Weather Eye

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BY PAUL SIMONS

IN the past couple of weeks, you might have seen one or two beautiful patches of rainbow-coloured light near the sun in late afternoon or evening. These were not rainbows but sun dogs, also known as mock suns.

If you are not used to seeing sun dogs they are easy to miss, but there are some telltale signs in the sky. Watch for wispy strands of cirrus clouds draped across a fairly low sun in an otherwise clear sky. Put your hand up at arm’s length to shield out the sun, and look about a hand’s breadth on either side of it for a bright patch of coloured light — a sun dog. It also helps to wear polarising sunglasses to cut the glare.

If the cirrus clouds are moving around you may find sun dogs come and go, and sometimes you can see a pair of them, one on each side of the sun, so it is worth spending some time watching the sky.

Cirrus clouds lie roughly about 6km (4 miles) high where it is so cold that the water in the clouds exists as ice crystals. These crystals can bend the sunlight like tiny glass prisms, casting a spot of light some 22 degrees to one side of the sun, and so creating a sun dog.

Link to Weather Eye source

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BY PAUL SIMONS

AS RAINS drench much of Britain, and the air turns uncomfortably muggy, something else is making life slightly unpleasant — flying ants. You may have noticed hundreds of the creatures crawling or flying around, but rather than try to stamp them out, they are worth marvelling at.

The common black garden ant looks for a mate at this time of year. Most of the males are wingless and infertile, but during the summer, fertile winged males hatch and are pampered by the flightless workers, often for several weeks.

The workers monitor the climate outside, waiting for the perfect mating weather — hot and humid — before releasing the flying males along with female queens. The amazing thing is that ants from thousands of colonies all take to the skies at once to mate in one glorious swarm.

Once they have mated, the male ants die and the females crawl underground and hibernate until next year, when a new colony is begun. Despite being larger than the wingless males, the flying ants do not sting or bite, but it seems that their huge swarms have a bad public image. In fact, they are a bonanza for birds, which snap up the flying insects.

Perhaps part of the problem is that the swarms are growing larger. Experts say our warmer, longer summers have helped ant populations to thrive.

Link to Weather Eye source

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BY PAUL SIMONS

THIS year’s hurricane season began with Arlene last month, six weeks earlier than last year’s first named storm.

Two weeks ago Hurricane Dennis ploughed through the Caribbean at Category 4, with wind speeds of 230km/h (145mph). This is the earliest Category 4 hurricane since records began in 1851.

Last week Tropical Storm Franklin spun off into the Atlantic without causing significant damage. But the worrying thing is that this was the sixth named storm of the Atlantic this year — the earliest that this many have formed. And much worse is expected. According to a team of scientists at Colorado State University, 15 named storms are predicted this season, and of these eight could become hurricanes.

One brief respite is expected this week. An enormous cloud of dust is blowing on the trade winds from the Sahara across the Atlantic towards the US. The tiny particles of desert dust help to stabilise the atmosphere and prevent the build-up of the storms, which can grow to become tropical storms or hurricanes.

The dust cloud is expected also to give poor air quality in the Caribbean and southern US, creating some dramatic sunsets as well as a surge in asthma and other breathing problems.

Link to Weather Eye source

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BY PAUL SIMONS

THE school holidays have got off to a soggy start with heavy rain across Southern Britain.The wet weather came from a slow-moving depression as hot humid air drifted up from North Africa and encountered cold air from the North Pole.

The best holiday weather this week is in Scotland, which falls under the enormous ridge of high pressure extending all the way from the sub-tropical Azores to Iceland. In fact much of Scotland is enjoying some of its driest weather for nine months, and could end up with only half its average rainfall for July — while the South looks likely to exceed its average July rainfall by a wide margin.

The sudden change in the South’s weather from dry to wet was caused by a shift in the jet stream. For most of the summer this high-altitude river of wind has run between Iceland and Scotland, dragging Atlantic depressions with it. But now the jet stream has snaked across southern England and brought the low-pressure system with it.

This depression is going to take time to shift and could give huge downpours in some places.

But holidaymakers in the South need not despair. Next week holds the promise of high pressure from the Azores building up and giving fine weather again — perhaps just in time for the second Test match at Edgbaston on Thursday.

Link to Weather Eye source

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BY PAUL SIMONS

ASTOUNDING monsoon rains fell on Bombay this week, with 944.2mm (37.2in) of rain in one 24-hour period. This is more than the city’s average rainfall for the whole of July. Even more rain fell in the city’s suburbs: 972mm (38.3in) in the same period was a new record for the wettest day in India. The rains came from severe thunderstorms, typical of the monsoon season.

