Lightning Safety Awareness WeekJune 25th, 2013 at 10:08 am by markmonstrola under Weather
LIGHTNING SAFETY WEEK JUNE 23-29, 2013
Summer is the peak season for one of the nation’s deadliest weather phenomena–lightning. Though lightning strikes peak in summer, people are struck year round. In the United States, an average of 53 people are killed each year by lightning, and hundreds more are severely injured.
Lightning: What You Need to Know
- NO PLACE outside is safe when thunderstorms are in the area!!
- If you hear thunder, lightning is close enough to strike you.
- When you hear thunder, immediately move to safe shelter: a substantial building with electricity or plumbing or an enclosed, metal-topped vehicle with windows up.
- Stay in safe shelter at least 30 minutes after you hear the last sound of thunder.
Indoor Lightning Safety
- Stay off corded phones, computers and other electrical equipment that put you in direct contact with electricity.
- Avoid plumbing, including sinks, baths and faucets.
- Stay away from windows and doors, and stay off porches.
- Do not lie on concrete floors, and do not lean against concrete walls.
Last Resort Outdoor Risk Reduction Tips
If you are caught outside with no safe shelter anywhere nearby the following actions mayreduce your risk:
- Immediately get off elevated areas such as hills, mountain ridges or peaks
- Never lie flat on the ground
- Never shelter under an isolated tree
- Never use a cliff or rocky overhang for shelter
- Immediately get out and away from ponds, lakes and other bodies of water
- Stay away from objects that conduct electricity (barbed wire fences, power lines, windmills, etc.)
How Lightning Forms
Lightning is a giant spark of electricity in the atmosphere or between the atmosphere and the ground. In the initial stages of development, air acts as an insulator between the positive and negative charges in the cloud and between the cloud and the ground; however, when the differences in charges becomes too great, this insulating capacity of the air breaks down and there is a rapid discharge of electricity that we know as lightning.
Lightning can occur between opposite charges within the thunderstorm cloud (Intra Cloud Lightning) or between opposite charges in the cloud and on the ground (Cloud-To-Ground Lightning). Cloud-to-ground lightning is divided two different types of flashes depending on the charge in the cloud where the lightning originates.
Thunder is the sound made by a flash of lightning. As lightning passes through the air it heats the air quickly. This causes the air to expand rapidly and creates the sound wave we hear as thunder. Normally, you can hear thunder about 10 miles from a lightning strike. Since lightning can strike outward 10 miles from a thunderstorm, if you hear thunder, you are likely within striking distance from the storm.
How Far Away Was That Lightning?The sound of thunder travels about a mile every 5 seconds. If you count the seconds between the flash of lightning and the crack of thunder and divided by 5, you get the number of miles away from you (10 seconds is 2 miles).
Understanding Lightning: Types of Flashes
There are two main types of lighting: intra-cloud lightning and cloud-to-ground lightning.
Intra-cloud lightning is an electrical discharge between oppositely charged areas within the thunderstorm cloud.
Cloud-to-ground lightning is a discharge between opposite charges in the cloud and on the ground. Cloud-to-ground lightning can either occur between negative charges in the cloud and positive charges on the ground (a negative flash) or between positive charges in the cloud and negative charges on the ground (a positive flash).
Each cloud-to-ground lightning flash consists of one or more leaders followed by one or morereturn strokes. The leader is the initial step in the lightning flash and establishes the conductive channel that the electrical discharge (lightning) will take. There are different types of leaders. The most common type of leader is the negative stepped leader. Once a charged leader makes a connection with the ground, the return stroke occurs. The return stroke is simply the rapid discharge of electricity that has accumulated on the leader. We see this discharge as the bright flash of lightning.