1. SCIENCE NEWS

2. Severe Weather

3. characteristics of a Severe Thunderstorm
Fueled by the increased instability of the air
Intense rotating updrafts as strong as 240km/h and lasting several hours
Know to produce: large hail, strong surface winds, heavy rain and tornadoes

4. Severe thunderstorms
National Weather Service: - 3/4 inch hail and/or 50 knot wind gusts at the surface required to use term “severe”
The big difference from ordinary t-storms is that many severe storms have a tilted updraft this keeps the downdraft from eventually killing the storm

5. SUPERCELLS Severe thunderstorms
What is the name of a severe thunderstorm that developed into a self sustaining extreme storm?
SUPERCELLS

6. SUPERCELLS

7. Remember ????
A cell is formed in the Mature Stage of a thunderstorm from the up/downdraft
An anvil shape of the cumulonimbus cloud appears as the updrafts hit the tropopause

8. SUPERCELLS

9. SUPERCELLS

10. SUPERCELLS & Strong Winds
Winds speeds over 160k/hm
Violent concentration of downdrafts in a local area known as downbursts

11. DOWNBURSTS Classified by size of affected area
Macroburst: destruction up to 5 km wide, wind exceeds 200 km/h, last up to 30 min.
Microburst: destruction up to 3 km wide, winds exceed 250 km/h, less than 10 min

12. Macrobursts

13. Microbursts

14. SUPERCELLS & Hail
Hail
Collision of super cool water drops forms layers
Formation from an abundance of strong up & down drafts

15. SUPERCELLS & Tornadoes
a violent whirling column of air in contact with the ground

16. Super cell that produced
a tornado

17. TORNADOES
Occurrence
Annually, the US has more than 1000 tornadoes but the highest frequency is observed in tornado alley of the Central Plains.
Nearly 75% of tornadoes form from March to July, and are more likely when warm humid air is overlain by cooler dryer air to cause strong vertical lift.

19. TORNADOES Features Violent windstorm
Rotating column of air that extends down from a cumulonimbus cloud
Low pressures inside causes the air to rush into
Smaller suction vortices can form inside stronger tornadoes

20. Rotating clouds are the first sign that a super cell may form a tornado

21. TORNADOES Diameter between 500 & 2000 ft
Characteristics
Diameter between 500 & 2000 ft
Speed across landscape about 30 mph
Cut about a 6 miles long path
Most move toward the northeast
Intensity measured by the Fujita intensity scale

22. Tornado Wind Speed
As the tornado moves along a path, the circular tornado winds blowing opposite the path of movement will have less speed.
Example if the storm rotational speed is 100 knots, and its path is 50 knots, it will have a maximum wind of 150 knots on its forward rotation side.

23. Tornados

24. Fujita Intensity Scale

25. Fujita-Damage Scale

26. Tornado damage

27. F5 Tornado damage

28. Tornado Damage

29. Other TORNADOES Funnel Clouds
Rotating columns of air
Wind speed may exceed 200 knots
When the funnel cloud reaches the ground it becomes a tornado
When the funnel cloud reaches the water it becomes a waterspout

30. Waterspout

31. Dust-devil

32. ANY QUESTIONS?

33. HOMEWORK
Read p 350 – 354