Recent rainfall totals

Rain has continued to cause disruption across parts of the UK, with overnight rain adding to significant totals over the past few days.

The wettest place in the UK (and Scotland) since the heavy rainfall began on 19^th December to 6am this morning has been Tyndrum in Perthshire, with 155.0 mm of rain.

Cardinham near Bodmin, Cornwall, is the wettest place in England with 128.8 mm of rain and the wettest place in Wales has been Mumbles Head, West Glamorgan, with 107.0 mm of rain.

Ballypatrick Forest in Antrim has been the wettest place in Northern Ireland, with 89.0 mm of rain.

Some areas have exceeded their full-month December average since the 19^th – such as Plymouth, Devon, which has seen 128.8mm of rain compared to a December average of 118.8 mm.

Below is a table of the wettest places in the UK from 0000 HRS on 19th December to 0600 HRS today, 24th December. The final column shows the monthly average for December, clearly showing some places have exceeded their monthly totals:

SITE NAME	AREA	PRECIP AMOUNT(mm)	DEC AVG(mm)
TYNDRUM	PERTHSHIRE	155.0	300.9
CARDINHAM	CORNWALL	128.8	155.1
PLYMOUTH	DEVON	127.4	118.8
LISCOMBE	SOMERSET	125.2	171.2
OKEHAMPTON	DEVON	115.0	184.2
MUMBLES HEAD	WEST GLAMORGAN	107.0	110.3
TREDEGAR	GWENT	102.2	169.0
CARDIFF, BUTE PARK	SOUTH GLAMORGAN	97.0	125.3
SENNYBRIDGE NO 2	POWYS	96.2	179.5
ST ATHAN	SOUTH GLAMORGAN	93.2	122.4
DYCE	ABERDEENSHIRE	92.4	76.1
CARTERHOUSE	ROXBURGHSHIRE	92.4	132.0
CRAIBSTONE	ABERDEENSHIRE	92.0	79.8
BALLYPATRICK FOREST	ANTRIM	89.0	133.9

There is more unsettled weather to come this week, so for the latest information keep up to date with our forecasts and warnings.

Is it the wettest UK summer on record?

This summer started with the wettest June in the UK in the national records which go back to 1910 and was followed up by a wetter than average July (16^th wettest), so are we set for the wettest summer on record?

Officially, in meteorological terms, summer runs from the start of June to the end of August – so there are still a few days to go for this year.

The Met Office holds many different climate datasets but uses the UK national series that goes back to 1910 when referring to records.

In this dataset, the record to beat was set in 1912, when the UK had 384.4mm of rain – although we don’t have to look too far back to find a very wet summer, as 2007 is third in the rankings with 357.8mm. The 1971-2000 average for the UK in summer is 226.9mm.

Looking at this year, we have the figures for June and July, but for the UK as a whole we currently only have data up to 15 August – which show rainfall had been slightly below average to that point.

That means we can say with some certainty that we have seen 300.8mm of rain so far this summer (145.3mm in June, 115.9mm in July, and 39.6mm to 15 August), ranking 20^th in the records.

There has been a fair amount of rain since then, so that ranking is sure to have climbed – but it’s not possible to say until all the numbers have been crunched at the end of this month.

It’s important to remember that the UK total rainfall is effectively an average of the rain that falls across the whole of England, Wales, Scotland and Northern Ireland – so looking at one station, or even one country, isn’t a reliable indicator of how much rain we’ve seen for the UK as a whole.

We can say that this summer is likely to be one of the wettest on record – some may argue that, as it’s already in the top 20% in records dating back to 1910, it already is one of the wettest on record.

We can also say that this year has continued a disappointing run of UK summers which started in 2007 – all of which have seen above average rainfall and, with the exception of 2009, below average sunshine hours.

However, we cannot say where this year will finish in the rankings or whether it will challenge the record set in 1912. For that final assessment, we’ll have to wait until after the end of August.

