ST. LOUIS, Mo. – This June, July, and August, our severe weather events displayed astonishing lightning and flash flooding, especially lightning.
Lightning is sneaky and dangerous. Negative lightning can strike 11 miles away from the thunderstorm and positive lightning can reach 25 miles, seeking tall objects. Bolts can be as narrow as the width of a quarter.
“It is very dangerous, superheating the air to 50,000 degrees instantaneously,” said Matt Beitscher, National Weather Service.
In fact, lightning ranks fifth in fatalities across the U.S. on a 30-year average. As hail and graupel form in the middle part of thunderstorms, positives charges are deposited high in the cloud by updrafts while negative charges sink to the base of the cloud. From there, step leaders of negative charge surge toward the ground in quick impulses, lasting less than 1/100 of a second. You can’t see them.
At the same time, positive charges stream upward along tall objects. When the positive charges collide with the descending avalanche of negative charges, a return stroke, about the width of a quarter, flashes skyward, producing the bolt you see and the thunder you hear.
Negative charges step down from the cloud, positive charges stream up from tall objects and collide with the negative charges releasing a brilliant flash from the ground to the cloud.
Negative cloud to ground lightning contains 300 million volts and 30,000 amperes, creating the bright discharge you see. Although more research has to be done, the hygroscopic condensing nuclei from forest fires and dust from dry conditions out west could have enhanced the lightning displays and flash flooding rainfall here and across the country this summer.