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Wednesday, 31 May 2006 00:00

The Naturalist's Corner — Thunderstorm

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The other evening with toddler and infant asleep, my wife and I found ourselves alone as a thunderstorm rolled over the Balsams. We turned out the lights and watched and listened as the storm approached with the sky flickering brighter, the thunder growing louder. It passed with dull thuds and faint flares in the dark.

Watching those shimmering flashes, I was taken back to my childhood in Louisiana. I was on a gravel road headed to the camp at Horseshoe Lake. The night was thick and black and smelled like locust blossoms. Across the miles of cotton fields the sky would suddenly and without a sound light up and flicker blue-green and orange like a backlit movie screen.

We knew this phenomenon as “heat” lightning — a common occurrence in the summer nights across the South. But what is heat lightning, or any lightning for that matter?

It comes as no shock that lightning is electricity. The simple scenario goes like this....

As thunderclouds build and grow higher the water droplets and ice crystals in the cloud begin to collide. These collisions create electrical charges in the cloud. The positive and negative charges separate, with the positive charges staying in the higher part of the cloud and the negative charges dropping to the lower part of the cloud. When the difference between positive and negative charges becomes large enough, a current of electricity shoots between them. This is generally a downward negatively charged current from cloud to ground or from cloud to cloud.

This typical pattern leads to several recognizable types of lighting. There is in-cloud lightning, cloud-to-ground, cloud-to-cloud, sheet lightning (where the whole cloud lights up), ribbon lightning (the flash is blown sideways by the wind), bead or chain lightning (the bolt appears fragmented), and more. Some newly discovered forms of high-altitude lightning include jets and sprites — charges that progress from clouds upwards.

You see, my beloved “heat” lightning is not mentioned. That is because most scientists don’t consider it a separate form of lightning. Rather, it is one of the common forms (often sheet lightning) that simply occur out of hearing range of the accompanying thunder.

Thunder is created when the lightning bolt instantly heats the air around it to temperatures of 50,000 Fahrenheit or greater. This air instantly expands sending out shock waves that we hear as thunder.

While some lightning may be seen for as many as 100 miles under the right conditions, the thunder is only auditory for 15 to 20 miles.

While other “stormophiles” and I enjoy a good thunderstorm, it is always prudent to use common sense. Below are some lightning precautions from the National Weather Service.

When a thunderstorm threatens, get inside a home or large building or inside an all-metal (not convertible) vehicle.

Inside a home, avoid using the telephone, except for emergencies.

If you’re outside with no time to reach a safe building or automobile, follow these rules:

Do not stand underneath a natural lightning rod such as a tall, isolated tree.

Avoid projecting above the surrounding landscape as you would do if you were standing on a hilltop, in an open field, on the beach, or from a small boat.

Get out of and away from open water.

Get away from tractors and other metal farm equipment.

Get off of and away from motorcycles, scooters, golf carts and bicycles. Put down golf clubs.

Stay away from wire fences, clotheslines, metal pipes, rails and other metallic paths, which could carry lightning to you from some distance away.

Avoid standing in small isolated sheds or other small structures in open areas.

In a forest, seek shelter in a low area under a thick growth of small trees. In open areas, go to a low place such as a ravine or a valley. Be alert for flash floods.

If you’re hopelessly isolated in a level field or prairie and you feel your hair stand on end — an indication that lightning is about to strike — drop to your knees and bend forward putting your hands on your knees. Do not lie flat on the ground.

 

Thunderstorm

I love to sit in the dark

And watch the thunderstorm.

The trees bend to and fro

Or, hardly breathe in the grey.

The rain comes down

Hard as stones.

The thunder rolls along like trains

Or explodes in a flash of lightning.

The storm may be quite fierce

Or, fiercely quietening.

Sometimes the wind will howl

And the rain

Will beat against the window

Like a scary movie.

God will shoot

Lightning bolts at your feet

And yell “Dance tenderfoot!”

Sometimes the thunder rumbles

Like the mother’s stomach.

The rain suspends you

In the womb.

And you sit in the dark

Waiting to be born.

— Don Hendershot

 

(Don Hendershot can be reached at This email address is being protected from spambots. You need JavaScript enabled to view it. )

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