Keep your eyes peeled for eyes in the sky

12 02 2016

On a clear night, when looking up at the heavens, it may be tempting to imagine that those little lights in the night sky are just stars, planets or aircraft, says Dr Simon Keogh, in the latest of a series of blogs on satellites. Dr Keogh leads the Met Office Satellite Data Products and Systems group

However, he adds, some of these lights in the sky are actually satellites. There are rather a lot of them up there and they’re not only there for weather forecasting. In the early morning or evening you can sometimes spot polar-orbiting satellites drifting slowly overhead. They appear as a small speck of light that moves from horizon to horizon over a period of a few minutes. The light you can see is actually sunlight being reflected off the large solar panels that the satellite relies upon for power. This light is sometimes referred to as a “flare”.


Photo (courtesy of NOAA) of the International Space Station tracking across the sky at night.

The International Space Station (ISS), Tim Peake’s new and temporary home, is perhaps the most well-known satellite, orbiting the Earth at an altitude of around 435km (270 miles). The flare from the huge solar panels on the ISS make it reasonably easy to spot in the night sky.

Interestingly, in recent times the ISS has even been contributing valuable information on ocean surface winds from the RapidScat instrument, which is great for marine weather forecasting applications. We very much hope that RapidScat continues to work well and that it never needs attention from Tim or the other ISS astronauts.

We take these satellites for granted, but we shouldn’t. Thanks to weather satellites we have accurate forecasts and timely warnings to help us prepare for the worst the weather can throw at us. Without weather satellites, we’d be living in a world where the next flood, the next heat wave and the next storm surge would come without warning with potentially disastrous consequences.

Fortunately, the Met Office is an active participant in the design of many future satellite missions so we look forward to having weather satellites around for a long time to come.

Working with colleagues internationally, we make sure that the needs of the UK for satellite data are represented on a global stage. If you want to find out more about weather satellites and what we do with them in the Met Office then please visit


The International Space Station is relatively easy to spot as it is the second brightest object in the night sky (after the moon), and orbits the earth around 16 times each day. Picture courtesy: NASA.

To see the ISS for yourself please visit the following website for details:

Dr Simon Keogh leads the Met Office Satellite Data Products and Systems group. He is a member of a United Nations WMO expert team on Satellite Utilisation and Products and is the UK delegate to EUMETSAT’s Operations Working Group.

Link to my page on the research pages:

Without satellites, would forecasting regress to the 1970s?

11 02 2016

The 1970s may be memorable for many things, but the accuracy of weather forecasting wouldn’t make the shortlist, says Dr Simon Keogh who leads the Met Office Satellite Data Products and Systems group with the third post in a four-part blog series about satellites.

Back in those days the accuracy of forecasts was far behind what can be achieved today, largely thanks to our modern-day constellation of sophisticated weather satellites.

We can’t feel too smug compared to our 1970s colleagues, though, because much of the modern forecast accuracy we take for granted today, would evaporate if we didn’t have our precious weather satellites.

Meteorologists use a process of data assimilation, where recent observations of the atmosphere are used to drive computer models to make predictions about how the atmosphere will change in future.


Global forecast map made from Met Office computer model output.

A fundamental principle of computer modelling is that the models are only as good as the data you put into them. What this means is that if the observations you put in to drive the model aren’t accurate enough or aren’t complete enough then the effect is like putting contaminated fuel into a sports car: you won’t get the best performance. The same happens with weather models. If the observations that go in aren’t accurate enough, or complete enough, then the model runs out of ‘skill’ quite early, potentially providing useful forecasts only hours ahead instead of days ahead as we’ve come to expect.

That’s important because society needs as much notice as possible to respond to severe weather emergency services. Sandbags need filling, personnel need putting on rota and people and equipment may need to be drafted in from other parts of a country to shore up weak spots in defences that severe weather might exploit. All this takes time and severe weather warnings are crucial in buying time for the emergency services. Without these timely warnings the snowploughs, helicopters, fire engines, sandbags and brave emergency workers won’t be where you need them, or  when you need them.

The next blog in this series, tomorrow, describes how you can spot weather satellites for yourself in the night sky.

Dr Simon Keogh leads the Met Office Satellite Data Products and Systems group. He is a member of a United Nations WMO expert team on Satellite Utilisation and Products and is the UK delegate to EUMETSAT’s Operations Working Group.

