Jet stream brings cool and changeable start to August

After an unsettled and cool end to July, August has continued in a similar vein. Many places have been showery and cool so far, with a southward-shifted jet stream to blame. This has directed areas of low pressure, which normally skirt to the north of the UK in summer, to instead move across the country.

In between spells of rain or showers brought by these low pressure systems, there have been some drier, brighter days and sunshine amounts have been close to normal. However, temperatures have been a little disappointing, with no locations recording a temperature in excess of 25 °C up to 15 August.

Provisional figures show mean temperatures have generally been below average for August by about 1 °C, but central southern England has seen the greatest differences compared to the 1981-2010 average. For south-east and central southern England the period 1-13 August 2017 has been the coldest since 1987. Interestingly, however, if you compare temperatures for this period to those experienced in the years 1961-1990 then it wasn’t so unusual to see such suppressed temperatures for the first half of August.

In terms of rainfall, many places have seen more than half of the whole-month average already, with locations around the Humber and across parts of central southern and south-east England getting close to their month average. Up to 15 August, the UK has received 60% of the whole-month average for rainfall. Looking back over the last ten years, several Augusts have been wet over large parts of the UK, so the month does have a tendency to disappoint those looking for dry weather.

You can read weather summaries of previous months and seasons for the UK here.

1-15 August 2017 provisional figures Mean temp (°C) Rainfall (mm) Sunshine (hours)
Actual  Diff to avg (°C) Actual % of avg Actual % of avg
UK 14.1 -0.8 53.9 60 79.6 49
England 15.2 -0.9 44.4 64 86.3 47
Wales 14.1 -0.9 61.8 57 75.7 45
Scotland 12.5 -0.5 67.7 58 70.1 52
N Ireland 13.8 -0.5 53.8 55 76.0 56

For the rest of August, it looks like the weather may settle down during next week, bringing some longer periods of dry weather with temperatures also recovering. However, low pressure is likely to bring further spells of wet and occasionally windy weather later this week and early next week.

You can keep up to date with the weather using our forecast pages, on our popular mobile app which is available for iPhone from the App store and for Android from the Google Play store and by following us on Twitter and Facebook, as well as using.

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Torrential monsoon rains wreaking havoc across parts of southern Asia

Torrential monsoon rains over the last seven days have reached life-threatening levels for communities south of the Himalayas from Nepal to Bhutan and northern India to Bangladesh.

Severe floods and landslides have wrought havoc. Already across the affected region communities have faced tragedy, including: loss of life; thousands of homes submerged; extensive crop damage; as well as collapsed bridges and blocked roads.

Further heavy rain is forecast over the next few days and this will extend the zone of flooding downstream to communities lining those major rivers which flow from the Himalayas.

Nick Silkstone is a Met Office forecaster working in the Global Guidance Unit. He said: “The region between the Himalayas and the Bay of Bengal is bisected by some of the world’s great rivers, such as the Brahmaputra and the Ganges, which drain the region normally taking water safely to the sea.

“Even though these are some of the world’s mightiest rivers the forecasts suggest even these giants are going to struggle with the amount of pressure these systems are currently facing.

“Global flooding indicators, such as GLOFAS, are indicating high probabilities of river flows that are only anticipated once every two decades in many of the region’s major rivers, giving an early warning of a significant event to come in the next week.”

There are already reports of extensive loss of farmland due to the flooding, and agencies are reporting waterborne diseases proliferating in flooded areas.

The monsoon is a natural part of south Asia’s weather, but this year rainfall in some areas has been over four times greater, when compared with the average between 1981–2010.

Clare Nasir is a weather presenter and meteorologist with the Met Office. She said: “The monsoon brings life-giving rains to the region, but the conditions in some years can be very cruel.  Extensive rainfall can be more concentrated in some parts than others. This year, the north region has received much more rain than other parts of India.”

With further rain forecast this coming week and a lag time from last week’s rain reaching communities downstream, the risk of extensive flooding continues.

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When will summer return?

It often seems that summer starts hot and sunny but by the time the main holiday period begins, the rain has set in … it is disappointing and frustrating that the weather doesn’t always live up to our hopes, as witnessed in the last couple of weeks.

