2017 Rainfall Observer Newsletter

The follow articles are from the annual rainfall observer newsletter that SEPA and the Met Office produce each year. Thank you to the Met Office for writing all of this years!

Storm Names 2017-18


The criteria used for naming storms is based on the Met Office’s National Severe Weather Warnings service. This is based on a combination of both the impact the weather may have, and the likelihood of those impacts occurring.

A storm will be named when it has the potential to cause an amber ‘be prepared’ or red ‘take action’ warning.

Other weather types will also be considered, specifically rain if its impact could lead to flooding as advised by the Environment Agency, SEPA and Natural Resources Wales flood warnings. Therefore ‘storms systems’ could be named on the basis of impacts from the wind but also include the impacts of rain and snow. Follow the Met Office on Facebook or Twitter for the latest updates.


When the criteria for naming a storm is met, either the Met Office or Met Éireann can name a storm.

The Met Office then let the public, partners in government and the responder community and the media know through various routes including publishing details on website and social media channels.

  • WHY ARE THERE NO STORMS FOR Q, U, X, Y AND Z? To ensure alignment with the US National Hurricane Centre names which begin with the letters Q, U, X, Y and Z are not included. This maintains consistency for official storm naming in the North Atlantic
  • HOW ARE STORM NAMES CHOSEN? In September 2015 the Met Office began the Name Our Storms campaign and asked the public to send in their suggestions for names. Thousands of suggestions were received and this years list includes some of the most popular of those together with suggestions from Met Éireann.
  • UK AND US STORM NAMES? To avoid any confusion over naming, if a storm is the remnants of a tropical storm or hurricane that has moved across the Atlantic, the well-established method of referring to it as, e.g. ‘Ex-hurricane X’ will continue. Only names that have been officially designated by the National Weather Service in the US will be used.
  • ARE WE HAVING MORE STORMS? Stormy weather is not unusual in the winter and we only need to go back to the winter of 2013-14to see a similarly stormy winter. Overall, the period from mid-December 2013 to mid-February 2014 saw at least 12 major winter storms, and, when considered overall, this was the stormiest period of weather the UK has experienced for at least 20 years. We have seen comparable or more severe storms in recent years, including 3 January 2012 and 8 December 2011, each of which caused widespread impacts.

You can find out more about some of the interesting weather we’ve had in recent years at the Met Office website


100 years of NWP

100 years ago, Lewis Fry Richardson, mathematician and scientist, started to see if he could forecast the weather.

As he experimented with Numerical Weather Prediction (NWP) on the Western Front during World War I, could he have imagined the advances in forecasting and accuracy since then? 

In 1913, before the outbreak of war, Richardson was in charge of the Met Office’s Eskdalemuir observatory in Scotland. While there, he started developing ideas on weather forecasting using mathematical methods.

As a Quaker and pacifist, Richardson was a conscientious objector during World War I. So, in 1916, he left the Met Office to join the Friend’s Ambulance Unit. Even while he was working at Passchendaele as an ambulance driver, he continued experimenting on the first ever numerical forecast based on scientific rules rather than past trends.

In 1917, instead of using mathematical models, weather forecasters would match current weather with patterns in past weather records, but Richardson eventually developed a more scientific method that is more accurate and still in use today.

Trials in the trenches

As war raged around him, Richardson began to experiment with creating a numerical weather forecast. For his first attempt, he re-created a past forecast for Central Europe, using published observations data. Modern forecasting uses complex algorithms run on powerful supercomputers in which observations of current weather are processed through a mathematical model of the atmosphere to forecast its future state. Richardson devised a gridded map of the forecast area and generated, by hand, the first numerical weather prediction.

The calculations took Richardson more than six weeks to produce a six-hour forecast for just one location. While this first forecast was not accurate, due to limitations with the data, his pioneering method was eventually to be proved correct. An early version of Fry Richardson’s gridded map is pictured here.

Forecast factory

After the war, Richardson continued to develop his theories, re-joining the Met Office in 1920 where he continued his work. In 1922, Richardson published his now famous book, Weather Prediction by Numerical Process. Incredibly, during the battle of Champagne in 1917, the draft of his book was sent to away from the frontline for safe keeping. However, it was lost and then re-discovered months afterwards under a heap of coal.