Link to my page on the research pages:

A man-made constellation in the night sky

10 02 2016

Thanks to a ring of satellites operated by Europe, USA, Japan, China, India, Russia and South Korea we now have large-scale coverage of the Earth and an insight into how our complex weather patterns are changing hour-by-hour, day-by-day and year-by-year, says Dr Simon Keogh who leads the Met Office Satellite Data Products and Systems group. This is the second part of Simon’s blog series on satellites, which began yesterday.


Global composite image made from European, American and Japanese geostationary satellite imagery.

To space experts a major group of satellites are known as geostationary, because they appear to be stationary in the sky, always staring down at us from the same position day and night. However, they are way up at about 36,000km (22,000 miles) above the Earth, so there are limitations on how much detail they can resolve from such a great distance. Nevertheless, these satellites are considered to be the workhorse satellites of the modern meteorologist, giving a panoramic view of what’s happening with our changing weather nearly everywhere on Earth – apart from over the poles.

Complementing this ring of geostationary satellites are many polar-orbiting satellites. These polar-orbiting satellites circle the Earth at a height of around just 705km (438 miles) and, as their name suggests, can provide detailed observations of the polar regions as well as other parts of the globe. They’re very much closer to Earth than geostationary satellites, which mean they can also be used to take close-up measurements of the atmosphere, revealing its detailed three-dimensional structure.


The A-Train of satellites (image courtesy of NASA).

One particular example of these polar-orbiting satellites is the ‘A-train’ of satellites operated by NASA. Each of these satellites orbit in quick succession, just a few minutes apart. Each satellite in the train yields a complementary view when compared to its successor and predecessor.

Tomorrow, the next post in Simon’s four-part series will examine the impact of weather satellites on our safety and security.

Dr Simon Keogh leads the Met Office Satellite Data Products and Systems group. He is a member of a United Nations WMO expert team on Satellite Utilisation and Products and is the UK delegate to EUMETSAT’s Operations Working Group.


Looking down on the weather: a brief history

9 02 2016

Today we can be inclined to take rocket launches for granted, says Dr Simon Keogh who leads the Met Office Satellite Data Products and Systems group in the first of a series of blogs on satellites. There was once a time, he adds, when every blast off to the heavens captured the public’s imagination. Families would be glued to TV sets to see the latest episode in the unfolding drama of mankind probing the universe. These days, launches happen so frequently they barely get a mention in the press: unless of course there is a significant incident or the mission happens to be carrying an important payload, such as Britain’s heroic astronaut Tim Peake.

A modern satellite launch. S-NPP weather satellite blasts off in 2011 (courtesy of NASA).

A modern satellite launch. S-NPP weather satellite blasts off in 2011 (courtesy of NASA).

We may have taken the launches for granted, but we mustn’t overlook the role that space missions and satellites play in our everyday lives. From communications and weather observation to GPS satellite navigation on your smartphone. This technology has revolutionised our existence and it is fundamental to our everyday lives.

From a meteorological point of view, satellites have given us a new insight into the world’s weather and climate.

The TIROS-1 satellite was launched way back in 1960 but operated for only a mere 78 days. Although its useful life was extremely brief, it was a glorious time and the mission was widely deemed to be hugely successful. The first imagery that came back marked the dawn of a new era in Earth observation. Never before had scientists had the ability to monitor large storms on their way to make landfall.


The TIROS-1 satellite’s technology enables it to capture detailed images of the earth, such as the view of Nile (inset). Picture courtesy: NASA

It was suddenly apparent to the world’s scientists that if only there were enough of these satellites then perhaps it would be possible to evacuate towns in the path of severe weather, saving lives and livelihoods in the process. This truly did seem at the time to be the most promising societal application for space technology – and so it has arguably continued to be. As basic as the TIROS-1 satellite was, its impact has clearly inspired a long-lasting boom in the construction of satellites for monitoring our changing weather.

If you’d like to know more about the legacy of TIROS-1 and the constellation of satellites we have today, then look out for our week-long series on satellites.

Dr Simon Keogh leads the Met Office Satellite Data Products and Systems group. He is a member of a United Nations WMO expert team on Satellite Utilisation and Products and is the UK delegate to EUMETSAT’s Operations Working Group.

