What does the weather have in store for ‘Super Saturday’?

31 07 2012

With 25 gold medals up for grabs this Saturday we look back at the weather on this day over the last 30 years.

Get the forecast for every Olympic event this Saturday on our Olympic weather pages.





Ground-breaking forecasting keeps Olympic rowing on course

28 07 2012

Ground-breaking high resolution weather forecasting lies at the heart of the Met Office’s services to the Olympic Games, providing the best advice available to both the organisers and competitors at venues in London and across the UK.

The London 2012 Olympic Games got underway in spectacular style on Friday night. As forecast, the Olympic Park saw a brief shower in the run up to the opening ceremony but the main event stayed dry.

The Met Office has been working with LOCOG, providing both longer term planning information and up to the minute details on the likely weather conditions as the focus now moves to the sporting events.

With the rowing events set to get underway on Saturday, accurate forecasts of wind conditions will be crucial to success. Predicting the subtle shifts in wind direction and speed over a small area like the Eton Dorney rowing lake is becoming possible thanks to the introduction of some new advances.

The Met Office weather forecasting model typically forecasts the weather using grid boxes of 4 x 4 km. But the new UKV model uses a much finer scale at 1.5 x 1.5 km over the whole of the country.

Just as increasing the number of pixels on a digital camera improves the picture, reducing the size of these grid boxes can add much more detail and clarity to the forecast.

For the Olympics, the Met Office is set to take high-resolution forecasting a step further by running multiple forecasts at the same time, a technique called ensemble forecasting.

Brian Golding, Deputy Director of Weather Science at the Met Office, explained: “By running multiple forecasts with slightly different starting conditions we can get a handle on how likely a forecast is. This means we can assess the chances of weather impacts in a certain area at a certain time, so we can give much more useful guidance.”

Using this system, detailed probability forecasts of head, tail and crosswinds will be used by the rowing teams at Eton Dorney as they look for that decisive edge that may bring that prized Olympic medal.

The high-resolution ensembles will be used throughout the Olympics. They will then be subject to further research, with a view that the facility could be introduced operationally in the future. This will potentially leave a legacy that will benefit the UK well after the Olympic and Paralympic Games are over.

You can keep up to date with our weather forecasts on our website or with our specific London 2012 Olympic Games forecasts.





Science and technology developments for Olympic and Paralympic weather forecasts

25 07 2012

Our science and technology developments for the Olympic and Paralympic Games will help to deliver increasing accuracy and detail in our weather forecasts during the Games and well into the future.

As part of the services provided for London 2012, we have installed additional weather observation equipment and developed enhanced forecasting capability to support our staff.

The developments include daily air quality forecasts, high resolution wind and wave modelling for Weymouth and Portland, high resolution ensemble forecasting at 2 km for the whole of the UK and additional weather observing technology at Olympic sites.

Daily air quality forecasts

Weather plays a big part in determining air quality and air quality forecasts are now available for all 5000 forecast locations on our website. During the Olympics, air quality forecasts will also be available in map format. We’ve also produced a guide to how the air quality index affects health.

Sample daily air quality index map

 

Wind and wave modelling for Weymouth and Portland

Currently, our models can generate atmospheric weather data for every 1.5 km over the whole of the UK. However, due to the complexity of the winds around Weymouth and Portland a model will be used which gives nearly 20 times more detail than is usually available.

This ensures the highest detail possible for forecasts for wind and waves in the area during the London 2012 competition. While the output from these specially run models is primarily intended to help Met Office forecasters at the Weymouth and Portland events, it will also be available for the public to see for the duration of the Olympics in the showcase of the high resolution wave model.

Example total significant wave height forecast for Weymouth and Portland

 

High resolution ensemble forecasts

Recently the Met Office introduced cutting edge technology into its operational forecasting to help improve the accuracy of forecasting for ‘small-scale’ weather features like thundery showers. For the Olympics, the Met Office is set to take high-resolution forecasting a step further by running multiple forecasts at the same time, a technique called ensemble forecasting.

