Archives for August 2011

Day 243: Nanmadol moves towards China and Katia intensifies over Atlantic

Distance travelled ~ 623'796'800 km

• In the UK weather conditions are expected to be fairly quiet through much of this week, with relatively light winds and rather cloudy skies.

• Over the Pacific Ocean Typhoon Nanmadol now close to Southern Taiwan and moving slowly north westwards towards China, where it is likely to produce very heavy rainfall in the far south east of China today.

• Also over the Pacific Ocean, Tropical Storm Talas has been moving slowly northwards towards Japan. See relevant advisories for latest information

Tropical storm Talas


• Another Tropical Storm has been developing over the waters of the equatorial Atlantic and been named Katia yesterday. Current forecasts expect the storm to become a hurricane later today.

Tropical storm katia 5-Day Forecast Cone

Other developments around the World:

• Potential for heavy thundery rain in parts of Portugal and western Spain on Thursday and Friday.

• Wet at times over the next few days over Uruguay and southern Brazil, then much colder conditions moving north to these areas later in the week with possible frost risk.

• Unusually warm or hot in parts of south and south west Australia later in the week.

• Unusually cool, looking wet and windy across northern Iran extending south across much of the country next few days.

UK and World weather report: A look back at an unsettled week

Distance travelled ~ 621'920'800 km

UK:
Last week brought some varied conditions over the UK and around the world there was some severe weather.

It was an unsettled week across many parts of the country during last week. On Tuesday there was a wet start across southern and central parts of England with heavy and thundery showers moving up from the continent.

Many parts of the UK saw heavy and thundery showers at times through the week, with large rainfall totals in places. Some spectacular thunderstorms with large hail developed over parts of East Anglia on Saturday.

Cool temperatures over the weekend were accentuated by persistent rain and unseasonably strong winds over northern parts of the UK. It was distinctly autumnal across north eastern parts of Scotland, with gusts of wind reaching 68 miles an hour at Rosehearty, on the Moray Firth coast and Wick, Highland.

On Sunday in the Highlands, Resallach recorded a 24-hour rainfall total of 85.6mm, whilst Wick and Loch Glascarnoch recording more than 60mm of rain.

Around the world:
Hurricane Irene, the first major tropical storm of the season in the North Atlantic claimed at least 40 lives as it moved through parts of the Caribbean and the USA. Hurricane Irene's winds peaked at around 110 miles per hour through the Bahamas. Irene is the first hurricane to hit the USA since Ike in 2008.

During Thursday it was reported that at least 16 people were killed when flash floods swept through a valley in the Kohistan district of Khyber-Pakhtunkhwa, Pakistan. Dozens of houses were destroyed by the flood, which was triggered by heavy rains and land sliding overnight in Kundian valley.

On Sunday, Typhoon Nanmadol left at least 8 people dead in the Philippines. Powerful winds and rain triggered floods and landslides, blocking major roads and destroying several bridges.

Meanwhile during last week, Eastern Europe was being hit by a near-record heat wave which has seen wildfires and people fainting in the streets. Authorities in Serbia, Montenegro, Croatia, Macedonia, Bosnia and Albania have issued warnings for people to stay indoors and drink water. In the central Bosnian city of Mostar, temperatures soared to 45 Celsius.

Hurricane Irene could still cross New York this weekend as category 3

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Peter Gibbs Peter Gibbs | 17:00 PM, Friday, 26 August 2011

Distance travelled ~ 613'398'400 km


Hurricane Irene track forecast cone

Image courtesy of National Hurricane Center/NOAA

They're calling it the biggest storm in a generation. Hurricane Irene is set to bring flooding, power cuts and travel disruption to the east coast of America this weekend and looks like it may be the worst storm to hit the region since hurricane Bob in 1991.

Irene is vast. On Friday, the core of hurricane force winds extended up to 90 miles or 140km from the centre, while storm force winds spread out as far as 290 miles or 465km. If Irene was centred over London, there would be gales from Edinburgh to Paris.

Irene weakened slightly during Friday as slightly drier air was pulled into the storm along with stronger upper-level winds, but as it continues to track northwards over sea temperatures as high as 29C it is likely to be a category 3 hurricane as it makes landfall in North Carolina. (Check out NOAA for description of hurricane categories).

Over the weekend, the continued northerly track will take the hurricane right along the heavily populated east coast from North Carolina to New England. While interaction with the coast should weaken it, Irene could still cross New York as a full hurricane during Sunday.

Devastating winds of over 100mph would seem to be the most obvious threat, but in fact most hurricane deaths are due to flooding. The storm surge ahead of Irene is expected to lift sea levels by 2 or 3 metres, with dangerous waves on top of that. Rainfall totals of 10-15 inches (25 to 37cm) will be falling in areas that have already seen record rainfall during August.

It's been a long wait for the first hurricane of the 2011 season, but Irene seems to be making up for lost time.

Looks like an interesting weekend!

Keep updated with Hurricane Irene's development over the weekend via BBC Weather.

Day 238 - weekly roundup - Top 5 Arizona monsoon photos/videos

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Aira Idris Aira Idris | 14:30 PM, Friday, 26 August 2011

Distance travelled ~ 611'308'000 km

Some truly awesome Images and video sent to the 23 Degrees team by Netweather.tv monsoon chasers in Arizona, currently on day 9 of their chase...


