Archives for November 2011

Day 332 Severe weather watch: deep depressions

Distance travelled ~ 853'365'600 km

UK and World weather report:

The UK's recent quiet weather took a dramatic turn last week as fog gave way to gales and heavy rain. The foggy start to the week, with visibility down to below 50m in places in the south and east on Monday and Tuesday.

Despite a colder night on Tuesday, with a minimum of - 2.3 °C and widespread ground frost across England and Wales, temperatures remained a little above normal throughout the week, with a high of 15.9 °C at Fyvie Castle in Aberdeenshire on Saturday.

On Thursday, a rapidly deepening area of low pressure moved past the north west of the UK, bringing severe gales over the far north west as well as persistent and increasingly heavy rain that continued into Friday and over the weekend.

storm force winds thurso, scotland

Storm force winds hit Scotland over the weekend. Image captured by Debbie Bozkurt Sunday 27 November

Cassley in Sutherland recorded 66.6mm of rain in 12 hours, gales affected northern Scotland, peaking with a gust of 90mph at Fair Isle on Sunday morning. The storms left about 400 homes without power in Orkney, caused landslides, and A cargo ship sunk after reportedly being rolled over by a wave and breaking in two in the Irish Sea.

Elsewhere in the world, heavy rain is continuing to cause problems. In the Philippines, six people were killed in flash floods after continuous rains in the area caused local rivers to overflow. In Australia, floods have left thousands cut off in the town of Wee Waa in New South Wales. The town will only be accessible by boat and helicopter for at least a week.

Meanwhile, Mexico is suffering its worst drought in 70 years. Due to the lack of rainfall the government has forced been to supply water to nearly 2.5 million people across eight states.

The week ahead

UK:

• A very unsettled week for the whole country, with several deep depressions moving in off the Atlantic.

uk infrared satellite image

 


Latest infrared satellite image of British Isles

uk forecast rainfall

 

• Periods of heavy rain, especially in the west of Scotland, could cause some flooding problems. Also windy at times, with a continued risk of gales. There is risk of snow over the higher ground of northern Britain at times.

 

Across the North America:

• A deep depression is moving eastward across Canada, bringing strong winds and snow to many areas.

satellite image canada

GOES-EAST/WEST infrared satellite image 14:45 UTC. Data courtesy of NOAA.

By Tuesday, it is expected to lie over the Hudson Bay, with particularly windy conditions on its southern flank possibly affecting coastal Ontario, Manitoba and Quebec.

• Another depression, moving northwards towards the Great Lakes from the Gulf of Mexico over the next few days, will also bring heavy rain to places in between as it passes.

Across Africa:

• Cooler than average conditions extending from Saudi Arabia across Sudan, Chad and perhaps even reaching northern Nigeria. Conversely, warmer than average across much of Madagascar.

Across Asia:

• A spell of wet weather is expected for Saudi Arabia, Kuwait, Bahrain, Qatar and the northern Gulf on Monday and Tuesday. Rainfall totals of 40-60 mm are likely, with flash flooding a possibility. This is the first significant rainfall since the spring in this area. It is also unseasonably cold, both in this region and more widely across the Middle East.

• Some rather windy conditions likely for Oman, especially coastal regions and particularly later in the week, in association with a deep depression. This is also likely to impact on coastal parts of Karnataka, Kerala and Goa in India for the next day or two.

Across Australasia:

• Some large temperature variations across southern Australia this week, with south western parts going from cool to warm and south eastern areas swinging from warm to cool.

• Heavy rainfall is set to continue in Australia and Asia due to a La Nina pattern in the Pacific Ocean.

Behind the scenes: Physicist in freefall

Post categories:

Helen Czerski Helen Czerski | 17:00 PM, Wednesday, 23 November 2011

Distance travelled ~ 840'555'200 km

helen czerski

 

Being surrounded by sky is not a natural place for a human being. We have evolved to scoot about on the bottom of the atmosphere, stuck to the ground, and we don't often look up. Even when we do, we tend to see the sky as flat - clouds, the moon and aeroplanes move sideways across the sky. It's easy to forget that the sky has depth too, and that air in the atmosphere moves up and down as well as sideways.

Your perspective changes quickly when you're in freefall, three thousand metres above the Earth's surface and travelling downwards at 120 mph.

sky full of cumulus clouds

 

Skydivers relish the sense of freedom that falling through the sky brings. There is nothing to get in the way, nothing touching you and a whole extra dimension to play in. For the air in our atmosphere, three-dimensional movement is normal. At the place where I jumped out of the plane, in Arizona, air that starts about 10 miles up is gradually sinking towards the ground. The air doesn't make the squeaking noises that I did, but then it isn't falling nearly as fast - it's a few millimeters per second on average. I was falling through a giant atmospheric waterfall, but a very slow one.

