Has there been a recent increase in UK weather records?

17 12 2014

There have been a striking number of temperature and rainfall records broken in recent years, according to an analysis by the Met Office which is published in the journal Weather.

The paper examines whether recent decades have seen an unusually high number of records broken in the UK. It looks at the number of records over time in the UK national statistics compiled by the Met Office’s National Climate Information Centre (NCIC).

Records were collated from long-running national and regional series of monthly, seasonal and annual temperature, rainfall, and sunshine.

The analysis counts records by decade and weights them according to their relative importance. More weight is given to national records compared to regions, and more weight to annual records compared to individual months.

The UK’s climate shows a large variability and this is bound to also be reflected in weather records. Even so, the analysis does reveal some interesting patterns.

Temperature records:

  • Since 2000, there have been 10 times as many hot records as cold records.
  • Taking into account the weighting, the period since 2000 accounts for two-thirds of all hot records in a national series from 1910, but only 3% of cold-records.
  • The longer Central England Temperature (CET) series, which dates back to 1659, reveals a similar trend – with seven out of a possible 17 records set since 2000 but no record cold periods.
  • The increase in hot records and decrease in cold records seen in recent decades is consistent with the long-term climate change signal. Seven of the warmest years in the UK series from 1910 have occurred since 2000.

Rainfall records:

  • Since 2000 there have been almost 10 times as many wet records as dry records.
  • Taking into account the weighting, the period since 2000 accounts for 45% of all wet records in a national series from 1910, but only 2% of dry records.
  • Remarkably, period since 2010 accounts for more wet records than any other decade – even though this only a 5 year period. The most prominent wet records in this period were winter 2013/2014 and April, June and year 2012.
  • The longer England & Wales Precipitation (EWP) series, which dates back to 1766, shows a similar trend – with six out of a possible 17 records set since 2000, but no record dry periods.
  • The large number of recent wet records may be indicative of trends in underlying rainfall patterns. We would expect an increase in heavy rainfall with climate change and this is an area of active research within the Met Office Hadley Centre.

Sunshine records:

  • In contrast with the other measures, there are no clear trends apparent in the sunshine records.

Exactly why we have seen these records is an ongoing area of research. You can see some discussion points related to this theme in a Met Office research paper on the drivers and impacts of our seasonal weather.

You can explore the Met Office’s climate data for the UK on our climate pages.





A closer look at ‘weather bombs’

10 12 2014

With strong winds affecting parts of the country today, there has been a lot of talk about ‘weather bombs‘ – but what are they and what do they mean for our weather?

First of all, it’s important to stress the UK is not being ‘hit’ by a weather bomb – the track of the low pressure system is well to the north of the UK, on roughly the same latitude as Iceland. We’re feeling its influence remotely.

This means we are not getting the very strongest winds associated with this system, but far north-western parts of the UK are seeing winds in the 70-80mph range as forecast. Further south the winds are much less strong – so London, for example, is unlikely to see even gale force gusts and mean wind speeds will be much lower.

Another point is that the ‘bomb’ element, the rapid deepening of the low pressure as explained below, happened on Monday – and its now just like any other powerful Atlantic low. In fact, the weather we’ll experience today is nothing unusual for the time of year.

Chart showing a low pressure in the north-west Atlantic at midday on Monday 8 December.

Chart showing a low pressure in the north-west Atlantic at midday on Monday 8 December.

Chart shows the same system 24-hours later, with a 26 millibar fall in pressure.

Chart shows the same system 24-hours later, with a 26 millibar fall in pressure.

So what is a ‘weather bomb?’

A ‘weather bomb’ is more usually referred to as ‘explosive cyclogenesis’ and is a meteorological term describing the rapid fall in central pressure of a depression (or low pressure) – it has to fall by 24 millibars in 24 hours in our latitudes to meet the criterion.

In many ways a ‘bomb’ can be seen as simply a more powerful, more intense version of the kind of Atlantic low pressure systems that normally affect the UK.

Climatologically speaking, explosive cyclogenesis events, or bombs, tend to occur most frequently over sea near major warm ocean currents, for example over the North Atlantic Ocean near the Gulf Stream or over the Western Pacific Ocean near the Kuroshio Current.

An explosive cyclogenesis event in these regions would then tend to happen as a particularly intense jet stream (which is a narrow band of strong winds high up in the atmosphere) interacts with an existing, and often weak, low pressure lingering near one of these warm ocean currents.

In other words, as with so many things in meteorology, it is the coming together of multiple ingredients that allow a ‘bomb’ to develop.

