Geography Case Studies - Extreme Weather

In March 1993, and intense pool of cold air moved southeastwards towards the east coast of the USA. When it reached the Gulf of Mexico, it collided with a tropical storm  heading north from the north from the Gulf of Mexico. The result was hurricane force winds, torrential rain and mountainous waves.

 During the storm;

• Winds from Flordia to Canada reached gale force 8-11, with gusts of storm force 12 common. A maximum of 232km h-1 was recorded in Nova Scotia.
• Snow fell at an average rate of 900mm h-1. Drifts in many states reached over 3m. Snow even fell in Florida.
• The National Weather Service estimated that the snowfakk during this 4-day period was equal to 40 days of flow on the lower Mississippi River. Off Nova Scotia, waves up to 20 m high sank the carrier Gold Bond Conveyor with all hands (33 people).
•  Inland Nova Scotia was flooded as 520mm of snow were followed by 580 mm of rain, when the warm sector of the storm passed over.
• Parts of New England and the barrier islands of Carolina were badly flooded as tidal surges lifted water locallly by up to 3 m above normal.

• Inland Nova Scotia was flooded as 520mm of snow were followed by 580 mm of rain, when the warm sector of the storm passed over.
• Parts of New England and the barrier islands of Carolina were badly flooded as tidal surges lifted water locallly by up to 3 m above normal.
•   Severe and unseasonal thunderstorms and tornadoes swept across Florida, triggered by the high sea temperatures, 

Human Consequences  

•  Every major airport on the east coast was closed at some point or another. 
•  Amtrack suspended all rail services from Chicago to the east coast,
• Interstate highways 75, 77 and 81 were closed
• Over 3 million people were left without electrical power. 
• The storm caused 291 deaths and affected people in 26 states.
• The total damage was estimated a over $6 million and several states sough disaster relief from federal funds.

Hurricane Katrina was the costliest and one of the deadliest hurricanes in history. It is estimated to have cause $84 billion in damage and claimed at least 1,836 lives, mostly in New Orleans, which flooded as the levée system protecting the city failed.

• Katrina formed over the Bahamas in August 2005, moving westwards across southern Florida as a category 1 hurricane.
• It reached category 5 at sea by 1pm on 25th August. The storm soon doubled in size, the pressure reading fell to 902 mb, wind speeds rose to 280km h-1 and gust reached 344 km h-1.
• Eventually it swung north-eastwards weakening to cateogry 3, and making landfall at 6am on the 29th August.

Effects

• The high winds destroyed many downtown buildings, such as the Hyat Regency Hotel, and damaged the roof of the Superdome, which was later used as an emergency centre.
• Katrina's storm surge caused severe damage along the Gulf coast, where 8m waves overwhelmed the flood protection system in New Orleans. These high water levels caused breaches in the levées along the Mississippi Gulf outlet. 
• The heavy rainfall increased the height of Lake Pontchartrain. This combined pressure broke the levées in 53 places, eventually flooding 80% of the city at depths of up to 6m.

Economic Impacts

•  30 offshore oil platforms damaged or destroyed and 9 refineries shut down. This reduced oil production by 25% for 6 months
• Forestry, port trade and grain handling severly affected.
• Hundreds of thousands of residents left unemployed. Trickle - down effect with less taxes being paid.
• Total economic impact in Louisiana and Mississippi estimated at over $150 billion.

Social Impacts

• Over a million people evacuated, displaced or made homeless
• Most major roads into and out of the city damaged as bridges collapsed
• Overhead power lines broguht down by strong winds. Water and food supplies contaminated
• Worst- hit groups were those with no personal transport, less well off, non-white and vulnerable.

