New cloud comes a step closer

16 06 2015

Newly discovered cloud Asperitas (Latin for roughness) has taken another step towards being officially recognized and named in the International Cloud Atlas.

The cloud has been named Asperitas because it looks like rough or turbulent seas and has been put forward for inclusion in the Atlas by the UK Cloud Appreciation Society.

Asperatus_Undulatus

Gavin Pretor-Pinney, founder of the Cloud Appreciation Society said “It’s really exciting to see Asperitas that bit closer to becoming official. It’s great that the general public and amateur observations have influenced the atlas, it feels very democratic. The internet has resulted in increased connectivity, these days everyone has a camera at their fingertips, and this has resulted overwhelming evidence for this new type of cloud”.

The World Meteorological Organization (WMO) is currently updating the International Cloud Atlas, first published in 1896, and has now presented details of the new cloud to the World Meteorological Congress.

The WMO are making the Atlas more user-friendly and accessible and expect to publish the new edition next year. It is also expected to include the new cloud species Volutus (Latin for rolled), as well as some new “special clouds” like Homogenitus (from the Latin homo meaning man, and genitus meaning generated or made).

Met Office Meteorologist and Royal Meteorological Society George Anderson is heavily involved in updating the Atlas and said “Science, technology and photography have moved on in the past 40 years, so there is a need to update the Cloud Atlas”.

Met Office Scientist, Graeme Anderson, completed a dissertation on Asperitas, for his Masters degree at the University of Reading. He said “The challenge with this particular cloud formation is its rarity. It is very difficult to get good measurement data from this type of cloud if you don’t know when or where it will appear, or how long it will last. It became clear to me that these cloud formations did not fit into the existing classifications. It’s good to see this update taking place to make the International Cloud Atlas fully comprehensive.”

A scanned version of both volumes of the Atlas is available on the WMO website.  You can use the Met Office cloud spotting guide to help you identify different types of clouds, this can be a fun activity to try with children.

 

 

 





Partial eclipse of the sun

19 03 2015

Friday morning will see a partial eclipse of the sun over the UK. So what does the weather have in store?

Friday Weather

There is expected to be a lot of cloud around for Friday morning. There may be some clearer spells across central England, Wales and the south west England, with a chance of some breaks in the cloud either side of this.

It looks like Southern England, Northern England, Northern Ireland and Scotland will have cloud and this will be thicker the further north you go.

Check out the expected cloud cover in your area on our cloud map.

If you’re interested in seeing the eclipse, it’s worth heading out to take a look regardless of the weather. If it’s cloudy it’ll still get noticeably darker as the moon passes in front of the sun, and you may just get a better look if the cloud thins or a small break in the clouds appears at the right time – but do remember to use appropriate viewing equipment.

Will the Eclipse affect Space Weather?

Earlier in the week we saw the biggest solar storm in 11 years which led to sightings of  the Northern Lights, or aurora borealis, as far south as Somerset.  The solar storm was caused by a large explosion on the Sun on Sunday (15 March) throwing huge amounts of the Sun’s atmosphere into space. This mass of atmosphere carries with it part of the Sun’s magnetic field and is called a Coronal Mass Ejection (CME).

The eclipse won’t have an impact on the space weather we experience, however it will give scientists an opportunity to study the corona of the Sun in more detail. The detail within the corona is only visible when the extremely bright light from the Sun is obscured during an eclipse. A number of instruments used for monitoring the Sun for space weather forecasting, such as the LASCO instrument on the SOHO satellite, produce an artificial eclipse by placing an obscurer in front of the solar disc. This produces images like the one below showing a ‘streamer’ to the left of the Sun and a twisted magnetic structure within a coronal mass ejection on the right.

Picture courtesy of NASA

Picture courtesy of NASA

In the image, the position of the Sun is indicated by the white circle, with a larger obscurer blocking out the bright light from the Sun exposing the finer and fainter structures.