It's not just in Arizona that this happens. Although weather maps tend to show sideways winds, the air making up those winds is all rising and falling as it travels around the Earth. The paths of air parcels weave in and out of each other, making the Tokyo subway map look simplistic by comparison.

tokyo subway map

Image courtesy of Tokyo Metro

All this is very interesting, but not much comfort to a plummeting physicist. I don't think that I really breathed during the 40 seconds of freefall. Then the parachute opened, everything slowed down, and my brain stopped panicking and started appreciating what was going on around it.

Seeing the layers of the sky is fascinating. Floating down past a cloud is amazing - a fluffy cumulous cloud is telling you that there's been a little puff of air upwards in that location. We can't really see the structure of the atmosphere, but seeing a cloud from the side makes it easy to imagine the turbulent swirls that are mixing all that air up.

After five minutes of sharing the three dimensions of the sky with the clouds, we arrived at the landing zone and my feet touched the ground again. I was very happy to feel something solid under my feet, but there was also a small sense of loss. I was back to crawling around on the bottom of our fabulous three-dimensional atmosphere, and my understanding of the depth of the atmosphere was again limited to hints given away by the clouds. But I remember what it felt like, and my view of the sky will never be quite the same again.

Day 325: This week's extreme weather watch

Distance travelled ~ 835'409'600 km

It was another mild week across the UK, with maximum temperature reaching the mid teens every day and a high of 16.2 °C recorded at Gravesend on Thursday.

Provisional figures show that November so far has been very mild across the UK. The UK average temperature for 1-15 November was 9.4 °C, 3.5 °C higher than the long term average.

We would normally expect the first half of November to be warmer than the second as we transition towards winter (which, meteorologically speaking, starts in December). However, even bearing this in mind, the temperatures seen in the first half of this month have been much warmer than normal.

Some areas did see lower temperatures overnight, leading to air and ground frost in parts, particularly in the north west. A minimum temperature of -3.6 C was recorded at Drumnadrochit, on Loch Ness, on Wednesday.

The weekend saw extensive fog form in eastern areas. On Saturday this was very slow to clear parts of Yorkshire, Lincolnshire, Cambridgeshire and the East Midlands. While on Sunday areas from the Vale of York through the East Midlands to southern England saw dense patches of fog with visibility of around 50 metres in places. Fog thinned or lifted into low cloud in many places, however for parts of the Vale of York, Lincolnshire, East Anglia and the London area, it stuck around all day causing some flights to be cancelled at Heathrow Airport.

It's been a relatively quiet week of weather for the rest of the world. In Bolivia, a rare tornado damaged parts of the city of Cochabamba on Wednesday.

Thunderstorms moving through the region produced the tornado which reportedly damaged dozens of buildings.

There's been heavy rain in Taiwan, with some parts of the country seeing over 400mm of rain this week.

Heavy snowfalls affected parts of the Upper Midwest in the USA where a foot of snow fell on parts of South Dakota. A thick fog in Germany may have been a factor in a 52 vehicle pile up on the Autobahn near Muenster. Three people were killed in the crash and another 35 were injured.


The week ahead

The UK:

• A gradual transition to temperatures closer to average by the end of the week, when windy conditions will dominate with heavy rain at times in the northwest of the UK.


Across Europe:

• Temperatures in Turkey and the eastern Mediterranean continue to be cold for the time of year, with hill snow expected at times.

Across the Americas:

 

tropical storm kenneth

 

Tropical storm Kenneth is currently 500 Miles SSW of Manzanillo, Mexico, but is expected to move in a westward direction, away from land. This is the latest in the season that a tropical storm has formed in the eastern north Pacific basin since Hurricane Winnie formed on 4 December 1983.

• The unusually cold conditions are set to continue across Alaska and NW Canada over the next few days, spreading into northern areas of the USA such as North Dakota and Minnesota. Temperatures are 10 Celsius colder than average, remaining well below zero in many places throughout the day. By Tuesday temperatures should rise to nearer normal as low pressure pushes in from the south.


Across Australasia:

• New Zealand's South Island may see 250 mm of rain during the early part of the week in parts of Westland and Buller.

Day 319: UK and world weather report

Post categories:

Dave Britton – Met Office | 14:00 PM, Tuesday, 15 November 2011

Distance travelled ~ 819'651'200 km

Last week was quiet week weather wise for the UK. Most of the country saw mainly cloudy, drizzly conditions with some mist and fog.