The high-resolution ensembles will be tested throughout the Olympics before being subject to further research with a view that the facility could be introduced operationally in the future, potentially leaving a legacy that will benefit the UK well after the Olympic and Paralympic Games are over.

Example high resolution ensemble forecast showing chance that temperature will reach 20 C





Weather and sports

24 07 2012

With just days to go until the opening ceremony of the London 2012 Olympic Games, we look at the affect of the weather on four Olympic sports – archery, hockeywindsurfing and triathlon .

Many sports are affected by the weather in some way and conditions are important to athletes and spectators alike. It can help or hinder – headwinds make running and cycling harder, while tailwinds help push us forward, certain conditions can even make world records invalid. For sports like windsurfing, the weather is central to the entire event – without wind, the event cannot take place.

On the whole, dry and settled conditions are favoured by competitors in most sports. However, high temperatures can be challenging, significantly affecting the performance of athletes and, in extreme cases, can cause heat illnesses such as heat cramps and heat stroke.

The Met Office is working closely with LOCOG to provide weather forecasts and information to teams and their trainers throughout the Olympic and Paralympic games. In the build up to the Olympics we’ve also been looking in more detail at how Olympic athletes and professional sportsmen and women look to the weather forecast to train and plan strategy and tactics.

“The weather, and especially the wind, has a fundamental impact on the score. I need to know how to prepare”, says Team GB archer Michael Pearte.

Read Michael’s full interview.

Great Britain Hockey player Maddie Hinch says that actually rain can be a welcome part of the forecast – as long as it’s not too cold.

Read Maddie’s full interview.

Triathlete Todd Leckie told us his ideal conditions would be cool temperatures, no rain and a favourable tail wind. In Britain, though, he admits this is often not the case.

Read Todd’s full interview.

Windsurfing and the weather are intrinsically linked – the wind has an impact on every single session, affecting those just starting out and experienced professionals.

Amy Carter, Editor of Boards Magazine, explains the conditions that windsurfers look out for.

For weather forecasts for all Olympic venues see our events forecast page.





Weather forecasts for the Olympic Games

23 07 2012

The Met Office is providing weather forecasts for all Olympic venues during the Games and beyond. As part of the services provided for London 2012, we have installed additional weather observation equipment and developed enhanced forecasting capability to support our staff.

During the Olympic and Paralympic games the Met Office will also be showcasing some cutting-edge weather techniques and technology in its forecasting, as well as providing additional services for the public. To add specialist knowledge and expertise, the Met Office will have 12 forecasters on site across the Olympic venues throughout the games.

For easy access to the latest forecast for each sport and Olympic venue, all the links you need are below.

Sports
Archery Cycling – Mountain bike Marathon swimming
Athletics Cycling – Road Rowing
Beach Volleyball Equestrian Sailing
Canoe Slalom Football Shooting
Canoe Sprint Hockey Tennis
Cycling – BMX Modern Pentathlon Triathlon
Locations
Olympic Park North Greenwich Arena Horse Guards Parade
Lords Cricket Ground ExCel centre Lee Valley White Water Centre
Wembley Arena Eton Dorney Hadleigh Farm, Essex
The Mall Box Hill Hampton Court Palace
City of Coventry Stadium Hampden Park, Glasgow Millennium Stadium
Old Trafford St James’ Park, Newcastle Hyde Park
Weymouth & Portland Royal Artillery Barracks Wimbledon

If you’re lucky enough to be attending an Olympic or Paralympic event, you can keep up to date with the local forecast while you’re there on our mobile applications for iPhone and Android, or on our mobile website.





Improving picture as many start school holidays

18 07 2012

After weeks of heavy rain across parts of the UK, conditions are set to improve for many areas this weekend.

More heavy showers will affect some parts during the rest of the week, but by Saturday most areas will see drier weather with any showers few and far between. Temperatures will reach the low 20s Celsius.

