9.3. Hurricanes Flashcards
Tropical Storms
A tropical storm is a low-pressure system up to 600km in diameter with wind speeds of up to 300km/h (typically
160km/h) and bringing up to 30–50cm of rainfall.
- a generic term that includes hurricanes (North Atlantic),
cyclones (Indian Ocean and the Bay of Bengal) and typhoons (Japan).
Types of Tropical Storms
1) Hurricanes
2) Cyclones
3) Typhoons
Hurricanes
Tropical storms in the Pacific and Carribbean Sea
Cyclones
Tropical storms in the Indian Ocean
Typhoons
Tropical storms in the South China Sea
Tropical Storm Features
1) Eye
2) Eyewall
3) Rainbands
Conditions for formation of Tropical Storms
- Sea temperatures over 27 degrees celsius to a depth of 60m (warm water gives off large quantities of heat when it is condensed - this is the heat which drives the tropical storm)
- Low-pressure area has to be far enough away from the equator so that the Coriolis force (force caused by rotation of the Earth) creates sufficient rotation in the rising air mass
Saffir-Simpson scale description
- 1 to 5 scale based on a hurricane’s sustained wind speed
- the scale estimates potential property damage
- tropical storms with category 3 and higher are considered major tropical storms because of their potential for significant loss of life and damage
Category 1 on Saffir-Simpson scale
- Winds 119-153 km/h
- Storm surge generally 1.2-1.5 km above normal
- No real damage to building structures
Category 3 on Saffir-Simpson scale
- Winds 178-209 km/h
- Storm surge generally 2.7-3.6 km above normal
- Some structural damage to small residences and utility buildings
- Mobile homes destroyed
Category 5 on Saffir-Simpson scale
- Winds greater than 249 km/h
- Storm surge generally greater than 5.5 km above normal
- Complete roof failure on many residences and industrial buildings
- Some complete building failures
Eye of a storm
- centre of the storm
- very low pressure, with calm air (Coriolis Effect) spins the cloud away from the centre
- 20-40 miles across
- no rain
Eyewall of a storm
- dense wall of thunderstorms surrounding the eye has the strongest winds within the storm
- changes in the structure of the eye and eyewall can cause changes in the wind speed, which is an indicator of the storm’s intensity
- the eye can grow or shrink in size, and double eyewalls can form
Spiral Rainbands of a Storm
- storm’s outer rainbands can extend a few hundred miles from the centre
- Spiral clockwise in the southern hemisphere. Spiral anticlockwise in the northern hemisphere
Hazards of Tropical Storms
1) High Winds
2) Storm Surges and Coastal Flooding
3) Intense Rainfall
4) Mass Movement