Despite a few frosty mornings in the north west of Scotland, temperatures remained mild for the time of year. Double figure highs were reached every day and a maximum of temperature of 18.1 °C was recorded on Sunday at Otterbourne, near Winchester, Hampshire.

Elsewhere in the world, flooding continues to cause havoc in Bangkok, where the death toll has now risen to over 500. The weather has started to ease after months of monsoon rain, but the volume of flood water is continuing to cause problems.

Floods surround two industrial estates east of Bangkok

Image credit: NASA


Heavy rainfall has also affected Italy, where thousands were forced to evacuate around the River Po in Turin when water levels rose by 4 metres. Seven people are thought to have died as a result of the storms and torrential rain in the country.

Over in North America, severe winter storms have hit both Canada and Alaska. In British Columbia a snow storm caused severe disruption to travel networks and power supplies, with ferries to Vancouver Island forced to stop sailing. Meanwhile, Alaska saw winds of up to 100mph combined with high seas and blizzard conditions. During the storm the rate of ice accretion - the process of ice building up on solid objects - was more than 15.6 inches an hour.

The week ahead

The UK:

• The quiet weather is expected to continue with temperatures remaining generally around or slightly above normal throughout. However, there is the potential for some heavy rain and strong winds across north-western parts of the UK later in the week.


Across Europe:

• Low pressure over the eastern Mediterranean brings strong northeasterly winds through the Aegean Sea early in the week. Severe weather warnings have been in place for much of Greece, with storm force winds forecast in some areas. Although the strongest winds are likely to be on Monday, it will stay pretty breezy in the area for the next few days.

• Bitterly cold weather continues in eastern Turkey, Armenia, Georgia and Azerbaijan, although temperatures should start to rise from Tuesday.


Across the Americas:
• Following the recent storms affecting the west coast of Alaska, the state is set to see temperatures falling dramatically over the next few days to be 10-15 °C below average by Friday. Night time lows of -35 °C look possible in places, with daytime temperatures at times not far above.

• In South America there's heavy rain, strong winds and some relatively low temperatures for a time in southern Brazil at the start of this week, before the associated low pressure system moves east into the Atlantic around Tuesday.

Across Africa:
• The same eastern Mediterranean low pressure that brings strong winds to Greece is also causing lower than average temperatures over large parts of Egypt, mainly the north east, over the next few days, with above average winds and precipitation as well at first.

Across Asia:
• A spell of unsettled weather is forecast for the Philippines over the next few days. The system causing this will move into the South China Sea around mid-week and may later affect parts of southern China.

• Some unseasonably low temperatures are expected in the Himalayas - Tibet, Bhutan and Nepal - with daytime temperatures at Lhasa, Tibet potentially around ten degrees below normal.

The Santa Ana winds and your bicycle pump

Post categories:

Helen Czerski Helen Czerski | 18:00 PM, Monday, 14 November 2011

Distance travelled ~ 817'507'200

Air is funny stuff. The oxygen that we take from it is our most fundamental necessity, but air is invisible, odourless, colourless and easily ignored. Day to day, we have better things to think about. But air is doing some interesting things while we're busy ignoring it, and one of those things has the potential to cause huge damage in Southern California this month.

Let's have a think about what air is. What you're taking into your lungs at this very moment is a bustling crowd of billions of molecules, zooming about at speeds of about 1150mph, bouncing off each other and anything else they hit. It's busy down there in the microscopic world that we can't see.

To get to Californian weather, we need to know something about gases. Air temperature is just a way of measuring how fast the gas molecules are all zooming about. If they're travelling on average at 1100 mph, it's about zero degrees Celsius. If they're moving at 1300 mph, it's 100 degrees Celsius, and so on. So temperature represents the amount of energy that's carried by those air molecules.

Now here's the really interesting bit. It happens every time you open a pressurized fizzy drink. As you unscrew the bottle, high pressure air rushes out and when it meets the lower pressure outside, it expands. But for the gas to expand, those molecules have to move further apart from each other and that takes energy. So they use some of their movement energy. As they move apart, the molecules slow down, and that means that the temperature goes down. Put your hand over the bottle opening, immediately after you open it, and you'll feel the cold. So when air expands, it cools, and when it's compressed, it heats up - that's why your bicycle pump gets hot as you pump air into a tyre. Physicists call this adiabatic heating.

