Hurricanes (DP IB Geography)
Revision Note
Written by: Grace Bower
Reviewed by: Bridgette Barrett
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
Examiner Tips and Tricks
Make sure you are aware of how climate change could impact the intensity of hurricanes. What happens if waters further from the equator start to get warmer?
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
Examiner Tips and Tricks
Remember, hurricanes need a perfect balance of several conditions to form. Just because the water is warm, doesn’t mean a hurricane will develop. It requires a combination of different factors.
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
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