A Bolt From Out Of The Blue

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Shows cloud-to cloud, cloud-in-cloud, cloud-to- air, and cloud-to-ground lightning.

What can be as hot as 54,000 degrees F. with an average peak current of 30,000 amperes, and produces 500 megajoules of energy? Look, up in the sky, it’s a bird, it’s a plane, no it’s a bolt of lightning. I already explained the many things that Oregon doesn’t have and I thought this time I would discuss one of our infrequent visitors lightning. Since I grew up in Upstate New York I was quite accustomed to the sound of thunder and the bright flash of lightning. Sometimes I actually miss thunderstorms with their rain pounding on the roof in waves and a bright flash of light followed closely by the loud crack or rolling thunder. I remember counting the seconds between the flash and the crash. Count the number of seconds, divide by five, and you get an approximation of how many miles away the strike was from your location. Using that as a measurement the closest I ever was to a lightning strike was about a quarter mile in Eau Claire, WI. That time my wife and I saw the flash and almost immediately heard the thunder crash so loud that it shook the window in the room and we both hit the floor at the same time.

Top of tree exploded by lightning strike at Resthaven Memorial Park
Top of tree exploded by lightning strike at Resthaven Memorial Park

The closest lightning strike for me here in Eugene occurred on July 12,2009 when a tree in a cemetery less than a mile from my house was struck and literally exploded into many pieces blowing the top off.

Now that we’ve seen the power lightning has I think it would be a good idea to explore what it takes to produce those dangerous but often beautiful lighting bolts that can crisscross the sky. Lightning is usually formed in a cumulonimbus cloud or thunderhead. It is the result of a build-up of electrical charges within the cloud. The upper part of the cloud which reaches into the colder part of the atmosphere forms ice crystals that are usually positively charged. Raindrops form in the lower portion of the cloud and they contain a negative charge.

Separation of charges in a cumulonimbus cloud| Diagramme foudre.png
Separation of charges in a cumulonimbus cloud| Diagramme foudre.png

As the cloud moves over the land the negative charge at the bottom of the cloud induces a positive charge at or near the surface. As you’ve heard many times before opposites attract and an electrical charge builds between the bottom of the cloud and the surface or something standing on the surface like a building, tower, or even a person standing outside. A leader comes down from the cloud toward whatever it is attracted to and an upward streamer moves from the object up to the cloud. When they meet the path to the ground is completed. A return stroke then follows the path back up to the cloud at an outrageous speed of 60,000 miles per second. That’s what forms the bright flash. The flash is actually moving from the object upward even though your eye sees it as striking down from the cloud. The noise of the thunder comes from he rapid heating and cooling of the air (expansion and contraction) around the lightning bolt.

Shows cloud-to cloud, cloud-in-cloud, cloud-to- air, and cloud-to-ground lightning.
Shows cloud-to cloud, cloud-in-cloud, cloud-to- air, and cloud-to-ground lightning.

Lightning displays can be beautiful, especially at night, but they can also be deadly. We should be thankful that there are four major categories of clouds: within-a-cloud, cloud-to-cloud, cloud-to-air, and cloud-to-ground. If all we had were cloud to ground lightning strikes people all over the world would be constantly ducking and weaving to keep away from the deadly electrical charges. Many people have studied lightning but Benjamin Franklin is probably the best known. His key on a kite string experiment was performed to prove that lightning was naturally occurring electricity. He did get shocked during one of his experiments and I have heard that some scientists say Franklin was very lucky he didn’t get electrocuted flying his kite with the key on the string.

Painting of Ben Franklin's lightning experiment | hqdefault
Painting of Ben Franklin’s lightning experiment | Benjamin West