Why should all this matter for California? It's because an atmospheric version of the bicycle pump happens there on a huge scale at this time of year. To the east of California there are vast deserts at an altitude of 2 km. Weather systems over those deserts push air westwards, so it flows down the slope towards the ocean. Air pressure gets higher as you go downwards, because there's a greater weight of air above you. So the air flowing down the slope is compressed as it goes and it heats up. Then there isn't just a wind, there's a really hot wind, about 20 degrees Celsius higher than temperature in the desert. These winds are called the Santa Ana winds, and as the air flows down towards the ocean they get funnelled down canyons, increasing the wind speed even more.

Satellite image of dust being blown offshore by the Santa Ana winds

Image credit: NASA/GSFC/LaRC/JPL, MISR Team

The result is that after the hot dry summer, San Diego, LA and everything in between get dried out even more by a massive atmospheric hair dryer blowing down from the high deserts. And if a spark starts a fire, there isn't much to stop it. This is why wildfires are such a hazard at this time of year, and why California's fire service is now on high alert. There have been huge destructive fires in the past few years, and Californians just have to prepare for them and do everything they can to prevent a blaze starting. It all happens because of a fundamental rule of physics - that air gets hot when you squash it. At this time of year, it's a rule that many Californians probably think they could do without.

Saturn's super-storms quite unearthly...

Post categories:

Mark Thompson Astronomy Mark Thompson Astronomy | 18:00 PM, Friday, 11 November 2011

Distance travelled ~ 809'788'800 km

High winds are a common occurrence on Earth but they don't often reach more than 150km/h. The record is held by the Tropical Cyclone Olivia as it moved across Australia in April 1996 which battered the land with gusts of 408 km/h. This is nothing compared to the rather more serene and beautiful looking planet Saturn. High in the atmosphere of this gas giant the wind speeds have been measured at a staggering 1800km/h.

The concept of what causes wind, which is effectively the flow of gas from one place to another, is pretty simple to understand. Take the Earth for example; warmth from the Sun heats the surface which then in turn heats the atmosphere in contact with it. As the air warms, it becomes less dense than the surrounding air causing it to rise which results in an area of low pressure as 'less air' is present. Other surface air will then rush in to effectively fill the void left from the rising air and we experience that as wind.

The storms we see on Earth are just extreme versions of this with areas of particularly low pressure at the centre. Typically they form over the oceans which are a vast reserve of energy. Water is very good at storing and retaining incoming solar energy and its this along with the moisture that gives storms their awesome power.

On Saturn the extreme storms that drive the winds are very similar in structure to those on Earth with low pressure systems but it's the source of the energy which sets them apart. Instead of vast bodies of water, the heat driving the storms on Saturn comes from deep within the planets core. When it formed around 5 billion years ago heat was generated when the pieces from the proto-planetary disk crashed together and its the slow but steady release of this energy which has driven Saturn's super-storms.


NASA's Cassini spacecraft captures a view of storm churning through the atmosphere in Saturn's northern hemisphere

Image credit NASA

The Cassini spacecraft witnessed first hand one of Saturn's ferocious storms whilst it was orbiting the planet in December 2010. It was quite lucky given that Saturn is usually relatively storm free, unlike Jupiter however the lucky break gave planetary scientists a unique insight into the local weather system. The images show the storm covering nearly 4 billion square km and analysis of the lightning strikes showed a ten times more flashes than in other storms studied since 2004.

Why are clear nights so cold?

Post categories:

Helen Czerski Helen Czerski | 15:00 PM, Wednesday, 9 November 2011

Distance travelled ~ 804'321'600 km

It's the season for baked potatoes, parkin, treacle toffee and bundling up to stay warm. I love the sharp, cold starry evenings and being able to see my breath - it's not every day that you get to make your own cloud! But in the past few days I've remembered that there's a price to pay for being outside on those fabulous clear evenings. It's cold. Frigid, frosty, freezing. Your knuckles go red and the inside of your nose feels like it's full of ice. Why can't we admire the autumn stars in comfort?

The answer is to do with how energy gets from place to place, and how much clouds get in the way. We may associate clouds with bad weather, but when it comes to nighttime, clouds are our friends.

Autumn clouds

Image credit NASA

Our planet's energy comes from the Sun, mostly as visible light. We know that - it lights up our world. Air is invisible, and by definition visible light travels straight through it. So on the way in, the Sun's energy is carried by all the colours of the rainbow, straight through the atmosphere and all the way to the ground. The ground absorbs that energy and warms up. Black tarmac absorbs more heat than white sand, but they all capture some.

Next time you make some toast, watch the element in your toaster. As it gets hotter, it glows, first dull red, then bright red and then orange and yellow. Hot things give away their energy by glowing - it's a fundamental rule of physics - and the colour tells you their temperature. The ground under our feet, along with you and everything else around you also glows. But because those things aren't as hot as your toaster, they glow in the infrared, which we can't see directly.