Visible satellite image of triple lows over the UK

14 05 2013

This visible satellite and rainfall radar image shows the three areas of low pressure affecting the UK today.

satellite and rain 14 May 2013

We can see three low pressure areas showing up as swirls of cloud to the north of Scotland near Shetland, north of Northern Ireland and off south-west England. The centre of the lows show up as cloud free areas.

The low to the south west has developed quickly through today and will bring strong winds this evening to parts of Cornwall.

Keep up to date with forecasts and warnings for your local area on our website.





It’s cold but why is there no frost?

25 02 2013

There’s no denying that we have seen some cold weather this winter with plenty of frost, ice and in many cases, snow. However, the last week has been cold – arguably perhaps feeling colder than any other time this winter – but we haven’t seen any evidence of this on the ground in the way of frost. So how is this possible?

For a classic frosty night we need a few ingredients: low temperatures, clear skies, calm winds and moisture. A clear, calm night gives excellent radiation conditions – by this we mean that the heat absorbed by the Earth’s surface during the day escapes readily back into space and allows temperatures to fall. If the temperature falls to the dew point (the temperature to which air must cool for it to become saturated with water vapour) moisture will condense and form droplets on the ground’s surface. When temperatures fall below freezing the droplets freeze and we get frost.

So what about the last few days? They have been cold but there hasn’t really been any prolonged or hard frost. How come? Well, much of Scotland and Northern Ireland has had the required ingredients and been frosty, but the rest of the UK has only had low temperatures. Much of England and Wales have seen a fair amount of cloud and some brisk winds.

25th Feb 2013 crop

Surface pressure chart from 25 February 2013

Cloud acts as a blanket and although temperatures have fallen during the night-time, cloud cover has stopped them falling well below freezing and therefore made it difficult for a thick frost to form. The wind is also important as it mixes the lower part of our atmosphere. Rather than having cold air pooling in one place and causing low temperatures, the wind can bring less cold air from another location or even bring it down from the upper atmosphere. This also helps to keep temperatures from falling too low. However, easterly winds this week have certainly made it feel very cold indeed!

25 Feb vis pic

Visible satellite image from 25 February 2013

Lastly, the air near the surface has been relatively dry. This is important because it means the temperature of the air must fall very low in order to reach its dew point. The cloud and wind has stopped this from happening easily and therefore reduced the risk of frost.

Cold weather, then, brings lots of different tastes of winter, especially to the UK, and we have seen nearly all of them this season. More information on all types of weather can be found here.





Nacreous or ‘mother of pearl’ cloud sightings

10 12 2012

Yesterday there was several sightings of an iridescent cloud in Scotland shared with us on Twitter and Facebook.

As we did not observe the cloud ourselves and are only seeing the pictures, it’s not possible to be 100% certain, however it is most likely that these are nacreous clouds, also known as mother of pearl clouds.

This eye-catching cloud is rarely seen, and has only been sighted in polar regions (such as Scotland and Norway) in the winter months, especially when there is a low over northern Scandinavia with a strong west/north-westerly wind blowing over Scotland. They only form in the lower stratosphere – around 15 miles up – when temperatures here are below -78 °C.

Although nacreous clouds are brightest when the sun is just below the horizon, illuminating them from below, they can also still be seen several hours after the sun has gone down.

Have you seen any interesting weather phenomenons lately? Add your pictures to our Facebook page or tweet them to us @metoffice.

Visit our website for more information on cloud spotting.





Cloud spotting infographic and video

17 01 2012

Having trouble telling a cumulus from a stratus cloud? In our video James Chubb explains how clouds form and how this can help you can tell one cloud from another. We’ve also put together a guide to identifying all the different cloud types and how clouds form on the Met Office website.

To help with observing clouds we’ve created this infographic. Feel free to share and use on your own website or blog, you can get the embed code and a printable version from our cloud spotting page.

Met Office guide to cloud types and pronunciations
Source: metoffice.gov.uk

If you spot any interesting clouds, why not take a picture and add them to our Flickr clouds group.








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