So, when will summer come back? Well, if you have read some media reports, you may think that August – the last month of meteorological summer – will be dominated by hurricanes or continual deluges. Attention-grabbing headlines may attract interest but they don’t inform readers about what the rest of summer may have in store.

To understand what the rest of the month may hold, let’s look at the weather situation now. After some hot spells in June and early in July, the UK’s weather is currently being dominated by a series of low-pressure systems, steered our way by the jet stream, which is sitting across the UK at present, rather than being positioned further north. Sadly, this relocation of the jet stream has coincided with many people taking holidays in the UK.

Laura Paterson is a Chief Forecaster with the Met Office. She said: “During the summer we would hope that the jet stream might be positioned well to the north of the UK, which brings an increased chance of warm, sunny weather. However many years defy this hope and, as at present, we end up with the jet stream shifted further south, guiding low-pressure systems right across us, rather than steering them to the north of Scotland.”

Will this situation persist? Well, indications are that until the middle of next week the weather will remain changeable – although parts of the country may see some improvement over the weekend, particularly across the south on Sunday, when some sunnier, drier conditions are on the cards. A further improvement may come to pass later next week but this is still quite a long way off and so confidence levels aren’t too high. This is especially the case, since the improvement may be influenced by the remnants of tropical storm Emily – which may actually help to nudge the jet stream further north.

After that it’s difficult to give too many details, but it looks like the second half of August may bring finer weather than the first half, especially for southen parts of the UK. This means that most of us will see some sunshine, but there is still likely to be some rain and showers in the forecast.

With many people on holiday, tourists often wonder about the weather during their vacation. Andrew Stokes, VisitEngland’s Director said: “Whatever the weather there is an outstanding range of quality destinations and attractions on offer and with the ease and convenience of holidaying at home, Brits are discovering more of England and driving the economic benefits of tourism across the country.”

Alex Deakin is a presenter with the Met Office. He said: “To a fair extent the outlook for the rest of August depends upon your philosophical bent and whether your rain gauge is half full or half empty. Pessimists may see rain in the forecast and assume that it’s going to be a washout: optimists see brighter periods in the forecast and make the most of it. However, the reality is that during the unsettled periods there will be brighter spells, which, with the strength of the August sun, could feel very pleasant.

“Despite the headlines it is certainly not all doom and gloom, and whatever the weather, smart people use their smart phones and plan their days and activities around the up to date information from the Met Office weather app.”

You can keep up to date with the weather using our forecast pages and by following us on Twitter and Facebook, as well as using our new mobile app which is available for iPhone from the App store and for Android from the Google Play store.

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The Fujiwhara effect: When Tropical Cyclones go dancing

Did you know that Tropical Cyclones sometimes go dancing? This interesting phenomena is called the Fujiwhara effect*, which can be seen this week in the Eastern Pacific Ocean off the coast of Mexico.

Hurricanes Hilary (right) and Irwin (left) in Eastern Pacific at 1400 UTC on 26 July 2017. Image courtesy of NOAA

Sometimes, when tropical cyclones get close to one another (within about 1,200km), they rotate around each other in an anti-clockwise direction (in the northern hemisphere). They tend to rotate around a point between them, rather like two dancers joining hands and spinning around, this is the Fujiwhara effect. If the Tropical Cyclones are of a similar size, then they can move around one another for perhaps up to a few days, then release and move away on their own paths, like the dancers letting go of each other’s hands.

If the Tropical Cyclones are of different sizes, then the larger of the two will tend to dominate, with the smaller one orbiting around it, similar to the way in which the moon orbits around the Earth. Sometimes, the smaller Tropical Cyclone will be “eaten up” by the larger one. The two systems then essentially merge, with the smaller storm dissipating and the larger storm remaining and moving away on its own. This is what is expected to happen through Thursday and Friday this week, with Hurricane Irwin being consumed by the stronger and larger Hurricane Hilary. Hurricane Hilary is then expected to move away to the northwest, before finally dissipating later this weekend.

