So what happened to our summer?

28 08 2015

Our Chief Scientist Professor Dame Julia Slingo OBE FRS reflects on this summer’s weather and what has influenced it:

No-one can deny that we have had a pretty disappointing summer with a lot of unsettled weather and only a few warm spells, especially through July and August. Our weather has been dominated by low pressure over and to the west of the country that has brought us periods of heavy rain from the south – what we call the Spanish Plume. So what has been happening?

If we look beyond our shores there have been some big changes in the global climate this year. El Niño is in full flight, disturbing weather patterns around the world. The low pressure that has dominated our weather is part of a pattern of waves in the jet stream around the world that has brought crippling heat waves to places like Poland and Japan. And, looking back over past El Niños, you could have expected that a more unsettled summer might be on the cards for the UK. Closer to home the North Atlantic is more than 2 degrees colder than normal. It seems quite likely that the unusually cold North Atlantic has strengthened and pushed our jet stream south, also contributing to the low pressure systems that have dominated our weather.

So could all this have been anticipated? Seasonal forecasts for this summer suggested that temperatures and rainfall would be near normal. However, as the season progressed all the leading models around the world failed to capture the signal for unsettled weather over the UK. We all know that forecasting months and seasons ahead is still in its infancy and much more research needs to be done. On the other hand our day-to-day forecasts have been really successful in allowing us to warn of bad weather, highlighting yet again the benefits of our research that has delivered year-on-year and decade-by-decade improvements in forecasting skill. Our 5-day forecast is now as accurate as our 1-day forecast was when I started my career. This enables us to make so many decisions that keep us safe, protect our property, keep our infrastructure running and even when to go out and enjoy the sunshine!

All of this cannot happen without improvements to research and technology, and this week the first phase of our new supercomputer went live, five weeks ahead of schedule. This will enable us to provide even more accurate and relevant weather and climate forecasts to all of us, our government, emergency responders, and our many other customers at home and abroad.

The news that the BBC has decided that the Met Office won’t be their main weather provider when the current contract ends has raised the question of where will the new provider get their information from. It’s important to understand that no weather forecasting organization, whether it is a National Met Service like the Met Office or an independent company, can provide a service without a forecast, and that it is the leading meteorological agencies, like the Met Office, that build and deliver those forecasts. So whoever the BBC chooses to deliver their weather services in future, you can be sure that Met Office observations and forecasts will continue to be at the heart of them. We are committed to driving forward the skill and usefulness of our forecasts and ensuring that all of us benefit from the advances the Met Office makes in the coming years with our new supercomputer.





On the record – observing a ‘heatwave’

7 07 2015

Last week on 1 July the UK saw its warmest July daily max temperature on record (records date back as far as 1853), with 36.7 °C at Heathrow. This has led to considerable interest in the wider context of the record temperatures. Here, Mark McCarthy, Manager of the Met Office National Climate Information Centre discusses records and how we record them.

Where were record temperatures observed on 1 July 2015?

Although Heathrow measured the highest temperature recorded by the Met Office observing network on a July day, record temperatures were reported across a wide stretch of the country, including from some of the Met Office’s very long running climate stations.

Temperatures exceeded 35 °C at a handful of locations in London and the south east, but also reached the low 30s across the Midlands, East Anglia and parts of north-west and north-east England. It is in these areas that July temperature records were broken.

Map showing stations recording new July temperature records, 1 July 2015

Map showing stations recording new July temperature records, 1 July 2015

The table below lists those stations with more than 50 years of observations for which 1 July 2015 was a record. These data show that record temperatures for July were not confined to London or other major urban centres. The records were, in fact, part of a larger scale pattern of high temperatures extending through Spain, Portugal and France.

SITE DATE OF PREV JULY RECORD PREV RECORD JULY MAX (°C) 1 JULY 2015 MAX (°C) YEARS OF DATA
Durham 31/7/1943, 10/7/1921 30.6 31 133
Sheffield 31/7/1943, 10/7/1921 31.7 33.3 130
Bradford 31/7/1943, 13/7/1935 30.6 30.9 106
Cranwell 22/7/1996 32.6 34.3 93
Sutton Bonnington 19/7/2006 32.9 33.6 84
Stonyhurst 3/7/1976 31.1 32.6 75
Manston 15/7/1983 31.4 33.6 74
Goudhurst 3/7/1976 32.8 33.3 74
Waddington 12/7/1949 32.2 33.1 67
Heathrow 19/7/2006 35.5 36.7 66
Nottingham (Watnall) 3/7/1976 32.3 33.9 64
Marham 3/7/1976, 5/7/1959 32.8 33.5 58
Wittering 5/7/1959 32.8 35.3 53
St James’s Park 5/7/1959 34.4 34.7 52

How does this compare to past heatwaves?