Sunday will see the improved weather continue for a large part of England and Wales, with mostly dry weather and bright or sunny spells expected. However, the north and west of the UK, can expect some rain – which will be heavy in places – with strong winds.

Drier weather for many, with rain where it’s needed

Martin Young, Chief Forecaster at the Met Office, said: “As we move towards the weekend we will see a return to a more normal summer weather pattern for the UK. This will bring dry and bright conditions to southern parts over the weekend, and some much needed rainfall to the far north west of Scotland – where it has been exceptionally dry.”

Jet stream returning to ‘normal’ position

There has been a lot of talk about the position of the jet stream in relation to the recent wet weather, with this narrow band of fast flowing winds having been much further south than we would expect at this time of year.

Over the next few days, the jet stream is expected to move to its more usual position to the north of the UK, guiding rain-bearing low pressure systems from the Atlantic away from the country. This is why we expect to see a move to more normal summer conditions, with the south and east seeing the best of any drier and brighter conditions.

The above picture shows the position of the jet stream on 18 July 2012.

The forecast for 23 July 2012 shows the jet stream much further to the north.

Looking to the Olympics

There is understandably a huge amount of interest in what the weather will be doing at the end of next week in time for the Opening Ceremony of the Olympic Games. However, it’s still a little early to give a detailed forecast for the Olympic Stadium for the big opening event.

Sandie Dawe, Chief Executive at VisitBritain said: “The weather is a peculiarly British obsession, our international visitors come all year round for our temperate climate and enjoy a dash of unpredictability. Sunshine will help to get us all in the party mood, as we show the warmth of our welcome and the British know how to host not just a great Games but a great party too. Come rain or shine – Britain is the place to be in 2012.”

As ever, we’ll be working round the clock to make sure everyone – from the UK public, to athletes, coaches, and the organisers of the Games – has the very latest picture of what the weather has in store. For the latest information, keep up to date with our online forecasts and warnings.





How is the weather affecting pollen?

17 07 2012

The weather has been very unsettled during June and the start of July, and this has been reflected in the pollen counts. As we predicted back in May, there have been some very high counts, but there have also been some days when the pollen has been washed out by the heavy rain.

The heavy rain we have seen has maintained the strong growth of native plants that started with the very wet April.  This means that there is an ample supply of pollen from grasses and weeds such as nettle. However, the unsettled weather has meant that pollen counts have fluctuated significantly from day to day and place to place.

Further high pollen counts are expected during any drier and sunnier interludes. This will increasingly come from weed pollens.

The graph below shows how the pollen count has changed significantly from day to day this summer, in response to the weather, and that on high days it has been much higher than last summer:

Pollen count has changed significantly from day to day this summer in response to the weather.

Patrick Sachon, Health Manager at the Met Office said: “The unsettled weather this summer has led to a fluctuating pollen count but as expected we have seen some very high levels when the weather has been good. Further high counts are expected during any settled, drier weather. We would therefore recommend that hay fever sufferers check the pollen forecast sponsored by Benadryl, every day and do all that they can to manage their symptoms.”





First half of July continues wet and gloomy theme

17 07 2012

Provisional mid-month statistics from the Met Office show that, after an exceptionally wet and gloomy June, the first half of July has continued the disappointing theme.

Normally at the halfway stage of a month we’d expect sunshine and rainfall to be somewhere around 50% of the average for the whole month, but the figures show a very different story.

Looking at the UK, we’ve already had more than the average rainfall we’d expect for the entire month – with 71.8mm (103% of the 1971-2000 average) falling up to the 15th of the month.

Within that there are some big variations, however. Northern Ireland and Scotland have seen close to normal levels of rain, with 35.9mm (49%) and 56.4mm (61%) respectively. England and Wales have seen much more relative to their monthly averages, with 81.2mm (150%) and 95.8mm (122%) respectively.

Looking in even more detail at Scotland, however, you can see bigger variations in rainfall patterns: Mid Lothianshire in south east Scotland has seen 105.8mm (167%) of rain, while the Western Isles in the far north west of Scotland have seen just 10mm (10%).