Storm Imogen brings gales to southern areas of Britain

7 02 2016

An area of low pressure, which will bring some very strong winds across southern parts of the UK as it moves eastwards on Monday, has been named as Storm Imogen.

Gusts of 60-70 mph are possible in southern England and parts of south Wales with 80 mph gusts possible in exposed coastal districts. Some very large waves are also likely along some coasts, especially along the north coast of Cornwall and Devon.

The Met Office has today (Sunday 7 February) issued an Amber “be prepared” National Severe Weather Warning for for wind for Storm Imogen which is valid from 3 am until 6 pm on Monday.  There is also a larger Yellow “be aware” Severe Weather Warning for wind valid from 3 am to 6 pm on Monday.

Surface Pressure Chart Monday 8 Februrary

Surface Pressure Chart Monday 8 Februrary

There remains some uncertainty just how far north and east the strongest of the winds will extend. However, you can keep up to date with the latest for your area using our forecast pages and by checking the Severe weather warnings.

Storm Imogen follows Storm Henry, which passed close to the north of Scotland through Monday 1 February 2016 into Tuesday 2 Feb.

Winds are expected to ease through Tuesday leading to a short drier, quieter and colder interlude for many on Wednesday before more wind and rain follows later in the week.

‘Mother of pearl’ clouds enthrall skywatchers

2 02 2016

Over the past few days, conditions in the upper parts of the atmosphere have allowed us to be treated to a rare glimpse of Nacreous Clouds.

What are they?
Found in the lower stratosphere, these clouds are mainly seen over polar regions in winter, where very cold air – minus 80˚C and lower – condenses the small amount of water vapour present into tenuous clouds. These clouds are normally found at altitudes of around 20 km.

Compared to the water droplets in clouds we see every day in the troposphere, the water droplets which make up Nacreous Clouds are much smaller. Their smaller size means that the way in which they scatter light is different to regular clouds. This gives them their characteristic pearly luminescence, and has led to them sometimes being known as ‘mother of pearl’ clouds.

Nacreous clouds are best seen in the twilight hours, just after sunset and just before sunrise, when the clouds are illuminated by sunlight from below the horizon.

How rare are they?
As these clouds are more usually seen over the polar regions in winter, it is quite rare to see them as far south as the UK. We usually get to see them for short periods of several days every few years.

Why are we seeing them now?
Currently, we are able to catch sight of them because cold air which usually circulates around polar regions in the stratosphere (the stratospheric polar vortex) has been displaced from its usual position over the north pole to be over the UK.

How much longer will we be able to see them?
Our weather forecast models indicate the cold polar vortex will remain nearby for the next few days, so we should be able to see Nacreous Clouds when the skies are clear. The position of the vortex shifts towards the end of the week taking the coldest air, and the Nacreous Clouds, away from above the UK.

These clouds are not to be confused with Noctilucent Clouds, which occur much higher up in the mesosphere – near altitudes of 85 km – and in the summertime.

Storm Henry forecast to bring severe gales in places on Monday

30 01 2016

A rapidly deepening area of low pressure pushing quickly across the Atlantic and expected to run close to the north of Scotland through Monday and into Tuesday has been named as Storm Henry. Keep up to date with the latest for your area using our forecast pages.

Forecast chart for Monday 1 February 2016

Forecast chart for Monday 1 February 2016

The Met Office issued an Amber National Severe Weather Warning for Storm Henry on Saturday morning. The Amber warning is valid from 3pm on Monday afternoon until 3am on Tuesday morning. Storm Henry closely follows Storm Gertrude, which tracked away from Shetland on Friday night.

The weather is expected to remain unsettled over the coming days with the prospect of further deep Atlantic depressions bringing spells of wind, rain and snow at times. You can stay up to date with the latest forecast for your area using our UK forecast pages and Severe weather warnings. You can also view our latest forecast Videos

During Saturday it will remain very windy in the north of the UK with severe gales across Scotland. These strong winds will be combined with frequent sleet or snow showers, leading to some drifting and blizzard conditions, especially over high ground, but even at low levels for a time. Severe weather warnings for wind and snow have been issued for Scotland, Northern Ireland, Wales and northern England to the Midlands.

For Saturday night snow showers will remain in the north and west and there will be some icy patches.

