Hurricanes If these huge tropical storms start in the Atlantic off the west coast of Africa, they are called hurricanes. Over a dozen hurricanes form over the Atlantic Ocean and head westwards towards the Caribbean, the east coast of Central America and the southern USA (Florida in particular) every year. Hurricanes may last as long as a month and although they travel very slowly - usually at about 24 km/h (15 mph) - wind speeds can reach over 120 km/h (75 mph). Hurricanes need a lot of heat to form and a sea surface temperature of at least 26C, which is why they usually occur over tropical seas. They also need to be between 5 and 20 north or south of the equator.

How hurricanes form1. When this warm and wet air rises, it condenses to form towering clouds and heavy rainfall. It also creates a low-pressure zone near the surface of the water. 2. Rising warm air causes the pressure to decrease at higher altitudes. Warm air is under a higher pressure than cold air, so moves towards the space occupied by the colder, lower pressure, air. So the low pressure sucks in air from the warm surroundings, which then also rises. A continuous upflow of warm and wet air continues to create clouds and rain.3. Air that surrounds the low pressure zone at the centre flows in a spiral at very high speeds - anti-clockwise in the northern hemisphere - at speeds of around 120 km/h (75 mph).4. Air is ejected at the top of the storm which can be 15km high and falls to the outside of the storm, out and over the top, away from the eye of the storm. As this happens, it reduces the mass of air over the eye of the storm - causing the wind speed to increase further. Some ejected air also cools and dries, and sinks through the eye of the storm, adding to the low pressure at the centre.5. The faster the winds blow, the lower the air pressure in the centre, and so the cycle continues. The hurricane grows stronger and stronger.6. Seen from above, hurricanes are huge circular bodies of thick cloud around 450 km (300 miles) wide. The cloud brings heavy rain, thunder and lightning.7. In the centre is the eye of the hurricane, about 45 km across (30 miles) across. Often there will be no clouds in the eye. Seen from below it will seem calmer, with a circle of blue sky above. The eye is formed because this is the only part of the hurricane where cold air is descending.8. In the northern hemisphere, the prevailing easterly tropical winds tend to steer hurricanes toward land - although their course is unpredictable. As hurricanes move inshore, their power gradually reduces because their energy comes from sucking up moist sea air.

MEDC disaster: MEDCs are better placed to reduce the effects of tropical storms More financial, educational and technological resources to deal with them Able to observe and predict storm behavior Able to invest infrastructure to withstand storms as well as spending more money on repairing the damage caused

Response to Hurricane Katrina: August 26, 2005, both Louisiana and Mississippi activated their emergency response plans and began preparations for evacuations along the coast. Most people (85%) evacuated from coastal Mississippi and Louisiana. Those who did not were unable to for medical reasons or had limited access to transportation. An evacuation order was issued but many of the poorest people remained in the city as they did not have the financial means to leave More than 18000 cars left/hour Around 1.2 million people evacuated the metropolitan New Orleans region and that about 100,000 people remained in New Orleans. Of those remaining, around 10,000 went to the Superdome shelter before the storm. People sought refuge in the Superdome stadium but the conditions were unhygienic and there was a lack of food and water Although many people evacuated, it was a slow process and the poorest and most vulnerable were left behind $50 billion aid was given by the government UK government send food aid during the early stages of the recovery process The National Guard was mobilized to restore and maintain law and order in what became a hostile and unsafe living environment Search and rescue began after Katrina hit New Orleans But later, communications were so badly destroyed that the rescue operations had to be stopped

Impacts of Hurricane Katrina: From August 23rd to August 30th, 2005 Katrina is the costliest U.S hurricane, with estimated damage over $81 billion and costs over $160 billion (2005 US dollars). 1800 fatalities, 200,000 home destroyed and 800,000 displaced, Louisiana, Florida, Mississippi Overall was a category 4 storm although it was, for a while a category 5 hurricane warning days in advance, predicted as a level 2 hurricane, turned into a level 5 over night The winds of tropical storms generate abnormally high waves and tidal surges. Due to the large size of the storm, there was a large wind field with maximum winds likely extending up to 55km from the center. The storm surge along the Mississippi coast was between 7 and 8.5metres. The surge went as far inland as 9.7km from the coast and 19km at bays and rivers. Additionally, more than 203mm to 254mm of rain fell across large parts of Mississippi and Louisiana along and to the west of the track. The most destructive elements of a storm are the subsequent high seas and flooding New Orleans was the worst affected as it lies below the sea level and although it was protected by levees (used for protection against the Mississippi river and Lake Ponchartrain), the levees broke and thus 80% of the city was flooded oil facilities were damaged and petrol prices rose in the UK and the USA

Secondary impacts of Hurricane Katrina: Looting was common throughout the city Many people felt vulnerable and unsafe When the waves and storm surge hit the coastline, structures along the coast in Mississippi were destroyed and further inland experienced catastrophic flooding. In New Orleans, the combination of surge and waves lead to the destruction of the levee system which lead to flooding 80% of New Orleans to depth above metres in some places. Since the city of New Orleans is mostly below sea level, and most of the pump stations used to remove rain water from the city were disabled by the storm, the water stayed in the city. In New Orleans, people were trapped in their houses and stranded on their roofs as the rapidly rising water caught many people by surprise. The flooding and widespread damage from Katrina delayed rescue and aid efforts for days. left many people homeless as more than 800,000 housing units were destroyed or damaged in the storm. Vulnerability: The African Americans were more vulnerable as a result of segregation in the past. They lived in inadequate housing to protect themselves 51% of fatalities in Louisiana were African Americans In New Orleans, 25.7% below poverty line compared to a 18.4% nation wide Although there are man-made levees and floodwalls, Hurricane Katrina proved that they were not strong enough to withstand the forces of nature So with the imminent threat of global warming, people are advised to move away from New Orleans The effects of Katrina on the coastal communities of Louisiana, Mississippi and New Orleans are still seen up to 5 years after the disaster