Unit 5 Lightning 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 ID: 585191
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Slide1
Meteorology
Unit 5 - LightningSlide2
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 fatalitiesSlide3
What is lightning?
Lightning - Energy
in the form of discharged
heat and light Slide4
How does lightning form?Slide5
Hang on… it gets complicatedSlide6
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 neutralizeSlide7
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 lightSlide8
Lightning Types
C
loud-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. Slide9
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 periodSlide10
St. Elmo’s fire
St. Elmo’s fire – A gap in electrical discharge. Can be seen as blue light sometimes preceding a lightning strikeSlide11
What is thunder?Slide12
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 lightningSlide13
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 flashSlide14
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 womenSlide15Slide16
Injuries - ExitSlide17
Injuries – Lichtenberg FiguresSlide18
Lightning InjuriesSlide19
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 bathsSlide20
Side FlashSlide21
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.Slide22
What do I do??Slide23
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.Slide24Slide25
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 groundSlide26
Worst Case Scenario
Now recommended – RUN.Slide27
Worst Case Scenario
RUN
Keeps you moving towards a safe place
Only one foot touching
the ground at a time
Distance from others