‘Super tides’, the weather and coastal flood risk

20 02 2015

UPDATED 27/02/2015 – this blog has been updated under the section ‘So what are ‘super tides” with the help of the National Oceanography Centre.

In this joint blog from the Environment Agency and the Met Office, we look at the issue of so-called ‘super tides’.

There has been a lot of media coverage about the potential impact of so-called ‘super tides’ which are due from today (Friday, 20 February) through to Monday.

So what are ‘super tides’?

Tides are governed by the gravitational pull of the moon and, to a lesser extent, the sun. Because the sun and moon go through different alignment, this affects the size of the tides.

When the gravitational pull of the sun and moon combine, we see larger than average tides – known as spring tides. When the gravitational pulls offset each other, we get smaller tides known as neap tides. We see two periods of spring and neap tides roughly every month.

Yet some spring tides are higher than others. This is because tidal forces are stengthened if the moon is closest to Earth in its elliptical orbit (astronomers call this perigee). Tide forces are also enhanced when the sun and the moon are directly over the equater. For ths Sun this happens on or around 21 March or September (the equinoxes). Spring tides are always higher at this time of year. The moon’s orbit also takes it above and below the equator over a period of 27.2 days. Just as with the Sun, the tide generating forces are at their greatest when the moon is directly overhead at the equator.

Very large spring tides occur when these astronomical factors coincide. Approximately every 4.5 years the moon is closest to the Earth, and is also overhead at the equator, at either the March or September equinox.

In some places, these extreme tidal conditions can cause water levels to be 0.5m higher than a normal spring tide, but the weather can have a greater impact than even these largest of tides

What is the role of the weather in sea levels?

It’s important to realise that just because we are expecting big astronomical tides over the next few days, these won’t cause the highest sea levels we’ve seen – even in the last few years. That’s because the weather can have a much bigger impact on sea level than the 18-year tidal cycle.

Strong winds can pile up water on coastlines, and low pressure systems can also cause a localised rise in sea level. Typically the difference in water level caused by the weather can be between 20 and 30cm, but it can be much bigger.

On the 5th December 2013, for example, the weather created a storm surge that increased the water level by up to 2 metres. Although an estimated 2,800 properties flooded, more than 800,000 properties were protected from flooding thanks to more than 2,800 kilometres of flood schemes. The Environment Agency also provided 160,000 warnings to homes and businesses to give people vital time to prepare.

This highlights the importance of the Met Office and the Environment Agency working together to look at the combined impact of astronomical tides, wind, low pressure and waves on flood schemes to assess the potential impacts for communities around our coast.

Will we see coastal flooding this weekend?

Given the height of the tides there may be some localised flooding. Weather isn’t playing a large part in water levels over the next few days, although strong winds on Monday are likely to generate some large waves and push up sea levels slightly. This is nothing unusual for winter. You can see more about what weather to expect with the Met Office’s forecasts and severe weather warnings.

The Environment Agency and the Met Office are working together to closely monitor the situation, and the Environment Agency will issue flood alerts and warnings as required.

In the Humber Estuary, for example, we are expecting total water levels of between 4.20-4.39 metres – well below record levels of 5.22m.

John Curtin, Environment Agency’s Director of Incident Management and Resilience, said:  “We are monitoring the situation closely with the Met Office and will issue flood alerts and warnings as required.

“It’s possible we could see some large waves and spray and urge people to take care near coastal paths and promenades and not to drive through flood water.

“However, we can only get a warning to you if you’ve signed up to our free service. People can also see their flood risk and keep up to date with the latest situation on the GOV.UK website at https://www.gov.uk/check-if-youre-at-risk-of-flooding or follow @EnvAgency and #floodaware on Twitter for the latest flood updates.”

For those in Scotland, you can see flood updates for your area on the SEPA website here.

For those in Wales, you can see flood updates in English and Welsh on the Natural Resources Wales website here.