India’s previous 24-hour rainfall record was 838mm (33in), recorded on July 12, 1910, at Cherrapunji. This remote town of 7,000 people in the northeastern state of Meghalaya (meaning “Abode of the Clouds”) is famed as one of the wettest places in the world. Perched on the edge of an escarpment looking down over Bangladesh almost a mile below, it is drenched in the monsoons every June. Huge clouds roll in from the Bay of Bengal and run into the steep wall of rock at Cherrapunji; as the moist air rises it cools and disgorges torrents of rain.

In 1833 the British established a colonial seat of government in this town, but the weather drove them to despair. The soldiers’ morale sank in the incessant rains, and some even committed suicide.

Cherrapunji’s reputation was confirmed between August 1860 and July 1861, when the rainfall reached 26,470mm (1,041in) — the world record for a 12-month period.

Link to Weather Eye source

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BY PAUL SIMONS

BIRMINGHAM could be the tornado capital of Britain. The violent twister on Thursday had winds of more than 100mph (161 kph) and left a trail of devastation and several injuries (The Times, July 29). An equally ferocious tornado struck a nearby area of Birmingham on June 14, 1931.

A big thunderstorm broke that afternoon and soon afterwards a tornado struck Hall Green to the south of the city, then carved through Sparkhill and Small Heath. “Windows blew in, pieces of wooden pailing flew in all directions,” described the Birmingham Mail. “Slates and pieces of roofing sped through the air like a flight of startled birds.”

Hundreds of trees were uprooted or stripped of leaves. One woman was killed sheltering at the side of a shop which collapsed; several other people were injured in their homes by falling masonry.

Photographs of the devastation showed houses half demolished as if a bomb had gone off, and it is amazing that there were not more casualties. Dozens of families were left homeless, the damage to their houses made worse by the storm’s intense rains and another huge downpour two days later.

Another tornado struck Selly Oak, Birmingham on July 6, 1999. This one was less powerful, but trees were bent and tiles were ripped from the roofs of 21 houses.

Link to Weather Eye source

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BY PAUL SIMONS

THERE is a suspicion that spiders can forecast rain by showing up indoors — especially in showers or baths (The Times, Letters, July 25). In fact, house spiders live indoors all the time and get trapped in baths after venturing in to drink water droplets.

Outside, spiders survive downpours by forming a tight bubble of air around their bodies by surface tension, creating a tiny diving bell. This also explains why they are difficult to wash down a plughole, because they just wait in the U-bend, wrapped in their air bubble.

Some spiders also take up special postures on their webs when it rains. They hang straight down beneath their webs with their front legs stretched out below as a sort of guttering — the rain runs off the webs, down their bodies and drains off their legs.

According to folklore, spiders use short threads to fix their webs to nearby supports before rainy weather, but if they make long threads then fair conditions will come for several days.

The idea persists that spiders running about indoors can indicate rain. As Thomas Hardy described in Far From the Madding Crowd, when sheep farmer Gabriel Oak noticed “two black spiders, of the kind common in thatched houses” it was, he thought, “Nature’s way . . . of hinting to him that he was to prepare for foul weather”.

Link to Weather Eye source

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BY PAUL SIMONS

THE small town of Hawarden (pronounced “Harden”) in Flintshire lies a few miles from Chester. Its most famous resident was William Gladstone, though others might argue that the footballer Michael Owen deserves an equal distinction.

Hawarden can boast also of a notable weather record. Ten years ago today it registered the highest temperature recorded in Wales, a blistering 35.2C (95.4F).

The explanation for that record comes partly from the geography of North Wales. To the west of Hawarden lies Snowdon, one of the wettest places in Britain, averaging around 4,570mm (180in) rain per year. But Hawarden lies 50 miles away as the crow flies, and has a yearly rainfall of only about 610mm (24in), roughly the same as London.

This sharp difference in climate is thanks to the “rain shadow” effect of the Welsh mountains. As depressions roll off the Atlantic, they meet the mountains of Snowdonia. Once the winds have passed over the mountains, their moisture is largely spent, leaving places sheltering in the shadow of the mountains much drier. Also, as the winds pass down the mountain slopes they warm, and this increases the dryness of the air even more.

It is this sheltered climate that makes Hawarden not only dry but also one of the hottest places in Wales.

Link to Weather Eye source

[J10]

Is this partly due to the foehn effect.

