Hurricanes: A hurricane is a large low pressure system characterised by high winds and heavy rain. Hurricanes are also known as typhoons in East and South-east Asia and cyclones around the Indian Ocean. To be classified as a hurricane, winds must exceed 119km/hr (74 mph). Small low pressure systems are called tropical storms (63-118km/hr) and tropical depressions (0-62km/hr).
Distribution of Hurricanes
Hurricanes are mainly found between the tropics. Because hurricanes obtain their energy from the sea, they are found in coastal areas. The main hurricane hotspots are:
The Caribbean, Central America and Southern US
SE and E Asia e.g. Japan, China, Indonesia and the Philippines
Northern Australia
Bay of Bengal e.g. India and Sri Lanka
East Africa and the Southern Arabian Peninsula e.g. Oman and Kenya.
It is possible for hurricanes to form and travel from these main locations but it happens very rarely.
Location of Hurricanes 1950-2000
Hurricane Formation and Location of Hurricanes
Hurricanes are intense low pressure systems that develop over warm tropical seas. Because hurricanes form at sea and are extremely dangerous, there development is not fully understood. What is known is that they gain their energy from warm water. The conditions needed for hurricanes to develop are:
Warm waters. At least 27 degrees centigrade to a depth of 60 metres.
The low pressure has to be sufficiently further enough away from the equator for the Coriolis force to create a hurricanes circular motion.
There has to be low pressure systems (depressions) that have the potential to grow. Less than 10% of tropical disturbances turn into hurricanes.
Hurricanes can turn into massive systems up to 800km wide, but the intense storm around the eye rarely exceeds 300km. Because hurricanes need warm water to develop they normally occur towards the end of the summer. Hurricanes are associated with very intense winds and heavy rainfall. The winds are generated by the difference in pressure between the eye (very low pressure) and the edge of hurricane (higher pressure). The high winds and heavy rainfall can also create a number of secondary hazards like storm surges, flooding and landlsides.
Because of the conditions needed for storms to develop (warm seas) it means that storms are only found in warm tropical areas - ideally over warm shallow seas like the Caribbean. Once hurricanes hit land, they lose their source of energy and lose their strength very quickly.
Hurricane Hazards and Key Terminology
The Eye: The centre of a hurricane is called the eye. As the eye moves overhead conditions can turn temporarily calm.
Landfall: The location that the storm hits the coast (land).
Formation: The location a hurricane is created.
Dissipation: Where a hurricane breaks up and loses strength.
Primary Hazards
Wind: Hurricanes are associated with strong winds. To be classified as a hurricane wind speed has to exceed 74mph (119 km/hr)
Rain: Because hurricanes suck up large amount of energy and moisture from the sea, they are associated with intense rainfall, up to 500mm in 24hours.
Secondary Hazards
Landslides: Because hurricanes bring very intense rainfall, they can cause hillsides to become saturated very quickly increasing the stress on them and the likelihood of landslides.
Flooding: The intense rainfall can also cause severe flooding. The rainfall may also be combined with a storm surge making the flooding worse.
Storm Surges and Heavy Seas: Because of the friction between the wind and the surface of the water, large waves can be created. Also the hurricane can literally drag water in land, causing coastal flooding. Storm surges can be especially bad if they coincide with high tides (especially spring tides).
Predicting and Measuring Hurricanes
Because hurricanes form at sea, meteorologists do have the chance to try and predict the movement of hurricanes (track hurricanes). However, hurricanes are enormously unpredictable an calculated courses can vary by hundreds of kilometers. Therefore even though stretches of coastlines can be put on general warnings, the exact landfall may not be known until 12 hours prior. This short period gives authorities and residents a much shorter time to evacuate.
The National Hurricane Centre in the US predicts and tracks storms in the Caribbean region. You can look at current storms on their website:
Hurricanes are normally measured by using the Saffir-Simpson Hurricane Scale developed by the National Oceanic and Atmospheric Administration. Hurricanes are measured on a scale of 1-5 depending on their wind speed and storm surge.
However, it must be noted that category five storms don't always cause the most damage. The amount of damage caused by hurricanes can depend on a number of factors including:
Where landfall is (populated or non-populated area)
The development of the country
The warning given to residents and the preparedness of residents.
