which are used along with guidance from other models in the production of forecasts and guidance. We also provide updates on current tropical storms via @metofficestorms on Twitter.

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A spring freeze and a bank holiday to please

It’s a testament to how often British Bank Holidays disappoint that, in the 40 years since it was introduced, temperatures had never exceeded 23.6 C on the early May Bank Holiday Monday.

At least, not until this year, says Aidan McGivern – a Met Office senior weather presenter.

This year, the usual Bank Holiday washout script was torn up and re-written. Rainclouds were replaced with sunshine. Records were broken, when 28.7 °C was reached in Northolt, West London: the previous top temperature was beaten by more than five degrees.

For any Bank Holiday beach-goers roasting in the afternoon sunshine, it may have been hard to believe that just two months earlier large parts of the UK were blanketed in deep snow.

Hard to believe, that is, until they took a dip in the toe-numbing waters. At just 12 °C around southwest coasts and 8 °C close to the northeast, the seas were still recovering from March’s Siberian winds.

Beast from the East part one, at the beginning of the month, brought sustained and brutal cold to every part of the UK from the Isles of Scilly to Shetland.  Tredegar in Wales recorded a maximum temperature on the 1st March of just -4.7 C, making it the coldest spring day in records that stretch back to 1910. Add into the mix a raw, easterly wind and many places felt a chill akin to the minus double digits.

Two rare Met Office red warnings were issued for disruptive snowfall in parts of Scotland as well as Wales and the South West between 28th February and 1st March. The snow stranded one-thousand vehicles overnight on the M80 and drivers were also stuck on roads such as the A38 and A30 in Devon.

Beast from the East part two swept across the country in mid-March and brought a return to sub-zero temperatures, icy winds and further disruptive snowfall in places.

Little wonder the seas remain so chilly in May. The air temperature may have switched from record-breaking cold to record-breaking heat in just two months but the sea has warmed sluggishly.

Water is a relatively slow conductor of heat. This means that, combined with the continuous moving and mixing of water molecules, it takes much longer for the sea to warm in spring and summer compared to the land. However, water also stays warm for longer – leading to a delay in cooling during autumn and winter.

These lag effects in warming and cooling can lead to a sea temperature frequently at odds with the surrounding air temperature from season to season. It’s also why the UK, a small island nation surrounded by seas, doesn’t often experience extremes of temperature.

The largest expanse of water near our shores lies to the west in the form of the Atlantic Ocean and that’s where our weather comes from much of the time. The jet stream, a ribbon of fast-flowing air high in the sky, tends to act as an atmospheric conveyor belt. Low-pressure systems form over the Atlantic and are carried towards the British Isles by the jet stream above, which typically flows from west to east.

When the jet stream is strong, we receive a full complement of cloud, wind and rain from the west. Atlantic weather, as well as being blustery and damp, acts as the UK’s thermostat, keeping us in mild winters and cool summers.

At times during Spring 2018, however, this moderating influence has been notably absent, resulting in some exceptional weather. A particularly dominant area of high pressure built up over Scandinavia during March. Known as a blocking anticyclone, this Scandinavian High held off the usual Atlantic westerlies and sent Siberian easterlies towards the UK. Beast from the East arrived – not once, but twice.

Fast forward to the early May Bank Holiday weekend and we encountered another blocking anticyclone lodged to the east of the British Isles. Once again, Atlantic winds en route to the UK were stopped. This time, however, Siberian winds had lost their bite. By May, winds from the continent tend to be warm and sunny.

Record-breaking cold early in spring followed by record-breaking heat later in the season; two very different outcomes but both the result of a Scandinavian High. However, whilst a blocking anticyclone can disrupt the eastward-moving jet stream, a weakened jet stream is ultimately responsible for the formation of blocking anticyclones. This ‘chicken and egg’ scenario illustrates just how complex and interconnected global weather patterns can be.

In fact, it’s during spring in particular that we are most likely to find blocking anticyclones and weakened jet streams. The jet stream is fuelled by temperature contrasts across the Northern Hemisphere and during spring these contrasts decline as continents warm but oceans remain cool.

For that reason, it’s not unusual at this time of year to find slow, meandering jet streams, blocking anticyclones, and continental-style swings in temperature in the UK.

The causes of Spring 2018’s particularly pronounced cold and hot spells are complex and varied. March’s Siberian easterlies were a response to a dramatic wind reversal 80,000 feet above the North Pole in the Stratosphere. This itself can be traced back to lively thunderstorms in the tropical West Pacific during January, which produced energetic reverberations high in the atmosphere throughout the Northern Hemisphere.

This year’s warm Bank Holiday Monday is more likely to be a quirk of fate. After all, particularly warm temperatures during early May are not unheard of, they’ve just never coincided before with the early May Bank Holiday Monday. It’s only taken 40 years for our fortunes to change.

 

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Scotland highlights weather contrasts during the first half of April

So far April’s weather is highlighting a month of contrasts, and perhaps nowhere is this contrast more apparent than in Scotland.

Between 1-15 April, parts of Scotland have seen both the most and least rainfall of any station in the UK, when compared with the long-term average (1981-2010).

The Edinburgh Botanic Gardens have so far received 63.4mm, which is equivalent to more than one and a half times the full month average for April (156%). Meanwhile, Loch Glascarnoch – in the north-west Highlands – has only received 12mm of rainfall, making it the driest location in the UK for the first half of April. This is equivalent to only 13% of the site’s monthly total rainfall. Elsewhere most of England and Wales have had a relatively wet start to April with some areas in the north east already at or above the average full month rainfall for April.

Much of the UK has had a dull start to April with hours of bright sunshine rather low for the time of year. The sunniest places have actually been in the far north and west of Scotland with Stornoway Airport observations showing that the site received 83 hours of sunshine in the first half of April, making it the sunniest place in the UK. In contrast, the weather station at Glasgow Bishopton has only received 20 hours: well below average and making it the dullest place in the UK so far this month.

Temperatures have generally been below average for April during the day, but night-time minima have been above average for most of southern England and Wales. Dr Mark McCarthy is the head of the Met Office’s National Climate Information Centre. He explains: “When you drill down in to the detail of the temperature records, you can see that cloudy and wet conditions have exerted a strong influence on the month’s climate records. Helping to supress daytime maximum temperatures, while the same cloud over night has an insulating effect, helping to keep night-time temperatures elevated.”

Provisional climate statistics for the first half of April.

Maximum Temperature Minimum Temperature Mean Temperature
Act °C Anom Act °C Anom Act °C Anom
UK 10.2 -1.3 3.9 0.5 6.9 -0.5
England 11.3 -1.2 4.9 1 8 -0.2
Wales 10.9 -0.7 4.3 0.6 7.5 -0.1
Scotland 8.2 -1.5 2.1 -0.3 5 -1
N Ireland 9.6 -1.9 3.9 0.2 6.6 -1
Precipitation Sunshine
Act mm Anom % Act hours Anom %
UK 52 72 41.8 28
England 51.7 88 35.9 23
Wales 71 80 40.7 26
Scotland 48.2 53 53.4 40
N Ireland 47.7 64 33.1 23

 

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