How many ‘bombs’ a year – and what is the impact?

There are gaps in the global observational record, so it’s difficult to give a definitive number of how many ‘weather bombs’ are seen globally each year. However, recent estimates based on a twenty to thirty year dataset suggest there are somewhere between 45 and 65 explosive cyclogenesis events per year, with more ‘bombs’ occurring in the northern than southern hemisphere.

Of course, it’s important to realise that the definition of a ‘bomb’ is somewhat arbitrary and ‘just a number'; a depression deepening only slightly less than 24hPa in 24 hours will still be a powerful depression more than capable of producing severe weather.

Another important point is that the track a ‘bomb’ takes relative to the British Isles, and at what stage of its development it does so, are key to its impact on UK weather – in general the closer the ‘bomb’ tracks to the British Isles the more severe the weather.





Max UK wind speeds – 10 December 2014

10 12 2014

UPDATED AT 11:30AM ON 10th DECEMBER 2014

Parts of the UK are being affected by strong winds today – particularly the north-western coast of Scotland.

Winds are generally much lighter in south-eastern parts, although still gusty – particularly around coasts.

We’ll be updating this post through the day with the maximum wind speeds (from non-mountain sites) seen so far.

Date and time Station Area Speed (mph)
10/12/2014 10:00 TIREE ARGYLL 81
10/12/2014 09:00 SOUTH UIST RANGE WESTERN ISLES 79
10/12/2014 05:00 ISLAY: PORT ELLEN ARGYLL 77
10/12/2014 03:00 MACHRIHANISH ARGYLL 73
10/12/2014 06:00 LOCH GLASCARNOCH ROSS & CROMARTY 70
09/12/2014 22:00 HIGH BRADFIELD SOUTH YORKSHIRE 70
10/12/2014 10:00 KIRKWALL ORKNEY 69
09/12/2014 22:00 WIGHT: NEEDLES OLD BATTERY ISLE OF WIGHT 69
10/12/2014 06:00 SULE SKERRY ORKNEY 69
10/12/2014 06:00 STORNOWAY AIRPORT WESTERN ISLES 69

Winds are almost always stronger at our high level weather stations (those that are sited at 500 metres of altitude or higher), which are also often very exposed.  For this reason the winds from those sites are unlikely to reflect what the vast majority of people are experiencing. Bearing that in mind, the strongest gusts from the high level sites are quoted below for reference:

Date and time Station Area Height (metres) Speed (mph)
10/12/2014 11:00 CAIRNGORM SUMMIT INVERNESS-SHIRE 1237 109
10/12/2014 05:00 BEALACH NA BA NO 2 ROSS & CROMARTY 773 105
10/12/2014 04:00 AONACH MOR INVERNESS-SHIRE 1130 98
10/12/2014 06:00 CAIRNWELL ABERDEENSHIRE 928 94
10/12/2014 03:00 GREAT DUN FELL NO 2 CUMBRIA 847 82




Autumn set to be third warmest on record

27 11 2014

This autumn is on course to be the third warmest on record for the UK but rainfall is close to average, according to early statistics from the Met Office.

The mean temperature from 1 September to 25 November, then assuming average conditions for the last few days of the season, is 10.8C which is 1.4C above the long-term (1981-2010) average.

This means it currently ranks behind 2006 (11.4C) and 2011 (11.3C) in the digital UK records dating back to 1910.

Looking at individual countries, England stands out as the warmest relative to the long-term averages, whilst Northern Ireland was the least mild. This autumn is the third warmest for all UK countries apart from Northern Ireland, where it is the 9th warmest.

The mild conditions through autumn follow on from a generally warm year overall, with all months except August having seen above average temperatures. The Met Office will make an early statement on the temperature for 2014 next week.

  Mean temp Sunshine Rainfall
Early autumn* Deg C Diff to avg Hours % of Atmn Avg Actual mm % of Atmn  Avg
UK 10.8 1.4 263.4 96 319.3 93
England 11.8 1.5 285.2 94 236.3 95
Wales 11.1 1.3 294.0 106 368.9 82
Scotland 9.3 1.3 215.5 95 440.3 92
N Ireland 10.3 0.9 280.5 110 333.4 103

* Note that early autumn figures use statistics from 1 September to 25 November, then assume average conditions to the end of the season.

Rainfall has been close to average for the season – despite record-breaking dry conditions across the UK in September. The rainfall of October and November has almost offset the very dry September for many areas, with a few areas having ‘caught up’ to the whole-Autumn long-term average.

