Sunday’s storm brought strong lightning to Lexington and Central Kentucky. Here’s why

Winds toppled trees, baseball-sized hail fell and lightning lit up the skies over Kentucky Sunday.

But for Brian Neudorff, a meteorologist with the National Weather Service in Louisville, the lengthy display of lightning during the storm was hardly shocking.

“It’s not surprising to me that there were such vivid lightning displays,” Neudorff said Monday, adding the storms, which left tens of thousands without power across Kentucky, showed several hallmarks forecasters associate with intense lightning.

So what factors produced those fantastic lightning displays seen over Lexington and elsewhere? Here’s what to know.

What is lightning?

Put simply, you can think of lightning as the discharge of static electricity, except on a much larger scale than the shock you get in winter when you walk across the carpet in wool socks.

As explained by the NWS, lightning occurs from the buildup and discharge of electrical energy between positively and negatively charged ice particles in storm clouds. Static builds up when these ice particles collide and as a result generate friction. This happens in updrafts and downdrafts, and when the static electricity builds up to a point when it can travel from the cloud to the ground, it results in a lightning bolt.

Why did Central Kentucky see so much lightning Sunday?

According to the NWS, there are three main factors that influence the amount of thunder and lightning during a storm.

1. Instability: As air rises within a thunderstorm, it reaches cooler parts of the atmosphere and glaciates, or freezes, the top of the storm. Meteorologists call this the anvil of the thunderhead. This creates a buildup of opposing electrical charges. When it happens rapidly, there will be large amounts of thunder and lightning. How fast the ice develops, the size of the anvil and how fast precipitation moves within the cloud are factors that contribute to the process that creates lightning.

2. Moisture: Another major factor is existing moisture in the lower troposphere, where we live. Again as explained by the NWS, moderate to high dew points (a measure of atmospheric moisture) lead to increased instability since updrafts of air often begin in the lower troposphere. When that atmospheric moisture hitches a ride on an updraft, it only increases the existing mass of ice and water in the storm cloud.

3. Wind shear: As explained by Neudorff, wind shear is a substantial change in wind speed, either height and direction or a combination of the two. It’s wind shear that gives a thunderstorm legs, so to speak. Normally, a thunderstorm’s updrafts and downdrafts are joined, but wind shear enables the updraft to tilt so rain and hail fall ahead of it. This allows the storm to hold onto its energy longer, since falling rain won’t smother the updrafts as it falls.

What about the hail Kentucky got Sunday?

The NWS reports hailstones form as a thunderstorm expands and sends water into below-freezing parts of the atmosphere. When the storm’s powerful winds push water droplets upward, they collide with others in a process that can produce hailstones several inches broad. The stronger the updraft, the larger the storm’s hail will become.

Kentucky Emergency Management, the leading disaster response agency in the state, received reports of hail ranging between a quarter-inch and 2.5 inches in diameter. In Lexington and Central Kentucky, the NWS warned of baseball-sized hail when the storm landed around 10 p.m. Sunday.

According to Neudorff, a rough average size of hail for Kentucky is less than an inch, or about the size of a coin.

“Keep in mind that 1 inch hail or a quarter is the criteria for a severe thunderstorm and we get a lot of pea, dime, penny and nickel size hail,” Neudorff wrote in a follow-up email. “To put yesterday in perspective, there were a lot of inch and a half to 2 inches with even near 3 inch size hail in parts of southern IN. That is very rare for this area. In our messaging leading up to the event, large damaging hail was mentioned.”

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