Dust Devil, Arizona, captured by Craig Hough 18 August,
Casa Grande (near Phoenix).

haboob

Image captured by Paul Sherman, 18 August, Casa Grande."Upon heading into Casa Grande an amazing Haboob was pushing out Northwards from the Parent Thunderstorm and heading towards Phoenix."



lightning

Image captured by Craig Hough 21 August, Grand Canyon. "Think it's fair to say I realised a dream yesterday, lightning photography at the Grand Canyon, does it get much better than this?"



arizona monsoon lightning

Image captured by Craig Hough, 23 August, Tucson Valley.


lightning strikes, tucson valley

Image captured by Paul Sherman 23 August. Vantage point above the Tucson Valley. "Well it just keeps getting better out here, elevated view of lightning over Tucson"


To submit your severe weather images and video into 23 Degrees for a possible feature or for next week's 'weekly roundup blog' - email them to 23degrees@bbc.co.uk or add them to the weather photography pool.

23 Degrees a global phenomenon

Distance travelled ~ 608'199'200 km

As it happens during the production of the series 23 Degrees there has been much discussion and many questions about whether this show reflects both the northern and southern hemispheres. For example, a comment left by a reader on one of my previous posts raised a fair point about the perspective we were taking:

excerpt of readers comment

The truth is, this is a planet-wise show. We are looking at how our cosmic dance with the Sun affects the whole globe. And to do that we are not looking at stories on a hemisphere by hemisphere basis, or for that matter continent by continent or even country by country. We are going to locations that provide us with the best opportunity to film events that illustrate our relationship with the Sun and how that affects our weather all over the planet. But if that means shooting both tornadoes and hurricanes in the US because that's where they hit, then that's where we will film.

We are going to have stories from all round the Earth, both at land and at sea, but we have to be pragmatic as well and choose locations that we can get to within our budget.

So for instance on a show like this we can't go Antarctica, it's just too expensive and difficult to get to. That doesn't mean we will ignore such places, we have access to footage taken by scientists and explorers, which we can use to tell our story.

Another interesting thing making this series that I hadn't really taken on board before I started, was just how unequal the distribution of land is between the hemispheres. The northern hemisphere has much more land compared to the southern hemisphere. In fact over 65% of the land is in the northern hemisphere.

That means that more of the observable and so filmable weather events take place in the northern hemisphere so we will inevitably do more filming there than in the south. That doesn't mean we don't go south of the equator, we've already crossed the Andes, filmed in the Atacama and sailed out onto the southern ocean off Tierra Del Fuego on the southern tip of South America.

Spacewatch - great red spot on jupiter leaves hurricane irene in the shade

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Mark Thompson Astronomy Mark Thompson Astronomy | 16:30 PM, Wednesday, 24 August 2011

Distance travelled ~ 606'376'800

As Hurricane Irene gathers strength it reminds me of the hurricane that has been raging on Jupiter for at least the last 350 years. Called rather imaginatively, the Great Red Spot (GRS) it was first observed in the 17th Century by Giovanni Cassini through the recently invented called the telescope. Its not just its longevity that brings it whirling into the record books though, its size is also impressive, measuring three times as big as the Earth, compare that to Irene which is about 400km in diameter and you realise quite how big a storm it is.

jupiter's great red spot

As Voyager 1 flew by Jupiter in 1979, it captured this photo of the Great Red Spot. Credit/Nasa

Jupiter, unlike Earth, is a planet made up almost entirely of gas with a fluid core but when we look at it through telescopes, its the tops of the dense atmosphere that we can see. Heating from the Sun and from internal sources, drives the convective activity in the atmosphere to produce the familiar high and low weather systems. Just like the Earth, its these high's and low's which effectively cause air to move and produce wind. Its here though that the similarities end. Simple observation from even modest telescopes will reveal strange belt structures in the atmosphere that seem symmetrical in both northern and southern hemispheres.

jupiter

NASA/Freddy Willems, Amateur Astronomer, July 26 2011

In one of these belts, called the Southern Equatorial Belt, we can readily see the GRS which is an anticyclonic storm (a storm which rotates anti-clockwise) taking about 6 days to complete one revolution. Its elliptical shape seems to be due to the fast jet streams that neighbour it, blowing easterly on the south and westerly to the north. Infrared observations have shown that the temperature of the GRS is lower than that of the surrounding clouds suggesting a higher altitude, estimated to be towering over neighbouring jet streams by 8km. From such a monstrous storm you might expect astronomical wind speeds but surprisingly modest speeds of 430km per hour are measured, compared to Irene's more sedate maximum speeds of 160km per hour.

The colour of the spot isn't even stable, changing from pale pink to a deep red but what causes this colour remains a mystery. We do know that its affected by environmental factors though as the darker central region always appears slightly warmer than the paler, cooler surroundings. Its perhaps the presence of complex organic compounds such as red phosphorous that gives it its distinctive colour but for now, the GRS remains one of the beautiful yet enigmatic mysteries of the Solar System.

Behind the scenes - hurricane Irene and the waiting game...

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Stephen Marsh Stephen Marsh | 17:00 PM, Tuesday, 23 August 2011

Distance travelled ~ 603'857'600 km

It's late August and the 23 degrees team are gearing up to head back on the road capturing some of the planets' most exciting weather phenomena. This time Helen Czerski and the team are planning to go south east USA to film one of the largest and most destructive weather events of them all. A hurricane.

With the help of scientists and meteorologists the team have been tracking the course of Hurricane Irene as it wreaks havoc across the Caribbean. Yesterday it hit Puerto Rico and next in line is the Dominican Republic and then the Bahamas and the Turks and Caicios Islands.

We are not heading to the Caribbean though, instead we are on standby to go to either Florida or New Orleans should Irene make landfall in the USA. The team and crew have their bags packed, flights on hold and if the experts say the storm is going to hit the US they will take the next flight out.



