1. Meteorology
Unit 5 - Lightning

2. History
Lightning as a safety threat receives less attention than hurricanes, tornadoes, and flash floods.
Usually kills only one person at a time
Lightning has historically been the leading cause of weather related death
In recent years, flash flooding has caused more fatalities

3. What is lightning?
Lightning - Energy in the form of discharged heat and light

4. How does lightning form?

5. Hang on… it gets complicated

6. Lightning Formation
Storms are positively charged on the top of the cloud and negatively charged on the bottom
The ground is usually negatively charged but reverses polarity when a storm passes over, becoming positive
Within a cloud, water and ice particles are constantly moving past each other due to the convective currents
The particles become charged (think like static electricity and a balloon)
More convection = more electrical potential
If there enough turbulence in the cloud, the charged particles begin to separate
Charged particles seek their opposites in order to neutralize

7. Leaders & Streamers
Streamers of negatively charged particles come down from the cloud and attract leaders of positively charged particles from the surface
When the pathway between the streamers and leaders is complete, a spark is formed, and energy is discharged as heat and light

8. Lightning Types
Cloud-to-ground lightning – the charged pathway reaches from the cloud to the ground
In-cloud lightning - The charged particles may find each other and discharge energy within the cloud.

9. Lightning Facts
A flash of lighting can produce 1 billion volts of energy or up to 200,000 amps.
Flashes can be 3 miles long, but only 1-3 cm wide
A single flash of lightning unleashes as much energy as blowing up a ton of dynamite
A strike is made up of between three and twelve individual lightning “strokes” each lasting only a few thousandths of a second
One storm in the Midwest produced over 15,000 lightning strikes to ground in a 6 hour period

10. St. Elmo’s fire
St. Elmo’s fire – A gap in electrical discharge. Can be seen as blue light sometimes preceding a lightning strike

11. What is thunder?

12. Thunder
Thunder is the sound produced by lightning’s discharge of energy
Lightning travels around 300 million m/s and sound travels at 300 m/s
The difference creates a shockwave, which is the sound we hear as thunder
To determine the distance you are from the storm, count the seconds between the lightning flash and thunder and divide by 5. This is the approximate distance in miles from you to the lightning

13. What happens when lightning strikes?
Lightning can cause structural damage, structural fires, and forest fires
Lightning kills and injures in two ways:
Direct strike
Side flash

14. Death and Injury Lighting deaths average around 40 per year in the USA
Lighting causes 2.5 times more injuries per year than deaths
Men are injured significantly more often than women

16. Injuries - Exit

17. Injuries – Lichtenberg Figures

18. Lightning Injuries

19. Side Flash Side Flash- lightning striking near a person
Can cause injury, blindness, deafness, or death
Depends on many factors
Distance to the ground strike point
Soil conductivity (wet soil conducts better than dry soil)
Strength of electric current
Most common outdoors but can happen indoors through phones, electrical appliances, and water pipes connected to sinks, showers, and baths

20. Side Flash

21. Death and Injury
The most common deaths and injuries due to lightning occur
Near or in water
Near or under a tree
Near a vehicle, home, or building
On a golf course, ball field, or in other open areas.

22. What do I do??

23. Safety Pay more attention to lightning than to rain Plan ahead
DON’T BE THE HIGHEST OBJECT
Don’t be near or connected to anything taller than its surroundings, like trees or buildings
Go into a building or vehicle with a solid metal roof. Do not contact any metal.

25. Worst Case Scenario Lightning may be about to strike if:
Your hair is standing on end
Your skin begins to tingle
You hear clicking sounds
You see St. Elmo’s Fire
No longer recommended –
Crouch on the balls of your
feet to minimize your surface
area in contact with the ground

26. Worst Case Scenario
Now recommended – RUN.

27. Worst Case Scenario RUN Keeps you moving towards a safe place
Only one foot touching
the ground at a time
Distance from others