GCSE Geography | How are Tropical Storms Measured? (Weather Hazards 7)
- AQA, OCR
Last updated 19 Jul 2023
The Saffir-Simpson Scale is used to measure the wind strength of tropical storms - the higher the category scale, then the more intense the tropical storm will be (and the stronger the wind).
The scale was simplified in 2012 - previously it included information on storm surge height, flooding impact and air pressure. However, storm surges and flooding are affected by local conditions as well as wind speed, so it was seen as a not very helpful way to compare tropical storms. It now just takes wind speed into consideration.
Category 1 - 74-95 mph (119-153 kmph)
Category 1 storms will cause minor damage to the roofs, guttering and facias of well-constructed buildings. Large branches of trees may snap off and some trees with shallow roots may topple over. The winds will cause some power lines and poles to come down, meaning that people could be without electricity for several days.
Category 2 - 96-110 mph (154-177 kmph)
Category 2 storms will cause major damage to roofs and sides of well-constructed buildings. Many trees with shallow roofs will fall down, causing blockages of roads and railway lines. The winds will bring down many power lines and poles causing widespread electricity blackouts which could last for weeks.
Category 3 - 111-129 mph (178-208 kmph)
Category 3 storms will cause major structural damage to well-constructed buildings, such as the roof being ripped off and gable ends collapsing. There will be widespread uprooting of trees, blocking transport routes. Electricity cables and water pipes will be destroyed, leaving people without electricity or clean water for a significant period of time.
Category 4 - 130-156 mph (209-257 kmph)
Category 4 storms will cause severe damage to well-constructed buildings, such as loss of the roof and exterior walls. Most trees will be uprooted and most electricity poles will be brought down - both blocking roads and cutting off power supplies for weeks - isolating residential areas. Widespread flooding and destruction will make most of the area uninhabitable for weeks or months.
Category 5 - 157+ mph (252+ kmph)
Category 5 storms will cause widespread destruction of buildings, including those made of steel frames - roofs will be destroyed and walls will collapse. Nearly all trees and electricity posts will be uprooted meaning that communities will be cut off and without power for weeks, maybe months. Widespread flooding and destruction will make most of the area uninhabitable, and most people will have to be evacuated and housed in temporary accommodation for weeks or months.