Temperatures over 36 °C reported at any station in the UK observing network are very rare, with only a handful of notable heatwaves seeing such extremes. The heatwaves of August 1990, August 2003, and July 2006 each saw a number of stations exceed 36 °C, whereas on 1 July 2015 Heathrow was the only station.

The Met Office maintains a list of climate extremes for the UK. It is standard practice to report the highest and lowest temperature every month as part of our routine monitoring of UK weather and climate. It is therefore always noteworthy when one of these records is broken.

While there is no doubt that some previous heatwaves have seen more extreme or more widespread high temperatures overall – particularly in the climatologically warmer period from late July into early August – 1 July 2015 has the honour of holding the highest recorded temperature for a July day with 36.7 °C at Heathrow.

How do you ensure the data are reliable?

To ensure consistency, Met Office weather records are only given for stations with standard instruments and exposure. This means that our records would not represent the extremes that may have occurred in places where we do not have standard instruments. This may have been the case on 1 July 2015, where the availability of additional data from amateur observers contributing to Met Office WOW show peak temperatures in the range 35 to 37 °C to the west London.

It is reasonable to ask whether Heathrow, as a major international airport, can provide a reliable climatological record. Are the observations biased by the presence of runways and air traffic?

The instrumentation and station enclosure are managed so that they meet the standards required by the Met Office and set out by the World Meteorological Organization. The site has been operating for 66 years and provides an excellent long observational series for west London.

The first thing we can do is compare the climatological temperatures with a nearby station at Kew Gardens. The average daytime maximum temperatures for the two sites are very close:

Site June July August
Heathrow 21.04 °C 23.54 °C 23.15 °C
Kew 21.02 °C 23.48 °C 23.15 °C

On 1 July the maximum temperature recorded at Heathrow (36.7 °C) was higher than Kew (35.7 °C). Modern instrumentation means we can look at the temperatures minute-by-minute at the two sites, as shown below. The two locations recorded very similar temperatures through most of the afternoon and the average temperature at the two sites between 12:00 and 18:00 GMT agree to within 0.02 °C. However, there was a peak in temperature at Heathrow between 14:00 and 14:30 GMT that was not seen at Kew Gardens. What could cause such a peak?

Temperature (°C) graph for Heathrow and Kew Gardens 1 July 2015

There were scattered clouds in the area that afternoon. Both Heathrow and Kew Gardens have instruments measuring solar radiation, shown in the graph below. Both sites recorded a general dip in solar radiation due to clouds from approximately 13:30 to 15:00 GMT which corresponds to a slight cooling at both sites. Heathrow saw a short gap in the clouds shortly after 14:00 GMT which resulted in a similarly short lived peak in temperature, while Kew Gardens remained cloudy. In turn Kew Gardens then saw a brief spell being sunnier than Heathrow just before 15:00 GMT and became warmer than Heathrow for about an hour.

Solar radiation (W/m2) graph for Heathrow and Kew Gardens 1 July 2015





Hotter weather for the start of July

25 06 2015

The weather is showing signs of heating up next week for the start of the Wimbledon fortnight.

In contrast to June so far, which has seen temperatures often near or just below normal, next week could see a real change in the way it feels – with hot days and humid nights, especially across the south.

It looks like heat will start to build across Iberia later this weekend and spread northwards across France early next week as a tropical continental airmass begins to dominate the weather. Temperatures across Iberia and southern France could reach the low 40’s Celsius by midweek with northern France seeing temperatures into the mid to high 30s Celsius.

Data: European Centre for Medium Range Weather Forecasts

Data: European Centre for Medium Range Weather Forecasts

The UK is likely to be near the boundary between this tropical continental airmass and a tropical maritime airmass over the Atlantic, but we do expect to see temperatures rise across the whole of the UK for the start of July.

Scotland could see highs in the low to mid 20’s (although it may be cloudy here at times), and highs across southern Britain are likely to reach the low 30’s Celsius with a small chance of values in the mid 30’s here.

It’s worth saying that there is some uncertainty about how much of the hot weather from the continent will reach us, and it may only last a couple of days before temperatures drop a little. As is traditional with hot weather in the UK in the summer it may end with thunderstorms.





Mixed bag for the start of June

17 06 2015

It has been a very varied weather picture so far this month.

It’s been dry and warm for the south east of the UK, with some places around London having received less than 5 mm of rainfall so far and areas such as Essex, Hertfordshire, Suffolk and Cambridgeshire receiving less than 20% of the month’s average in places.

