Nelson, who works at the NWS office in Peachtree City, said the January storm did not appear to be that large of an event from a meteorological standpoint.
“The one in January, really meteorologically, was not a big storm. I don’t think anyone received more than 3 inches anywhere in the state. So as far as our radar goes, here’s all these historical storms, all of our computer forecast. When we get closer to the event we’re looking at observations, we’re looking at radar, satellite, seeing if the models are on track. Nothing was telling us meteorologically this was going to be a big day,” Nelson said.
Although NWS service predicted 2 inches of snow for Atlanta two days before the storm, Nelson said, outside models were predicting the snow would stay south of Atlanta or perhaps stay only along the coast. However, Nelson said there was something “unique” going on with the Jan. 28 storm that meteorologists were not aware of.
“We were worried that some extremely dry air near the ground that was going on, the computer models weren’t handling that. There was — the observations were supporting it,” he said. “They didn’t forecast that. Maybe that would delay the snow from later than what we were even talking about, so more like the afternoon.
“Some of our forecasts said it’s going to start at noon, to kind of cover ourselves, but deep down we were kind of worried it would come later because of this incredibly cold air. But, guess what? That sure didn’t care that there was dry air. It went ahead and snowed right on top of it as early as 11 o’clock in the morning. I think they were reporting snow flurries in the air as early as 10, 10:30 in Atlanta. That’s what happens. We had trouble predicting it.”
Compounding the 2 inches of snow during a weekday — an echo of a 1982 storm that also paralyzed Atlanta, Nelson added — was the ice that formed on the ground. The wet snow melted in spite of the 26 or 27 degree temperature because of the warm ground, Nelson explained. Then the snow quickly refroze.
“That’s what I wished we could have done a better job [at] was to predict the temperature. We kind of had a good handle on the temperature because we knew it was going to be cold. Looking back I wish we’d done a better job of highlighting that, but maybe that was the missing ingredient we were missing,” he said.
Part of the NWS’ job is to brief elected officials and municipal employees on what they can expect in terms of weather, Nelson continued. The NWS does not make decisions such as school closings.
“Our job, we don’t actually push the button to sound the sirens. We don’t activate road crews, we don’t tell schools to close. We give them what our best guess is of what is going to happen. We provide some basic facts to support it so it doesn’t take up much of their time,” he said.
As for the forecasts themselves, Nelson said the computer models are created using collected research.
“In a nutshell the computer [model] is basically science. It’s not a computer forecasting the weather for you,” he said. “All the scientists worked hard and built their knowledge of the atmosphere to make these models work. That’s the reason they’re successful. It’s a gradual process. It all comes from research and science.”
One snowstorm where the models and forecasts were accurate was the 1993 snowstorm. Although many were concerned about the wind more than the snow during that storm, Nelson said, the forecasts were successful.
“On this particular day it was an amazing success story for computer models. They were forecasting that even a week in advance. The forecast never changed. It was amazing, because usually they drift apart and they’ll say the storm’s going to go over to the east, maybe not as strong in the west,” he said.
During his lecture, titled “Winter Weather Frequency and Trends in Georgia,” Nelson also looked at the history of snowstorms in Georgia. Beginning with more than 12 inches of snow during the Revolutionary War, to storms in the 1880s and all the way to the 1993 snowstorm, Nelson highlighted the cyclical nature of how some decades were colder than others and produced more snow.
“Just to kind of emphasize the point that in previous decades, and even centuries, we were definitely in a colder pattern,” he said. “There’s no mistake about that. You can bring politics into it if you want, but to me climate change is objective. Looking at history — it’s history. For better or worse, it’s as accurate as it’s going to get.”