During Sunday milder, cloudier and wetter conditions will spread slowly northeastwards across the UK, but only slowly with northern, eastern and some central regions staying cold for much of the day and these wetter conditions preceded by some transient snow over higher ground in northern, western and central Britain..

On Monday the vigorous low pressure system – named as Storm Henry –will be approaching the UK from the Atlantic. Currently, this system is expected to pass just to the north of Scotland, bringing very strong west or southwesterly winds across much of the UK. Gales or severe gales with heavy rain are expected across northwestern parts. These winds could bring disruption to transport as well as power supplies.

Dan Suri, Chief Operational Meteorologist said: “With several periods of severe weather forecast to affect the UK over the coming days, it’s a good idea to keep a close eye on the forecast and the National Severe Weather Warnings as the details of what areas are to be affected and when, are likely to change. Our forecast pages, Facebook and Twitter sites and our Weather App can all help you keep up to date with the weather so that you can plan ahead and be prepared.”

Snowstorm to affect Northeastern and Mid-Atlantic US states

22 01 2016

A potentially record-breaking ‘nor’easter’ snow storm is expected to move towards Washington D.C. and Mid-Atlantic States in the next few days. This is the first big storm of the winter and will be accompanied by very strong and chilling winds, more especially on the northern flank of the storm, leading to blizzard conditions and significant associated impacts. Road and air travel in and out of the region will be affected, along with likely disruption to power supplies.

Currently the weather system is developing over Northern Alabama and Tennessee. The storm is expected to intensify on Friday night and during Saturday as it moves towards the Atlantic coastline of North Carolina, before moving away from the eastern seaboard overnight into Sunday.

Snow and ice have already affected parts of the northern Mississippi Valley. This is forecast to extend northeastwards on Friday, initially towards Ohio, then onwards to the Mid Atlantic States and southern New England overnight and during Saturday.

Very warm and humid air originating from the Gulf of Mexico will be drawn north with the storm and interact with the very cold air across the central northern states and southeastern Canada. On the boundary between the warm and cold air is where the most significant snowfall is likely.

Eastern US states to be affected by snow this weekend

Eastern US states to be affected by snow this weekend

Very strong winds are also expected with gusts of 50 to 60mph possible on the northern flank of the storm, affecting areas such as Manhattan, Washington and Baltimore.

A ‘State of Emergency’ has been declared across the Mid-Atlantic States region in readiness for the 30 to 90cm of snow expected. The heaviest snowfall is predicted just to the west of Washington DC and blizzard warnings have been issued by the National Weather Service.

There is the potential for greater snow amounts if the track and the intensity of the storm deviates from its current forecast. Also the strong wind may lead some drifting and enhance the impact of the snow.

Trans-Atlantic flights in and out of the snow and blizzard hit airports will be affected for a time. Schools across the region closed on Friday and Washington DC’s transport system (the 2nd busiest in the US) is expected to be closed throughout the weekend. You can see how the storm develops and impacts on the US here.

The record snowfall for Washington is 28in (71cm) that fell during a two-day period in January 1922.

Further north, Boston, which was significantly affected by numerous snowstorms last year, is unlikely to see major snow during this event, with only 5 to 10cm predicted.

Could this weather affect us here in the UK?

It is sometimes said that ‘the weather in the US reaches the UK 7 days later’. Although there is the potential that, as the storm tracks across the Atlantic towards our shores, it will bring a spell of strong winds and heavy rain next week, we are not expecting any snow as temperatures will remain close to, or above the seasonal average.

World weather roundup

21 01 2016

In this blog we take a look at what’s happening around the world where the weather is straying away from what’s normal or has the potential to bring disruption.

North America
A deep area of low pressure will bring the threat of severe weather across the Gulf States of Louisiana, Mississippi, Alabama and Georgia with heavy rain and severe thunderstorms combined with gale force winds. This rain may lead to more flooding in the lower Mississippi River basin.

Further north and east this system a ‘nor’easter’ will bring a risk of disruptive snow combined with gale force winds. Areas from Washington and Philadelphia up to New York are most at risk, and the US National Weather Service have issued blizzard watches for the risk of 8-12 inches of snow. There is also a risk of coastal flooding with the strong winds leading to rough seas too. Impacts on travel in the area could be significant.