This year’s highest UK temperature so far, 26.8 °C, occurred at Kew Gardens (Greater London) on the 12 June.

Much of the rest of the UK has seen temperatures in general noticeably below average for June, continuing on from the rather cool May.  While rainfall totals are already close to the whole-month average in the central Scottish Highlands and in Nottinghamshire.

MeanTemp June

June began with two very unseasonal days, due to a deep low-pressure system to the west of the UK, bringing large amounts of rain and some strong winds to the UK, particularly southern areas. Apart from this, and some showery rain on the 5th/6th,

June so far has been relatively settled, especially over southern areas, although we saw a period of thundery outbreaks on 12th June affecting mainly southern areas due to a plume of very humid and warm unstable air moving in from France/Spain.

Mean temperatures for the UK so far this month have been 2 °C below normal in most areas, but colder in the far north-west of the UK and a little closer to normal in southern England. While the minimum temperatures have been well below average, by as much as 3 °C over some northern areas.

mean temperature sunshine duration rainfall
1-15 June 2015 Act (°C) Diff from avg (°C) Act (hrs) % of avg Act (mm) % of avg
UK 11.2 -1.8 117.6 69 31.3 43
England 12.5 -1.6 128.3 70 23.1 37
Wales 11.6 -1.6 121.6 70 41.8 49
Scotland 9.3 -2.0 99.3 66 43.9 49
N Ireland 10.3 -2.5 114.3 76 21.4 28

We would expect figures to be around 50% of the average figures by the mid month point.

For the latest weather forecast go to www.metoffice.gov.uk/weather





Summer returns but no heatwave

2 06 2015

There have been some stories in the press that a heatwave is on the way later this week.  Although we are expecting temperatures to rise over the coming days with some pleasant early summer weather, any very warm weather will be fairly short-lived.

After an unseasonably cold, wet and windy start to June and the meteorological summer, high pressure is expected to build across southern parts of the UK from Wednesday, resulting in a much quieter and more pleasant spell of weather.

By Friday, a plume of hot air from the continent could bring temperatures in the mid 20s°C  across south eastern parts of the country, but this in turn is likely to trigger some thundery showers. So although temperatures are likely to peak on Friday, this may not necessarily be accompanied by blue skies and sunshine, as a good deal of cloud is possible along with rather humid and hazy conditions.

Deputy Chief Meteorologist Martin Young said “although things will be a good deal warmer than of late, there still remains considerable uncertainty about how hot it will be and exactly where will see the highest temperatures on Friday, and the public should keep in touch with the latest forecasts”.

This coming weekend is likely to see temperatures a little lower than Friday’s in the south east, but plenty of pleasantly warm sunshine is expected across much of the UK with temperatures widely in the high teens, and reaching the low 20s°C  in parts of the south.





More warm weather this week – but what’s in store for the summer?

13 04 2015

This week is set to see some unseasonably warm weather for parts of the UK – with temperatures expected to climb to the low to mid-20s Celsius in the south on Tuesday and Wednesday.

Warm air flowing up from the south west will combine with high pressure, bringing settled conditions and sunny spells for many.

Warmest days of the year so far

This week’s above average temperatures follow on from a similar spell last week, which saw temperatures top out at 21.9C at St James’s Park in London on Friday.

This was the ‘warmest day of the year so far’, but It looks like Tuesday and Wednesday will top that – which is to be expected as we head through spring and edge closer to the start of summer.

Unfortunately, the weather we get in April doesn’t necessarily tell us anything about the kind of summer we can expect. We’re still in the midst of spring, so it’s far too early to say what the months of June, July and August may hold.

Summer ‘heatwave’ speculation

That hasn’t stopped speculation about heatwaves, the warmest summer ever and record temperatures in the media. Some stories cite our three month outlook for contingency planners as proof of the impending heatwave, but this is in no way an accurate reflection of what it shows.

The outlook shows probabilities attached to different scenarios for temperature and rainfall over the whole three-month period it covers. This is useful for those who use probabilities to plan ahead on longer-timescales, but not very useful for deciding where and when to go on your UK summer holiday, for example.

What does the longer outlook show?

Our current three month outlook does show that above average temperatures are more likely than below average temperatures for the April-June period. The outlook is essentially the scientific equivalent of factoring the odds on a horse race and, just like a horse race, the favourite doesn’t always win.

It’s also important to note that above average temperatures over a three-month period could come about in a variety of ways in terms of actual weather – we can still see warmer than average temperatures when it’s cloudy and wet, for example. Also, even in an above average three-months not all individual months would need to be above average.