It's now a waiting game to see where the storm goes, it could turn west and hit Louisiana or Texas or it could veer east out into the Atlantic and miss the US altogether, Filming these destructive weather events raises a real moral dilemma for me as Series Producer. I want to film one of the monster storms for the show to explain how they work, and to do that I need it to make landfall. But I don't want it to hit anywhere where lives and livelihoods could be put at risk. It's something I struggle with, and whenever I am involved in filming this kind of event where local people could be in danger, I sit at home watching the news and hoping that no-one has been hurt or killed.

Which brings up another issue when filming wild weather; the safety of the team. We want the footage to be exciting and to get as close as possible to the storm but we also must be safe. So we spend a lot of time planning how to achieve what we want safely. To do that we talk to experts in the field and watch footage of previous events so we know what we are getting into. We also travel into these storms guided by local teams of scientists who do this for a living. On top of that we have safety briefings with safety experts at base before travel, going through all possible scenarios and making plans to make sure we avoid dangerous situations but also how we will react if something unexpected should happen.

Talking of the unexpected we have to plan for that as well. That may sound stupid planning for something you don't expect, but when we are entering any potentially dangerous situation we have to plan for what we expect and what we don't. And once we are in the storm we have to act as safely as possible, that means wearing the right gear, following the instructions of the experts and staying alert. Hurricanes can be hairy places, powerful winds gusting at over 100 km an hour and storm surges bringing giants tides of sea water rushing inland. No footage is worth anyone getting hurt.

All that preparation should keep the team safe but that doesn't stop one worrying back at base.

All being well the team will head out to the US later this week, and hopefully they will be sending back some on location blogs from inside the heart of the storm.

How likely is 2013's 'perfect solar storm'?

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Dr Lucie Green | 11:30 AM, Tuesday, 23 August 2011

Distance travelled ~ 603'268'000 km

(Lucie Green is a solar researcher based at the Mullard Space Science Laboratory, UCL's Department of Space and Climate Physics. She studies activity in the atmosphere of our nearest star, the Sun, with particular focus at immense magnetic fields in the Sun's atmosphere. Lucie is also a Science writer and has been involved in a variety of Science programmes such as Sky at night and recently Radio 4's programme the infinite Monkey cage.)

It seems that barely a week goes by at the moment without the Sun being in the news, for seemingly contradictory reasons. One minute we are being told that the Sun is going to cause a global disaster as the result of super-sized solar activity, the next that Sun is going into hibernation. So, what exactly is going on?

CME blast 2 December 2003

Courtesy of SOHO/EIT consortium. SOHO is a project of international cooperation between ESA and NASA

The Sun has a cycle in which its magnetic field pulses in size and complexity roughly every 11 years. Coronal mass ejections (CMEs), huge bubbles of magnetic field containing charged particles, are a natural part of this cycle. At the moment we are approaching solar maximum (expected to occur around 2013) which means that the number of ejections is on the rise and so too are some worrying consequences here on Earth.

CMEs can inject charged particles into the Earth's magnetic field which, if accelerated, lead to the beautiful aurora. The flipside is that these particles can also damage our satellites, lead to satellite failure and produce currents in our power lines causing problems for national power grids. Most notably, in 1989 a transformer in the Canadian national grid failed due to such currents and several million people lost their electricity for over nine hours. So, the increasing number of CMEs is good news for people wishing to view the aurora but bad news for our space-based and electrical infrastructure.

Some news articles are predicting that in 2013 the perfect solar eruption will occur that will cause a global disaster through the simultaneous failure of electricity networks all over the world and the loss of the satellites that modern society relies on for communication, navigation and banking. However, many aspects need to come together to produce this 'perfect solar storm' which makes such an event hard to forecast. This scenario isn't pure fiction though.

The reasoning is based on studying previous events, in particular a solar eruption that occurred in 1859 which produced such a strong display of the aurora that they were seen down toward the equator. If this event repeated itself today it is likely that the worldwide damage caused would cost a trillion dollars. [For more information on how coronal mass ejections affect us: NOAA/Space weather prediction center ]

No individual solar cycle is the same as the next though, and this brings me to another reason that the Sun has been in the news. The Sun has only recently come out of the deepest solar minimum for 100 years. Things have been very quiet on the Sun. So whilst some are worried that the Sun might cause global destruction, others are worried that the Sun is going to switch off. On the face of it these are contradictory stories but on closer inspection this is not so.

On the timescale of a few years solar activity and the number of CMEs is on the rise and we will experience more effects on our technology. However, on the timescale of decades, it looks like the magnetic cycle of our Sun may decline. This idea could be extrapolated to conclude that the Sun will switch off altogether but in reality there is an very small chance of this happening. Things may quieten down, but they will pick up again.

Ultimately, we are living in a gusty outflow of magnetic field and charged particles coming from the Sun. This has led to a new era of 'space weather' prediction where we are monitoring the near-Earth space environment to make sure we protect ourselves from the harmful effects of the Sun's emissions. Whatever level of activity the Sun decides to produce we will feel the consequences. Understanding and predicting the weather in space should be given a high priority.

Day 234: UK and World weather report - hurricane Irene and tropical cyclone harvey

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John Hammond Met Office Forecaster John Hammond Met Office Forecaster | 16:00 PM, Monday, 22 August 2011

Distance travelled ~ 601'177'600 km

It was another week of mixed weather across the UK and around the world last week.

During Thursday, very heavy rain with thunderstorms moved across parts of southern England. Across many parts of Dorset and Hampshire, rainfall totals were between 25 and 40 mm with flooding across Bournemouth and Poole. 58.4mm of rain fell at Portland on Thursday and under the cloud and persistent rain parts of the south and the Midlands recorded maximum temperatures of between just 12 and 14 Celsius.

This heavy rain was associated with very warm and humid air over the near continent which also triggered violent thunderstorms over the 'Low countries'. One of these storms with high winds and torrential rain hit a music festival in Belgium, killing five people and injuring dozens.