So the ground glows in the infrared all day and all night, constantly emitting invisible energy back upwards. Some of this energy heats the air near the ground, but some keeps going upwards. And here's where clouds matter at night. Clouds are really good at capturing that infrared radiation and sending it back down the Earth. They act like a blanket, trapping heat between the ground and the clouds. If there are no clouds, the energy from the ground just goes up, up, and away...

Whenever it's a clear night and you can see lots of stars, there is nothing to trap all that infrared energy, so it's lost to space and we feel cold. If it's cloudy, there are no stars to see, but we have a nice warm blanket above us, keeping the heat in. The fact that Earth gains energy as visible light and loses it as infrared light is really important for the heat budget of our planet, not just for freezing astronomers.

Sadly, this means that stargazing will always require extra layers. Happily, that means extra excuses in life for hot chocolate. In fact, just writing this has made me feel chilly. It might be hot chocolate time right now!

UK and World weather report: unseasonable snowstorms & monster icebergs

Distance travelled ~ 799'068'800 km

October was a mild month - with some exceptionally high minimum temperatures for the time of year - ending with another mild day on Monday. Several locations did not dip below 15 °C all day and a top temperature of 19.3 °C was recorded at Kinloss. As the week continued into November, the mild temperatures carried on, with a high of 18 °C at Heathrow and St James' Park on Thursday.

Rain dominated the week, with occasional rain on Monday turning into a band of heavy rain on Tuesday and widespread heavy and sometimes thundery outbreaks on Wednesday and Thursday. There were also some possible funnel cloud sightings, one of which may have touched down in Astwood Bank, just south of Redditch.

Friday bought more wet weather, with intense rain in parts. Alice Holt Lodge near Odiham, Hampshire, recorded well over 50mm of rain between midnight and 7am, and there were numerous reports of localised flooding in the Home Counties.

The weekend was slightly cooler, with a chilly start to both days and frost in many northern areas on Sunday morning.

Elsewhere in the world, flooding continues in Thailand. A third of the country has now been affected by flooding after three months of heavy rain. Over 500 people are said to have died and there are fears that the flooding could worsen in the capital Bangkok.

Thailand Floods October 2011

Image Credit Remko Tanis


Deadly flash floods also hit the Liguria region of Italy on Friday after heavy rain. Two rivers in Genoa reportedly broke their banks as floodwaters poured through the port city for the second time in eight days, killing six people. Much of northern Italy was affected by the heavy rain during the day, including Venice, which also suffered flooding.

Close to two million homes are still without power after an unseasonable snowstorm hit the US east coast last weekend. The storm, which brought up to 76 cm of snow in parts, has been blamed for as many as 19 deaths. At the storm's height, three million homes were without power, while states of emergency were declared in New Jersey, Connecticut, Massachusetts and parts of New York.

Scientists are monitoring the birth of a monster iceberg in west Antarctica. The iceberg is expected to break away towards the end of the year or early in 2012. Currently, the crack is 30 kilometres wide and 60 metres deep and growing every day. Researchers from NASA expect the eventual iceberg to cover 880 square kilometres - an area the size of Berlin.


Operation Ice Bridge

Image Credit NASA

Path of Ice bridge

Image credit NASA


The week ahead

In the UK:

• Monday and Tuesday will be dull and cloudy and occasionally damp across the country, but temperatures will be mild. Wednesday and Thursday see more persistent rain moving into western areas, while the east may become a little brighter. Staying mild, especially overnight, with light southerly winds. As we head into the weekend mild southerly winds should bring broken cloud to many parts.

Elsewhere in the world:

• There is the potential for a tropical cyclone to form in the Arabian Sea. A depression was centred about 700km east-southeast of Salalah on Monday and the system is forecast to intensify further into a deep depression and move towards the Oman coast over the next three days.

• A tropical depression formed close to Hainan Island in the South China Sea on Monday. China mainland provinces of Guangdong and Fujian, the island province of Hainan, as well as Taiwan, will be subject to the periods of heavy rain through much of the week.

• Unsettled periods of weather look set to affect the western Mediterranean, parts of Canada and northern Russia, although nothing particularly exceptional is currently signalled.

• Over the USA, an outbreak of potentially damaging thunderstorms and tornadoes looms for the southern Plains on Monday. The thunderstorms may ease for a time overnight and into Tuesday, but is forecast to increase once again on Tuesday afternoon with the threat zone stretching from central Missouri to East Texas and Louisiana.

• Unseasonably cold conditions are forecast across the Caucasus', spreading to much of the Middle East through the week.

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