This just reinforces the point that the contingency planners outlook doesn’t tell us what specific weather we are going to see at a specific location. For the best information on the weather ahead, people should use the Met Office’s 5-day weather forecast supplemented with our 30-day outlook.

By keeping up to date with the latest forecast, you’ll always have the most up-to-date and accurate view of the weather in store for the UK.





Rain totals for 19th July 2014

20 07 2014

As forecast there were severe thunderstorms across the UK on the 19th July bringing heavy rain and gusty winds. See the tables below for the largest rain totals across the UK.  Gloucestershire recorded the highest rainfall with 66mm between 6am and 6pm yesterday, the counties monthly average rainfall is 60.6mm.

The Heat-health watch put in place in parts of southern and eastern England in conjunction with Public Health England has now been downgraded. Temperatures in parts of the area covered topped 28C during 19 July, see table below.

Today, 20 July, temperatures are expected to reach low to mid 20’s across central, south and south east of England, with London seeing around 27C.  Northern England will reach mid to high teens and Scotland and Northern Ireland mid to low teens.

More thundery downpours are expected to develop today over some eastern and central parts of the UK.  A yellow, be aware, weather warning for rain is in place for the areas likely to be affected. Not everywhere will see a storm but where they do occur, torrential downpours are possible with lightning, hail and strong gusts of wind. The areas most likely to be affected are across eastern and southeastern England.

Many places will have a good deal of fine and very warm weather this working week although there is the risk of some heavy showers in parts of the south and west later in the week.

 

UK MAX TEMPERATURE 19 JULY 2014
TIME SITE NAME AREA MAX TEMP (Celsius)
16:22 London St Jamess Park GREATER LONDON 28.5
15:13 Northolt GREATER LONDON 28.4
15:22 Heathrow GREATER LONDON 28.3
15:59 Santon Downham SUFFOLK 28.3
13:29 Gravesend, Broadness KENT 28.1
16:51 Cambridge NIAB CAMBRIDGESHIRE 27.7
15:49 Marham NORFOLK 27.7
13:55 Hampton W Wks GREATER LONDON 27.6
16:52 Writtle ESSEX 27.6
14:51 Frittenden KENT 27.5

 

 

12hr UK RAINFALL 19 JULY
SITE NAME AREA PRECIP. (MM)
WESTONBIRT GLOUCESTERSHIRE 66.0
PERSHORE COLLEGE HEREFORD & WORCESTER 36.4
PERSHORE HEREFORD & WORCESTER 30.8
NEWPORT (SALOP) SHROPSHIRE 29.4
KEELE STAFFORDSHIRE 28.2
ASTWOOD BANK HEREFORD & WORCESTER 27.6
NOTTINGHAM, WATNALL NOTTINGHAMSHIRE 26.0
LIBANUS POWYS 25.8
NANTWICH, REASEHEATH HALL CHESHIRE 22.6
MARKET BOSWORTH, BOSWORTH PARK LEICESTERSHIRE 22.6




The Met Office’s outlook for the UK summer 2014

9 06 2014

There are headlines in the media today which suggest the Met Office is forecasting that this summer will be one of the hottest on record. However, the Met Office hasn’t issued a forecast along these lines.

The news stories are based on information taken from our three month outlook for contingency planners, so let’s take a closer look at that.

What does our three month outlook say?

As we’ve discussed previously, this outlook assesses the level of risk connected to five different scenarios for both temperature and rainfall for the whole season. It’s a bit like the science-equivalent of factoring the odds on a horse race.

However, as with any horse race, it’s always possible that the favourite won’t win – so these probability scenarios have to be used in the right context. This is why they’re useful for planners and businesses who plan ahead based on risk, but not that useful for the general public who would like to know which fortnight in August will have the best weather for a holiday.

The current outlook for the whole of the June-July-August period for the whole of the UK says the chance of the warmest scenario happening is 25% and the chance that the period will fall into the coldest scenario is 10%.

So, while the current three month outlook suggests there is a higher chance of above average temperatures than below average, it does not tell us about the type of weather we may see.

Above average temperatures could be reached by milder nights, as can occur in summer in cloudy and wet conditions (for interest, average maximum temperatures for the UK in summer are about 18.6C and average minimum temps are about 10.2C). There is also only a small forecast signal for summer rainfall and therefore, we cannot make any strong assumptions about the weather we’ll see.

We saw a good example of this recently – the UK has just had the third warmest spring on record but the season didn’t have long stretches of blue skies and high temperatures. Instead we saw mixed weather with a lot of mild nights which contributed to the overall above-average conditions.

