Automatic alerts from the Weatheradio receiver are getting a lot of attention at our home these days. On March 25-26, the city of Newnan was severely damaged by a tornado. Just a few days later, while our internet connection was still down, the Weatheradio forecast announced “strong thunderstorms in the morning.”
This made it immediately clear to me that another strong storm front was coming, one of those systems where Canadian air fights with Gulf of Mexico air. Morning thunderstorms in North Georgia are parts of severe weather. Afternoon thunderstorms are more common in summer, because summer weather in our region is quite different from springtime.
In the summer, the clash between the frontal systems stays well to our north because the U.S. South is consistently warm and moist. Air masses from Canada rarely find their way into Georgia during that season. When thunderstorms develop, they are usually local. As soon as the sun rises, about 6:30 a.m. in July, the ground warms up. Storms can’t form until the area is hot enough because the atmosphere is heated by the ground, not by the sun. A few hours after noon, the air gets lightweight enough to rise in big invisible bubbles. This is called convection. At maximum convection, the clouds take on a towering appearance and lightning may occur.
In April, we don’t see that much heat from the ground yet, so when a set of strong thunderstorms is forecast during morning hours, they must be getting their jump start from something else. That would usually be a cold front. The front tends to be the leading edge of a cold, dry mass of air visiting us all the way from Yukon or Saskatchewan, Canada. It bumps violently into the mild, humid air that’s been here. Even without very hot ground surfaces, the front forces strong convection and thunderstorms are likely.
People living at one of Georgia’s sea shores like Jekyll, St. Simon’s or Tybee Island may be getting ready now to pronounce me wrong. Morning thunderstorms in summer are common at the coast. But this happens at the edge of the ocean, not in North Georgia. Sea water retains its heat overnight, kicks the air above it into convection and forms storm cells. Sunrise breakfast at a beach house often comes with a great lightning show, miles offshore over the ocean.
Rudi Kiefer, Ph.D., is a professor at Brenau University, teaching physical and health sciences on Brenau’s Georgia campuses and in China. His column appears Sundays and at gainesvilletimes.com.