North Austin, Elgin and Steiner Ranch saw hail sizes in the ping pong ball to golf ball range, while Marble Falls recorded baseball size hail!During a thunderstorm, there are large updraft and downdraft winds.
Within the updraft, debris and super-cooled water droplets ascend high up into the thunderstorm, where temperatures are much, much colder. In the higher atmosphere, temperatures are well below freezing. The droplets freeze, fall back down below the freezing level and gather additional water. Then the updraft takes over again, and the original ice pellet will gather another layer of ice from the water surrounding it.
For the April 9 storm, the National Weather Service got reports of hail as small as a marble, to as large as a baseball, so it's fair to say updrafts were as strong as 81 mph.Both types of hail form when strong updrafts are present. However, spiky hail occurs when the turbulent upper-atmospheric winds of a thunderstorm, make hailstones collide into one another. Water is also needed for spiky hail. The more moisture a thunderstorm holds, the more potential it has to carry supercooled water.
When hail stones collide, and have plenty of moisture and near-freezing temperatures surrounding them, the water on the outside of the hailstones acts as a glue, mixing of ice and water and congealing them together. Meteorologists call this"wet growth."Alternatively, there is also"dry growth," which occurs more so for the smooth hailstones.
It's worth noting that hailstones can get bigger by both wet and dry growth within one thunderstorm. This is why we saw variations in the type of hail during Tuesday's storms.