You can also see John explaining the Environment Agency’s flood warnings here:





One year on – A look back to last winter

17 02 2015

This weekend marked the one-year anniversary of the Valentine’s Day storm, which also marked the end of a particularly stormy three-month period. A new review article – ‘From months to minutes – exploring the value of high-resolution rainfall observation and prediction during the UK winter storms of 2013/2014’ – written by 16 Met Office co-authors reviews the accuracy of our forecasting and warning of severe weather during winter 2013-14, and assesses its performance.

The paper concludes that the “prolonged period of high impact weather experienced in the United Kingdom during the winter of 2013/14 was very well forecast by the operational tools available across space and time scales.”

Here Huw Lewis, the paper’s lead author, and Derrick Ryall, Head of the Public Weather Service, look at the extreme weather last year and the role of the Met Office in communicating severe weather through the National Severe Weather Warning Service.

Analysis chart 1200 GMT 26 January 2014

Analysis chart 1200 GMT 26 January 2014

Winter 2013/2014 in the United Kingdom was remarkable. The country was battered by at least 12 major winter storms over a three month period and was officially assessed as the stormiest period that the United Kingdom has experienced for at least 20 years.

The series of storms resulted in the wettest winter in almost 250 years (according to the England and Wales precipitation series from 1766), significantly wetter than the previous wettest winter in 1914/1915.

Snapshot of UK rain radar surface rainfall rate for 2200 GMT on 23 December 2013

Snapshot of UK rain radar surface rainfall rate for 2200 GMT on 23 December 2013

The extreme weather caused widespread flooding throughout Southern England and coastal damage – most notably in the South West and Norfolk coasts. The impact of the severe winter storms on individuals, businesses and the government were substantial, including several fatalities, widespread power cuts and damaged infrastructure.

Recent advances in forecasting, technology and the scientific developments in meteorology have been considerable. These developments and improvements in accuracy mean that a four-day weather forecast is as accurate as a one-day forecast was just thirty years ago. During the course of last winter, the Met Office was able to use these forecasts to warn of any severe weather well in advance. In the case of the St Jude’s Day storm at the end of October 2013 warnings went out to the Government and the public five days before the storm even existed.

rainfall

As the accuracy of weather forecasts has evolved, so has the communication of the potential impacts of severe weather. The National Severe Weather Warning Service enables more ‘weather decisions’ which in turn help to minimise the consequences of severe weather. The Met Office was at the heart of the government response to the storms, providing advice on weather impacts through the National Severe Weather Warning Service and Civil Contingency Advisors. The Met Office also worked very closely with both the national and regional media, who in turn played a key role in ensuring that the public were fully informed about the potential impacts of any up-coming weather.

In addition to the Public Weather Service, commercial partners and customers were also provided with detailed updates throughout the period in order for them to plan effectively for logistical issues. Together, these advanced warnings helped authorities, businesses and individuals to be better prepared to take mitigating actions.

Driving further improvements in accuracy and therefore reducing the lead time and increasing the detail of severe weather warnings is one of the Met Office’s key priorities . The ultimate aim is to improve the potential for users to plan preventative measures for severe weather events much further ahead. Underpinning all of these developments is a continuing programme of scientific research and access to enhanced supercomputing over the next few years.





Guest blog: ‘Risk of summer drought at normal levels’

17 06 2014

There have been some reports in the press that the Met Office has warned dry weather this June could bring a return of drought conditions to the UK – this is not the case. Here Victoria Williams, Water Resources Advisor at the Environment Agency, explains what the real risks are at the moment:

Every week we measure water resources in England to assess how dry the soils are and how much rain they can soak up, the amount of water flowing in rivers, stored below ground in aquifers and above ground in reservoirs, and the outlook for the coming months.

As we move into summer the overall water resources situation across England is looking generally healthy. This is not surprising given England has experienced the wettest six month period (Dec-May) on record.

Regionally it has also been a record breaker with the wettest six months experienced in southeast and southwest England and the second wettest in central and northwest England.

All our rivers have responded to the rainfall and are currently within normal ranges.  Groundwater levels throughout England are within normal ranges and are now starting to recede as expected for the time of year.

We also look ahead by modelling how rivers and groundwaters may respond to different future rainfall patterns over the summer. The results shows a broadly positive picture even if rainfall is below average and point to the risk of drought this summer being no greater than average.

