Extreme Weather: Hurricanes

Hurricanes Aims: To be able to describe where Hurricanes form and explain why they form in these locations. Explain what they need to occur and makes them more likely. Revise the Impacts and Responses to Hurricane Katrina

What is Hurricane? What is a Tropical Storm or Cyclone?

Hurricanes are Tropical Storms What are Tropical Storms? Tropical Storms are areas of extreme low pressure. This means air is rising, causing 'low pressure' on the earth's surface. This generates High Winds. The maximum sustained surface wind speed ranges from 34 knots (39 mph or 63 kph) to 63 knots (73 mph or 118 kph).

The strongest tropical storms are called hurricanes, typhoons or tropical cyclones. The different names all mean the same thing, but are used in different parts of the world. If these huge storms start in the Atlantic, off the west coast of Africa, they are called hurricanes. Tropical storms have different names according to where they form. Each one is then given it’s own name so it can be tracked by meteorologists to forecast where they will travel and warn people of the hazards they could cause.

Where do Tropical Storms form?

How Do Tropical Storms like Hurricanes form?

Why do Hurricanes form here?

Add illustrations to help describe each point!

What conditions are needed for hurricanes to form? Tropical Storms start within 8º and 15º north and south of the equator (not on the equator) and between the tropics where surface sea temperatures reach 26/27ºC. The air above the warm sea is heated and rises. This causes low pressure. Sea depths of at least 50 metres

This pushing causes the clouds to spin. Warm water heats the air causing it to rise really quickly, then it gets pushed aside as it cools. This pushing causes the clouds to spin. When does it become a hurricane and no longer a tropical storm? Hurricanes are tropical storms where the winds get faster than 118 km/h (73 mph). The storms have a central area of calm known as the "eye", which is the funnel through which the warm air rises and cold air sinks. Overland, the storms no longer have warm water to power them and die out within a few days, but not before winds do a lot of damage.

A. The Coriolis Effect! Q. Why do they spin? The rotation (spin) of the earth “bends” the winds to the right in the Northern hemisphere and left in Southern hemisphere. This causes tropical storms to spin. Watch this clip from the BBC’s Orbit: Earth's Extraordinary Journey. It helps to explain how hurricanes form and are made to spin by the Coriolis effect… https://www.youtube.com/watch?v=i2mec3vgeaI&spfreload=10

How do hurricanes form? What do they need? How do tropical storms form? Hurricanes need a lot of heat to form, which is why they usually occur over tropical seas (at least 27°C). Tropical storms usually form between approximately 5° and 30° latitude and move westward due to easterly winds The sun is close to the equator, providing energy to heat the ocean. The warm ocean heats the air above it causing it to rise rapidly. Water evaporates quickly from the hot surface of the ocean, so the rising air contains great amounts of water vapour. The rising air starts to spin (clockwise in the northern hemisphere). The Coriolis force sends them spinning towards the poles. The centre of the storm - the eye - is calm. As the air rises it cools, condenses and forms towering cumulonimbus clouds. The rapidly rising air creates an area of intense low pressure. The low pressure sucks in air, causing very strong winds. Once the storm moves over land it starts to lose energy and fades.

Key points for the formation of tropical storms… Oceans must reach temperatures of 26/27oC – Sea temperature creates rapid evaporation and creates a lot of energy/deep low pressure system, therefore causing a Tropical storm. The earth’s spinning (Coriolis effect) causes air movement to be circular, this starts the spinning towards the centre of the storm. They need to be above oceans as Tropical storms get their energy for the warm oceans including the moisture needed for the storm, when they hit land they start to lose that energy and are no longer tropical storms.

What causes Tropical Storms like Hurricanes to spin?

What are Hurricanes typhoons and tropical cyclones? For this activity you will watch a video clip, make notes from the clip. Click link above for the video clip

Exam question preparation Describe the location of where tropical storms form (3 marks). Explain why Tropical Storms occur in these parts of the world (3 marks).

Where do Tropical Storms form? Tropical storms form between approximately 5° and 23.5° latitude North or South of the equator.

Would global warming have an impact on Tropical Storms? Increase in sea surface temperatures. If they were to increase above 27oC then they are more likely to allow Tropical Storms to develop. Wider area of sea surface to develop Tropical Storms. Therefore Tropical Storms can become larger and this will increase their magnitude and the damage that they cause. Also due to wider areas more Tropical Storms might occur.

