Photo courtesy of: NOAA Photo Library, NOAA Central Library; OAR/ERL/National Severe Storms Laboratory (NSSL)
Welcome to Summer!..Its Lightning Safety Awareness Week...
Summer is the peak time to enjoy the outdoors, but it is also the peak time for exposing oneself to the dangers of lightning. At any given moment, there are 1,800 thunderstorms in progress somewhere on the earth. This amounts to 16 million storms each year! Each spark of lightning can reach over five miles in length, soar to temperatures of approximately 50,000 degrees Fahrenheit, and contain 100 million electrical volts.
As a storm forms, ice particles move about inside the cloud. The positively-charged crystals migrate to the top of the thunderstorm while you'll find the majority of negatively-charged particles near the bottom of the cloud. Lightning can originate from the top or the bottom of the cloud, and while you might not often hear the phrase 'negative lightning' during the course of our weather coverage, you will hear us use the phrase 'Positive lightning' when flashes, depicted with a purple lightning bolt, show up on our radar. You'll hear us say that positive lightning is particularly dangerous.
Positive lightning is particularly dangerous for several reasons. It frequently strikes away from the rain core, either ahead or behind the thunderstorm. It can strike as far as 5 or 10 miles from the storm, in areas that most people do not consider to be a lightning risk area. The other problem with positive lightning is it typically has a longer duration, so fires are more easily ignited. Positive lightning usually carries a high peak electrical current, which increases the lightning risk to an individual.
I'm a huge fan of the research done by Dr. Mary Ann Cooper of the University of Illinois (Bio: http://www.uic.edu/labs/lightninginjury/macbio.htm ). She has managed to find differences in the way lightning injures a person versus direct or alternating electrical current exposure. She has also identified particular ways that lightning can injure an individual. Knowledge of these differences by an emergency physician can make a difference, especially if you are unable to speak for yourself after being injured by lightning.
She cites 6 ways by which lightning may injure an individual:
1) Direct strike (approximately 3-5% of injuries)
2) Side splash from another object (approximately 30% of injuries)
3) Contact voltage from touching an object that is struck (approximately 1-2% of injuries)
4) Ground current effect as the energy spreads out across the surface of the earth when lightning hits a distance away from the person (approximately 40-50% of injuries)
5) Upward leader that does not connect with the downward leader to complete a lightning channel (approximately 20-25% of injuries)
6) Blunt trauma if a person is thrown and barotrauma from being close enough to experience the explosive force of lightning
I'll post a link to some of her work here. Some of it is of course quite complex, but it may give you an appreciation for why we urge you to get to a place of safety when lightning moves into your area.
A sample of links to Dr. Cooper:
http://www.uic.edu/labs/lightninginjury/macbio.htm
http://emedicine.medscape.com/article/770642-overview
Here is the link to the National Weather Service website for Lightning Safety Awareness Week:
http://www.noaanews.noaa.gov/stories2009/20090617_lightning.html
Here are some additional websites so that you can research lightning on your own!
Global Hydrology and and Climate Center.. http://thunder.msfc.nasa.gov/
National Geographic Lightning Page: http://environment.nationalgeographic.com/environment/natural-disasters/lightning-profile.html
National Weather Service Lightning Safety: http://www.lightningsafety.noaa.gov/pdfs/LightningMyths-1.pdf
National Weather Service Photo Library:
http://www.photolib.noaa.gov/nssl/lightning1.html