So, what will the summer be like?

Obviously there’s always a lot of interest to know what summer will be like – how hot will it be, how much rain will we get and where and when will it fall?

Our 30-day outlook (under the text forecast tab) provides a look ahead to the general type of weather we’re likely to see in the UK.

Currently it says that after today, the weather is expected to settle down with many areas having some warm sunshine, although showers are still likely in the northwest.

From mid June to early July, the indications are that the weather will be close to what is climatologically normal for this time of year – giving us a tendency for occasional spells of unsettled weather interspersed with fine and warm spells, much as we have seen recently.

If there is any sign of significantly hot spells or heavy downpours in the forecast, we will keep the country up to date through our forecasts and warnings. Our ‘Get Ready for the Great British Summer’ webpages also provide useful tips and information to make the most of the summer months, whatever the weather.





No heat wave just sunshine and showers this weekend

21 08 2013

You may have seen more headlines in the newspapers today talking about a heat wave heading our way for the weekend. Once again these stories seem a little over-hyped.

The Met Office forecast for the rest of the week does, indeed, show rising temperatures, peaking in the high 20’s Celsius in south-east England on Friday. Temperatures are then expected to return to around average during the course of the weekend, so not a heat wave.

The weather is expected to turn more unsettled from the west during Friday and Saturday, with the risk of some heavy, showery rain around. The rest of the weekend should see some good dry and sunny spells of weather at times, but the risk of occasional showers remains and there is some uncertainty about which areas will see the showers and when.

The uncertainty this weekend comes from complex weather patterns developing over the Atlantic and these will ultimately determine where the showers will be from day to day. For those who like technical speak, it’s called a trough disruption and forecasting this phenomenon continues to be a major challenge to both computer models and humans alike.

So the best thing to do is keep up to date with the forecast to get the latest on how things are expected to develop over this weekend.





July finishes in top three sunniest and warmest

2 08 2013

Met Office figures show that, with a mean temperature of 17 °C, July 2013 was the third warmest in the national record going back to 1910, behind 2006 (17.8 °C) and 1983 (17.3 °C).

This July’s heatwave was more notable for its duration than its intensity, although it is not particularly unusual in a historical context. The last year in which 30 °C was not recorded at any station was in 1993. However, this July stands out in contrast to the run of unsettled summers from 2007 to 2012, and was the most significant UK heatwave since July 2006.

Through the month we saw high pressure sitting over the UK bringing a prolonged period of high temperatures between Saturday 6 July and Thursday 24 July, when a maximum of 28 °C was recorded at one or more locations on each of those 19 days.

The last time the UK saw such a long period of hot weather was August 1997 which also had a 19- day run of high temperatures. The highest temperature for July 2013 was recorded jointly at Heathrow and Northolt on 22 July (33.5 °C). (Although this high temperature has already been surpassed in August, with 34.1 °C recorded at Heathrow on 1 August.

July 2006 still stands as the hottest month on record in the UK with a mean temperature of 17.8 °C and also saw the record July temperature of 36.5 °C at Wisley (19 July 2006).

The heatwave broke on 22 July with thunder and some very heavy downpours. The wettest day in July was in Cumbria, when 79.8mm of rain fell at Carlisle on 28 July (97.4 mm on a 48 hour rainfall total between 0900 GMT 27 July to GMT 29 July 2013).

Looking at the individual countries, the hottest day in Scotland was on 20 July (30.5 °C) at Glenlee, with Castlederg in Northern Ireland and Porthmadog in Wales recording their highest temperatures on 19 July (30.1 °C and 31.4 °C respectively). England’s hottest day was also the aforementioned UK’s hottest day (33.5 °C on 22 July Heathrow and Northolt).

July’s UK rainfall total was 64mm, with Scotland receiving near normal levels at 83.1 mm and the whole of England drier than average at 52.3 mm (but with Northern England registering above average rainfall with 75.8 mm and Southern England below average at 39.8 mm). Wales (58.0 mm) and Northern Ireland (78.2 mm) were slightly drier than average.

Statistics:

Mean Temperature Sunshine hours Rainfall  
July Actual Diff from Avg Actual % of Avg Actual % of Avg
  degC degC hours % mm %
UK 17.0 1.9 250.7 145 64.1 82
England 18.1 1.8 274.1 142 52.3 83
Wales 17.2 2.0 288.9 161 58.0 63
Scotland 15.2 1.9 205.8 146 83.1 84
N Ireland 17.0 2.4 227.3 162 78.2 96







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