Forecast track showing Hurricane Hilary and Hurricane Irwin as they dumbell round each other

When Tropical Cyclones dance around each other due to the Fujiwhara effect, it can be challenging for numerical weather prediction models to accurately represent the interactions that the two Tropical Cyclones have with each other. In fact, if you get three Tropical Cyclones coming within close proximity of each other, they can all interact in a complex fashion, making forecasts even more difficult. The accurate forecast of Tropical Cyclones is very important as these storms can sometimes have huge impacts on tropical regions if they make landfall in populated areas. Fortunately, in this case, Hilary and Irwin are forecast to stay well away from land, remaining instead over the open waters of the eastern Pacific, so are not expected to cause any significant impacts.

Further Information

For more information on Hurricanes Irwin and Hilary, including the official forecast tracks and warnings, please see the US National Hurricane Center’s website.

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.

*The Fujiwhara effect was named after Sakuhei Fujiwhara, who described it in his 1921 paper about symmetrical motions in the atmosphere (http://onlinelibrary.wiley.com/doi/10.1002/qj.49704720010/pdf – QJRMetS, October 1921, pages 287-292)  

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What is causing my hay fever?

It’s that time of year again when grass pollen is in the air across the UK. For many people this brings all the symptoms of hay fever: runny nose, itchy eyes, and sneezing. The NHS says hay fever is one of the most common allergic conditions, with an estimated 13 million people affected in the UK. If you are one of those affected, or you know someone who is, you might want to understand what is causing hay fever, and what you can do to minimise symptoms.

Rachel McInnes is a senior climate impacts scientist at the Met Office working on climate interactions with health, while helping to advance pollen research. In this post she explores all things pollen related:

Hay fever is caused by allergenic pollen released by certain grasses, trees and weeds. Pollen contains proteins that can cause the nose, eyes, throat and sinuses to become swollen, irritated and inflamed. Grains of pollen are released into the air from these types of plants when they flower. From here, people can breathe in the pollen grains.

Pollen can disperse long distances and, depending on the weather conditions, can travel a huge distance from the plant. Lots of meteorological conditions influence when pollen is released, how much is produced, and where it travels. Wind speed, direction and rain affect pollen levels in the air. When it rains pollen is ‘washed out’ of the atmosphere and brought to the ground, where we can’t breathe it in. Sufferers often notice symptoms improve on wet days. Although pollen can travel huge distances (even from country to country), most pollen travels less than 20km, and the majority doesn’t go further than a few kilometres.

Recently researchers from the Met Office joined with scientists from the University of Exeter to produce maps of allergenic trees, grass and weeds in the UK (see grass map example below) *. These maps provide a good indication of the distribution of different allergenic plants, and they can be used to improve understanding of pollen impacts on health. They are also a step towards a pollen forecast which, when combined with weather data, could provide detail about pollen from individual species.

* This work was part of the Health Protection Research Unit in Environmental Change and Health, and collaborators on the mapping work included researchers from the Devon Wildlife Trust, The University of Worcester, Bluesky International and Public Health England.

Map of grass density in the UK. Units are percentage cover of grass per 1km x 1km grid square. Image Crown Copyright, 2016, The Met Office. Based on digital spatial data licensed from the Centre for Ecology & Hydrology, copyright NERC (CEH).

These different trees, grasses and weeds produce pollen at different times during the ‘pollen season’:

  • The UK pollen season begins with trees coming into flower, which can be as early as January or February, and peaks from mid March to May.
  • Grasses in the UK flower from mid May to July. This is when most people experience symptoms, with grass pollen being the most common UK allergen for asthma and hay fever.
  • Finally, weed pollen is present from the end of June to September. Noticing the time of year sufferers experience symptoms may help understand which of these plants they are most allergic to.

What can be done to manage hay fever and reduce symptoms?

Firstly, stay informed about when pollen levels are highest in your area by looking at our pollen forecast. To get the latest pollen forecast, view our Pollen forecast which provides a UK forecast of the pollen count and provides sufferers with an early warning. You can also download our free app to get daily updates of pollen alerts in your region to your phone or tablet. The Met Office runs the only pollen-count monitoring network in the UK and we provide a forecast up to five days ahead during the pollen season.

