1. SCIENCE NEWS

2. Thunderstorms

3. What are thunderstorms?
A storm which contains
lightning and thunder

4. Why Study Thunderstorms ?
Fatalities
Injuries
Property Damage
Crop Damage

5. Weather related deaths in the u.s.

6. Weather damage cost in the U.S.

7. According to NOAA’s National Weather Service
The US has sustained 90 weather related disasters over the 29 years
Total cost of all 90 events?
$700 billion

8. ILLINOIS
According to NOAA, 2008 Summary of Hazardous Weather Fatalities, Injuries, and Damage Costs by State
Fatalities 35
Injuries 48
Property Damage $ million
Crop Damage $ million
Total - $ million

9. Average number of days per year with thunderstorms

10. FACTS OCCURANCES FEATURES 2000 in progress at any one time
100,000 per year in the United States
Most frequent in Florida and eastern Gulf Coast region
FEATURES
Cumulonimbus clouds
Heavy rainfall
Lightning
Occasional hail

11. All thunderstorms need
Moisture - source typically over water, cloud formation & rain
Lifting- mechanism for condensing moisture to release its latent heat
Unstable air- rising air warmer than the surrounding air, produce upward growing clouds and vertical updrafts keep precipitation suspended

12. 2 Types of Thunderstorms
Classified by lifting mechanism
1. Air mass - unequal heating of surface
Mountain : Orographic lifting
Sea breeze : difference between land/water storage & release of thermal energy
2. Frontal – advancing cold fronts and
more rarely warm front

13. Stages of development 3 distinct stages make up a t-storm

14. Cumulus stage
Warm, humid air rises vertically and condenses into a cumulus cloud
Large amounts of latent heat are release inside the cloud
As the cloud grows, particles eventually get heavy enough to
fall also sides of the cloud evaporates forming a downdraft
No precipitation during this stage

15. Cumulus Stage

16. Mature stage The appearance of a downdraft
Updraft/downdraft is called a “cell”
An “anvil” top appears as the updrafts hit the tropopause
Heavy rain possible in this stage
Strong/gusty surface winds

17. Mature Stage

18. Dissipation Downdrafts basically choke out the updrafts
Cuts off the warm, moist air which is the energy supply for the storm
Light rain only

19. Dissipating Stage

20. Multi cell thunderstorms
If new thunderstorms forms due to downdrafts from the air mass, they are called “multi cell” thunderstorms
Most severe storms & ordinary storms are multi cell storms

21. Multi cell Thunderstorm

22. Thunderstorm hazards Hail
Collision of super cool water drops forms layers
Cause extensive & quick damage
Largest Aurora, Nebraska 6/03
7 in diameter & in circumference almost a soccer ball

24. Lightning & Thunder
Charge differences between the thunderstorm and ground can cause lightning strokes of 30,000°C, and this rapid heating of air will creates an explosive shock wave called thunder, which requires approximately 3 seconds to travel 1 kilometer

26. Lightning Stroke Development
Charge layers in the cloud are formed by the transfer of positive ions from warmer hailstones to colder ice crystals.
When the negative charge near the bottom of the cloud is large enough to overcome the air's resistance, a stepped leader forms.
A region of positive ions move from the ground toward this charge, which then forms a return stroke into the cloud.

27. Lighting
Several names, such as forked, bead, ball, and sheet lightning describe forms of the flash
Distant, unseen lightning is often called heat lightning

29. 2007 Lightning Fatalities
45 lightning fatalities
Above the 10-year average of 44 fatalities.
For the 9th consecutive year, Florida was hardest hit with 11 fatalities
Illinois 1 fatality

31. ANY QUESTIONS?

32. HOMEWORK QUIZ? Read Ch 13 p 344- 349 Ch 13 Study Guide Due Tues 4/28
Ch 12 test corrections due TR 4/30

33. Good References http://www.eoearth.org/article/Thunderstorm
USE THIS FOR SEVERVE TSTROMS