Arizona Lightning

It can happen between a cloud and the ground, between clouds, and even from one part of a cloud to another part.

Cloud-to-ground lightning forms when rising air currents in a thunderstorm cause lots of collisions between ice particles.

All that colliding results in the separation of positively and negatively charged particles, creating huge electrical charge differences.

The negatively-charged particles drop to the middle and lower parts of the storm.

The traveling thunderstorm also gathers positively charged particles along the ground that move within the storm.

As the difference in charges between the particles increases, the positive particles rise up, the negative particles travel downward and an invisible electrical channel of energy develops.

A nighttime thunderstorm briefly lights up the city. Photo: iStockphoto

The electrical transfer in this channel is the lightning that we see.

As the air is heated by the channel, it rapidly expands, causing the shock wave we hear as thunder.

If you hear a sharp, loud "crack," you just heard a bolt hit the ground.

Storm chasers know that southern Arizona is an excellent place to watch for stikes. Why?

Because the air is generally clear and the cloud bases are often very high.

How can you tell how far away that strike was?

Here’s a simple rule: When you see the flash, count the number of seconds until you hear thunder and divide by 5.

This will tell you how many miles you are from the strike.

A triple strike Photo: iStockphoto

Essentially this equates to 1 mile for every 5 seconds - more or less the speed of sound (761 miles per hour).

Thunderstorms are generally several miles in diameter and lightning can originate from any part of the storm.

There is no way to predict where and when it will strike.

• Before heading outside for the day, know the weather forecast. Plan your outdoor recreation early in the day.
• During your outdoor activity, keep an eye on the sky and watch for the formation of towering cumulus clouds, which are often the first signs of a developing thunderstorm.
• The National Weather Service (NWS) now recommends: "When Thunder Roars, Go Indoors." That is, if you hear thunder of any kind, you are within striking distance of lightning. Head indoors to a safe building immediately. If no building is nearby, get inside a metal-topped vehicle.

  In the past, the NWS recommended the 30/30 Rule: if less than 30 seconds pass between the time you see a flash of light and hear the first roll of thunder, immediately seek shelter in the nearest building. However, they now state that the safest course of action is to go indoors as soon as you hear thunder.

• Remain inside for at least 30 minutes after you see the last flash of light and hear the last sound of thunder.
• If you can't see any flashes of light but are hearing thunder, lightning is within striking range of you.
• Do not wait for rain before finding shelter as you can be struck even if no rain is present.
• If no building is available, seek shelter in a metal-topped vehicle. Roll up the windows. Lean away from the door. Put your hands in your lap and keep your hands and feet off any metal parts, the steering wheel, gear shift, etc. Do not use the radio or other electronic devices.

There's a widely held myth that a car will protect you because the rubber tires ground the charge.

Unfortunately that's not true. You can still be hit if you're in a vehicle.

However, if you only option for shelter is the vehicle or being outside, get in the car. Electricity travels around the metal frame to the ground, providing some, though not foolproof, protection.

Outdoor Safety

(If you are unable to find shelter in a building or a metal-topped vehicle.)

• The Lightning Position: If a bolt strikes nearby, assume this position. Crouch down like a baseball catcher on the balls of your feet with your feet together in the lowest spot you can find. Place your hands on your knees with your head between them, cover your ears and close your eyes. You want to make yourself as small as you can with as little contact with the ground as possible.
• Do not stand under a tree.
• Do not lie flat on the ground.
• If you are with a group, do not huddle together. Each person should be at least 15 feet apart from the next person.
• If you hear crackling, smell ozone, feel your skin tingle or your hair stands on end, a bolt may be about to strike. Crouch down in the lightning position where you are, as described above.
• Do not stand under ramadas, picnic or rain shelters, bus stops, dugout, bleachers, trees, or other tall structures.
• Avoid standing bodies of water, fishing docks or boating ramps, high ground, open spaces, golf courses, wire fences, over-ground pipes and rails.
• If you are swimming or boating, get out of the water immediately.
• If you are on a peak, descend as far as possible to a flat shelf or depression. Place your backpack a few feet away and assume the lightning position.
• If you’re on a ridge, stay in the middle away from the edges. Avoid tall, lone trees.
• Avoid sitting on damp grass or wet rocks.
• Aiding a lightning strike victim: Call 9-1-1 immediately. It is safe to touch the victim as he or she will not carry a charge. Cardiac arrest is the immediate cause of death for victims, so perform CPR if the person is not breathing or unresponsive.

• Arizona ranks number 23 in lightning frequency in the lower 48 states.
• There is lightning risk even if it is not raining where you are. Strikes can happen outside the rain area in thunderstorms. This is especially true in southern Arizona, which often has dry thunderstorms that produce strikes with no rain.
• Two-thirds of all strikes occur between June and August.
• Most strikes occur during the afternoon or early evening. Late afternoon is the deadliest period.
• A strike can spread out to around 60 feet from where it first hit the ground.
• A bolt can strike in the same place twice.
• Fatalities and injuries tend to occur more often at the end of a storm than at any other times; least often in the middle of storms.
• The Federal Emergency Management Agency (FEMA) estimates there are 750 severe injuries from cloud-to-ground lightning annually in the United States.
• Over the past 30 years, there have been an average of 58 fatalities annually from lightning, more than for tornadoes or hurricanes (National Weather Service)
• According to the National Weather Service, your chance of being struck by lightning in the United States in your lifetime is 1 in 3,000.
• 9 out of 10 people struck survive, though they frequently suffer lifelong, debilitating symptoms such as memory loss, dizziness, weakness, muscle spasms and depression.
• The United States gets about 25 million cloud-to-ground strikes every year.
• One bolt strikes the ground for every three flashes you see in the clouds.
• The most common locations to be struck are open fields or under trees.
• The distance between successive flashes can be anywhere from 2 to 6 miles apart.
• Lightning can travel 60 miles or more, often extending up to 10 miles away from the cloud that formed it. Generally, however, a bolt travels 10 miles or less.
• A bolt is about 1-inch in diameter.
• The temperature of lightning peaks around 50,000 degrees Fahrenheit - 5 times hotter than the surface of the sun.

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