On days where the pollen levels are high in your area, try to avoid pollen as much as possible. For example:

  • Keep windows closed when at home and overnight. Most pollen is released in the early morning and falls to ground level in the evenings, when the air cools.
  • After being outside, change clothes, shower and wash hair to remove pollen.
  • Avoid drying clothes outside when pollen counts are high. If you do, shake items before bringing them inside.
  • Other tips about avoiding exposure to pollen can be found here.

How might things improve in the future for hay fever sufferers?

The Met Office is part of a team of researchers investigating grass pollen in the UK, using state-of-the-art genomic technology to read the DNA ‘barcode’ of grass pollen. The team hopes to discover which of over 150 species of grasses in the UK have the largest effect on people’s health. This work, as part of the PollerGEN project, could lead to a detailed species-level pollen forecast, to help individuals better manage their condition.

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Measuring the hot spell of June 2017

The last week has seen high temperatures across large parts of England and Wales in what has been the longest continuous hot spell in June since the hot, dry summer of 1976. Temperatures of 30°C or more were recorded somewhere across England and Wales for the last five days, peaking on Wednesday 21 June at 34.5°C at Heathrow, London which was the hottest day of the year so far. However, for Scotland and Northern Ireland it was hotter on 26 May (Lossiemouth, Moray, 29.4°C and Castlederg, Tyrone, 26.2°C)

Below is a rundown of the top temperatures recorded in each of the home nations through this hot spell:

Location Date Temperature / °C
ENGLAND
Heathrow, London 21 June 34.5
WALES
Cardiff, South Glamorgan 21 June 31.0
SCOTLAND
Floors Castle, Roxburghshire 18 June 26.5
NORTHERN IRELAND
Helen’s Bay 18 June 25.6

Although notable, this hot spell didn’t break any national temperature records, it was for many of the long running weather stations the hottest June day since the 1976 heatwave. One exception was that on Monday 19 June, Newport in Shropshire recorded a temperature of 30.8°C which narrowly beat the previous record of 30.7°C from 29 June 1976 in an 85 year record.

The images below show how the pattern of heat altered over the course of this period. With high pressure dominating, bringing a warm south or southwesterly flow of air, heat was concentrated across southern parts of the UK, but temperatures in the north of England and Wales were in the high 20°C’s over last weekend and the early part of this week.

Maximum temperatures June 2017

Many sites recorded their highest June maximum temperatures since 1976 this week. However the hot spell in June 1976 remains the UK’s most significant for the month when temperatures exceeded 32°C widely across England and the current UK maximum temperature record for June was set at Mayflower Park, Southampton on 28 June when 35.6°C was recorded. The maps below show the extent and longevity of the heat over that period.

Maximum temperatures June 1976

The Met Office are responsible for maintaining the network of observing sites across the UK and their readings play an important first step in helping meteorologists to forecast the weather. Our weather station sites are selected to ensure that the observations are representative of the wider area around the station and not disproportionately affected by local effects. This means that weather stations in urban areas, although carefully sited to be representative of that area, will always be warmer than surrounding rural locations, but still reflect the conditions being experienced by people living and working there.

The map below shows the temperature measurements which were recorded by people contributing to our Weather Observations Website (WOW) alongside the Met Office official observations on the afternoon of the 21 June.

WOW observations 21 June 2017 http://wow.metoffice.gov.uk/

The Met Office sites recorded maximum temperatures from 32.9 °C at London, St James’ Park to 33.8 °C  at Kew Gardens and 34.5 °C at London Heathrow a range of 1.6 °C. The WOW readings clearly show a much larger range and the importance of having a well-sited thermometer which isn’t in full sun or in a very sheltered location to provide observations that are representative of the wider area. However, the WOW data are very useful to add context and show that some people may experience temperatures higher or lower than the official observations around their home or workplace.

If you’d like to find out more about contributing to WOW you can sign up or enter an observation here.

More information about this hot spell of weather is availble on our UK climate pages.

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Could navigational buoys help with Met Office forecasts?

For the first time the Met Office has set up a trial to see if it is possible to use navigational buoys to gather weather data from near coastal areas.