[shuggee]

That's exactly what it is Jackone:

Foehn (or Föhn) effect: mechanisms which give rise to a warm, dry wind on the leeward side of mountains or significant hills. Broadly, there are two: (i) the 'subsidence' type where air at & just above the hill/mountain crest descends by lee-wave action, becoming even drier & warmer than when it started out; (ii) all air in a moist airstream on the upstream side of the hill/mountain rises, leading to cloud/precipitation formation, thence lowering the humidity content, this air then descending/warming adiabatically on the leeside.

Taken from a good glossary of weather terms at:

http://homepage.ntlworld.com/booty.weather/FAQ/AF.htm

Edited August 2, 2005 by shuggee

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BY PAUL SIMONS

SIXTY years ago the US was preparing to drop the atomic bomb on Hiroshima. The bomb components were assembled on the Pacific island of Tinian, with the uranium core delivered on July 26, 1945, by the cruiser Indianapolis, which had steamed in from San Francisco.

But soon after delivering her secret cargo, the Indianapolis met her own fate as she sailed towards the Philippines. Two huge explosions ripped her open just after midnight on July 30.

The cruiser had been hit by torpedoes from a Japanese submarine and she sank after only 12 minutes. Only 317 of nearly 1,200 crew members survived — it was the worst US naval disaster of the war.

How the submarine spotted the Indianapolis was not clear, though. The weather was overcast and visibility was poor.

But three years ago scientists found that it was moonlight which sealed the ship’s fate. Using astronomical computer programs, records and weather reports, they discovered that visibility that night was best toward the east, where a three-quarter moon had just risen.

By chance the moon emerged from behind clouds just as the Japanese submarine surfaced and it would have seen the Indianapolis silhouetted against the bright moonlit sky. In these circumstances the cruiser was a clear and easy target for a torpedo attack.

Link to Weather Eye source

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BY PAUL SIMONS

THE Air France passenger jet that caught fire at Pearson airport, Toronto, on Tuesday, had landed during a severe thunderstorm. Conditions were treacherous, with strong winds, torrential rain and poor visibility, and the aircraft may have been hit by lightning. Normally, aircraft are well insulated from lightning by their metal bodies. Lightning bolts rarely penetrate the aircraft, although they can leave pit marks or burns, and occasionally even puncture holes.

On April 8, 1977, however, lightning did rip the nose cone off a private jet flying over England. The pilot of the Hawker Siddeley 125 executive jet managed to land safely at Luton airport.

Cockpit instruments are vulnerable to the massive surge of electromagnetic power from a nearby lightning strike. This potentially dangerous situation could explain the crash on May 24, 1995, in Yorkshire, when a commuter aircraft was flying through torrential rain.

A schoolboy nearby was using a radio scanner to listen to the conversation between the pilot and air traffic when he heard the pilot suddenly shout that the aircraft had been hit by lightning. The radio went dead, and the aircraft plunged to the ground, killing all 12 people on board.

It is thought that the lightning strike scrambled the artifical-horizon display instrument, and since the pilot could not see where he was going, he accidentally flew the aircraft into the ground.

Link to Weather Eye source

[highcliffe2]

BY PAUL SIMONS

TODAY is the 150th anniversary of the birth of the meteorologist William Dines, who was famous for his study of winds. Dines served on the committee set up to investigate the Tay Bridge disaster on December 28, 1879, when the bridge collapsed during a storm just as a train was crossing. A huge gust of wind destroyed a central span of the bridge, the train plunged into the River Tay, and some 75 people were killed.

The committee established new engineering standards for the design of large structures such as bridges, to enable them to withstand storm wind speeds. He invented the Dines pressure tube anemometer, the first instrument to measure both wind speed and direction. This reliable instrument could record sudden gusts of wind, such as the one that caused the Tay disaster, and gave engineers and meteorologists a much clearer picture of wind turbulence.

Dines also flew kites with weather recording instruments to measure high-altitude weather conditions. He set up a kite station in Scotland, and used a boat to take kite readings at sea. Dines later used high- altitude balloons to measure weather conditions through the troposphere.

This work gave insights into how storms develop a few miles up in the atmosphere away from any turbulence on the ground.

Link to Weather Eye source

[shuggee]

Megalightning brings down aircraft.

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BY PAUL SIMONS

IN THE commemorations of the end of Second World War, one campaign deserves a mention for the role the weather played in it.

In June 1942 the Japanese invaded the westernmost part of the Aleutians, a remote chain of islands stretching a thousand miles from Alaska across the North Pacific. It was the only US territory occupied by the enemy in the war.