Enviromental Impacts

• Storm surge destroyed sections of the barrier islands and Gulf beaches
• 20% of the wetland lost, affecting breeding of pelicans, turtles and fish. 16 National Wildlife Refuges damaged
• 5,300 km2 of forest and woodland destroyed
• Flood waters containing sewage, heavy metals, pesticides and 24.6 million litres of oil pumped into Lake Pontchartrain

Winter 2009/10 was the most severe in the UK for over 30 years - the coldest since 1978/79. As snow and ice swept across the country, our forecasts and warnings helped the emergency services, our customers and the public to manage the difficult circumstances.

• From mid-December, cold air from Eastern Europe started a cold spell in the UK with widespread frost, ice and snow affecting many areas with the first significant snowfall on the night of 17 December.
• By 19 December, there was cold air across most of the UK with widespread snow and ice causing travel disruption in the run-up to Christmas. Low temperatures continued into the New Year as winds from the north and north east brought freezing temperatures to the UK

• The mean UK temperature over the entire winter was 1.5 °C, the lowest since 1978/79 when it was 1.2 °C. 

The winter of 2010 saw the UK's earliest widespread winter snowfall since 1993 with snow falling as early as 24 November across NE England.

• Temperatures
• As well as disruption due to the amounts of snow, some very cold temperatures were experienced too. A minimum of -21.1°C was recorded at Altnaharra in the Scottish Highlands on 1 December.
• On the morning of 3 December a minimum of -19.0°C was recorded at RAF Topcliffe in North Yorkshire and at RAF Leeming -17.9°C was recorded.

• Impacts

• The emergency services, transport organisations and utilities were all put under great pressure by the snow. The freezing temperatures also caused water supply problems due to burst pipes.

Impacts - Transport

• This snow event was forecast well in advance by the Met Office. Despite the advance warning the snow fell at such at rate that many roads were blocked and airports closed. On 29 November motorists were stranded overnight in Scotland and the A9 was closed for a time.
• On 2 December the Forth Road Bridge was closed for over 10 hours. The first time it has ever been closed due to snow.
• Edinburgh airport was forced to close a number of times through the period and was closed for the best part of three days.
• Gatwick was forced to close for two days.
• The secretary of State estimated that the cost of the travel disruption to the economy was £280 million per day.

Health

• Sadly by 4 December seven people had died due to the severe weather..

• The number of people suffering broken bones, fractures and sprains always rises markedly during cold spells.

Economy

• The cold spell was estimated to cost the UK economy £1.6 billion (Office for National Statistics).
• The cold wintry spell took place in the run up to Christmas when the shops are usually busiest. Retailers were hit by lost sales.
•  Fewer people ventured out to the shops in such extreme weather. Another aspect is that deliveries did not make it to the shops due to closed roads and many supermarket shelves looked decidedly empty.
• This kind of weather often leads to panic buying with people buying more food than they need in case the cold spell lasts for a long time.

Education

Around 7,000 schools were closed on 2 December. Pupils couldn't make it to school due to closed roads etc. In the event of children with both parents working there were a lot of instances where one parent had to take time of work to look after the children who are affected by closed schools. This in turn had a knock-on effect on the economy.

On 16 August 2004, a devastating flood swept through the small Cornish village of Boscastle.

Very heavy rain fell in storms close to the village, causing two rivers to burst their banks. About two billion litres of water then rushed down the valley straight into Boscastle.

Residents had little time to react. Cars were swept out to sea, buildings were badly damaged and people had to act quickly to survive. Fortunately, nobody died - thanks largely to a huge rescue operation involving helicopters - but there was millions of pounds worth of damage. 

Physical Impacts

Flooding

• On the day of the flood, about 75mm of rain fell in two hours - the same amount that normally falls in the whole of August.
• Huge amounts of water from this sudden downpour flowed into two rivers, the Valency and Jordan (which flows into the Valency just above Boscastle).
• Both overflowed, and this caused a sudden rush of water to speed down the Valency - which runs through the middle of Boscastle.

Destruction of houses, businesses and gardens

• Floodwater gushed into houses, shops and pubs.Cars, walls and even bridges were washed away. The church was filled with six feet of mud and water.
•  Trees were uprooted and swept into peoples' gardens. The weight of water eroded river banks, damaged gardens and pavements.