Sunshine totals for the season are also close to average.

For November so far (to the 25th of the month), it has been the joint fourth warmest for the UK in our records back to 1910. Like most individual months this year, it has been warmer than average but not remarkably so.

It has also been wetter than average for the UK, but not record-breakingly so.

  Mean temp Sunshine Rainfall
1-25 Nov** Deg C Diff to avg Hours % of Nov Avg Actual mm % of Nov Avg
UK 7.7 1.5 45.9 80 118.4 98
England 8.4 1.5 49.1 76 100.9 114
Wales 8.0 1.2 56.7 100 156.1 96
Scotland 6.5 1.5 36.0 79 127.7 77
N Ireland 7.5 1.0 55.6 103 172.1 153

** Early November statistics include figures from 1-25 November. Final numbers for the month will change after the final few days have been included.





Untangling the global drivers of UK winter weather

25 11 2014

As we head towards the start of winter, which starts for meteorologists on 1 December, there’s always a great deal of media and public speculation about what weather we might have in store.

To answer that question, we need to look beyond the UK. The worlds’ weather is interconnected, and there are certain large scale global drivers which we know have influences on UK weather at this time of year – so what are these doing at the moment?

El Niño, which sees unusually warm sea surface temperatures across the tropical Pacific and can increase the risk of cold winter conditions in the UK, has been much discussed after initial signs of development earlier this year.

Its progress has been slow, however, and while there remains a good chance of a weak event by the end of the year it is also possible that El Niño conditions will remain neutral. In any case, this factor is not expected to be strong enough to exert much influence on weather patterns in Europe during the next three months.

The North Atlantic Oscillation (NAO) describes differences in the usual pressure patterns over the North Atlantic – with positive and negative phases.

A positive phase is thought more likely than a negative one on average over the next three months. This is characterised by enhancement of the westerly winds across the Atlantic which, during winter, brings above-average temperatures and rainfall to Western Europe.

As we head later into winter, confidence about the heightened likelihood of positive NAO reduces – suggesting chances of drier and colder conditions return closer to normal.

The Quasi-Biennial Oscillation (QBO) sees high level (stratospheric) winds over the equator change from westerly to easterly phases – and it’s currently in the latter of the two.

In winter months this can lead to a greater incidence of high pressure blocking patterns over the northern hemisphere, which would increase the probability of colder and drier weather across Europe. Essentially this is providing an opposite signal to the NAO.

There are other factors to consider too. For example, Arctic sea ice extent is slightly below average but as yet it is not clear whether this might have an impact on weather patterns in the UK.

No single one of these drivers will determine the UK’s winter on its own – instead they all interact together to govern the weather trends we can expect over the coming months.

Disentangling these different influences remains a challenging area of science which the Met Office is improving all the time, but detailed and highly certain UK outlooks are not possible over these timescales.

The Met Office’s long-range outlooks give probabilities based on scenarios of being considerably wetter or drier, colder or milder than usual.

Currently the outlook for December 2014 to February 2015 suggests that milder and wetter than average winter conditions are slightly more likely than other outcomes. However, compared to day-to-day weather forecasts, the probabilities are much more finely balanced – for example, the outlook gives a 1 in 4 chance of the mildest scenario and a 1 in 10 chance of the coldest scenario. These numbers suggest it would be a mistake to interpret the outlook for a very mild outcome as ‘highly likely’; likewise very cold conditions cannot be ruled out.

The outlook gives similar probabilities for precipitation (rain, hail, sleet and snow), with the chances of the wettest scenario being 1 in 4 and the chances of the driest around 1 in 10.

These three month outlooks cover a whole three month period, taking into account both day and night, as well as the whole of the UK. This means that even in the event of, say, an overall mild winter we could still see spells of cold or very cold weather.

With this in mind, what exactly we’ll see for the winter ahead remains uncertain. In terms of strong winds, heavy rainfall, cold snaps or even snow, while longer-range outlooks can give us general tendencies, the details can only be predicted by our day-to-day weather forecasts.

The Met Office’s accuracy over all timescales is world-leading, however, so you can trust that we’ll keep everyone up-to-date with all the latest information on the weather whatever the winter has in store.





US snowfall and will it impact the UK?

20 11 2014

Parts of the US and Canada are seeing particularly cold weather and heavy snowfall at the moment.

Chart showing the position of the jet stream over North America as at 00:01 on 20 November.

Chart showing the position of the jet stream over North America as at 00:01 on 20 November.

