Why tornadic storms often also produce large, damaging hail
After a volatile Thursday that saw tornado watches and 2-inch hail reports across the Midwest, Central Missouri is finally seeing a break in the action. Something you may have noticed, though, is that the majority of these tornado-producing storms also had this large hail to accompany them.
While they look like two completely different beasts, one being a falling ball of ice and the other being a rotating column of air, hail and tornadoes are actually caused by the exact same atmospheric engine: the rotating updraft.
In a typical spring thunderstorm, air rises and falls in a relatively simple cycle. However, in the supercell thunderstorm, the rising air, or updraft, begins to rotate. This rotation, or mesocyclone, acts like one massive vacuum.
To grow a hailstone to the size of a golf ball or a baseball, you need a vacuum strong enough to keep a heavy chunk of ice suspended miles high in the "growth zone", or the freezing upper levels of the storm. The stronger the updraft, the longer the ice stays suspended, layering on more water and freezing until it finally becomes too heavy for the wind to support.
That same intense, rotating "suction" is what provides the foundation for a tornado. When that vertical rotation is stretched and tightened near the ground, a tornado can form. Essentially, if a storm is powerful enough to produce destructive hail, it has already proven it has the "engine" necessary to produce a tornado.
If they come from the same engine, why don't they always hit the same spot? Think of a supercell like a house with different rooms.
Most of the public experiences the forward flank downdraft first. This is the "front room" of the storm where heavy rain and the hail core are located. If you are standing in the driveway and see large hail falling, you are likely just north or northeast of the storm's most dangerous rotation.
The tornado typically lives in the "back room" or the hook echo. On radar, this looks like a small tail curling around the back of the storm. Because of the way these storms move, the hail often acts as the opener, providing a final warning before the tornado-producing portion of the storm arrives.
This is a pattern that can be measured over years of data. During the peak months of hail production in March, April, and May in Missouri, the climatology of tornado-producing storms falls right in line with it. This is because the ingredients required for both, that being moisture, instability, and wind shear, are at their most volatile during that period of time.
Tornadoes will not always be present when hail storms are, but if the right conditions are met, the hail can be treated as a warning sign for more impactful weather to come. No matter the type of severe weather, whether it is damaging winds, large hail, or tornadoes, it is always good practice to stay in your safe spot until you are completely in the clear from storm threats.