Human Impacts

There was a huge financial cost to the floods. This included:

• the rescue operation - involving helicopters, lifeboats, and the fire service.
• the loss of 50 cars
• damage to homes, businesses and land
• a loss of tourism, a major source of income for the area

The flooding also had several other key impacts on Boscastle and its inhabitants. These included:

• environmental damage to local wildlife habitats
• coastal pollution caused as debris and fuel from cars flowed out to sea.
• long-term disruption to the village, as a major rebuild project had to be carried out.
• long-term stress and anxiety to people traumatised by the incident.

Response to Flooding

• John Prescott, the Deputy Prime Minister, and Prince Charles visited members of the emergency services and the local GP surgery, which acted as the emergency centre, in the days following the disaster.
• Prince Charles, who is the Duke of Cornwall, made a large donation to a fund to help rebuild parts of Boscastle.
• The Environment Agency is responsible for warning people about floods and reducing the likelihood of future floods. The Environment Agency has carried a major project to increase flood defences in Boscastle, with the aim of preventing a similar flood happening again.
• We are investing in new ways of predicting heavy rainfall events on a small scale to produce better warnings

The wind is blowing anticlockwise about the low pressure area, so the air is arriving into Boscastle from a south-westerly direction. It is a warm and moist tropical maritime air mass.

The line labelled (known as a trough line) caused very heavy rain and thunderstorms. A trough is an area of localised rain and thunderstorms. A line of convergence formed near the coast line, where air moving in almost opposite directions collides, this helped toincrease the rate of ascent and produced very heavy rain.

More than 20,000 people died after a record-breaking heatwave left Europe sweltering in August 2003. The period of extreme heat is thought to be the warmest for up to 500 years, and many European countries experienced their highest temperatures on record.

Physical Impacts

Low river flows and lake levels

• The River Danube in Serbia fell to its lowest level in 100 years.
•  Bombs and tanks from World War 2, which had been submerged under water for decades, were revealed, causing a danger to people swimming in the rivers.
• Reservoirs and rivers used for public water supply and hydro-electric schemes either dried up or ran extremely low.

Forest fires

•  The lack of rainfall meant very dry conditions occurred over much of Europe. Forest fires broke out in many countries. In Portugal 215,000 hectares area of forest were destroyed. This is an area the same size as Luxembourg.
• It is estimated millions of tonnes of topsoil were eroded in the year after the fires as the protection of the forest cover was removed. This made river water quality poor when the ash and soil washed into rivers.

Effects of a Heatwave

 About 15,000 people died due to the heat in France, which led to a shortage of space to store dead bodies in mortuaries. There were also heat-related deaths in the UK (2,000), Portugal (2,100), Italy (3,100), Holland (1,500) and Germany (300).

• Heat-stroke - normally we sweat, and this keeps us cool on hot days. On very hot days our bodies may not be able to keep cool enough by sweating alone, and our core body temperature may rise. This can lead to headaches, dizziness and even death.
• Dehydration - this is the loss of water from our bodies. It can cause tiredness and problems with breathing and heart rates.
• Sunburn - damage to the skin which can be painful and may increase the risks of getting skin cancer.
• Air pollution - it is thought that one third of the deaths caused by the heatwave in the UK were caused by poor air quality.
• Drowning - some people drowned when trying to cool off in rivers and lakes.

Environment and social effects

• Water supplies - drinking water supplies were affected in some parts of the UK and hosepipe bans introduced.
• Tourism - many parts of the UK reported increased levels of tourism as people decided to holiday in the UK while the weather was unusually dry and hot.
• Agriculture - many chickens, pigs and cows died during the heat in Europe and crops failed in the dry conditions. This led to higher food prices. It is thought to have cost European farming 13.1 billion euros.
• Transport - some railway tracks buckled in the heat. The London Underground became unbearable. Some road surfaces melted. Low river levels prevented some boats from sailing.
• The London Eye closed on one day as it became too hot in the cabins.
• Energy - two nuclear power plants to close down in Germany. These rely on water for cooling in the power generation process.