Others who have tried to duplicate Franklin’s experiment have reportedly been  electrocuted and I have heard they died trying. I know of a true story that happened in the Midwest. A farm worker loved flying kites, but he got tired of constantly having to replace kites lost when the string broke in the wind. So, “Mr. genius” decided to use a large spool of industrial strength copper wire figuring it was much stronger than string and he would never lose a kite again. Well, he used his copper wire and ran it out so the kite was so high he could hardly see it. I’m sure you already figured out what comes next. Lightning struck his kite, followed the copper wire down to his hands, and instantly electrocuted him. His death reminds me of my favorite quote from the movie Forrest Gump “Stupid is as stupid does.” Lets clear up some myths about lightning. Lightning never strikes twice in the same place. Wrong. If the target still stands it can be struck again and quite often is. As long as you stay inside during a thunderstorm you are safe from lightning. Wrong. Lightning has been known to strike people through windows and it can strike a telephone, cable, or power line and follow it into your house through the wire. A neighbor of mine in Memphis, TN, about twenty five years ago, had the bolt of lightning strike the power line into the house and burned the inside of their dishwasher, fried the toaster, and blew out the microwave oven all of which were connected into the same circuit. Here in Eugene while working as Chief Meteorologist for KVAL-TV lightning struck the TV tower and blew out all of the computers in the building along with their connections to the news control room. My weather computers were not harmed and I was a bit cocky about mine being the only ones not knocked. About an hour later I realized mine did work but I had no new data coming. That was also the day that one of the communications satellites died backing out a lot of medical pagers and other devices. That just happened to be the satellite that transmitted data to my system. Lesson learned. Don’t make fun of someone else’s problem because it just might become your problem too. There were, incidentally, only two booms heard which means only two possible strikes occurred, but at least one caused a lot of damage. There are other ways to produce lightning. Dust storms and forest fires can produce the elements needed to produce lightning and another example is the eruption of Mt. St. Helens on May 18, 1980.

Mt. St. Helens Eruption with lightning at top | Charlie Palmer
Painting of Mt. St. Helens Eruption with lightning at top | Painting by Charlie Palmer

Pyroclastic explosions spew various sizes of material from large boulders to fine particles of dust and ash. Sending hot gasses upwards of 6 miles into the colder part of the troposphere added to the particulates equals a good recipe for lightning above the cone of the volcano. Now that we’ve seen the dangers of lightning I think we should discuss what you can do to be more protected from it’s deadly charge. What if you are outside without shelter of any kind? The National Weather Service recommends that you immediately squat down putting your hands over your ears.

The National Weather Service emergency lightning safety position. Sorry that's my best crouch.
The National Weather Service emergency lightning safety position. Sorry that’s my best crouch.

That way you are a smaller target and if you do get struck the charge would pass through your body more quickly, hopefully doing less damage. Is a car a safe place to be in a thunderstorm? If you can’t get to a building a car is a relatively safe place. Don’t touch any metal inside and the metal shell of the car will shield you. The same goes for being a passenger in an airplane flying in or near a thunderstorm. Most of the strikes to the body of the plane have no effect, but a strike to one of the engines could do some serious damage. If you are inside a building remember to stay away from windows and stay off the telephone or any electrical equipment as long as the storm is near you. Can lighting effect more than one person at a time? It certainly can. During a baseball game a thunderstorm built up and lightning struck the pitcher. The lightning continued along the ground and knocked down the entire infield. There is one man who is in the Guinness Book of World Records for being struck 7 times (from 1942 until 1977) and living to tell his story.

Ranger Roy Sullivan survived being struck by lightning 7 times | Oddee.com
Ranger Roy Sullivan survived being struck by lightning 7 times | Oddee.com

Roy Sullivan started working as a park ranger in Shenandoah National Park in Virginia back in 1936. After being struck a number of times people stayed away from him for fear of being struck with him. They began calling him the “Human Lightning Rod.” The last time he was struck he was fishing and just after being struck a bear came up and tried to steal the trout he had on his fishing line, but he had the strength and courage to hit the bear with a tree branch and keep his fish. Does the storm have to be overhead for you to get struck by lightning? No. That is where the title for this column is derrived. “A bolt out of the blue” is a lightning bolt that comes from a storm that is not overhead, but can be 10 or more miles away. If you can hear thunder or see even the glimmer of the lightning in the distance you are at risk for being struck. Stay indoors until the storm is well away from your area. Just in case you were wondering, the odds of being struck by lightning are computed to be 1 in 10,000. I’ll bet Roy Sullivan would have some choice words to say about that. Be safe out there.

Suggestions for future column topics are welcome. Let me know what you would like me to talk about or explain. You can email me at: [email protected]

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