We have had some weird weather here in Chicagoland lately. It’s unseasonably cold for April, and last Saturday the weather changed about 10 times! When I looked out the window at 3 pm, it looked like blizzard conditions, with the light snow whirling madly against strong winds. But at 5 pm, two hours later, the sun was shining!
The ground is too warm now for snow flurries to stay on the ground long. Especially when those snowflakes were not really snowflakes – they were actually graupel!
Most people who live in areas with cold, snowy winters and volatile springs are probably familiar with graupel, even if they’ve never heard the word – I never had, until Monday, when my stepdaughter told me about it. She gets a daily email with an unusual word and its definition. It just happened to be appropriate for these last few days of strange weather.
Graupel is precipitation that is formed when water forms around a snowflake and freezes. Similar in appearance to hail, it is distinguished by the fact that it is not solid like hail. If you squeeze a piece of graupel between your fingers, it will disintegrate, because only snow is inside. Since hail is actually a solid bit of ice, it will not disintegrate when you squeeze it.
Wikipedia gives this scientific explanation of the phenomenon:
Graupel, also called soft hail, snow pellets, or “grail” is formed when supercooled droplets of water are collected and freeze on falling snowflakes, forming 2-5 mm of rime. …
Under some atmospheric conditions, snow crystals may encounter supercooled water droplets. … Contact between a snow crystal and the supercooled droplets results in freezing of the liquid droplets onto the surface of the crystal. … When this process continues so that the shape of the original snow crystal is no longer identifiable, the resulting crystal is referred to as graupel. Graupel was formerly referred to by meteorologists as soft hail. However, graupel is easily distinguishable from hail in both the shape and strength of the pellet and the circumstances in which it falls. Ice from hail is formed in hard, relatively uniform layers and usually falls only during thunderstorms. Graupel forms fragile, oblong shapes and falls in place of typical snowflakes in wintry mix situations, often in concert with ice pellets. Graupel is also fragile enough that it will typically fall apart when touched.
The National Weather Service/NOAA has a chart describing different types of precipitation. For graupel to form, surface temperatures should be 45 degrees Fahrenheit or lower. Cloud temperatures are mostly below freezing with some portion colder than 15 degrees Fahrenheit. It usually occurs when the lower atmosphere is very unstable.
When you see graupel on the ground, it may remind you of the dessert “Dippin’ Dots”:
In fact, one “Idaho Dad” has a blog post for “Graupel Delight”!
Origin: The origin of the word graupel is from German, according to dictionary.com: 1885-90; < German; diminutive of Graupe hulled grain. However, its actual origin is probably from Serbo-Croat krupa; related to Russian krupá peeled grain.
Because of English speakers’ tendency to create verbs out of nouns, I began to use graupel this way: Instead of “It’s snowing!” or “It’s hailing!” I could be more specific by saying, “It’s graupeling!”