However it is still as important as ever to use water wisely. If the weather does turn hot and dry there can be localised impacts on rivers, the environment and for farming. If this happens we work with abstractors to reduce the effects where possible and water companies will keep their customers informed if needed.

For more information see the Environment Agency water situation reports.





UPDATED: Wind and rainfall data 4 to 5 December 2013

5 12 2013

UPDATED TO INCLUDE LATEST WIND SPEEDS AS AT 3PM, 5 DECEMBER 2013

As forecast, there have been severe gales with widespread gusts of between 60 and 80mph across Scotland and northern parts of England. Some very high level mountain sites have reported speeds of over 140mph, but these are in very exposed areas and not representative of the winds most people have experienced.

UK MAX HOURLY GUST SPEED 4 DEC 1800HRS – 5 DEC 0600HRS
SITE NAME AREA ELEVATION MAX GUST SPEED (MPH)
ALTNAHARRA SUTHERLAND 81 93
LOCH GLASCARNOCH ROSS & CROMARTY 269 92
DRUMALBIN LANARKSHIRE 245 90
SOUTH UIST RANGE WESTERN ISLES 4 89
HIGH BRADFIELD SOUTH YORKSHIRE 395 87
EMLEY MOOR WEST YORKSHIRE 267 86
STORNOWAY AIRPORT WESTERN ISLES 15 85
ORLOCK HEAD DOWN 35 84
KINLOSS MORAY 5 83
SPADEADAM CUMBRIA 285 83
ESKDALEMUIR DUMFRIESSHIRE 236 83
SKYE: LUSA WESTERN ISLES 18 83
TIREE ARGYLL 9 82
DUNSTAFFNAGE ARGYLL 3 82
 MOUNTAIN SITES MAX GUST SPEED 4 DEC 1800HRS – 5 DEC 0600HRS
SITE NAME AREA ELEVATION MAX GUST SPEED (MPH)
AONACH MOR INVERNESS-SHIRE 1130 142
CAIRNWELL ABERDEENSHIRE 928 137
BEALACH NA BA ROSS & CROMARTY 773 116
GREAT DUN FELL CUMBRIA 847 113
GLEN OGLE PERTHSHIRE 564 106

It has been very wet in some areas overnight as well with 50.8mm of rain being recorded at Tyndrum, Perthshire and 42.4mm at Cluanie Inn, Ross & Cromarty.





Unsettled weather to come – but no repeat of ‘St Jude’ in sight

29 10 2013

There have been a few mentions in today’s media of another storm coming in for this weekend – with the Daily Express suggesting that a ‘new deadly storm’ is on the way.

It’s fair to say we are expecting a spell of unsettled autumnal weather over the next week, with some strong winds and heavy rain possible – but comparisons with the ‘St Jude’s Day storm’ (as some in the media have called it) are wide of the mark.

Currently forecasts suggest that we will see several low pressure systems affecting the country over the next week – which is a fairly typical picture for UK weather at this time of year.

These could bring gale force winds at times to some areas, but we don’t expect gusts to be anything like the exceptionally strong winds we saw on Monday. In fact, the winds are more likely to be similar to those we saw during the day last Sunday – the day before the big storm.

Of course, even gale force gusts do bring some risks and the Met Office will closely watch developments to assess any impacts.

The low pressure systems coming through over the next week are likely to lead to some rough seas and big waves around some coasts, as well as some heavy rain.

The Met Office, Environment Agency and Scottish Environment Protection Agency (SEPA) will be working together to monitor the risk of any impacts from these over the next few days.

Given the outlook for unsettled weather, we’d advise people to stay up to date with the latest forecasts and warnings from the Met Office and to sign up to receive free flood warnings from the Environment Agency and SEPA website.





July starts dry, sunny and warm

17 07 2013

Early Met Office figures for the first half of July show that it has been warmer, drier and sunnier than usual so far this month.

We’ve now had 11 days with temperatures over 28 °C somewhere in the UK, making it the longest hot spell since 2006.