On the other side of the world, the first half of last week saw a cold blast from Antarctic bring snow to many parts of New Zealand for the first time in almost 40 years and Wellington airport was forced to close. Crews and airport staff worked round the clock to keep Christchurch Airport operating, clearing 25mm of new snow from the airport runways and re-opening the terminal.

Further west strong winds and heavy rain affected southwestern parts of Western Australia. The Cape Leeuwin area was hit by the strongest winds, which gusted up over 60 miles per hour. Pemberton recorded 33mm of rain by Tuesday morning, their heaviest rainfall in 6 years for August and Albany recorded a daily total of 37mm. Further inland, Wiluna picked up 17mm and this was their highest for August in 13 years.

Elsewhere around the world last week:

• A flashflood hit a village in Polomolok, South Cotabato in the Philippines left 215 people homeless.

• Pittsgrove Township in Salem County, New Jersey, USA received 11 inches of rain since a rain storm began on Sunday.

• Rainfall records were shattered at John F. Kennedy International Airport, USA which had the wettest day on record with 7.80 inches, smashing the 1984 record of 6.27 inches.

• Several planes received damage in a storm, which included golf ball to baseball sized hail at Eppley Airfield in USA.

The week ahead...

• Back in the UK heavy thundery showers are expected to move across southern England tonight. This should move northeast through Tuesday to affect eastern England and parts of southern Wales. Heavy rain on Monday and Tuesday gives a risk of localised surface flooding.

• Hurricane Irene, currently near the Dominican Republic will move west and then northwest through this week and passing through the Bahamas later this week and close to Florida's east coast during Friday.

• Tropical Storm Harvey will continue moving WNW'wards but stay as a weak system. Heavy rainfall, strong winds and flooding can be expected over parts of Central America as a result.

tropical storms Irene and Harvey

The GOES-13 satellite saw Tropical Storm Irene over Puerto Rico on Sunday, August 21, at 6 p.m. EDT. Credit: NASA/NOAA GOES Project

NASA satellite GOES East 1 km Infrared Hurricane Sector Pictures

• Windy conditions are expected across Alaska and NW Canada. Some warmer than average temperatures may also affect parts of northern Canada for a time. Some heavy rain/strong winds also affecting NE Canada at first.

• A tropical cyclone is currently forming just east of the Philippines. This has the potential to affect southern Japan by the end of the week.

Day 231: weekly roundup in pictures and video

Distance travelled ~ 592'816'000 km

Sunset SurpiseImage taken by Wayne Karberg, August 16 in the Laramie Valley in Wyoming. "Several minutes before sunset (about 8:00 PM MST). This is the view east from my driveway. Rainbows occur frequently here due to the vast open sky and broken weather that passes over the Great Laramie Plains."


August Lunar
Full moon August 14, 2207hrs. Image taken by Dave Armstrong, Durham England. "I had the dogs out for their final walk of the day and spotted how beautiful the moon was and amount of light that was coming off it, on arriving back at the house grabbed the camera and tripod and set up in the garden and took approximately half a dozen shots"

 


perseid meteor shower Perseid meteor shower. Image taken by Mavroudakis Fotis, 13 August over the mountains of Drama, a city in the Northern part of Greece . "This image is a stack of images which I took from 01:00 am to 02:00 am."

 

And lastly, this video which was uploaded by weathernut27 of the snow brought about by a strong Antarctic storm over New Zealand, spreading over northern areas such as Christchurch, Wellington and Auckland, where this extent of snow hasn't fallen in decades...

Behind the scenes: The kindness of strangers

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Arif Nurmohamed | 17:00 PM, Thursday, 18 August 2011

Distance travelled ~ 590'993'600 km: Day 230

(Arif is a Producer for 23 Degrees, currently in edit, but no stranger to the world's severe weather. He has directed films for 23 Degrees in the US, Mexico, Egypt and lastly India to name a few)

We're in Udaipur, in the Indian state of Rajasthan, to film the monsoon. Only it's not raining.

While we wait for a downpour, there's plenty of other stuff we can do. I need a driving sequence through the city's streets, so Toby the cameraman mounts a minicam on the bonnet of our car. Toby's done a lot of work for Top Gear so he's rigged this particular shot hundreds of times.

The minicam mounts on the hood with a specially designed suction cup. Normally it sticks on like a limpet... Normally, though, it doesn't have to cope with India's potholes.

 

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After about 10 minutes driving, we notice the camera is no longer with us. Cue rapid fire expletives. We think it must have fallen off in the last kilometre or so. While Sam the sound recordist stays behind in the car, Toby and I jump out and head back down the street. I run ahead, Toby's maybe 30 meters behind. We're at full pelt; both of us realise we've just seconds to retrace our route and find the camera before it is run over or vanishes. Some of the people we run past get the wrong idea; what was this white guy doing chasing an Indian looking man (me) down the road? Has the white guy been robbed? I suddenly find a couple of locals on my tail, and slow down in confusion. A couple more bystanders stop Toby to find out what I'd done. By the time Toby clears up the misunderstanding, a crowd has gathered, and one of them reveals our camera has already been found. In fact, as we'd been running around headlessly, the finder was on his moped looking for our car. 

What's great is that the minicam was on all the time, and filmed everything. It's all there: the camera's initial bump and tumble, the finder's determination to track us down, and the delighted, slightly incredulous look on sound recordist Sam's face when the camera is returned.

This accidentally shot footage is testimony to the wonderful generosity of spirit of ordinary Indians. It absolutely made our day.

Cloudbursts in Kullu-Manali India cause havoc...