The Immediate Response

• France requested aid from the European Union to deal with the effects.

• Public water supply shortages occurred in several countries, including the UK and Croatia, which led to a temporary ban on using hose pipes.
• TV news, internet and newspapers informed the public on how to cope with the heat - drinking plenty of water, wearing cool clothing, and staying in the shade in the middle of the day.
• Network Rail in the UK imposed speed restrictions for trains when the temperature was above 30 °C. This was to help avoid trains derailing when railway lines might have buckled

• Workers around Europe altered their working hours. Some refuse collectors started earlier to pick up rapidly decomposing rubbish from the streets.

With winds gusting at up to 100mph, there was massive devastation across the country and 18 people were killed. About 15 million trees were blown down. Many fell on to roads and railways, causing major transport delays. Others took down electricity and telephone lines, leaving thousands of homes without power for more than 24 hours.

Buildings were damaged by winds or falling trees. Numerous small boats were wrecked or blown away, with one ship at Dover being blown over and a Channel ferry was blown ashore near Folkestone. While the storm took a human toll, claiming 18 lives in England, it is thought many more may have been hurt if the storm had hit during the day. 

• Four or five days before the storm struck, forecasters predicted severe weather was on the way. As they got closer, however, weather prediction models started to give a less clear picture. Instead of stormy weather over a considerable part of the UK, the models suggested severe weather would pass to the south of England - only skimming the south coast.
• During the afternoon of 15 October, winds were very light over most parts of the UK and there was little to suggest what was to come. However, over the Bay of Biscay, a depression was developing. The first gale warnings for sea areas in the English Channel were issued at 6.30 a.m. on 15 October and were followed, four hours later, by warnings of severe gales.
• At 10.35 p.m. winds of Force 10 were forecast. By midnight, the depression was over the western English Channel, and its central pressure was 953 mb. At 1.35 a.m. on 16 October, warnings of Force 11 were issued. The depression moved rapidly north-east, filling a little as it went, reaching the Humber estuary at about 5.30 am, by which time its central pressure was 959 mb. Dramatic increases in temperature were associated with the passage of the storm's warm front.

• During the evening of 15 October, radio and TV forecasts mentioned strong winds but indicated heavy rain would be the main feature, rather than strong wind.
• By the time most people went to bed, exceptionally strong winds hadn't been mentioned in national radio and TV weather broadcasts.
• Warnings of severe weather had been issued, however, to various agencies and emergency authorities, including the London Fire Brigade.
•  Perhaps the most important warning was issued by the Met Office to the Ministry of Defence at 0135 UTC, 16 October. It warned that the anticipated consequences of the storm were such that civil authorities might need to call on assistance from the military.
• In south-east England, where the greatest damage occurred, gusts of 70 knots or more were recorded continually for three or four consecutive hours. During this time, the wind veered from southerly to south-westerly.
• To the north-west of this region, there were two maxima in gust speeds, separated by a period of lower wind speeds. During the first period, the wind direction was southerly. During the latter, it was south-westerly.
• Damage patterns in south-east England suggested that whirlwinds accompanied the storm. Local variations in the nature and extent of destruction were considerable.

Comparisons of the October 1987 storm with previous severe storms were inevitable. Even the oldest residents of the worst affected areas couldn't recall winds so strong, or destruction on so great a scale.

• The highest wind speed reported was an estimated 119 knots (61 m/s) in a gust soon after midnight at Quimper coastguard station on the coast of Brittany (48° 02' N 4° 44' W).
• The highest measured wind speed was a gust of 117 knots (60 m/s) at 12.30 am at Pointe du Roc (48° 51' N, 1° 37' W) near Granville, Normandy.
• The strongest gust over the UK was 100 knots at Shoreham on the Sussex coast at 3.10 am, and gusts of more than 90 knots were recorded at several other coastal locations.
• Even well inland, gusts exceeded 80 knots. The London Weather Centre recorded 82 knots at 2.50 am, and 86 knots was recorded at Gatwick Airport at 4.30 am (the authorities closed the airport).