The UK mean temperature up to the 15th July is 16.1 °C, a degree above the long term average for the whole of the month. The days have been particularly warm so far, with the average maximum temperature for the UK being 21.3 °C, 2 degrees above normal.

Rainfall for the UK from 1-15 July was 9.2 mm. At this stage we would expect to have seen about 48 % of the full month average, however we have only seen 12 %. We have seen less than 5 mm widely across much of England and parts of eastern Scotland (many locations with only 1 or 2 mm).

Up to the 15th we have seen 132 hours of sunshine across the UK, which is 77 % of the full month average. Again, we would have expected to have seen about 48% at this point in an ‘average’ month.

Looking at the individual countries, Scotland’s mean temperature has been 14.4 °C (1.2 °C above average) and Northern Ireland’s has been 16.3 °C (1.7 °C above average). England’s has been 17.0 °C (0.7 °C above average), and Wales’ has been 16.3 °C (1.1 °C above average).

Wales had the most sunshine with 155 hours, which is 86 % of the full-month long-term average.

England has seen the least rainfall for the first half of the month with 4.0 mm, just 6 % of the long term July average. Scotland has seen the most rain with 16.8 mm, but even that is only 17 % of the full-month average.

To put this in context, the driest July on record across the UK was in 1955 when there was 30.6 mm of rain. With only 9 mm of rain so far in the UK this July, this is likely to be a very dry month but – with two weeks to go – it’s too early to say where it will end up in the national series dating back to 1910.

For the longer running England and Wales precipitation record which dates back to 1766, the record driest July was in 1825 with just 8 mm of rain. England and Wales have seen just 4 mm so far this month, but – again – it’s too early to judge where it will end up in the records.

With regards to sunshine hours, 1955 is the sunniest July on record with 256 hours of sunshine, with 2006 close behind with 253 hours.

The warmest July on record is 2006 with a UK mean temperature of 17.8 °C; this is also the warmest month in the national record which goes back to 1910.

Mean Temperature Sunshine hours Rainfall  
1-15 July Actual Diff from Avg Actual % of Avg Actual % of Avg
  degC degC hours % mm %
UK 16.1 1 132.1 77 9.2 12
England 17 0.7 147.2 76 4 6
Wales 16.3 1.1 154.7 86 8.7 9
Scotland 14.4 1.2 104.1 74 16.8 17
N Ireland 16.3 1.7 114 81 15.7 19

The reason behind this very warm weather is an area of high pressure which has been sitting right above the UK since the start of the month.

This dry weather is in sharp contrast to last year’s wet weather and follows on from a dry June this year.

The Environment Agency measures water resources in England every week to assess how dry the soils are and how much rain they can soak up, the amount of water flowing in rivers, stored below ground in aquifers and above ground in reservoirs, and the outlook for the coming months.

Trevor Bishop, head of water resources at the Environment Agency, said: “Last year’s exceptionally wet summer and autumn has left us in a fairly good water resources position, with most rivers, reservoirs and underground water stores around normal for the time of year. Some river levels are dropping as a result of the hot, dry spell that we are enjoying, and we would urge everyone to continue use water wisely, to protect water supplies and the environment.”

More information can be found in their latest water situation report.





Guest blog: Commemorating the 60th anniversary of the 1953 floods

31 01 2013

Craig Woolhouse is Head of Flood Incident Management at the Environment Agency. He looks at how flood risk management has progressed since 1953 and how you can keep flood aware.

Canvey Flood

Today marks the 60th anniversary of the 1953 floods where over 300 people died, 24,500 houses were damaged and over 30,000 people were evacuated. Outside the towns and villages, thousands of animals were drowned and great tracts of farmland were made infertile by salt water. This was one of the worst peace time calamities to hit Britain with Winston Churchill declaring it a “National Disaster”.

Those affected by the floods would have gone to bed without a flood warning and many of the flood defences today along the east coast, including London’s Thames Barrier, didn’t exist at all.