The causes and effects Creating a case study

A reason or explanation for why something has happened Key terms and definitions – Hurricanes have huge impacts on people’s lives as a result of their power and energy. Knowing key words and definition – It is important that you understand and know what key terms mean when asked to answer questions – Match up and write these down - The natural world or surroundings in which people live and things people might need to survive The result of an action or hazard – this might happen straight away (short term) or in the near future (long term) Effects Cause A reason or explanation for why something has happened Related to people and day to day living, for example housing, jobs or families Economic Based around money, employment and industry. For example destruction and insurance. Environmental Social

Case Study: Hurricane Katrina Hurricane Katrina was a devastating storm that hit the area around New Orleans, USA, on 25 August 2005. It had social, economic and environmental impacts. New Orleans is in the United States of America. The USA is a Most Economically Developed Country.

Click link to the left for the video clip on some economic problems Katrina 25 August 2005 Katrina was a category 4 storm. Storm surges reached over 6 metres in height. New Orleans was one of the worst affected areas because it is below sea level and protected by levees. These protect it from the Mississippi River and Lake Ponchartrain. The levee defences were unable to cope with the strength of Katrina, and water flooded into the city. Despite an evacuation order, many of the poorest people remained in the city. People sought refuge in the Superdome stadium. Conditions were unhygienic and there was a shortage of food and water. 1 million people were made homeless. and about 1,200 people drowned in the floods. Oil facilities were damaged and as a result petrol prices rose in the UK and USA. Looting was commonplace throughout the city. Tension was high and many felt vulnerable and unsafe. Click link to the left for the video clip on some economic problems

Using the statements: Are they causes, social effects, economic effects or environmental effects?

Using the statements: Are they causes, social effects, economic Effects or environmental effects?

Measuring a Hurricane – Saffir-Simpson Scale

What Impacts did Hurricane Katrina have? Social impacts of the hurricane (effects on people) 1,800 people died. 300,000 homes were destroyed. 3 million people were left with no electricity. People had to move out of the area. Economic impacts of the hurricane (effects on money and jobs) $300 billion of damage. Oil platforms were destroyed. Shops were looted. Fuel prices rose. Tourism decreased. Environmental impacts of the hurricane The storm surge flooded large areas of the coast. 80% of New Orleans flooded as man-made levees (Embankments used as flood defences). overwhelmed by extra water, broke. Cotton and sugar cane crops were destroyed. Delicate coastal habitats were destroyed. Tornadoes were created.

Responses to the Disaster There was much criticism of the authorities for their handling of the disaster. Although many people were evacuated, it was a slow process and the poorest and most vulnerable were left behind. $50 billion in aid was given by the US government. The UK government sent food aid during the early stages of the recovery process. The soldiers from the US National Guard were mobilised to restore and maintain law and order in what became a hostile and unsafe living environment.

Hurricane Katrina Day by Day Watch this national Geographic video clip telling the story of Hurricane Katrina. You will need to complete the diary extract on what happened

What is hurricane Katina doing? Response? What are people doing? Day Wednesday 24th August Thursday 25th August Friday 26th August Saturday 27th August Sunday 28th August Monday 29th August Tuesday 30th August Wednesday 31st August Thursday 1st September Friday 2nd September Aftermath What is hurricane Katina doing? Effects and problems? Response? What are people doing?

How might you immediately respond to a Tropical Storm? Temporary hospital Tents Clean water Infra-red Helicopters Choose two and explain why you think this will help people immediately after the tropical storm. Mark Scheme: Temporary hospital – Quicker treatment for people who were injured (1)/ less people die from the storm (1) Tents (1)– Provide shelter to displaced people (1) / So they are protected from the weather (elements) (1) Clean water kits(1) – As water is likely to be contaminated (1)/It will prevent the spread of water borne diseases(1) Infra-red cameras(1) – To find people trapped in collapsed buildings (1) …….. Helicopters(1) – Roads are likely to be blocked so therefore (1)

Documentaries: https://www.youtube.com/watch?v=Cp1RWhYQdCE https://www.youtube.com/watch?v=4Fhc0oWxF1Q