As well as his methodology, Richardson described his ideas of what has since been called his ‘forecast factory’. Imagining a large circular theatre like hall, with a map of the world painted on its walls, he estimated that 64,000 ‘computers’ (not computers as we know today, but mathematicians tasked with ‘computing’) would be needed to calculate weather forecasts in real time, each responsible for one small part of the globe.

Pioneer of modern forecasting

Richardson’s foresight was remarkable, and the mathematical methods, which he instigated, started to become a practical reality using electronic computers after World War II. Supercomputers today use parallel processors to undertake the huge numbers of calculations needed to run global forecast models.

While his vision of the forecast factory was never fully realised quite in the way he had imagined it, he will be forever remembered as a pioneer in the field of numerical weather prediction whose work set the foundation for modern forecasting.

These days, the Met Office provides accurate forecasts for all around the world, with most people accessing them on demand at an instant touch of a button or screen without giving the science behind the forecasts a second thought. In the background, is the Met Office Unified Model, a numerical model of the atmosphere used for both weather and climate. Together with our partners around the world, we continually develop the model, adding state of the art understanding of atmospheric processes to new releases.


Weather Radar Renewal

15 radar sites. A 30-year-old network. One ambitious plan. In 2017 the Met Office’s project jointly funded with the Environment Agency to renew all the weather radars draws to a close – but the benefits it will bring are only just beginning.

Spanning the UK, the Met Office radar network provides real-time precipitation data to forecasters, scientists and a range of organisations. Together with our partners we use that data in two key ways: for monitoring the current weather situation, and forecasting via computer modelling. It’s a job the radars have been doing for decades, feeding everything from television reports to weather alerts and helping partners monitor flood risk. But with the advent of new technologies, fresh infrastructure needs and inevitable weathering, it was time for an upgrade. Following an extensive planning phase, 2010 saw the start of a seven-year roll-out.


The radars and the information they can now deliver are of vital importance to the Environment Agency which co-funded this project.

“For the Environment Agency, a clear, timely picture of weather behaviour is crucial for mapping rainfall rates and locations, then forecasting potential flood impacts on communities downstream so that people and responders can take action to save lives and livelihoods,” said Liz Anspoks from the Environment Agency.

Enhanced real-time data, thanks to dual polarisation in particular, will bring huge benefits to the Met Office too – supporting decision-making and potentially improving the speed at which we can get alerts out in extreme weather.



At a practical level, the radars will also operate more resourcefully than before, leading to less call-outs and downtime. And the Met Office sees those efficiencies extending long into the future. “We’ve developed and deployed a system ourselves rather than using something off-the-shelf,” says Richard. “That gives us the flexibility to develop it even more as the network grows.” Future-proofing has been front of mind throughout the project. These state-of-the-art systems should equip the radar network for at least the next 10-15 years.

Now that the project is coming to a close – with the last few upgraded radar sites due to be up and running again shortly – Richard is reflecting on a job well done: “Looking back, it’s been a real team effort. As we’ve switched one enhanced radar back on, we’ve been testing another and starting the upgrade on the next one. But we’ve had the support of a range of local suppliers, and the Environment Agency which co-funded the project. It’s good to celebrate what we’ve achieved together – and personally, to witness progress happening has been a great feeling.”


Anniversary of the Great Storm of 1987

October marked the 30th anniversary of the Great Storm of 1987, which hit the south of England.

Forecasters at the time had been predicting severe weather up to four days ahead, but, as time went by, weather prediction models of the time gave an unclear picture. Models suggested severe weather would pass to the south of England only skimming the south coast.

Most of our autumnal storms head in from the Atlantic to the west of the UK. However, this storm developed over the Bay of Biscay to the south.

Particularly warm tropical air and very cold polar air collided, forcing warm air to rise creating an area of low pressure. A big difference in temperature between the warm and cold air helped to cause a rapid ascent and therefore a particularly low pressure. To the west of the low, pressure rose rapidly leaving a big differential in pressure, which can be seen in the tightly drawn isobars of the chart below.

The forecast – a hurricane or not?

Many of us remember the words of Michael Fish at lunchtime before the storm struck:

‘…earlier on today apparently, a woman rang the BBC and said she’d heard there was a hurricane on the way. Well, if you are watching, don’t worry, there isn’t…..’

