Why some storms produce excessive lightning

Weather

June 9, 2021: Michael Ward, 70, was playing golf in New Jersey when he was struck by lightning and killed.
June 12, 2021: A 15-year-old woman was struck by lightning while swimming on Tybee Island, Georgia. 

Until June 9th, we held a record for the latest in the year the nation has made it without recording a lightning fatality.

As one of the leading killers associated with thunderstorms, the death toll that lightning incurs sometimes rivals that of tornadoes. In 2020, 17 Americans were killed by lightning. 


On Saturday, I was driving back to Savannah from Alabama. From Emanuel County to Chatham County, I drove in and out of thunderstorms on I-16. Each one produced drenching rain and excessive lightning. My hands were gripping the steering wheel so tightly that I was sore by the time I reached home. 

After posting the heart-breaking news of the teenager that was killed by lightning while swimming on Tybee Beach, I had many viewers asking why these storms produced so much lightning. Well, there are three main reasons.

First, HIGH INSTABILITY RELEASE. When instability is high, thunderstorm updrafts will be more intense. The stronger the thunderstorm updraft, the deeper the thunderstorm column will be. As air rises in a thunderstorm it cools. When the storm height is very high, the top of the thunderstorm will cool to very cold temperatures. This intense cooling glaciates the top of the storm and this can be seen as the thunderstorm anvil. The glaciation process produces a charge differential in the storm cloud. In cases where very rapid and intense glaciation occurs, lightning and thunder will be generated to a significant degree. All thunderstorms have ice in the upper portions of the storm. How fast the ice develops, the depth of the icy portion of the storm and how quickly the precipitation moves within the cloud are important to the lightning process. There is still much research that needs to be done to fully understand this process.

Next, HIGH MOISTURE CONTENT. Dewpoints of 60 degrees Fahrenheit or higher will bring significant moisture into a storm. Well, on Saturday in Savannah, we had dewpoints in the 70s. Low level moisture helps in that it increases instability. This in turn leads to a stronger updraft, as discussed in the first reason above. An increase in moisture also means more ice can be produced when the moisture begins to glaciate in the updraft. 

Finally, WIND SHEAR. Wind shear is wind speed changing significantly with height and/or wind direction changing significantly with height. Wind shear enables a thunderstorm to last for a longer period of time since it helps displace the updraft from the downdraft. These storms are often in the form of multi-cell or supercell storms. Wind shear also increases turbulence within a thunderstorm. This violent mixing of precipitation in the air could help enhance charge separation in a storm. 

On Saturday, we had all of these categories. 

Lightning fatalities don’t tend to get as much media attention that deaths from other disasters such as tornadoes or hurricanes do, because the death tolls, while tragic, are comparatively lower during individual events. But in 2018, only 10 Americans were killed by tornadoes, but 21 died from lightning. 

Men are struck three to four times as frequently as women.

A long-term average of 41 people die from lightning strikes each year in the United States, but this number has been continuing to trend downward thanks in part to increased awareness, safety campaigns, and growing access to weather forecasts and alerts and warnings. 

But sometimes… an alert doesn’t come or it doesn’t come soon enough.

A typical lightning flash measures about 300 million volts and 30,000 amps – enough to kill.

Most of the electrical discharge spreads horizontally rather than vertically. This is bad news for people, who tend to float or swim on or near the surface.

The lightning current is likely to radiate across the surface.

Lightning doesn’t strike the ocean as much as land, but when it does,it spreads out over the water, which acts as a conductor. It can hit boats that are nearby, and electrocute fish that are near the surface.

For this reason, as soon as the skies get dark, I recommend packing up and going somewhere safe.

Don’t wait on the first sight of lightning or the first sound of thunder. Download a reliable weather app and look at the radar. Many weather apps, including the free WSAV weather app, provides lightning data. You can also get alerts when lighting is within 10 miles of your area. 

If you are outdoors when a thunderstorm approaches… here is what you need to do.

Be aware
Check the weather forecast before participating in outdoor activities. If the forecast calls for thunderstorms, postpone your trip or activity, or make sure adequate safe shelter is readily available.

Go indoors
Remember the phrase, “When thunder roars, go indoors.” Find a safe, enclosed shelter when you hear thunder. Safe shelters include homes, offices, shopping centers, and hard-top vehicles with the windows rolled up.

Seek shelter immediately even if caught out in the open
If you are caught in an open area, act quickly to find adequate shelter. The most important action is to remove yourself from danger. Crouching or getting low to the ground can reduce your chances of being struck, but does not remove you from danger. If you are caught outside with no safe shelter nearby, the following actions may reduce your risk:

  • Immediately get off elevated areas such as hills, mountain ridges, or peaks.
  • Never lie flat on the ground. Crouch down in a ball-like position with your head tucked and hands over your ears so that you are down low with minimal contact with the ground.
  • Never shelter under an isolated tree.
  • Never use a cliff or rocky overhang for shelter.
  • Immediately get out of and away from ponds, lakes, and other bodies of water.
  • Stay away from objects that conduct electricity (barbed wire fences, power lines, windmills, etc.).

Separate
If you are in a group during a thunderstorm, separate from each other. This will reduce the number of injuries if lightning strikes the ground.

Don’t

Don’t stay in open vehicles, structures, and spaces
During a thunderstorm, avoid open vehicles such as convertibles, motorcycles, and golf carts. Be sure to avoid open structures such as porches, gazebos, baseball dugouts, and sports arenas. And stay away from open spaces such as golf courses, parks, playgrounds, ponds, lakes, swimming pools, and beaches.

Don’t stay near tall structures
Do NOT lie on concrete floors during a thunderstorm. Also, avoid leaning on concrete walls. Lightning can travel through any metal wires or bars in concrete walls or flooring.

(sources: National Weather Center, NOAA, Washington Post, Lightning Stats, Professor Jeff Haby)

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