The Met Office has just 10 weather observation buoys around the UK coast, meaning this area, which is vital when it comes to the understanding of weather systems transitioning from the open ocean to the land, is particularly data sparse.

Trinity House buoys around the coast of England and Wales

Trinity House, the lighthouse authority for England, Wales, the Channel Islands and Gibraltar, joined forces with the Met Office to help look at ways to get the latest weather information to ships of 300 tonnes or more.

Met Office weather stations are already placed on Trinity House’s Lightvessels* in the English Channel. Anyone who’s heard the shipping forecast may well have heard Lightvessels mentioned as their readings are regularly used.  Trinity House also has over 400 navigation buoys around the coast.

Barrow 6 Buoy

The joint project looked at placing weather observation equipment on one of the existing navigation buoys and transmitting that data to the Met Office as another source of coastal observations.

Location of Barrow 6 in relation to our closest stations

A buoy in the Thames Estuary, Barrow 6, and  another in the Bristol Channel,  have now been equipped with wind, temperature, humidity, barometric pressure and sea surface temperature sensors.

AWS system being put onto Barrow 6

This is a similar set of sensors to the other buoys in the Met Office network, although it uses  a different set up, so the systems can easily be installed on a third party buoy. In the future the data from the buoy will hopefully not only be sent to the Met Office but also to ships via Automatic Identification System (AIS**).

This new project opens up the possibility of increasing observations from this data sparse marine location.

*Lightvessel – ships that act as light houses out at sea.

**AIS is a VHF network of transceivers on ships of 300 tonnes or more which aids navigation. It is primarily an anti collision system but has dedicated message formats for other data, including meteorological data.

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Heavy rain boosts rainfall totals for Southern England

The mid-month statistics for May (1-17 May) show the month got off to a dry start, although the heavy rain yesterday brought up rainfall totals in some areas. It has also been a sunny and moderately mild early May for many.

The anticyclonic theme that dominated the UK weather in April continued into the start of May, meaning in some regions there was little rainfall aside from the rain on Wednesday. East Anglia and most of Scotland have been particularly dry so far this month, with only around 10% of the whole-month average up to 17 May. It has been wetter towards the south-west and west, with some places in the Lake District and western Wales already approaching their monthly rainfall averages. From a national perspective, the UK has so far seen 44% of the whole-month average so far.

Following the heavy rainfall on 17 May, Dorset and Hampshire are now at 79% of their long term average for the whole of May. South Farnborough in Hampshire for example had only received 12.8mm of rain up to 15th May, just 24% of the monthly average. The rain over the past two days has pushed the total up to 52.2mm which is 99.7% of the site’s average for the month. On average South Farnborough sees only 9 days in May with more than 1mm of rain recorded so it’s not that unusual for a large proportion of the monthly average to fall in a few notably wet days.

In contrast, Loch Glascarnoch in the Scottish highlands has so far this month received only 6.4 mm of rain, just 7% of its monthly average. Overall Scotland has so far received 19.5mm which is 23% of its average rainfall for May.

Temperatures for the month so far have been close to average from a UK perspective, with the mean temperature being just 0.2°C above the long term average. Northern Ireland has been the mildest region compared to its long term average with mean temperatures 1.1°C above the average so up to 17 May.

With the widely settled conditions, there were some rather chilly nights for the time of year with air frosts in certain areas. Ground frost was even observed in rural Devon on the morning of 10 May. Cloud-cover and high humidity meant an unusually warm night on 15/16 May with minima of 15 °C in places, and the highest temperature of the year so far was recorded at Gravesend in Kent with 25.8 °C on the 16th.

In line with the milder temperatures in Northern Ireland, sunshine hours have also been highest in this region. Northern Ireland has seen 92% its average monthly sunshine hours already this month with 168.2 hours. In contrast some eastern counties in England are some way below where you would expect them to be by this point in the month, with Suffolk and Norfolk recording 36 and 37% of their monthly average sunshine hours respectively. The UK as a whole has recorded 63% of its average monthly sunshine.

