Thunderstorms Has lightning, thunder, heavy rain and sometimes hail Need two conditions: Moisture to form clouds and precipitation Strong lifting of air to make clouds that reach high in the atmosphere.
Thunderstorms Cont’d Low temperature at high altitude creates a large temperature difference with the warm air that is lower. The warm air rises quickly because of this temperature difference. Water vapour rises and hits the cold air where it condenses making clouds. Once the clouds are heavy enough rain falls in the downdrafts.
Tornadoes Because of their extremely high winds tornadoes can cause more damage in a short time than any other storm on Earth. Tornadoes are a severe component of a thunderstorm. It is very difficult to predict their path or even exactly where they are going to occur.
Tornadoes cont’d Fast rising air in a thunderstorm sometimes begins to spin forming a funnel of air and moisture. Rising air is replaced by cooler air which increases rotation. The funnel cloud produces a pressure difference that can pick objects up. Wind speed can be as high as 500 km/h.
Flash Floods Little or no warning. Can happen in cities if the water can’t drain fast enough. Happens more when mountain valleys or gorges can’t accommodate spring rain and melting snow. Can also occur when a dam bursts or overflows
Broadside Floods Can cover large areas of land for months. Can be predicted days or weeks before. Causes: Rivers flood from mountain snow melting. Winter of heavy snowfall followed by rainy spring. More rain than normal so soil becomes saturated. Tropical storms bring lots of rain.
Hurricanes, Typhoons and Tropical Cyclones Same type of storm just located in different places of the world. Has to be near the equator where the water surface temperature is high enough (about 27ºC) Happen when cyclones become large enough. If wind speed is 63km/h its called a tropical storm; if wind speed is 119km/h its called a hurricane. Typhoons and tropical cyclones can be worse than hurricanes.
Hurricane: western Atlantic Ocean, Caribbean Sea, Gulf of Mexico or eastern Pacific Ocean Typhoon: northwestern Pacific Ocean or China Sea Tropical Cyclone: Australia area or Indian Ocean
Hurricane Development Warm air above warm water rises quickly carrying moisture with it. As this air reaches higher altitude the water vapour condenses releasing heat and increasing speed of rising air. Rising air creates a low pressure area that cool dry air moves into. Cool air at the top also swirls outward and back down to be warmed again.
Hurricanes cont’d The core of the hurricane is called the eye. The eye is the low pressure area that is calm with clear skies. Hurricanes can carry lots of rainfall inland creating floods and destruction.
Blizzards Severe snow storm with strong winds and low temperatures. Winds must exceed 55km/h and visibility must be less than 0.5km. Blizzards develop similarly to thunderstorms but with snow because of the cold temperatures. What are some dangers of blizzards?