In his fine book, The Thousand-Mile War, Brian Garfield describes how the US, fearing that the Japanese would use the Aleutians as stepping stones to invade North America, rushed in troops to repel the invaders.

But they reckoned without the weather. This island chain is where the tropical Japan Current hits cold polar air and the Bering Sea. Winds can reach 140mph, and the violent squalls known as “williwaws” sweep down from the mountains, kicking up spray and mist into what look like huge waterfalls. The fog, which can persist despite the gales, is so thick that some islands have only ten clear days each year.

US losses from the weather were worse than from enemy action. Ships were battered on shorelines, pilots were lost in the fog or crashed in the high winds, and the troops suffered from bitter cold and exposure.

After months of bitter fighting, the Japanese were finally driven out in August 1943.

Link to Weather Eye source

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BY PAUL SIMONS

AFTER the atomic bombs were dropped on Hiroshima and Nagasaki in 1945, the Japanese physicist Theodore Fujita studied the devastation across each city and discovered a unique “starburst” pattern of damage caused by the bomb blasts.

Fujita later emigrated to the US where he studied storm damage. In 1974 he flew over an area that had been swept by violent thunderstorms and noticed that trees were flattened in a similar starburst pattern. He realised that the storms had produced violent downbursts of wind whose effects were akin to the blast damage at Hiroshima and Nagasaki.

“If something comes down from the sky and hits the ground it will spread out,” he said. “It will produce the same kind of outburst effect that was in the back of my mind from 1945 to 1974.”

These downbursts are jets of cold air that can plunge out of thunderstorms at 150mph. The winds smash into the ground, pancake outwards for a mile or more to create the typical starburst pattern of damage.

Fujita’s discovery bore unforeseen fruit a year later. On June 24, 1975, a Boeing 727 crashed as it came in to land during a thunderstorm at John F. Kennedy Airport, New York, killing 113 people. Fujita realised that the aircraft had been crushed under a downburst, and his finding led to improvements in airport weather warnings.

Link to Weather Eye source

[johnholmes]

thanks Ryan, as a Meteorologist I was very aware of Fujita but had not realised it stemmed from the atom bomb over Hiroshima.

thanks for that.

[highcliffe2]

BY PAUL SIMONS

LAST Thursday many people on the South Coast were amazed by a circle of light around the Sun.

What made the spectacle even more fascinating were its colours of yellow, red and blue, arranged in concentric circles. Although it looked like a faint rainbow, there was not a drop of rain in sight; it was centred around the Sun and it formed a complete circle in the sky, not a bow. This was a wonderful display of a halo — an optical phenomenon caused by ice crystals, not raindrops. This came from cirrus clouds, often called “mare’s tails” for their wispy strands flicked upwards. These clouds float a few miles high where their water freezes into ice crystals. If the crystals are hexagonal shapes, they bend sunlight into a 22-degree halo around the Sun. As the sunbeams are bent, their wavelengths often split up into the colours of the spectrum, looking like a rainbow. There is a fabulous array of different halo shapes and angles, depending on the shape and orientation of the ice crystals.

On truly rare occasions, the sky can be criss-crossed by these coloured arcs of lights. Actually, some of these halos are more common than you might suppose. Look out for thin veils of cirrus clouds draped across a fairly low Sun. It helps to wear polarising sunglasses and hold out a hand to blot out the Sun’s glare.

Link to Weather Eye source

Interesting Has anyone actually seen the sky 'criss-crossed', as described above?

[frogesque]

I haven't seen all the arcs and tangents (great description on clara.co.uk BTW) but I have seen a perfect halo in a clear blue sky with no aparant cirrus. Unusually it was about noon on a hot June day. Within an hour or so though the weather changed completely and we had thick dark clouds with torrential rain.

Sun dogs are fairly common but we were treated to a gorgeous sun pillar earlier this year (Feb/March ??) stretching up about 1/4 of the sky that lasted until well after sunset. Unfortunately by the time I got home it was too faint to photograph

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BY PAUL SIMONS

WHAT do elephants, volcanoes, storms and haunted places have in common?

They all generate infrasound — sound waves with such low frequencies that we cannot hear them.

Elephants send a rumbling infrasound through the ground to talk to other elephants, and volcanic eruptions pass infrasound waves around the world. As for haunted places, some have been found to be subject to infrasound, possibly from the rumble of traffic, and this seems to produce a deep sense of unease and “ghostly” feelings in people.