Provisional 1-17 May 2017 data Mean Temp Sunshine Hours Precipitation
Actual (°C) Diff to average Actual hours % of average Actual (mm) % of average
UK 10.6 0.2 116.5 63 30.5 44
England 11.2 0 94.6 50 33 57
Wales 10.9 0.3 120.1 64 50.2 58
Scotland 9.4 0.5 142.3 80 19.5 23
N. Ireland 11.3 1.1 168.2 92 38.5 53

 

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Early April statistics

Early provisional statistics for April (1st-26th) show that overall it has also been a sunny and warm month so far compared to the long-term 1981-2010 average.

Following on from the mid-month statistics, Middlesex remains the driest historical county with 2.7mm of rainfall so far this month just 6% of the long-term average for April which is 45mm. In comparison Sutherland has so far been the wettest historical county with 130.8mm of rain, 41% above the expected monthly rainfall.

The UK as a whole has seen just 41% of the average April rainfall; the wettest region has been Scotland with 62.5mm and the driest southern England with 8.1mm.

It is likely many of the rainfall statistics will change as we expect an area of low pressure to move in from the south-west over the Bank Holiday weekend. As a weather front pushes eastwards across the UK on Sunday and Monday, we could see 10-15mm of rain in some areas, especially in the south-west. Read more about this weekend’s weather in our latest news release.

Despite the recent low temperatures, with the coldest night reaching -6.2°C (Cromdale, Moray 18 April 2017), April has also so far been a warmer than average month. On 9 April 25.5°C was recorded at Cambridge, the warmest day of the year so far. Overall the UK mean temperature has so far been 0.6°C higher than the long-term average. The warmest area against its long-term average was in Scotland, with Forfarshire recording 1.1°C above its long-term monthly average.

Nearly all of the UK has already had the sunshine we would expect for the whole month, and there are still several days left to include in the statistics. Only Scotland and Northern Ireland are below the average with 88% and 63% respectively. The UK as a whole has already reached its monthly average with 148.4 hours of sunshine. The district with the most sunshine hours is the south east and central south of England with 188.3 hours of sunshine, 11% above the April average.

Early April Mean Temp Sunshine Hours Precipitation
1-26 2017 Actual Diff to average Actual hours % of average Actual % of average
UK 8C 0.6% 148.4 100 29.7mm 41%
England 8.8C 0.7% 169.9 110 11.9mm 20%
Wales 8.2C 0.6% 161.0 104 18.4mm 21%
Scotland 6.6C 0.5% 119.4 88 62.5mm 69%
N. Ireland 8.2C 0.6% 92.7 63 27.8mm 37%

You can keep up to date with the weather using our forecast pages and by following us on Twitter and Facebook, as well as using our new mobile app which is available for iPhone from the App store and for Android from the Google Play store.

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Big data – big challenge

The Met Office is facing new and increasing challenges because of the huge volume of data that we manage and produce. Alex Longden, who leads the team responsible for data provision for the data re-use community and private weather sectors, examines the situation in this blog.

The 335 million observations of data we store every day require huge computational capability. Our new supercomputer provides the processing power needed to manipulate the data in a timely and effective way. The complex numerical models developed by our scientists and meteorologists in turn create enormous data outputs, used for climate and weather prediction and by data users throughout the world to make weather outlooks more accurate than ever before.

The state of weather data infrastructure

The Met Office recognises that increases in observational and forecast data volumes have implications across both the public and private weather sectors. To understand this better, we recently partnered with the Open Data Institute, to carry out a review on ‘The state of weather data infrastructure’.

The review is encouraging discussion on how the global weather data infrastructure can be sustainable, and continue to deliver value to society, as well as looking at the need for continuing investment in technical infrastructure and supercomputing resources. It also looks at the role of global, regional and national meteorological services in collecting observations and generating forecasts.

In addition, the review highlights the technology creating new data and in turn generating new, big data challenges. Supercomputing is enabling new and improved weather models which are harnessing a variety of sources of weather observations from ground, air, sea and space based monitoring and sensors. These trends exist within a wider landscape of innovation and changing consumer expectations where instant and real-time access to data is increasingly essential.

We are striving towards making our data more openly accessible and useful to realise the social economic benefits brought by the new supercomputer, which delivers ever increasing accuracy yet exponential increases in data volumes that makes this more challenging.

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