He was talking about a separate storm over the western part of the North Atlantic Ocean that day. He said it wouldn’t reach the UK, and it didn’t. But the rapidly deepening low from the Bay of Biscay did.

This storm wasn’t officially a hurricane as they need specific conditions found in the tropics, but actually hurricane force winds did occur in some locations in the UK during the Great Storm.

Impacts…Several factors came together to make this storm particularly ferocious, but it was the track of the storm that was probably most significant.

Arriving over the south coast of the UK, it tracked north and east before reaching the Humber estuary at about 5.30am on 16 October. This path took in a large built up and densely populated area of the UK, exacerbating the damage caused.

In southeast England, where the greatest damage occurred, gusts of 80mph were recorded for three to four consecutive hours. The highest gust recorded over the UK was 115mph at Shoreham on the Sussex coast at 3.10am. Gusts of more than 100mph were recorded at several other coastal locations.


Even inland, gusts exceeded 90mph with 94mph being recorded at London Weather Centre at 2.50am.

After the storm…The Met Office and other European forecasters had failed to predict the intensity of the storm. It was clear that the forecasting capabilities at the time couldn’t always predict this type of event.

This was to become a catalyst for a program of investment and improvement in the science, technology and communication of forecasting, which has transformed the way the UK responds to severe weather.

Forecasting improvements since 1987…The Met Office works with leading international research centre to push the boundaries of forecasting to deliver ever-better accuracy, but also to improve the understanding of weather phenomena.

A sting in the tail… The strength of the 1987 storm was boosted by a phenomenon known as the ‘Sting Jet’. This is where cold dry air from high in the atmosphere descends into weather systems, creating an area of particularly strong winds at ground level. At the time of the storm, no one knew these existed, but now they are well understood and included in forecast models. For example, a storm, which affected Scotland in December 2011, was boosted by a sting jet, explaining the maximum gust of 164mph recorded on the top of Cairngorm.

Observations…An increasing amount of data from satellites has played a pivotal role in weather forecasting. In 1987, very few observations were received from satellites. Now, of the 215 billion observations received every day, the majority come from satellites and contribute more than 65% to the performance of our global numerical weather prediction model.

At the time, we had very few observations from the Bay of Biscay where the storm formed. As a direct result of the Great Storm, deep ocean weather buoys were located around the British Isles to provide hourly weather information and help us to monitor developing weather conditions.

Technology… Supercomputing capability has also hugely advanced since 1987. A typical smartphone of today has a least five times more computer power than our supercomputer of 1987 that could perform 4 million calculations per second. Today our latest supercomputer is able to perform 14,000 trillion calculations per second helping us to unlock new science and provide more detailed forecasts and warnings.

In 1987, computing capacity limited the resolution of the global model we used for weather prediction to grid boxes of 150 km. Now the model works at 10 km on a global scale, giving vastly improved resolution. Over the UK, these grid boxes have been reduced to just 1.5 km leading to improved forecast accuracy, enabling us to give better information about the weather that affects us all.

Additionally, unlike 1987, we now run multiple forecasts (called ensembles) that help us to understand the probabilities involved in a forecast and give a better estimate of the risk of high impact weather events. These improvements mean that the Met Office four-day forecast is now as accurate as our one-day forecast was 30 years ago.


Seasonal rainfall

Ex-Hurricane Ophelia 16 October 2017

On 16 October 2017 ex-hurricane Ophelia brought very strong winds to western parts of the UK and Ireland. This date fell on the exact 30th anniversary of the Great Storm of 16 October 1987.

Ex-hurricane Ophelia (named by the US National Hurricane Center) was the second storm  of the 2017-2018 winter season, following Storm Aileen on 12 to 13 September. The strongest winds were around Irish Sea coasts, particularly west Wales, with gusts of 60 to 70 Kt or higher in exposed coastal locations.


The most severe impacts were across the Republic of Ireland, where three people died from falling trees (still mostly in full leaf at this time of year). There was also significant disruption across western parts of the UK, with power cuts affecting thousands of homes and businesses in Wales and Northern Ireland, and damage reported to a stadium roof in Barrow, Cumbria. Flights from Manchester and Edinburgh to the Republic of Ireland and Northern Ireland were cancelled, and in Wales some roads and railway lines were closed. Ferry services between Wales and Ireland were also disrupted. Storm Ophelia brought heavy rain and very mild temperatures caused by a southerly airflow drawing air from the Iberian Peninsula.


