In the days following a winter storm, it’s the perfect time to dive into a fun winter precipitation experiment. In this Kayleigh Weather Workshop experience, meteorologist Kayleigh Thomas shows everyone the different types of winter precipitation and how it forms.
What do you need:
- A few towels
- A dull knife or something else used for scraping
- A permanent marker
And that’s all!
What is happening:
During the first week of February, we saw a winter storm move across the Big Country, and you’ve heard meteorologists talking about this system for about a week before that. In my forecast, I said several times that the type of precipitation that fell was; “temperature dependent”, but what does that mean?
Simply put, the type of precipitation we see on the surface – rain, freezing rain, sleet or snow – depends on the temperature of the surface, all through the atmosphere. It also depends on where the freezing line is.
A freezing line is the height in the atmosphere where the temperature is at the freezing point, 32°F or 0°C. Above this line, the temperature is below zero. Below this line, the temperature is above zero.
It can be difficult to predict where this line settles in advance, which is why meteorologists often use the phrase “winter mixing.” It just means you can see any type of winter precipitation.
So in this week’s experiment, we’re going to create a column of atmosphere to see what kind of precipitation would result from that setup.
All you’ll need are Oreos, or any type of cream-filled sandwich cookie, and a napkin or plate. You need about 11 cookies, if you want to configure them all at the same time.
First, take out your cookies and carefully separate the center of the two cookies.
Place the biscuits on one side and the cream on the other.
Label the napkin with the cookies, “Above 32°F,” and label the other napkin, “Below 32°F.”
Now, we’ll start with the simplest type of precipitation: snow.
For snow to fall, the surface, as well as the entire column of atmosphere above it, must be below zero. This is my favorite column because everything is icing!
The next easiest configuration is rain. Most of the time, rain starts out as ice or snow because it is so high in the atmosphere. However, when this ice crystal falls, it falls through warmer parts of the atmosphere and melts.
So you start with a disk of frosting and then the rest of the column is cookies, because it’s above freezing.
Freezing rain and sleet are a little trickier.
We’ll start with the sleet. The pattern is similar to snow, except it has something meteorologists call “a hot nose” in the middle.
It starts below freezing, but then drops into a layer of temperatures above freezing. This allows the ice crystal to partially melt before falling into another layer of sub-freezing temperatures. This allows the crystal to refreeze into pellets of ice.
This column of atmosphere is mostly glazed with a small piece of biscuit to represent that warm nose.
And our last type of precipitation – freezing rain!
Freezing rain starts as an ice crystal in the clouds, like all other types.
Then, just like rain, it falls through more of the atmosphere that is above 32°F.
Unlike rain, the surface for Freezing Rain must be at or below freezing point. Indeed, when the rain falls, it freezes on contact with freezing objects.
Freezing rain is one of the most dangerous types of winter precipitation, due to how quickly ice can build up. This column of cookies will be mostly cookies, but reserved by frosting.