You can see a discussion about the causes of this year’s unsettled summer in an article posted earlier on our blog.

Improving picture as many start school holidays

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?

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.”

Is this the wettest June on record?

Update: Provisional Met Office figures for the whole of June are now available at: Met Office confirms wettest June in over a century

We all know that, so far, it has been a very wet June in many parts of the UK – but just how wet has it been?

Met Office figures show that, up to the 24^th of the month, the UK had seen 122.3 mm of rain –ranking as the third wettest June since records began in 1910 and well over one-and-a-half times the UK average.

So this month is currently just behind the second wettest June in 1912, which saw 124.5 mm of rain, and a little way off the wettest June in 2007, which saw 136.2 mm.

Clearly there are several more days to go and there is some rainfall in the forecast, so not possible to categorically say exactly where the month will finish in the overall records – however it is safe to say it has been a disappointingly wet month.

It’s important to note the rainfall this month hasn’t been evenly spread over the UK. Some areas have seen a great deal of rain, with 52 observation sites breaking record rainfall totals.

Not all of these records are significant as some of stations only have a very short history – for example, Usk in Monmouthshire has only been taking measurements for one year. However, at the other extreme, Otterbourne in Hampshire has been operating for 119 years.

While some areas have already seen record rainfall, others are lingering close to their all-time June minimum. Six stations are currently still below their lowest June rainfall total – but this could change by the end of the month.

What is interesting as that most of the drier stations are in the far north and west of the UK – areas which we would normally expect to see the most rainfall.

Map showing rainfall up to the 24 June 2012 compared to the1971-2000 average. Many parts of the country have seen double their normal amount, while the far north west has seen much less than usual.

 

This illustrates the story behind this month’s weather, as the rain-bearing low pressure systems moving in from the Atlantic which normally track to the north of the UK have been taking a much more southerly route, soaking parts of the south while the far north west has remained unusually dry.

One of the main reasons for this is the position of the jet stream. This is a narrow band of fast flowing westerly winds (ie blowing from west to east) high in the atmosphere.

This band moves around and changes its track, and where it sits can impact the UK’s weather. When it flows to the north of the country it can guide low pressure systems away from the UK (but they often clip the far north west of the country as they pass by).

Throughout this June the jet stream has had a much more southerly track, allowing those low pressure systems – with their wind and rain – to come straight over the UK to bring heavy rain to more southern areas while the north west remains relatively unscathed.

You can find out more about the jet stream in our YouTube video.

Why does it always rain on the UK?

After the wettest April in records dating back to 1910 and an unsettled start to May, parts of the UK are set to see more heavy rain today and tomorrow.

With all the wet weather, many people have been asking what is to blame and whether something unusual is going on.

In an earlier article on this blog we looked at how the jet stream has influenced the recent spell of unsettled weather, but stressed it is not the only factor at play.

While the jet stream may be an influence, there is nothing unusual about its current position and it regularly behaves in this way.

With that in mind, it’s possible to go a step further and say there is nothing unusual about the UK’s weather over the last few weeks.

That may sound odd on the back of a record-breaking wet month, but we do expect to see records broken and they do topple fairly regularly for one area or another.

The past April fits into this expectation – it was exceptionally wet, but only slightly wetter than the previous record set just a few years ago in 2000 and there are several years close behind.

We only have to look back another month to see that March was the joint warmest on record for Scotland. Looking further back, parts of the UK have seen some of their driest months on record in the last year or so, and we saw the coldest UK December on record in 2010.

The mixture of record-breaking months in recent history illustrates what’s called natural variability – which is a way of summing up the inherent random or chaotic nature of weather. This is why our weather is different from one week, month or year to the next.

Here in the UK that variability is particularly noticeable because of our location. We sit in the mid-latitudes where cold air from the poles meets warm air from the tropics, and have the Atlantic on one side and the large landmass of continental Europe on the other.

