LANSING, Mich (WLNS) — Even if you’ve never heard of the word ‘graupel’ before, odds are you’ve experienced it if you live in Mid-Michigan.
Graupel is a unique type of frozen precipitation. Pronounced ‘graw-pull’, it’s the name given to the small pellets that form when supercooled water droplets (below 32°F) freeze onto the surface of snowflakes as they fall from the cloud to the ground.
“A lot of people will naturally confuse graupel with hail and sleet,” said National Weather Service Meteorologist Walt Felver. “They’re similar, but the formation processes are different.”
Graupel starts as snowflakes that form up in the clouds. As the snow falls from the clouds towards the surface of the earth it encounters a pocket of supercooled water droplets. These droplets flash-freeze onto the snowflakes in a process called riming. This transforms the snowflakes into small balls, typically pea-sized or smaller.
Its soft, pellet-like appearance is the reason why it’s called graupel. According to the Merriam-Webster dictionary, the word graupel comes from the Germanic word Graupe, meaning “pearl barley”, a clear reference to the appearance of this weather phenomenon. The word graupel was first used in a weather update back in 1889 and has been used by meteorologists ever since.
Sadly we don’t get to use this unique word as often as rain or snow due to graupel’s specific atmospheric condition requirements to form.
“To get graupel, you need certain conditions to occur,” said Felver. “These conditions, most of the time, occur in autumn and again in early spring. You need cold air aloft but you also need warmer air near the surface.” This means it’s typically too hot for graupel in the summer and too cold for it in the winter.
This winter in Mid-Michigan you have a better chance to encounter graupel than in recent years. This is because we are now in an El Niño year. El Niño is the name given to a large-scale weather pattern that we see peak in the winter months in North America. Due to warmer waters in the Pacific Ocean, our average weather pattern shifts and as a result, it typically becomes warmer and drier than normal across much of the Midwest.
Unlike hail, graupel is relatively safe to go outside in and experience. Despite its icy appearance, graupel is quite fragile, and will rapidly melt in your hand. Plus it’s typically too small to damage vehicles or roofs, however, it can still sting if it hits exposed skin.
Sadly graupel can cause problems on the roadways in mid-Michigan. “If you get enough of it on the ground and the roads get slippery, someone can wipe out,” said Felver. “You always have to pay attention to what’s going on and exercise caution.”