The existing conditions (saturated ground or not)
The timing of landfall (high tide or low tide)
However, even developed country's like the US can suffer massive damage. Hurricane Katrina which was category 5 caused widespread damage and loss of life despite warning and defences.
For information about Hurricane Katrina and Cyclone Nargis go to: Measuring Disasters
Hurricanes (typhoons, cyclones, tropical storms)
Hurricanes: A hurricane is a large low pressure system characterised by high winds and heavy rain. Hurricanes are also known as typhoons in East and South-east Asia and cyclones around the Indian Ocean. To be classified as a hurricane, winds must exceed 119km/hr (74 mph). Small low pressure systems are called tropical storms (63-118km/hr) and tropical depressions (0-62km/hr).
Distribution of Hurricanes
Hurricanes are mainly found between the tropics. Because hurricanes obtain their energy from the sea, they are found in coastal areas. The main hurricane hotspots are:
It is possible for hurricanes to form and travel from these main locations but it happens very rarely.
Hurricane Formation and Location of Hurricanes
Hurricanes are intense low pressure systems that develop over warm tropical seas. Because hurricanes form at sea and are extremely dangerous, there development is not fully understood. What is known is that they gain their energy from warm water. The conditions needed for hurricanes to develop are:
Hurricanes can turn into massive systems up to 800km wide, but the intense storm around the eye rarely exceeds 300km. Because hurricanes need warm water to develop they normally occur towards the end of the summer. Hurricanes are associated with very intense winds and heavy rainfall. The winds are generated by the difference in pressure between the eye (very low pressure) and the edge of hurricane (higher pressure). The high winds and heavy rainfall can also create a number of secondary hazards like storm surges, flooding and landlsides.
Because of the conditions needed for storms to develop (warm seas) it means that storms are only found in warm tropical areas - ideally over warm shallow seas like the Caribbean. Once hurricanes hit land, they lose their source of energy and lose their strength very quickly.
Hurricane Hazards and Key Terminology
The Eye: The centre of a hurricane is called the eye. As the eye moves overhead conditions can turn temporarily calm.
Landfall: The location that the storm hits the coast (land).
Formation: The location a hurricane is created.
Dissipation: Where a hurricane breaks up and loses strength.
Primary Hazards
Wind: Hurricanes are associated with strong winds. To be classified as a hurricane wind speed has to exceed 74mph (119 km/hr)
Rain: Because hurricanes suck up large amount of energy and moisture from the sea, they are associated with intense rainfall, up to 500mm in 24hours.
Secondary Hazards
Landslides: Because hurricanes bring very intense rainfall, they can cause hillsides to become saturated very quickly increasing the stress on them and the likelihood of landslides.
Flooding: The intense rainfall can also cause severe flooding. The rainfall may also be combined with a storm surge making the flooding worse.
Storm Surges and Heavy Seas: Because of the friction between the wind and the surface of the water, large waves can be created. Also the hurricane can literally drag water in land, causing coastal flooding. Storm surges can be especially bad if they coincide with high tides (especially spring tides).
Predicting and Measuring Hurricanes
Because hurricanes form at sea, meteorologists do have the chance to try and predict the movement of hurricanes (track hurricanes). However, hurricanes are enormously unpredictable an calculated courses can vary by hundreds of kilometers. Therefore even though stretches of coastlines can be put on general warnings, the exact landfall may not be known until 12 hours prior. This short period gives authorities and residents a much shorter time to evacuate.
The National Hurricane Centre in the US predicts and tracks storms in the Caribbean region. You can look at current storms on their website:
National Hurricane Center
Hurricanes are normally measured by using the Saffir-Simpson Hurricane Scale developed by the National Oceanic and Atmospheric Administration. Hurricanes are measured on a scale of 1-5 depending on their wind speed and storm surge.
However, it must be noted that category five storms don't always cause the most damage. The amount of damage caused by hurricanes can depend on a number of factors including:
However, even developed country's like the US can suffer massive damage. Hurricane Katrina which was category 5 caused widespread damage and loss of life despite warning and defences.
For information about Hurricane Katrina and Cyclone Nargis go to: Measuring Disasters