A southward buckle in the jet stream has seen cold polar air flow south to north eastern parts of North America.

In the Buffalo region of New York state, temperatures have fallen as low as -15C and 4-5 ft (about 1.5 metres) of snow has fallen – enhanced by what’s known as the ‘lake effect’. Another 2-4 ft (about 1 metre) is expected through today.

The snowfall is set to ease on Friday with much milder conditions through the weekend giving a rapid and significant thaw – which could bring a risk of flooding.

This risk could increase through the start of next week when some very heavy rain is expected across the area.

What is lake effect snow?

Lake Superior (top left) and Michigan (centre) can be seen generating 'lake effect' snow. Provided by the SeaWiFS Project, NASA/Goddard Space Flight Center, and ORBIMAGE

Lake Superior (top left) and Michigan (centre) can be seen generating ‘lake effect’ snow. Provided by the SeaWiFS Project, NASA/Goddard Space Flight Center, and ORBIMAGE

This is an effect which applies to areas around large lakes like those seen in the northern US – Lake Superior has an area of more than 30,000 sq miles.

When cold air moves across the relatively warm waters of the lake, air rises due to convection which creates clouds and heavy showers. In cold conditions, the moisture in the clouds will fall as heavy snow.

As Buffalo as it the eastern tip of Lake Erie it has been particularly susceptible to this effect during the recent weather.

While we don’t have any lakes big enough for this effect in the UK, we can occasionally see a similar scenario when we get easterly winds in the winter.

Cold air from the continent can be warmed by the relatively warm North Sea as it moves across the water, bringing snow showers to eastern parts of the UK. However, there’s no sign of this in the immediate future for the UK.

Will the US weather affect the UK?

Many people believe that there’s a rule of thumb that weather in the US will arrive in the UK a few days later – but that’s by no means always the case.

In this instance, there’s high confidence that the cold snowy weather will stay on the western side of the Atlantic.

Also, in past winters similar weather situations in the US have strengthened the jet stream and increased the risk of storms across our shores. Again, in this instance, this isn’t expected at the moment.

What we do expect to see is further changeable weather over the coming few days.





Wet wet wet this winter?

17 11 2014

Every year there’s a huge amount of media speculation about what weather we’ll see during winter, and this year is no different.

After a recent slew of stories claiming we’re in for the coldest winter on record (which weren’t based on information from the Met Office), there are now stories claiming we’re forecasting the wettest winter in 30 years.

That’s not the case and appears to be a misunderstanding of our three-month outlook for contingency planners.

First of all, last winter was the wettest in our digital records dating back to 1910, so if we were to have a wetter winter than that it would be the wettest in over a century – not just for 30 years.

But that’s not what our contingency planners outlook says. As we’ve pointed out here many times in the past, this product isn’t like our short range forecasts – it doesn’t tell you definitively what the weather is going to be and that’s why it’s not really that useful for the public.

What it does do is make an assessment of the likelihood of seeing wetter or drier than average, and milder or colder than average conditions for the whole of the UK for the whole three month period.

Recent outlooks have been signalling increased risk of milder and wetter conditions for the past couple of months, and indeed that’s what we have seen through October and the start of November. So the most likely predicted outcome is what actually happened for these months – but that won’t always be the case.

While the recent three month outlooks also highlighted the risk of more unsettled than average conditions, this does not give specific details or tell us whether any records will be broken.

For detailed weather forecasts, our five-day forecasts and weather outlooks to 30-days give the best and most up-to-date advice.





Warm and wet, but October is no thriller

30 10 2014

Early Met Office figures up to the 28th of October show it has been a warm and rather wet month compared to average, but it’s not going to break any records.

The UK mean temperature for the month so far is 11.0C, which is 1.5C above the long-term (1981-2010) average.

Map showing the UK mean temperature for 1-28 Oct compared to the long-term (1981-2010) average.

Map showing the UK mean temperature for 1-28 Oct compared to the long-term (1981-2010) average.

While well above average, that’s well short of the record of 12.2C set in 2001 and would currently rank 11th warmest in our digitised national records dating back to 1910.

Last year’s October (11.2C), and that of 2011 (11.3C), were both warmer than this year’s early figure.

As ever there are regional variations within the UK for this year, with the far north west of the UK hardly above normal while much of England has seen mean temperatures around 2C above normal.

This October continues the theme of above average temperatures for 2014. Nine out of the ten months this year have seen above average mean temperatures, with only August having been below average.

It’s a similar story with UK rainfall in that it is wetter than average, but with no chance of breaking any records.