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Helen Czerski Helen Czerski | 15:00 PM, Wednesday, 17 August 2011

Distance travelled ~ 588'206'400 km

"Cloudburst" sounds dramatic, doesn't it? As though a cloud was a large balloon filled with water and someone had just arrived with a very large pin. Pop! And then what went up must come down and the one place that you don't want to be is right underneath.

Although the real thing isn't quite like that, the people underneath can be forgiven for not caring about the difference. This week a cloudburst in the town of Kullu produced 176 mm of rain in three hours and drenched three villages. A cloudburst is defined as any rainstorm where the rain rate is greater than 10 cm each hour, and they are usually only a few km wide. Just stop and think about that... 10 cm of rain in one hour. That is enough to turn an entire village into a temporary river bed. And these are large damaging drops, accompanied by strong winds and thunder. Cloudbursts are very hard to predict, but devastating to the places that they hit.

Not long ago the 23 Degrees team were in India to film the monsoon rains

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A cloudburst is a hard thing to study, because it's tough to be in the right place at the right time. So we don't have a good description of exactly how they form or what causes them. They're relatively common during the monsoon in India, especially close to the mountains. Scientists think that these huge amounts of rain come from very tall clouds, reaching up to 15 km into the air, and so the droplets falling from the top of that huge cloud have been able to hoover up lots of smaller drops along the way. That's why the raindrops are so big when they get to the bottom.

The trigger for the storm seems to be that something nearby (for example shape of the local mountains) starts a huge upside down fountain of air that's very strong but only covered a very small area. Warm moist air pours upwards, releasing energy as it rises, and this builds the storm cloud very quickly. Once it gets big enough and if the conditions are right, all the water that had been lifted up comes down. Very quickly. This is similar to the process that generates normal storms, but what makes cloudbursts different is that this whole process happens inside a small area and very powerfully.

The problem for the areas that are vulnerable to these events is that accurate prediction of cloudbursts is hard to do and would require some really detailed weather monitoring. You would need to have a weather station every couple of kilometres all over those areas, and installing and maintaining that system would be very expensive. To understand and predict really local events, you need to have really local measurements.

Hopefully, new technologies and new monitoring systems will solve some of these problems soon. But until then, cloudbursts are going to remain a dramatic reminder of the invisible complexity of the air we breathe, and how little control we have over it.

Turbulent weekend across USA leaves a trail of destruction

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Peter Gibbs Peter Gibbs | 11:30 AM, Tuesday, 16 August 2011

Distance travelled ~ 585'258'400 km

A turbulent weekend across the USA left a trail of destruction from the Midwest to the east coast.

Forecasters began warning of severe thunderstorms during Saturday, as a developing area of low pressure began to interact with warm, humid air across the Great Plains. Towards evening, weather radars in Indiana showed storms lining up and advancing towards Indianapolis. Tragedy followed, when a freak gust of 60-70mph toppled a stadium at the Indiana State Fair as the storm front approached.

weather radar

Image from Accuweather.com

Severe thunderstorms produce vicious downdraughts as heavy rain and hail falling through the cloud cools the surrounding air, making it heavier and denser. As this hits the ground, it spreads outwards as a gust front which can arrive several minutes ahead of the main storm. These "downbursts" are a major hazard for aircraft as they can change the airspeed over the wings in a matter of seconds, causing it to stall. They are also very difficult to forecast precisely, as the strongest gusts can be very localised with all the energy focused into a narrow zone. This seems to be what may have happened at the Indiana State Fair.

The developing area of low pressure created different problems as it pushed further east. Slowing as it reached the east coast on Sunday, the swirling system began to replenish its store of warm, moist air from the Atlantic waters. This was converted into torrential rain which fell for hour after hour across New Jersey and New York City. JFK airport smashed their all-time daily rainfall record with a massive total of 198mm, nearly twice the amount they would normally see in the whole of the month.

Some of that rain would have been very welcome further south. In Waco, Texas, they've had 62 days this year with a temperature of 100F (38.4C) or above. One more and they'll equal the record set in 1980.

Day 227: UK and World weather report

Distance travelled ~ 583'007'200 km

(The Met Office is the UK's national weather service, and a trading fund of the Department for Business, Innovation and Skills. John Hammond is the lead for road and rail, utilities, health and climate statistics and a BBC weather forecaster. Each week the Met Office will bring us the UK and World weather report on the 23 Degrees blog; looking ahead at the week's global weather developments)

Last week's weather saw some big differences once again across the UK. Parts of southern England basked in warm sunshine and temperatures well into the 20s. Further north it was a very different story, as a slow-moving Atlantic weather front brought prolonged and at times heavy rain over the southern half of Scotland and parts of northern England.

Salsburgh in North Lanarkshire recorded around 75mm of rainfall between 10pm on Tuesday 9th August and 1pm on Thursday lunchtime. The average for the whole of August is 90mm

Meanwhile, heavy rainfall just a few days earlier between Saturday 6th and Monday 8th August 2011 resulted in saturated ground conditions and localised flooding, particularly in Aberdeenshire.

Wet weather this month means that Leuchars in Fife has already recorded 134mm of rain up to the 11th August - the average for the whole of the month is 47mm.

Elsewhere around the world, devastating rains in Pakistan killed at least 21 people, destroying crops and houses in the flood-prone southern province of Sindh, a government official said on Friday. The Pakistani meteorological office forecast more rains for this week.

Further east, Tropical storm Muifa lashed China's north-east coast, creating a surge in waves and threatening to breach a dyke at Dalian, in Liaoning province. The full force of Muifa missed Shanghai, but power to at least two residential areas was briefly lost. Heavy rain was also expected in western areas of North Korea.