Ex-hurricane Ophelia moved on a northerly track to the west of Spain and then north along the west coast of Ireland, before sweeping north-eastwards across Scotland. The sequence of analysis charts from 12 UTC 15 to 12 UTC 17 October shows Ophelia approaching and tracking across Ireland and Scotland.

Rain-radar image of Ophelia at 1200 UTC 16 October 2017. The centre of the storm is over south-west Ireland, corresponding to the satellite image above.

An image of the sun during the morning of 16 October 2017 from Met Office Headquarters in Exeter, likely to be caused by a combination of Saharan dust and smoke from Portuguese wild-fires drawn north by the warm southerly airflow; a phenomenon observed widely across southern England. Image courtesy Dan Harris, Met Office.

Highest max gust speeds (Kt) 16 October 2017 from Ophelia. The strongest winds of 60 to 70 Kt were around Irish Sea coasts, particularly west Wales. The highest recorded gusts were 78 Kt (90 mph) at Capel Curig and Aberdaron (both Gwynedd), 70 Kt (81 mph) at Valley (Anglesey) and 69 Kt (79 mph) at Mumbles Head (Swansea).

Ex-hurricane Ophelia occurred on the 30th anniversary of the Great Storm of 16 October 1987. For comparison, maximum gust speeds in 1987 are shown below, exceeding 70 Kt widely across south-east England and 80 to 90 Kt or higher across the far south-east, with 100 Kt (115 mph) at Shorham (Sussex).

The October 1987 storm has been referred to as the worst storm to affect southern England since the Great Storm of 1703 (impacts from the latter were recorded in detail by Daniel Defoe, author of the novel Robinson Crusoe. He estimated at least 8000 deaths, and over 400 windmills overturned or burnt down when their wooden machinery overheated. The Eddystone rock lighthouse, off Plymouth, was swept away, taking its designer Henry Winstanley with it).

Highest hourly mean wind speeds (Kt) 16 October 2017 from Ophelia. The highest hourly mean wind speeds were 40 to 50 Kt, and again these occurred around Irish Sea coasts, particularly west Wales, with 56 Kt (64 mph) at Aberdaron.

Previous ex-hurricanes

There have been a number of ex-hurricanes affecting the UK in recent years (this is not a definitive list).

Ex-hurricane Bertha on 10 to 11 August 2014 brought strong winds and heavy rain, resulting in some flooding in Moray (Scotland), with 56 Kt (64 mph) at Needles Old Battery (Isle of Wight).

Ex-hurricane Nadine on 24 to 26 September 2012 caused flooding in north-east England, some fallen trees in the Scottish Borders and a fatality from a fallen tree in London, with 61 Kt (70 mph) at Warcop Range (Cumbria).

Ex-hurricane Katia on 12 September 2011 resulted in widespread transport disruption and one fatality from a fallen tree in northern England, with 63 Kt (72 mph) at High Bradfield (South Yorkshire).

Ex-hurricane Gordon brought strong winds to southern and western parts of the UK on 21 September 2006 with 61 Kt (70 mph) at St Marys Airport (Isles of Scilly).

Ex-hurricane Lili brought strong winds to southern parts of the UK on 28 October 1996, with 76 Kt (87 mph) at Solent (Hampshire).

Ex-hurricane Charley on 25 to 26 August 1986 brought strong winds, widespread heavy rain and boats were driven onto rocks at Abersoch, west Wales. Bank Holiday Monday 25 August 1986 was exceptionally wet with over 50mm of rain falling widely across much of England and Wales. The highest gust was 62 Kt (71 mph) at Gwennap Head (Cornwall).

Examples of other severe storms to affect the UK at this time of year include the St Judes’ Day storm of 28 October 2013, the storm of 27 October 2002, and the storm of 30 October 2000 – the latter autumn also seeing significant flooding across England and Wales.

However, there are no compelling trends in maximum gust speeds to indicate increased storminess of the UK’s weather, as recorded by the UK wind network in the last four decades. Further details are given in the State of the UK Climate 2016 report.





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