Lightning is one of the most beautiful atmospheric phenomenons around. Despite its beauty, lightning is an incredible force of nature that can be deadly for those caught off guard by a sudden thunderstorm. MORECAST meteorologist Gina Medici studied lightning for her Master’s at the University of Arizona and shares some of the science behind lightning along with some safety tips.
The Science Behind Lightning
The electrical charge that forms in a cloud is due to small ice crystals and water droplets that collide into each other, creating an electrical field. A typical thunderstorm cloud has layers of electrical charge composed of an upper positive charge, a midlevel negative charge region, and a smaller positive charge layer below it (figure 1). Intercloud (cloud-to-cloud) flashes “neutralize” built up charge between the upper positive and midlevel negative charge regions in a cloud while cloud-to-ground (CG) flashes transfer negative charge to the ground. There are positive and negative CG lightning that occurs in the atmosphere. Roughly 95 percent of CG flashes are negative, leaving only five percent as positive flashes. While they are rare, positive flashes are responsible for the majority of forest fires and power line damage because they are up to ten times more powerful than their negative counterpart, which also makes them more lethal.
Where there’s lightning, there is also thunder. It’s a result of the rapid expansion of air caused by a lightning bolt, which can reach temperatures up to 50,000 degrees Fahrenheit, hotter than the surface of the sun. There is a common myth that lightning can happen without thunder, known as heat lightning, but it’s not possible. ‘Heat lightning’ is a result of being too far away from the storm, where it’s possible to see the lightning, but not hear the resultant thunder. For example, in the Central Plains, it’s possible to sometimes see lightning more than 100 miles away, but that’s too far for the sound of thunder to travel.
Safety
On average, more than 400 people are struck by lightning each year in the U.S., with around 55 of those being fatal. Those who survive a strike typically suffer severe burns, nerve damage and memory loss.
What makes lightning dangerous beyond its immense power is its unpredictability. Any thunderstorm, even weak ones, are capable of producing a potentially deadly bolt. Figure 2 shows lightning strikes can occur almost everywhere during the year across the continental United States, but is most common in the Midwest, Great Plains and Deep South. But there are safety measures you can follow to avoid putting yourself or others in a dangerous situation.
- Be aware of your location relative to storms: You don’t have to be right under a storm, as lighting has been known to strike up to 50 miles away
- Avoid plugged-in devices and plumbing: Lightning can conduct through plumbing and electric wiring
- If outside:
- Avoid open areas and tall objects, such as trees.
- Water and metal are great conductors of electricity, so stay away from metal fences and bleachers, and get out of the water if swimming
- If you get caught in a storm, don’t lie down flat on the ground to get lower. When lightning strikes the ground, the current spreads outward. Laying flat would increase your surface area and make it easier to conduct if a bolt struck the ground. Also, crouching down is not recommended anymore. This is why it’s important to get into a car or sturdy building.
Finally, as with any type of weather, the best way to stay safe is to know the forecast. The MORECAST app has you covered, with daily and hourly forecasts that will tell you when thunderstorms and lightning could be near, so you’re never caught off guard.
MORECAST meteorologist Gina Medici
Twitter photo (c) Anthony Quintano via flickr