Thunderstorms

1. Thunderstorms 2009

2. Storms • A violent disturbance in the atmosphere. • Involve sudden changes in air pressure, which cause rapid air movement.

3. Thunderstorms • Heavy rainfall with thunder and lightning. • Form within cumulonimbus clouds. • Warm air rapidly rises, causing updrafts that bring moisture to the tops of the cloud. • The moisture condenses, and eventually forms rain.

4. Thunderstorms need three things: Moisture - to form clouds and rain. Unstable Air - relatively warm air that can rise rapidly. Lift - fronts, sea breezes and mountains are capable of lifting air to help form thunderstorms. TS Ingredients

5. When Do Ts Occur? • Most likely to occur in the spring and summer months and during the afternoon and evening hours. • Can occur year-round and at all hours of the day or night. • Along the Gulf Coast and across the southeastern and western states, most thunderstorms occur during the afternoon. • Thunderstorms often occur in the late afternoon and at night in the Plains states.

6. Thunderstorms affect small areas when compared with hurricanes and winter storms. The typical thunderstorm is 15 miles in diameter and lasts an average of 30 minutes. Nearly 1,800 thunderstorms are happening at any moment around the world. Facts

7. Life Cycle of thunderstorms • All thunderstorms, whether or not they become severe, progress through a life cycle which may be divided into three main stages

8. Developing Stage • Moist air, heated by the sun, rises which causes an updraft of air. • As warm air rises, it cools and forms clouds. As the water vapor condenses it gives its energy to the surrounding air, making it warmer and causes it to rise more. This energy powers the thunderstorm. • Usually little if any rain during this stage. • Lasts about 10 minutes • Occasional lightning

9. Mature Stage • Most likely time for hail, heavy rain, frequent lightning, strong winds, and tornadoes. • Storm occasionally has a black or dark green appearance • Lasts an average of 10 to 20 minutes but may last much longer in some storms.

10. Dissipating Stage • Rainfall decreases in intensity • Can still produce a burst of strong winds • Lightning remains a danger • When the downdrafts in the cloud begin to dominate over the updrafts, this happens • Since warm moist air can no longer rise, cloud droplets can no longer form • The storm dies out with light rain as the cloud disappears from bottom to top

11. Thunderstorm Stages

12. Single-cell Thunderstorm • A single, isolated thunderstorm • Have a lifespan of about 30 minutes • Are not very severe • Very rare and occur randomly • Are difficult to forecast

13. Multi-cell Cluster Storms • Are the most common type of thunderstorms • Occur in a group • Persist for a few hours • Produce modern size hail • Weak tornadoes occur during this storm

14. Multi-cell Line storm • Consists of long line thunderstorms usually associated with fronts. • Can produce hail the size of golf balls • Weak tornadoes • Can easily be predicted with the help of radar

15. Super Cell • Although rare, highly organized thunderstorms • Pose of high threat to life and property, as these can produce strong to violent tornadoes

16. Friction between updrafts and downdrafts cause electrons to be stripped from some atoms and given to others. Just like walking across a carpet in your socks. So the clouds develop charges. Lightning is the spark when the discharge occurs. Lightning is one big static electricity discharge! Thunder and Lightning

17. What Causes Lightning? • In a cloud, swift air separates water droplets, causing electrical charges. • The electrical charges build up and causes huge electric shocks. It generates about 100 million volts of electricity.

18. Thunder is caused by lightning. When a lightning bolt travels from the cloud to the ground it actually opens up a little hole in the air, called a channel. Once then light is gone the air collapses back in and creates a sound wave that we hear as thunder. The reason we see lightning before we hear thunder is because light travels faster than sound! Thunder

19. Sound travels roughly 1-km in 3 seconds or 1-mile in 5 seconds. So if you see the flash of lightning, and it takes 10 seconds for the thunder to reach you, the lightning was about 2 miles away. How Far Away?

20. Forked lightning: Bolts that most commonly occur between clouds and the earth. Forked Lightning

21. Ball lightning: A very rare. It is a sphere shape that glows and moves slowly. It forms in a storm cloud, and can last five seconds. Ball Lightning

22. Heat - Lightning from storms that are so far away that we can't hear the thunder or see any rain. Heat Lightning

23. Sheet Lightning: covers a wide area, and can be inside or between clouds. Sheet Lightning

24. Go inside! Get in car if you can’t make it to a sturdy building (basements are good). If caught outside, stay away from tall objects like trees. Make sure that you are not the tallest object by crouching down. Crouch down, bend forward, and grab your ankles. Keep your head down. Do not lie flat on the ground and try to keep out of puddles or other standing water. Do not use a phone or a computer during a thunderstorm. Do not take a shower or wash dishes. If there are downed power lines anywhere around you, DO NOT touch them Thunderstorm Safety

26. Severe Thunderstorm Watch -conditions are conducive to the development of severe thunderstorms in and close to the watch area. Severe Thunderstorm Warning - a severe thunderstorm has actually been observed by spotters or indicated on radar, and is occurring or imminent in the warning area.Time to take cover! Thunderstorm Watch/Warning