Hurricanes (DP IB Geography)

Distribution of Hurricanes

• “Hurricane” is one of the names given to tropical storms:

  • Other names used for tropical storms include cyclones and typhoons

  • Storm names vary depending on the location in which they form

• Hurricanes form over waters in tropical or subtropical regions:

  • Hurricanes usually form in the Atlantic Ocean, the middle or northeast of the Pacific Ocean, the Caribbean Sea and the Gulf of Mexico

  • Hurricanes form in these regions as the waters are warmer

• Hurricanes tend to occur over the months of June – November

• The Pacific Ocean has the largest number of hurricanes per year

• More hurricanes occur in the northern hemisphere than in the southern hemisphere

Distribution of tropical storms

Formation of Hurricanes

• Hurricanes are low-air-pressure systems formed over oceans

• Hurricanes need warmer waters to form (minimum 27 degrees Celcius)

• Warm and moist air above the ocean rises upwards, leaving behind a pocket of low pressure underneath

• Cooler air moves into this low-pressure area, heats up and rises

• This air cools and condenses as it rises and releases heat energy, forming clouds and storms

• The Coriolis Effect causes a spinning action. Storms in a low-pressure system will spin clockwise in the southern hemisphere and anti-clockwise in the northern hemisphere

• As this process intensifies with more heat energy, winds will increase and the spinning will worsen

• Wind with low wind shear helps storm clouds rise straight upwards

• The centre of a hurricane is the eye:

  • This is a large area of low-pressure air that is colder and drier

  • It results in a calm centre inside the storm

• When hurricanes reach land or move over colder waters, they will lose energy and slow down

• The Saffir-Simpson scale shows the intensity of hurricanes, by measuring wind speed 

Formation of a hurricane

Impact of Hurricanes

• Hurricane paths are hard to predict. This makes it more difficult to prepare for and manage hurricanes

• Hurricane winds can rip up trees, cause airborne debris and damage infrastructure, e.g. homes, power lines etc.

• Hurricanes can cause a rise in the water level, resulting in storm surges. This can cause dramatic coastal flooding as the wind moves the water inland

• Flooding can occur inland as a result of heavy rainfall after the hurricane

• Hurricanes can affect boats and offshore oil/gas stations out on the ocean

Case Study: Hurricane Katrina

Case Study – Hurricane Katrina

• Hurricane Katrina was a category 5 hurricane that hit the Gulf Coast in 2005

• It formed over the Atlantic Ocean, building up to be one of the most deadly hurricanes in history

• It battered the areas of Florida, Mississippi and Louisiana, among others

The path of Hurricane Katrina as it hit the southwest coast of the US

Impacts of Hurricane Katrina

• Roughly 1833 people died with millions of people left homeless

• Damages cost roughly $300 billion 

• New Orleans was the worst hit area:

  • Storm surges caused intense flooding

  • Levees and floodwalls were not strong enough to deal with the Category 5 storm

  • This failure of flooding protection resulted in the dramatic loss of life

• Coastal erosion destroyed beaches

• Land and forests were destroyed, impacting habitats and ecosystems

• Residents were left stranded, causing tensions. This resulted in increased crime e.g. looting

• People did not have any electricity for up to a week

• Tourism was severely affected

• The hurricane affected the agriculture and oil/gas industry, negatively affecting the economy

Responses to Hurricane Katrina

• Evacuation during Hurricane Katrina was poorly planned:

  • Many underprivileged people were left stranded

• The US government provided $50 billion, whilst other countries sent aid relief 

• The Superdome (stadium) became a space for people to find shelter and food:

  • There were issues with food availability and unsanitary conditions 

• Eventually, repairs were made to the levees and floodwalls, however, it took many months until the water was gone

• Many people living back in New Orleans cannot get home insurance or have to pay very high premiums as a result of hurricane risk