Across eastern and southeast Asia a large surge of cold air will spread across China and Taiwan with further heavy falls of snow anticipated across Japan. Parts of China and Taiwan will experience temperatures some 15 degrees below the average for January, with Taipei seeing highs of 6C instead of the low 20s Celsius. Some snow is also likely here over fairly modest hills.

Further south the unseasonal weather will bring a spell of heavy rain across northern Thailand, Laos and Vietnam, bringing a risk of flooding.

In the South Pacific Ocean, Tropical Storm Victor lies to the east of Tonga and is expected to pass just to the south of the islands on Friday, bringing a period of gale force winds, heavy rain and thunderstorms and a risk of coastal flooding. The weakening storm is then expected to head towards New Zealand over the weekend.

Official warnings for the latest tropical cyclones in the South Pacific are produced by the Fiji Meteorological Service. The Met Office routinely supplies predictions of cyclone tracks from its global forecast model to regional meteorological centres worldwide, which are used along with guidance from other models in the production of forecasts and guidance. We also provide updates on current tropical storms via @metofficestorms on Twitter.

A large blocking area of high pressure over central and southeastern parts of Europe, which until recently also brought cold weather to the UK, will persist across these areas into the weekend.

Forecast pressure chart for midday Saturday 23 January 2016

Forecast pressure chart for midday Saturday 23 January 2016

Across Scandinavia, the Baltic States, Poland and Western Russia very cold conditions will be maintained with temperatures around 5-10C below average, but with dry weather expected.

Much of southeast Europe will also continue to feel the effects of this cold air with temperatures across inland areas well below average by day and some areas struggling to rise above freezing. Overnight minimums widely in negative double figures will compound the cold. Snowfall is also likely to lead to some disruption over Romania and then parts of Turkey, Serbia and Croatia over the coming days as weather fronts affect these areas. Next week should see a return to conditions more typical for the time of year as milder air arrives from the south and west.

Further north, the cold, still conditions are the perfect recipe for fog and freezing fog with parts of France, Belgium, the Netherlands and Germany being affected by this during Thursday and Friday before milder air arrives over the weekend.

Another unusual January hurricane forms

14 01 2016

Just two days ago we reported how Pali had become a very unusual out-of-season hurricane in the North Pacific. This afternoon another unusual hurricane has formed – this time in the North Atlantic. The hurricane season for both these regions usually runs from about June to November.

Earlier in the week a non-tropical area of low pressure developed near Bermuda. This was a depression primarily driven by the clash of cold air from the north and warm air from the south, similar to the kind of depressions we experience in the UK. Strong winds were recorded on Bermuda as the depression tracked to the east. Then in the last two days the depression has started to develop a concentrated area of storm clouds near its centre to the extent that the National Hurricane Center declared it to be ‘Subtropical Storm Alex’. Being ‘subtropical’ is a hybrid state for storms which exhibit some, but not all the characteristics of a fully tropical storm. Alex became the first subtropical storm to develop in the North Atlantic in January since 1978.

In the last day Alex has continued to develop a strong central mass of storm clouds rotating around a small eye and the National Hurricane Center has now designated it as a full blown hurricane. Alex is the first North Atlantic hurricane to exist in the month of January since Alice in 1955 and the first to actually form in the month of January since 1938.

Hurricane Alex at 1315 UTC on 14 January 2016 Image courtesy of the US Naval Research Laboratory

Hurricane Alex at 1315 UTC on 14 January 2016                                                  Image courtesy of the US Naval Research Laboratory


Alex is currently situated about 1000 km to the west of the Canary Islands. It is expected to move northwards bringing stormy conditions to the Azores where hurricane warnings have been issued. Winds over 75 mph and 100 mm rain or more is possible. An area of high pressure is expected to develop over the UK this weekend which should keep Alex over the ocean and away from our shores. Alex is eventually expected to be absorbed into a larger depression in the Atlantic near the southern tip of Greenland on Sunday.

Official warnings for the tropical cyclones in the North Atlantic are produced by the US National Hurricane Center. The Met Office routinely supplies predictions of cyclone tracks from its global forecast model to regional meteorological centres worldwide, which are used along with guidance from other models in the production of forecasts and guidance. We also provide updates on current tropical storms via @metofficestorms on Twitter.

Hurricane Alex at 1330 UTC on 14 January 2016 Image courtesy of the US Naval Research Laboratory

Hurricane Alex at 1330 UTC on 14 January 2016


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