The week ahead:

Looking ahead and the coming week over the North Atlantic Ocean, Tropical Storm Gert is expected to take a northerly track, reaching Bermuda during today, and then undergo extra tropical transition during Tuesday and Wednesday.

tropical storm gert

Image courtesy of NOAA/National weather service

At this stage it is not expected to strengthen further.

Over in the USA it remains exceptionally hot in southern parts of the country, especially Texas.

Day 224: This week in pictures

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Aira Idris Aira Idris | 16:00 PM, Friday, 12 August 2011

Distance travelled ~ 575'449'600 km

Laramie Sunset 8_6_11 Image taken by Wayne Karberg 6 August, The Buttes, Wyoming. "Dark clouds drop virga as they pass over the Snowy Range west of Laramie, Wyoming near sunset."


clouds

Sunday morning mix of cumulus clouds taken by Fenwalker1, 7 August, Dereham, Norfolk. "A breezy sunny morning"

sunset
Timeless. Cirrus clouds taken by Garry Prescott, 8 August, Moors Valley Country Park.

If you would like to submit your weather/space photos for next week's photo blog or a feature, you can do this via the 23 degrees weather photography pool or email your photos to 23degrees@bbc.co.uk

Next few days of rain in UK great for rainbow appreciation

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Helen Czerski Helen Czerski | 15:30 PM, Thursday, 11 August 2011

Distance travelled ~ 572'823'200 km

What is a rainbow?

We all love rainbows. Even though we take it for granted that the sky changes colour all the time, there's something about these enormous semicircles that makes us want to smile, point and take photographs. And they're worth looking at, because you're seeing nature's paintbox directly. The entire spectrum of visible light is in there, and every single thing that we can see comes to us as a combination of those colours.

The next few days could be great for rainbow appreciation, especially on Saturday and Sunday. A mixture of sunshine and rain is forecast for all of the UK, as several weather fronts pass over us.


met office rain forecast 13 aug 2011

Image courtesy of the Met Office

So keep your eyes on the sky, and if you see bright sunshine appearing suddenly after a shower, turn away from it so that you are facing your shadow. If you're lucky, you'll then be looking at a giant arc of colour.

A rainbow is a beautiful example of physics in action. The only ingredients are direct sun and water droplets (rain or mist) some distance away. When sunlight travels into these water droplets, it changes direction (this is called refraction) and the important part is that the path of blue light is bent a bit more than red light. We see sunlight as white, because it's a mixture of all the visible light colours. When sunlight goes into water droplets, bounces off the inside once and then comes out, the blue light comes out at a slightly different angle to the red light. You can only see a rainbow when the sun is behind you, and that's because the light that goes into those droplets and bounces once comes out at about 40 degrees to the direction it went in. The different angles of red and blue light mean that you have to look a bit higher up to see droplets which are sending red light in your direction - that's why red is on the outside of a rainbow.

A rainbow is a very personal thing. Imagine a line that comes from the sun, goes through your head and then keeps going forwards in front of you. You will see a rainbow 40-42 degrees away from that line, and it would be a full circle if the ground didn't get in the way. But the person standing next to you is seeing a different rainbow, because the line joining their head and the sun is a different line. They see the colours from different droplets. You are the only person who can see your rainbow. This is why you can never get to the end of a rainbow - if you move closer to where you think the end is, the rainbow you see is a different one and you can't touch that one either.

If you can't wait for the next shower to see all this, it's easy to make your own rainbow. All you need is a sunny day and a garden hose. I had a go last weekend with my mum wielding the hose (she also saw it as an opportunity to water the garden), and the photo I took is below. Stand with the sun behind you - the lower it is in the sky, the better - and get your helper to spray water a couple of metres in front of you. The shadow of your head will be at the centre of the rainbow circle. It'll be easier to see the rainbow if there's a darker background - in the photo below you can see that the rainbow is easier to see against the darker plants. A rainbow in the sky is exactly the same, but bigger because it's further away.

home made rainbow

Even though a rainbow looks ethereal and delicate, bear in mind that the energy from the sun carried by those colours is what powers our world.

If you happen to spot any rainbows over the next coming days, send them to 23degrees@bbc.co.uk

Even with the full moon there's hope left in the Perseid meteor shower

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Mark Thompson Astronomy Mark Thompson Astronomy | 10:00 AM, Wednesday, 10 August 2011

Distance travelled ~ 569'660'800 km

GUEST POST

(Mark Thompson is the BBC One Show's Astronomer and when not reporting for them, he is most likely writing about the sky or looking at it! You will often find him zooming in on, or through it, as not only is Mark an enthusiastic astronomer but he is also a qualified pilot. January 2011 saw Mark as part of the successful BBC Stargazing Live Presenting team. He also regularly writes for Discovery.Com and a host of other astronomy and space websites and will be producing a monthly space watch blog for 23 Degrees.)

Morning Meteors of the Perseid Kind
Image taken by Michael Menefee 7 August, Larimer County, Colorado, US. The peak of the meteor shower should make visible 20-30 per hour.

It may not seem like it but the Earth is hurtling around the Sun at the breakneck speed of about 107,000 km per hour. We don't often get a chance to see evidence of this motion but around the middle of August every year, something happens which gives it away. Planet Earth passes through a field of debris that has been left by Comet Swift-Tuttle as it orbits around the Sun which gives rise to one of natures most amazing spectacles, the Perseid meteor shower.

There are about 30 different meteor showers each year where the Earth passes through the debris left by other comets and they happen at broadly the same time every year. If you watch the meteors carefully during any particular shower, you may notice that they all seem to come from one point in the sky, we call this the radiant. They don't actually come from one point in space, its a visual effect arising from something we call perspective. You can see a similar effect if you stand on a bridge over a motorway, all the parallel lanes seem to come from one point on the horizon. The location of the radiant determines the name of the shower, for example the radiant for the Perseid shower sits in the constellation of Perseus.