There has been 148.1mm of rain for the UK up to the 28th of the month, which is 116% of the long-term full-month average (you’d expect about 91% of the average after 28 days in a ‘normal’ month).

This would rank it around mid-table in the records – nowhere near the October record of 194.8mm set in 2000. While the rainfall will go up when the final few days are added, it’s not going to top that.

Again there are regional variations, with some parts of Scotland, the Isle of Man and Cumbria much wetter than average while some parts are slightly drier than average.

Sunshine hasn’t been too remarkable, with figures below average for most areas.

  Mean temp Sunshine Rainfall
1-28 Oct Deg C Diff to avg Hours % of Oct Avg Actual mm % of Oct Avg
UK 11.0 1.5 77.8 84 148.1 116
England 12.2 1.8 86.6 84 100.8 110
Wales 11.4 1.6 73.1 79 160.2 94
Scotland 9.2 1.2 62.6 83 226.7 129
N Ireland 10.3 0.9 86.7 99 124.0 104




Top UK wind speeds as Gonzalo’s remnants felt

21 10 2014

TABLE UPDATED AT 11:50AM

Many parts of the UK are seeing strong winds today as the remnants of ex-tropical storm Gonzalo pass over the north of the country.

Below are the top ten strongest gusts of wind we have recorded so far today. We’ll be updating this through the day with the latest information.

Time Station Area Elevation Max gust (MPH)
0600AM WIGHT: NEEDLES OLD BATTERY ISLE OF WIGHT 80 70
0300AM ABERDARON GWYNEDD 95 70
1000AM ST BEES HEAD CUMBRIA 124 69
0400AM MUMBLES HEAD WEST GLAMORGAN 43 67
1000AM ISLAY: PORT ELLEN ARGYLL 17 66
0300AM CAPEL CURIG GWYNEDD 216 66
1000AM EMLEY MOOR WEST YORKS 267 66
0400AM LAKE VYRNWY POWYS 360 63
0600AM SALSBURGH LANARKSHIRE 277 63
0400AM MACHRIHANISH ARGYLL 10 62

The Met Office has issued a severe weather warning for the winds today – you can see the details of this on our warnings pages.

Winds are expected to be strong through much of the day, and people are advised that there may be some traffic and travel disruption.

Rainfall

Ex-Gonzalo also brought a band of heavy rain across the UK earlier this morning, bringing some notable rainfall totals in places.

The table below shows the top ten UK rainfall totals recorded between 1am and 8am this morning.

Station Area Total (mm)
CLUANIE INN NO 3 ROSS & CROMARTY 38.0
CAPEL CURIG NO 3 GWYNEDD 34.4
ACHNAGART ROSS & CROMARTY 30.6
TYNDRUM NO 3 PERTHSHIRE 27.6
KINLOCHEWE ROSS & CROMARTY 25.8
RESALLACH SUTHERLAND 23.4
SHAP CUMBRIA 21.8
LOCH GLASCARNOCH ROSS & CROMARTY 21.8
MORECAMBE NO 2 LANCASHIRE 20.2
LEVENS HALL CUMBRIA 20.0




Windy weather on the way

19 10 2014

As forecast, Hurricane Gonzalo made landfall over Bermuda on Friday with rain and winds of up to 110 mph causing power cuts, flooding, felled trees and damaged buildings.

The storm has continued in its journey since then, and passed the Canadian island of Newfoundland during Sunday morning.

The remnants of this tropical storm are being caught up in the westerly flow across the Atlantic and will be drawn towards the UK, crossing the country on Monday night and early Tuesday.

By the time Gonzalo crosses the Atlantic, however, it will be a very different system to the hurricane that affected Bermuda.

It will undergo what meteorologists call ‘extra-tropical transition’, which means it loses the warm-core typical of a tropical cyclone and becomes a much more standard Atlantic low pressure system – like we regularly see around the UK at this time of year.

As such the low pressure is expected to produce wind strengths and rainfall amounts which are not unusual over the British Isles during the autumn and winter months.

Whilst there is good confidence that this system will cross the UK on Monday night and Tuesday morning, there is still something to play for in pinning down the exact location of the strongest winds.

The Met Office has issued a weather warning for wind for much of the UK for Tuesday, particularly since the strongest winds look to coincide with rush hour for some locations, leading to possible travel disruption.

You  can see details of what to expect in the warnings page on our website. You can stay up to date with all the latest for the windy weather and what to expect for the rest of the week with our forecasts and warnings.








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