This illustrates how rainfall patterns have really bucked their usual trend, with the far north west – which is usually one of the wettest places in the UK – continuing to be one of the driest areas. This is partly due to the position of the jet stream, as discussed in previous articles.

Looking at sunshine, there is a more consistent pattern across the regions. The UK has seen 45.5 hours of sunshine, just 26% of the average for the whole month, so around half what we would normally expect to see by this time. So far, England, Wales, Scotland and Northern Ireland have all seen about a quarter to a third of their monthly quota – making for a very dull month thus far.

Temperatures have also been on the disappointing side – with the UK seeing an average temperature so far of 13.7 deg C, which is 1.1 deg C below the monthly average.

With figures only going up to the 15th of the month, it is of course impossible to say how the month could finish overall. It’s certainly too early to say whether this month will be a record-breaker, as that will depend on how the second half of the month plays out.

While more rain is expected in parts of the UK today there will also be some dry and sunny weather too.  The good news is that the weekend is set to bring drier and brighter weather to many parts of England and Wales – while the far north west of Scotland is likely to see some much-needed rain.





Does the jet stream affect hurricanes?

16 07 2012

Many news and weather articles, including our own blog, have reported recently that the UK’s wet summer is caused by the jet stream being situated further south than usual for this time of year.

However, some have questioned whether there is a link between this and the hurricane activity seen so far in the Atlantic.

So how is the Atlantic hurricane season shaping up and has it been influenced by the weather at higher latitudes?

Atlantic hurricane season so far

The Atlantic hurricane season officially started on 1 June, but in 2012 it began early with two tropical storms, Alberto and Beryl, forming in May.

After a break of almost three weeks there were two more storms, Chris and Debby, in the latter part of June, with Chris becoming the first hurricane of the season.

Since then there has been another lull of almost three weeks in Atlantic tropical storm activity.

Has the Atlantic hurricane season been unusual?

In mid-July it is far too soon to make judgements about how unusual a hurricane season is likely to be based on activity so far. However, it was certainly unusual to see four tropical storms before the end of June as this has never been observed before in over 150 years of records.

The recent quiet spell in Atlantic hurricane activity is by no means unusual. Atlantic hurricane seasons are often characterised by bursts of activity followed by quiet spells.

The peak of activity usually runs from the second half of August through to October. Even in some years which turned out to be very active, early season activity was low.

For example, by this time in 2010 and 2011 there had been just one tropical storm. Each of these seasons ended up yielding a total of 19 storms.

Is the jet stream involved?

The jet stream which affects UK weather is much further north than where the majority of tropical storms develop and hence has no direct impact on their formation.

However, once a tropical storm develops and starts to move to higher latitudes the jet stream can influence where it ends up. For example, in September 2011 as Hurricane Katia moved northwards in the Atlantic it met a powerful part of the jet stream and was swept eastwards as a strong ‘post-tropical’ storm which brought stormy conditions to the northern UK.

Will it be an active hurricane season?

The Met Office seasonal forecast for Atlantic tropical storm activity issued in May predicted a near-average season with the most likely number of storms in the June to November period being 10. Since June two tropical storms have occurred so far (the two May storms fall outside of this prediction period).

One of the major influences on the season’s activity includes the existence of La Niña or El Niño conditions (natural cycles which affect sea temperatures in the equatorial east Pacific).

Having just come out of an extended period of La Niña conditions, forecasts suggests an El Niño could develop before the end of the current hurricane season.

This would suppress hurricane activity in the Atlantic by disrupting the airflow over the regions where they usually develop.

However, it is worth remembering that it is 20 years since the quiet El Niño influenced Atlantic hurricane season of 1992. Despite being a quiet season overall, it still managed to spawn the deadly and powerful Hurricane Andrew which brought devastation to parts of Miami in Florida.

For more information on tropical cyclones worldwide visit our web pages or follow @metofficestorms on Twitter.