During the shower, you can expect to see a number of fast moving lights zipping, unannounced across the sky, all seeming to come from Perseus. These lights are produced as tiny pieces of rock slam into our atmosphere at speeds in excess of 200,000 km per hour. On hitting our atmosphere the gasses in front of the rock get compressed to such a degree that they give off the characteristic flash of light. Typically, most of the pieces of rock (meteoroids) will burn up high in the atmosphere and when they do we call them meteors, if they are big enough to land then they are called meteorites.

This year then, in the early hours of 13th August, we will be treated to the peak in activity of the Perseids although it is possible to see meteors from this shower from now until the end of the month. Unfortunately the Full Moon will be present overnight on 12/13 August which means its bright light will block the fainter ones from our view. The best thing to do is get outside, away from bright street lights anytime before dawn between now and then and you should see plenty. Its best to look for them in the early hours as you are then on the front face of the Earth as it moves through space. Its a bit like all the flies you find stuck to your car windscreen but hardly any on the back window. Wrap up warm and set up a comfortable chair outside, lay back and watch. If you are lucky and you do see some, don't forget to make a wish.

If you plan on viewing the show, send your pictures in to 23degrees@bbc.co.uk

Meteorites continue to explain crucial elements about our planet

Aira Idris Aira Idris | 15:00 PM, Tuesday, 9 August 2011

Distance travelled ~ 567'624'000 km

"NASA-funded researchers have discovered that some building blocks of DNA (the molecule that carries the genetic instructions for life), found in meteorites were likely created in space. The research gives support to the theory that a "kit" of ready-made parts created in space and delivered to Earth by meteorite and comet impacts assisted the origin of life."

This is absolutely fascinating, particularly for us, as the 23 Degrees team are currently researching possible stories about meteors and asteroids for the series. They tell us so much about our planet.

At this stage it seems unlikely that we will explore the link between meteorites and the origins of life - but the impact of asteroids on our planet's climate is of huge significance. The KT impact being one of the major examples of this.

The KT boundary marks the time between the Cretaceous and Tertiary periods, and the KT impact is one of the leading theories behind the extinction of the dinosaurs.

It's been discovered that this was when a massive asteroid hit the Earth near Mexico. It is argued this caused flash fires, a nuclear winter and global warming. All of which contributed to mass extinctions (75% of species, supposedly 99.999% of individual animals on Earth). In turn however it may have allowed mammals to evolve.

It would be great to hear your thoughts on Earth's relationship with meteors, asteroids and comets and what it tells us about our planet.

Double CME hit Earth's magnetic field 5 August producing beautiful Auroras

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Aira Idris Aira Idris | 11:00 AM, Monday, 8 August 2011

Distance travelled ~ 564'622'400 km

auroral display Scotland

This photo was taken on August 5, 2011 in Elgin, Scotland, by Alan Tough.

This week in pictures: 30 july - 5 august

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Aira Idris Aira Idris | 14:00 PM, Friday, 5 August 2011

Distance Travelled ~ 557'306'000 km

clouds

Unsettled. Photo taken by John Parish, 4 August, Bocking Essex. "After a day of heavy rain and with a thunderstorm still rumbling, I took this photo of the clouds as they sort of complimented the wires and pylons."



sunset


Sunset and Glory Beams. Photo taken by Judith Rogers, 2 August, Campfield Marsh, looking north towards Scotland across the Solway Estuary, Cumbria. "As the sun was setting it was obscured by clouds on the horizon probably causing the shafts of light that were thrown up into the sky."



clouds

Evening At Big Moor Photo taken by Colin Jackson. "This photo was taken yesterday evening on the southern edge of Sheffield".


Sphinx on Sunset LightSphinx on Sunset Light, Laramie, Wyoming, USA. Photo taken by Wayne Karbeg. "This photo was taken on August 2, about a half hour before sunset from the front patio of my home south of Laramie, Wyoming. I was looking to capture the low light glancing across the prairie grasses and striking Sphinx Rock in the distance. A troubled sky above added to the sense of space and isolation."



sunset

Sunset in the peak district. Photo taken by Laura Adams, Matlock Moors, Derbyshire, 30 july. "A warm sunset over Matlock moors"


If you would like to submit your weather/space photos for next week's photo blog or a feature, you can do this via the 23 degrees weather photography pool or email your photos to 23degrees@bbc.co.uk

Tornadoes, ah those lovely tornadoes...

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Eileen Inkson | 19:30 PM, Wednesday, 3 August 2011

Distance travelled ~ 552'669'600 km

(Eileen is the Assistant producer on 23 Degrees. From chasing the storms in the US to capturing the monsoon season in India, she has experienced a mixed range of our global weather)

As we drove through our 6th US state, our 5th consecutive day of torrential rain and the 17th playing of Stairway to Heaven from the cameraman's iPod, I wondered where it had all gone wrong... Just a week before, it was looking so promising. We were heading out to the USA's famous 'tornado alley' to shoot the ultimate weather phenomenon.

storm chase, 2011

 

With a mountain of water-proofs, an SUV the size of a small English village and a crash course in weather lingo (note - if you want to sound like a storm-chaser, just call rain 'precip'), we were ready to go and had visions of bringing home a Hollywood style twister... And we had reason to be optimistic. We were going on the road with one of the world's most eminent tornado scientists, 2 of his state of the art 'Doppler on Wheels' radar trucks, 3 scientific support vehicles and a team of professional storm-chasers. If anyone could find us a tornado, it would be this lot...

eileen inkson bbc 23degrees

 

