The graupel or small
hail can be seen as the round ice balls on the hood of this car.
They are all quite
small (note size comparison to the coins) and spongy.
___________________________________________________________
| Yes, that was thunder and lightning mid-day
today, December 15, 2000 in Lincoln, NE. It is called "thundersnow".
During the October 1997 snowstorm in eastern Nebraska, we had thundersnow
for several hours during the height of the storm.
Is it unusual? Yes, it is rare, but it has happened in Lincoln on several occasions over the years, averaging at least once per winter season. Was that hail? It was a type of hail known as "graupel". It is a soft spongy hail and can be seen in the photograph below. It commonly occurs in summer in the Rocky Mountains and can occur here in winter and in very early Spring. We also had sleet which is refrozen rain, which begs the question, how could it be raining with the temperature at 20 F? It is warmer than freezing over Lincoln today. The cold air is in a shallow layer less than 1500 feet thick. The snow that was falling from the mid layers of the troposphere melted as it fell into a layer of temperatures around 40 F, then as it fell into the shallow layer near the surface the raindrops flash froze creating sleet. There was some instability, just like spring, in the atmosphere as the clouds moved in from the south and some of the raindrops were sent back up to a much cooler layer forming the small hail stones known as graupel. They didn't take as many round trips as spring and summer hailstones so they were not layered. The links below take you to the radar and
lightning maps from this midday event.
|
The graupel or small
hail can be seen as the round ice balls on the hood of this car.
They are all quite
small (note size comparison to the coins) and spongy.
___________________________________________________________
|
University of Nebraska-Lincoln High Plains Regional Climate Center |