Ocean storms and waves are two significant generators of infrasound — the regular up-and-down movements of the waves behave like a giant loudspeaker, pushing the air at infrasonic frequencies.

The swirling winds of hurricanes generate their own type of infrasonic signals and these could be useful for weather forecasters. A new array of infrasonic detectors is being deployed in the Cape Verde islands, off the West Coast of Africa, an area which spawns many of the small storms that can develop into hurricanes. It is hoped that detecting the rumblings of the storms will give early warning of gathering hurricanes.

Another use for infrasound warnings could be to detect clear-air turbulence. This type of disturbed air, often caused by high-altitude jet stream winds, can toss aircraft violently. The turbulence is difficult to detect ahead, but the infrasound it gives off could alert pilots to the danger and allow them to take avoiding action.

Link to Weather Eye source

[Shiny_Bottom_1]

I never knew that about aircraft and turbulence HC.

Its amazing how much we can use nature to our advantage.

[highcliffe2]

BY PAUL SIMONS

IT MAY be the height of summer, but some first intimations of autumn can already be detected — blackberries are ripening, for example, and now the BBC has launched Autumnwatch. Run with the Woodland Trust and the UK Phenology Network, it plans to follow the progress of autumn across the UK, and volunteers are invited to record the first signs of autumn in their areas.

Volunteers have an important role in this work. The BBC’s Springwatch survey this year involved more than 15,000 people and was the biggest project of its kind in the world. By comparing the results of the survey with historical records of the seasons, scientists can obtain a national picture of how climate change is hastening the arrival of the seasons.

Britain has some of the world’s longest records of the seasons. For example, in 1736, the landowner Robert Marsham began to record the first signs of spring in the village of Stratton Strawless, Norfolk. He made his observations every year until he died in 1797, aged 90, and, remarkably, five generations of his family continued the survey until 1958.

These records reveal that today many of our spring flowers have finished blooming by the date that Marsham would have noted the first sightings of them.

You can find more about how you can contribute to Autumnwatch at bbc.co.uk/autumnwatch.

Link to Weather Eye source

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BY PAUL SIMONS

THIRTY years ago tomorrow, Hampstead, North London, was devastated by rainfall of monsoon proportions. The day had been hot and muggy, and vast cumulonimbus clouds built up.

In the late afternoon, a terrifying thunderstorm erupted, with ear-splitting thunder and dazzling lightning. In just over two hours, 171mm (6.73in) rain crashed down and set off a flash flood through Hampstead and neighbouring areas.

The storm flooded the local Underground system and left thousands of commuters stranded. The sewers could not cope with the deluge and manhole covers were forced open by fountains of water, turning roads into rivers up to 1.2m (4ft) deep. Homes were flooded and in some buildings water reached the ceilings of basement flats. One man died.

Yet the thunderstorm was so localised that just a few miles away the London Weather Centre recorded about 5mm (0.2in) rainfall from the same storm.

Moist warm winds converging over North London had been thrust up over the high ground of Hampstead, and received extra uplift from the baking hot ground. That humid air eventually cooled and condensed into thunderclouds.

This was no isolated incident –— another disastrous thunderstorm and flash flood struck Hampstead on August 2, 2002.

Link to Weather Eye source

[Shiny_Bottom_1]

Thanks HC.

I love factual stories like this. In todays world, at times, I think we precieve exceptional weather events as a relation to GW.

But such stories go to show that exceptions to the rule have always occured.

[highcliffe2]

BY PAUL SIMONS

DO YOU remember, back in May, weather predictions in much of the media that we could expect a scorching hot summer in Britain? In fact, this summer has been blowing hot and cold in quick succession, so what happened to the heatwaves?

High in the sky, a ribbon of fast wind known as the jet stream blows towards the east and is responsible for much of our weather. To get a gloriously hot summer, the jet stream needs to pass to the north of the UK. This allows the Azores High, an area of high pressure usually centred over the sub-tropical Atlantic, to build up and when it gets a firm footing gives increasingly hot weather.

Around mid-June, the jet stream passed to the north and much of Britain was roasted in an Azores High. On June 19, the highest temperature of the year so far was recorded in Central London, 33.1C (92.7F), the hottest June day since 1976.

But the jet stream naturally wavers around and lately it has been passing directly over the UK. This has steered in low-pressure systems off the Atlantic, giving the wet weather we had to put up with across the country on Saturday.

Since then the Azores High has returned, but more depressions are trying to barge in from the Atlantic. In fact, it is unlikely that any more heatwaves will appear this summer.

Link to Weather Eye source