• Media reports accused the Met Office of failing to forecast the storm correctly. Repeatedly, they returned to the statement by Michael Fish that there would be no hurricane - which there hadn't been.
• It did not matter that the Met Office forecasters had, for several days before the storm, been warning of severe weather. The Met Office had performed no worse than any other European forecasters when faced with this exceptional weather event.
• However, good was to come of this situation. Based on the findings of an internal Met Office enquiry, scrutinised by two independent assessors, various improvements were made.
• For example, observational coverage of the atmosphere over the ocean to the south and west of the UK was improved by increasing the quality and quantity of observations from ships, aircraft, buoys and satellites, while refinements were made to the computer models used in forecasting.

A fog so thick and polluted it left thousands dead wreaked havoc on London in 1952. The smoke-like pollution was so toxic it was even reported to have choked cows to death in the fields. It was so thick it brought road, air and rail transport to a virtual standstill. This was certainly an event to remember, but not the first smog of its kind to hit the capital.

• Smog had become a frequent part of London life, but nothing quite compared to the smoke-laden fog that shrouded the capital from Friday 5 December to Tuesday 9 December 1952. While it heavily affected the population of London, causing a huge death toll and inconveniencing millions of people, the people it affected were also partly to blame for the smog.
• During the day on 5 December, the fog was not especially dense and generally possessed a dry, smoky character. When nightfall came, however, the fog thickened. Visibility dropped to a few metres. The following day, the sun was too low in the sky to burn the fog away. That night and on the Sunday and Monday nights, the fog again thickened. In many parts of London, it was impossible at night for pedestrians to find their way, even in familiar districts. In The Isle of Dogs area, the fog there was so thick people could not see their feet. 

• Britain has long been affected by mists and fogs, but these became much more severe after the onset of the Industrial Revolution in the late 1700s. Factories belched gases and huge numbers of particles into the atmosphere, which in themselves could be poisonous. The pollutants in the air, however, could also act as catalysts for fog, as water clings to the tiny particles to create polluted fog, or smog.
• When some of the chemicals mix with water and air, they can turn into acid which can cause skin irritations, breathing problems, and even corrode buildings. Smog can be identified easily by its thick, foul-smelling, dirty-yellow or brown characteristics, totally different to the clean white fog in country areas.
• There are reports of thick smog, smelling of coal tar, which blanketed London in December 1813. Lasting for several days, people claimed you could not see from one side of the street to the other. A similar fog in December 1873 saw the death rate across London rise 40% above normal. Marked increases in death rate occurred, too, after the notable fogs of January 1880, February 1882, December 1891, December 1892 and November 1948. The worst affected area of London was usually the East End, where the density of factories and homes was greater than almost anywhere else in the capital. The area was also low-lying, making it hard for fog to disperse.

• Under normal conditions, smoke would rise into the atmosphere and disperse, but an anticyclone was hanging over the region. This pushes air downwards, warming it as it descends. This creates an inversion, where air close to the ground is cooler than the air higher above it. So when the warm smoke comes out of the chimney, it is trapped. The inversion of 1952 also trapped particles and gases emitted from factory chimneys in the London area, along with pollution which the winds from the east had brought from industrial areas on the continent.
• Early on 5 December, in the London area, the sky was clear, winds were light and the air near the ground was moist. Accordingly, conditions were ideal for the formation of radiation fog. The sky was clear, so a net loss of long-wave radiation occurred and the ground cooled. When the moist air came into contact with the ground it cooled to its dew-point temperature and condensation occurred.
• Beneath the inversion of the anticyclone, the very light wind stirred the saturated air upwards to form a layer of fog 100-200 metres deep. Along with the water droplets of the fog, the atmosphere beneath the inversion contained the smoke from innumerable chimneys in the London area.