All these factors mean our weather can be highly variable and we can see periods of unsettled, wet and windy weather at any time of year – a challenge that the Met Office has to rise to every day to provide the accurate weather forecasts that you, businesses and our government partners have come to expect.

Wet and windy weekend

Large parts of the UK have seen very wet and windy conditions over the weekend.

Winds have gusted up to about 70mph in the most exposed locations, with many parts of the country seeing gusts of 40-50mph.

The strongest gust (at a non-mountain site) was 71mph at Mumbles Head in West Glamorgan, Berry Head in Devon was just behind with 70mph.

Leek, Thorncliffe in Staffordshire saw 68mph, Avonmouth in Avon saw 61mph, and two locations on the Isle of Wight also saw 60mph.

Persistent and heavy rainfall has also been widespread across a large part of the country, with some areas seeing a significant proportion of their normal monthly average within a 24-hour period.

The heaviest rainfall has been focused on southern England with Liscombe in Somerset seeing the most rainfall so far, with 48.8mm falling between 1pm on Saturday, 28 April and 6pm today, 29 April.

Hampstead in Greater London saw 39.2mm of rain during the same period, with Wiggonholt in West Sussex seeing 32.4mm and Rothamstead in Hertfordshire seeing 29.8mm. Several other stations across the south saw rainfall at a similar level.

Other parts of the country, particularly in the far north, have seen very little or no rain at all, however.

Looking ahead, there are Severe Weather Warnings in place for both Monday and Tuesday in parts of the UK, so we’d advise people to stay up to date with the latest forecasts and warnings on our website.

The Environment Agency has also issued many Flood Warnings and Alerts - you can stay up to date with the latest information via their website.

Sunny March, wet April – how the jet stream is (partly) to blame

UPDATE: We’ve written a further post explaining a little more behind the continuing dissapointing weather that we have seen through the summer so far.  You can read this at ‘The UK’s wet summer, the jet stream and climate change*‘

After an unusually dry, sunny and warm March, April has seen some very wet and unsettled weather with below average temperatures. So what has caused this about-turn in the UK’s weather? There are many factors which can impact the notoriously changeable weather in the UK, so no single one on its own can be said to be fully responsible. However, it is possible to isolate contributing factors and, in this case, one of those is the northern hemisphere jet stream. This is a narrow band of fast flowing westerly winds (ie blowing from west to east) in the high atmosphere. This band moves around and also changes its track, from a fairly straight line to something more closely resembling a meandering river. Its position can, and does impact weather in the UK and other parts of the northern hemisphere. In both March and April we have seen what we term a ‘blocking pattern’ in the jet stream, where it meanders north and south instead of making its more usual eastward progress. Despite this, March was the 3rd warmest and 5th driest March in the all-UK record going back to 1910, while April has so far been relatively cool with rainfall already 30% above the average for the whole month across England and Wales. So what is causing the difference? It comes down to the position of the blocking feature. In March, the meandering of the jet stream caused it to pass to the north of the UK – anchoring high surface pressure over the UK. This suppressed cloud, increased sunshine and temperatures, and prevented the usual rain-bearing Atlantic weather systems coming in from the west from reaching us. Soon after the start of April, however, the whole pattern moved westwards, so the peak of the northerly meander moved over the North Atlantic Ocean. The UK, in contrast, found itself under the adjacent southerly meander, with the jet stream passing to the south of the UK over France and Spain. This atmospheric set-up brings low surface pressure, cloud and rain. Because the pattern is still blocked, without a west-to-east jet stream to blow the weather system through, the low gets stuck over the UK, resulting in high rainfall totals overall. Like the weather, we can predict the path of the jet stream with a good deal of accuracy up to about five days ahead but it is more difficult to give detail on longer timescales. Therefore it’s not possible to say exactly what the jet stream will be doing in a month’s time, for example, or exactly how it will impact our weather. You can find out more about the jet stream in our YouTube video. http://www.youtube.com/watch?v=GpsRQtk6IfM