1. The Atmosphere B6: Storms

2. Storms Storm – A violent disturbance in the atmosphere as the result of sudden changes in air pressure and rapid air movement – Conditions that bring one kind of storm can often cause other types of storms in the same area – Example – conditions that cause thunderstorms can also cause tornados

3. Thunderstorms Thunderstorm – A storm frequently accompanied by heavy precipitation, thunder, and lightning – Formation – Form in cumulonimbus clouds usually in hot, humid weather – They also form when warm air is forced upward along edge of a cold front

4. Thunderstorms – In both cases, warm, humid air rises rapidly – Inside the thunderheads, drastic changes in air pressure cause strong updrafts and downdrafts – The air cools forming dense thunderheads – Heavy rain falls, sometimes along with hail – Lightning – A powerful, sudden discharge of electricity within a thundercloud – As water droplets move within the cloud, collisions occur knocking electrons free

5. Lightning – These collisions create positively and negatively charged areas within the cloud – An electrical field builds between the charged areas – As the fields gather strength, the air around them become ionized – This leads to a sudden, powerful electrical discharge called lightning – The discharge can occur within a cloud, between clouds, or between a cloud and the Earth

6. Thunder – Thunder – the sound created when lightning discharges – A lightning bolt can heat the air around it to as much as 30,000 o C which is much hotter than the sun – This rapidly heated air expands suddenly and explosively – Thunder is the sound of the explosion – Since light travels faster than sound, you can see the lightning before you hear the thunder

7. Thunderstorms – Thunderstorm Damage – Can cause severe damage – Floods – Heavy rains can cause flooding in low-lying areas – When lightning strikes the ground it can damage trees and structures in addition to starting fires – When lightning strikes people or animals it can cause burns or even death – Floods occur when too much water pours into a stream or river, causing it to overflow its banks.

8. Floods – The new water cannot soak into the ground causing it to build up on top – Areas where the ground has been covered by buildings, road, and parking lots make this problem even worse – Floods can also occur when it rains in areas where the ground is already saturated – Flash Flood – is a sudden, violent flood that occurs shortly after a storm

9. Tornadoes – Formation – Most commonly develop in the same thick cumulonimbus clouds that produce thunderstorms Tornado – Rapidly spinning funnel-shaped cloud that reaches down from a storm cloud to touch Earth’s surface

10. Tornadoes – Warm, moist air flows in at the bottom of a cumulonimbus cloud and moves upward – A low pressure area forms inside the cloud – The warm air begins to rotate as it meets winds blowing in different directions at different altitudes – Forms a spinning funnel inside the cloud with very strong winds – If the funnel touches the ground, it becomes a tornado

11. Tornadoes – Tornado Alley – Tornadoes occur more often in the U.S. than in any other country. – About 800 tornadoes occur in the U.S. every year, most of which form in the Great Plains in an area known as ‘Tornado Alley’ – Tornado Damage – Damage is a result of both strong winds and flying debris – The low pressure inside the tornado sucks dirt and other objects into it

12. Tornadoes – Can pick up large objects like sheds, trailers, cars, and debris and deposit it miles away – The damage is unpredictable, destroying 1 house but leaving a house across the street undamaged – Scale – Tornadoes are ranked on the Fujita scale by the damage they cause – Scale starts at F0 where little damage occurs To an F5 with extreme damage over a large area

13. Hurricanes – A typical hurricane is about 300 miles across Hurricane – Tropical cyclone that has winds of 70 miles an hour or greater – Formation – Hurricanes begin over warm ocean water as a low-pressure area or tropical disturbance – As warm, humid air from the ocean’s surface rises it forms clouds – As more air is drawn into the system, bands of high wind and heavy rains form

14. Hurricanes – Winds begin to spiral inward towards the area of lowest pressure at the center – The lower the air pressure at the center, the faster the winds – Winds are strongest in a narrow band around the center of the storm in a ring called the eyewall – Inside the eyewall, the ‘eye’ of the storm is calm

15. Hurricanes – Movement – Hurricanes can last for weeks and travel over large distances – Form over the ocean and are pushed along by the trade winds towards the Caribbean and U.S. – When it passes over land, it looses the warm moist air that fuels it, and gradually weakens

16. Hurricanes – Damage – Most of the damage is caused by high winds and severe flooding – High winds damage trees and buildings creating debris that becomes flying missiles – Storm Surge – a dome of water created by a hurricane that sweeps across coast lines

17. Predicting Weather – In the mid 1800’s the electric telegraph provided the first real improvement to weather forecasting – Allowed data to be swiftly gathered and analyzed by experts Predicting Weather – Has often been a tragic failure for most of history – By the 1930’s the weather bureau had created a network of weather observers taking readings – Used weather balloons – at first they could only tell wind direction and velocity

18. Predicting Weather – Later, with radios attached, the balloons could report conditions up to 15 miles high – Slow – It took the computers 24 hours to simulate a 24 hour forecast – In 1950, the first computers were used to simulate weather patterns – For the first time forecasters could see the interactions of weather systems worldwide – The first dramatic improvement came with weather satellites in the 1960’s

19. Predicting Weather – Today, vast networks of satellites, sea buoys, and weather balloons gather data all over the world – More advances computers analyze the data faster and create more accurate weather models – However, the models must still be interpreted and the science behind it is still young

20. Predicting Weather – In addition, the models cannot always account for all the factors that might affect the forecast – Small variations can result in very different models using the same data How many times have they predicted a storm and we all hoped for a snow day that didn’t happen?

21. In Closing – Why is it important to understand and be able to predict weather patterns?