During the period of the fog, huge amounts of impurities were released into the atmosphere. On each day during the foggy period, the following pollutants were emitted: 1,000 tonnes of smoke particles, 2,000 tonnes of carbon dioxide, 140 tonnes of hydrochloric acid and 14 tonnes of fluorine compounds. In addition, and perhaps most dangerously, 370 tonnes of sulphur dioxide were converted into 800 tonnes of sulphuric acid

The fog finally cleared on December 9, but it had already taken a heavy toll.

• About 4,000 people were known to have died as a result of the fog, but it could be many more.
• Many people suffered from breathing problems
• Press reports claimed cattle at Smithfield had been asphyxiated by the smog.
• Travel was disrupted for days

Response to the smog

• A series of laws were brought in to avoid a repeat of the situation. This included the Clean Air Acts of 1956 and 1968. These acts banned emissions of black smoke and decreed residents of urban areas and operators of factories must convert to smokeless fuels.
• People were given time to adapt to the new rules, however, and fogs continued to be smoky for some time after the Act of 1956 was passed. In 1962, for example, 750 Londoners died as a result of a fog, but nothing on the scale of the 1952 Great Smog has ever occurred again. This kind of smog has now become a thing of the past, thanks partly to pollution legislation and also to modern developments, such as the widespread use of central heating.

Fire crews are tackling dozens of bushfires in south-east Australia, as forecasters predict another spell of hot weather for the weekend.

• More than 100 separate fires are burning in New South Wales. Some 3,000 sq km of land has been razed.
• One of the fires is encroaching on a disused army range littered with unexploded bombs, though fire crews are confident they can tackle the blaze.
• Dozens of homes have been destroyed, but no-one is believed to have died.
• Wildfires plague Australia most years during the hot, dry summers.
• The worst fires in recent memory killed more than 170 people in early 2009.
• This year, a spell of record-breaking hot weather across the south-east has helped fan the fires.

'Tornadoes of fire'

• Tasmania was the first state to be affected, before fires broke out in New South Wales.
• Some blazes have also been reported in Victoria and Queensland.
• Officials said of some 120 fires in New South Wales, 17 remained uncontained, and more than 3,000 sq km (1,160 sq miles) of land has been destroyed.

• The worst blazes are in the state's south near Yass, Sussex Inlet and Cooma.

• In Cooma, there are at least 80 firefighting aircraft, 360 fire trucks and more than 1,000 RFS volunteers trying to contain the fires in the area, local reports say.

• Bushfires also continue to cause concern in Tasmania.

• A large blaze is still burning out of control by the Tasman peninsula, near areas already hit by major blazes over the weekend.
• More than 200 sq km of land and 120 homes have been destroyed

Temperatures have been so high the Australian Bureau of Meteorology has increased its temperature scale to 54 degrees, and added a new colour code.

• The fires follow days of searing heat.
• The national average maximum daily temperature exceeded 39C (102F) from 2-8 January, breaking a previous record of four consecutive days of such heat.
• Average national top temperatures on Monday of 40.33C set a new record.
• The bureau has added new colours to its forecast chart to indicate temperatures above the previous 50C limit because of the heatwave.
• It said extreme weather temperatures would continue in Australia for the next week.

The autumn of 2000 - September to November - was the wettest on record over England, Wales and Northern Ireland, as well as over the UK as a whole (in a series from 1914). Over Scotland it is the ninth wettest autumn in a series from 1914. There is an England and Wales rainfall series from 1766 and the value for autumn 2000 is the highest in this series.

The wet weather brought widespread flooding to England and Wales as rivers rose to record levels and burst their banks. The worst flooding was in mid-October and then from late October into early November. The disruption was compounded by some very strong winds at the end of October, damaging buildings, trees and power lines and cutting road and rail links.