But by Day 3, I realised I might have to revise the energetic, adrenaline-fuelled storm-chasing sequence I had in my head. It turns out that the real grunt work of tornado chasing is about as action-packed as a paint drying convention. Each morning our scientists would park themselves in the lobby of whatever glamorous motel we'd ended up in, fire up their laptops and stare intently at satellite pictures of weather. I mean it was pretty rigorous staring to be fair, sometimes with accompanying pointing and the occasional mumble about ridges and troughs, but not quite the gripping, high-drama telly sequence I'd had in mind...

tornado alert message

 

After an agonizing 3 or 4 hours of this (during which I'd only just manage to resist posting a photo of them on Twitter with the heading 'Storm-chasing - Not as exciting as you might think...') a decision would finally be made about where we should head to for the best chance of tornadic activity and we would hit the road.

bbc 23 degrees tweet

 

Ah the road. With romantic visions of how to make the perfect blend of 'classic American road movie meets classic force-of-nature movie' I knew things would start to look up once we hit tarmac.

DOW

 

And yet somehow, despite knowing that tornadoes are the product of 'severe thunderstorms', what I hadn't quite counted on was the rain. Not nice, gentle, intermittent British rain. No this was relentless, pounding, torrential rain that laughed in the face of our extreme weather gear.

But in true documentary filming style, we made the best of it and filmed whatever we could. Which was mainly our presenter Helen Czerski- in the rain. We filmed her walking, talking, sitting and driving in the rain. Looking up at the rain, down at the rain and through the rain. We had the makings of a truly great rain sequence totally covered...

By the beginning of Day 5, we'd driven over 2000 miles, but still no tornado. It was our final day on the road and we all knew it was our last chance.

By 6pm, we were ready to give up. We had a 5-hour drive ahead of us to reach Kansas City for our flight home the next morning. But there was 'one last storm' on the horizon that looked promising so we decided to give it one final go. We'd had many supposedly 'promising' storms already so expectations were low. But as we drove through the rain, a crackling voice came over the radio saying 'Tornado to our immediate North East - all vehicles use extreme caution'.

We turned a corner and there it was. A large, black, funnel-shaped twister travelling steadily across the Nebraskan countryside.

5 minutes later it was all over. But we had our footage, we'd seen a twister and were returning to London happy...

Photo of the day: Delta Aquarid meteor travelling through the milkyway

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Aira Idris Aira Idris | 12:00 PM, Monday, 1 August 2011

Distance travelled ~ 546'612'800 km

delta aquarid july 2011

Image captured and sent in by Bob Johnson Saskatoon Saskatchewan, Canada. Amazing photo of Delta Aquarid meteor travelling through the Milky Way, Jupiter far left.

If you witness weather phenomena and space events you can send your photos and video to the 23 degrees team for a possible feature.

150 years since the first UK weather "forecast"

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Helen Czerski Helen Czerski | 08:00 AM, Monday, 1 August 2011

Distance travelled ~ 546'291'200 km

Victorian England in 1861 must have been a brilliantly exciting place to live. Fabulous inventions and intriguing new scientific ideas were popping out of the population like endless possibility popcorn. London was the largest city in the world, the theory of evolution was being debated in Oxford, Maxwell had just written down the fundamental equations of light, and solar flares and Neanderthal fossils had just been discovered.

first forecast issued by the Met Office on 1st August 1861

Image courtesy of the Met Office

(The forecast itself appears immediately below the table of station data and consists of the following:

General weather probably for the next two days in the-
North-Moderate westerly wind; fine.
West - Moderate south-westerly; fine.
South - Fresh westerly; fine
. )

But no-one really knew much about large scale weather patterns. Weather just happened. Every year an enormous number of lives were lost at sea, as ships sailed into storms and never sailed out again. In the late 1850s there was the first hint of a possibility of changing this situation because communications technology had just taken an enormous leap. The electric telegraph now made it possible to collect weather observations from all over England, assemble them and send them out again to whoever needed to know, all in less than a day.

Telling people what had happened was useful, but not as useful as telling them what was going to happen. The man who made the first attempt to bridge that gap, and who coined the phrase "weather forecast", was Admiral Robert Fitzroy. Thirty years before, he had been captain of the Beagle voyage that carried Charles Darwin, so he was no stranger to the perils of weather when at sea. In 1854, Fitzroy was given the job of collecting data on weather at sea, leading what later became the Met Office. After a few years, he saw that weather systems could be tracked. He became convinced that predictions were possible and that storm warnings would save many lives. His bosses did not agree that predictions were realistic, but in spite of them Fitzroy started to issue storm warnings in 1861. Then, on the 1st of August 1861 (exactly 150 years ago), Fitzroy issued the first ever weather forecast for the general public, published in The Times. This earned him a slap on the wrist and a huge amount of criticism, because it was considered that the forecasts could not possibly be accurate. After a lot of debate, the public forecasts ended in 1866.

I think that you have to admire Fitzroy for trying. He saw the big picture, and walked the first few steps along a very hard path. Even now, when we have a sky full of satellites and enormous computational weather models, we don't always get it right.

In the end though, Fitzroy was given the most appropriate recognition possible. When the region that used to be known as Finisterre on the shipping forecast was renamed in 2002, they decided that it would be called Fitzroy. So now, four times a day on longwave radio, Fitzroy's name is broadcast to all shipping in the vicinity of the United Kingdom. Next time you hear "Trafalgar, Fitzroy, Sole, Lundy..." as you fall asleep, think of the man who started the journey towards the weather forecasts we all take for granted today.

(With thanks to Malcolm Walker of the Royal Meteorological Society's History Group for his help with information about the history of Fitzroy's contribution)

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