We’re lucky enough to have a lot more tools at our disposal to keep flood aware and safe these days. For example, you can join the 1.2 million people in England and Wales already signed up for free flood warnings. Where there was major loss of life in 1953, major flood defences have been built – for example Canvey Island, Jaywick, Felixstowe, Lincolnshire, Kings Lynn and Great Yarmouth. The Thames Barrier, celebrating its 30th birthday tomorrow as one of the world’s largest moveable defences, was also constructed as a result of the 1953 floods.

There have also been massive improvements in long range flood forecasting since 1953 like the joint Environment Agency and Met Office flood forecasting centre which provides 24/7 flood guidance to emergency services and local authorities.

We’re much better prepared than in 1953 but we cannot afford to be complacent. Despite the low probability, extreme floods like 1953 could strike at any time and we need to be prepared as a country and as communities for when these happen.

Visit the Environment Agency website to see what you can do to stay flood aware.

You can find out more about how weather and flood forecasting has improved on our website.





UK rainfall over the last eight days

27 11 2012

After a dry start to the month, the last eight days have seen some very wet weather affect the UK, causing widespread flooding and disruption. So just how much rain has the UK seen and where has been wettest? The following maps show the full picture.

UK rainfall from 19-27 November 2012

The darkest blues on the map above show the areas that have seen the most rainfall, with South West England, Wales and parts of Northern England being particularly affected. How do these totals compare with the monthly average for November?

Eight day rainfall totals compared to whole November average

This map shows that areas from North East England through the Midlands to South West England have seen above average rainfall during the last eight days. However, parts of Northern Ireland and Scotland have seen very little.

As always, we have worked closely with the Environment Agency throughout the recent weather and have issued a series of accurate and useful forecasts and warnings which have helped emergency responders, county councils and members of the public stay informed about the latest developments.

Assistant Chief Constable of Devon and Cornwall Police, Paul Netherton, said: “I would like to formally thank and recognise the hard work of the Met Office over the past week. The information provided was invaluable and enabled the responders in Devon, Cornwall and the Isles of Scilly to prepare and respond effectively to assist our communities.”

For the rest of this week it looks as though there will be some respite from the rain with much drier conditions forecast. It will be colder though, with an increased risk of frost, fog and even ice towards as we head through the next few days.





24 – 25 November rainfall update

25 11 2012

Overnight rainfall recorded at Met Office observing stations from 6pm Saturday 24 November to 8am Sunday 25 November:

Station     Amount
Fylingdales, North Yorkshire 36.6 mm
Pershore, Hereford & Worcester 32.6 mm
Sheffield, South Yorkshire 32.6 mm
Gingley-on-the-Hill 31.8 mm
Leek, Staffordshire 31.6 mm
High Mowthorpe, North Yorkshire 31.4 mm
Exeter Airport, Devon 31.2 mm
Dunkeswell, Devon 30.8 mm
Scarborough, North Yorkshire 30.6 mm
Normanby Hall, Humberside 30 mm

Below are the highest rainfall totals recorded at Met Office observing stations between midnight on Saturday and 8am this morning:

Station     Amount
St Mary’s Airport, Isles of Scilly 58.2 mm
Plymouth, Devon 56.8 mm
Cardinham, Cornwall 49.2 mm
Exeter Airport, Devon 48 mm
Dunkeswell, Devon 47.8 mm
Camborne, Cornwall 44.6 mm
Culdrose, Cornwall 41 mm
Pershore, Hereford & Worcester 40.6 mm
Astwood Bank, Hereford & Worcester 39.6 mm
Liscombe, Somerset 38.4 mm

 





Rainfall totals 24 November 2012

24 11 2012

It has been another wet day across much of the southern half of the UK. Here are some rainfall totals between midnight and 9pm from Met Office reporting stations:

Station     Amount
St Mary’s Airport, Isles of Scilly 57 mm
Plymouth, Devon 49.2 mm
Camborne, Cornwall 42.8 mm
Culdrose, Cornwall 40 mm
Cardinham, Cornwall 39.2 mm
Exeter Airport, Devon 31.6 mm
Dunkeswell, Devon 27.6 mm
North Wyke, Devon 26 mm
Bournemouth Airport, Dorset 24 mm
Liscombe, Somerset 21.4 mm

There is more rain to come over the rest of the weekend and into the start of next week.








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