The UK’s wet summer, the jet stream and climate change*

12 07 2012

There’s no disputing it has been a very disappointing summer so far in 2012 – with the wettest June for over a century followed up by a very wet start to July.

In fact, barring a warm and dry spell towards the end of May, the weather has been persistently dull and wet since April – which was also the wettest in records dating back to 1910.

Our weather here in the UK is complex and determined by many different factors, including the position of the jet stream.

This is the narrow band of fast moving winds which runs from west to east across the Atlantic high up in the atmosphere.

How does the jet stream affect UK weather?

Weather (or low pressure) systems bearing rain and unsettled conditions move across the Atlantic on a regular basis. The jet stream guides these systems, so its position is important for UK weather.

In summer, we would expect the jet stream to be north of the UK – dragging those weather systems away from our shores to give us relatively settled weather.

So far this year it has been to the south of the UK, guiding those systems straight to us. This is the position we’d normally expect the jet stream to be in during winter, when we are more accustomed to these wet conditions.

So why is the jet stream stuck so far south?

The jet stream, like our weather, is subject to natural variability – that is the random nature of our weather which means it is different from week, month or year to the next.

We expect it to move around and it has moved to the south of the UK in summertime many times before in the past. It has, however, been particularly persistent in holding that position this year – hence the prolonged unsettled weather.

This could be due to natural variability – a bad run of coincidence, if you will – but climate scientists are conducting ongoing research to see if there are other factors at play.

Changes in sea surface temperatures due to natural cycles may be playing a part, but there is more research to be done before anyone can establish how big a role they play.

Research has also suggested that reducing amounts of Arctic sea-ice could be affecting weather patterns, but more research needs to be done to confirm this link. Currently Arctic sea-ice is at a record low for this time of year.

Is climate change playing a role?

In the long term, most climate models project drier UK summers – but it is possible there could be other influences of a changing climate which could override that signal on shorter timescales.

If low levels of Arctic sea ice were found to be affecting the track of the jet stream, for example, this could be seen as linked to the warming of our climate – but this is currently an unknown.

The Met Office Hadley Centre, working with climate research centres around the world, is making strides in determining how the odds of extreme weather happening have been influenced by climate change.

However, it is very difficult to do this type of analysis with such highly variable rainfall events, so it may take many years before we could confirm how the odds of this summer’s wet weather happening have been altered by greenhouse gases.

We do know that the warmer air is, the more moisture it can hold. We have seen a global temperature increase of more than 0.7 deg C (since pre-industrial times) and this has led to an increase of about 4-5% in atmospheric moisture.

This means that when we do get unusual weather patterns such as we’re seeing now, it’s likely there will be more rainfall than the same patterns might have produced in the past. In short, it seems when it does rain, it is heavier.

Taking into account this effect, perhaps it’s not surprising new records like those for this April and June are being set. In fact, the wettest July and November in the records dating back to 1910 happened in 2009, making a total of four record wettest months in the past four years. If wet months occurred randomly, we would expect only one record to have been broken since 2006.

For temperature, April (2011), May (2008), July (2006), September (2006) are all recent warmest records. Again, this is much more frequent than would be expected if temperatures were not rising.

What about elsewhere in the world?

Looking at the bigger picture, the jet stream may be having an impact elsewhere in the northern hemisphere.

It is stuck in a persistent pattern of waves, with one of these ‘waves’ taking it to the south of the UK.

Figure shows upper level wind patterns in early July 2012, with the northern hemisphere jet stream marked with arrows.

The figure gives a picture of the upper level winds for the first week in July, but the wavy nature of the jet stream has been persistent throughout June.

Meanders of the jet north and south can be seen across the US, the Atlantic and into Europe.

While the wet weather in the UK has been under a southward meander of the jet stream, the recent Russian floods near the Black Sea appear to have been beneath the next trough to the east.

The US heat wave is also beneath a northward meander and a ridge of high pressure.

* This article has been written in collaboration with the Walker Institute for Climate System Research, University of Reading.








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