Graupel, sleet, hail, what is the difference?

11-21-hail-image

Columbus (WCMH) – Over the weekend, most of us were lucky enough to see a little snow.   I also heard people say they saw sleet too, but was it really sleet or “graupel”?   Well, the clouds might be able to answer that question, or I can here for you🙂

 

The temperature of the clouds and near the ground can tell us what to expect, and we start with RAIN:

 

11-21-rain

 

Rain falls when the temperature is above freezing from the clouds all the way down to the ground.

 

What makes snow?

11-21-snow

Snow falls when water droplets in the clouds freeze and form ice crystals, they stick together and get big enough to fall as snow.   The warmer the temperatures are in the clouds, the bigger and wetter snowflakes could be as they melt on the edges and stick together.

Also, snow can fall when surface temperatures are a bit above freezing.  The snowfall will generally melt as it is falling, but the bigger flakes will still be visible before melting completely.

 

What makes freezing rain?

11-21-freezing-rain

Freezing rain occurs when rain droplets fall through a warmer than freezing cloud, through the air below the cloud that is above freezing keeping the droplet as rain.   The air near the ground is cooled and sub-freezing, and that droplet freezes on contact, forming a coating of ice.  On the ground and other surfaces freezing rain looks like a shiny, slippery, rather smooth coating.

 

What makes sleet?

11-21-sleet

Sleet forms when melted snowflakes from the clouds, or rain that falls out of the clouds falls through a thicker, and higher sub-freezing layer.   It causes the rain, or melted snow to refreeze again as an ice pellet.

Typically these little tiny balls of ice hurt a little when they hit you, and because they are small, they will bounce too.   When you look at sleet, it will appear to take on a bit more of a clear appearance, like an ice cube, but round like a tiny ball.

 

How can I tell sleet and hail apart?

An easy way is the time of year.   Sleet will fall in late Autumn, Winter, and early Spring.   Hail will fall in Spring, Summer, and Autumn.

This isn’t 100% perfect though, so the next thing you can do is see the process that caused the item to fall.   If it is associated with a thunderstorm, it is hail.   Hail forms when rain droplets are pulled upwards by strong updrafts associated with thunderstorms.   The updrafts are strong enough to pull the droplet past the freezing level in the cloud and turn it into an ice pellet.

As hail gets heavy, it will fall, the stronger updrafts will lift the hail back up, colliding with cold rain drops which will make it bigger.  It will then refreeze as it gets higher in the clouds and get bigger and fall.   If the updrafts are strong enough, hail will repeat this process several times, even connecting with other hail to make bigger, odd shaped hail.

Eventually, the hail will be too heavy and fall to the ground.   This is why when hail is huge, we know the storm is massive and strong, because the updrafts are strong enough to push this heavy object up high enough into the clouds repeated times.

 

What is Graupel then?

11-21-graupel

Graupel is a snowflake that falls through the cloud and gets covered by a supercooled rain droplets.  They freeze and cause a coating of water around the snowflakes.   When they hit the ground they sometimes will bounce a bit too, but are much softer than hail, but harder than a snowflake.

They also have a white appearance to them, vs the clear look of sleet.   Graupel is generally pretty smooshy if you push on it with your hand as its basically a snowflake that has a thin layer of ice over it.

 

The easiest way I can describe what Graupel looks and feels like is, Dippin’ Dots.   I can’t vouch for the taste, but I am guessing Dippin Dots taste a lot better, and less atmospherey🙂

vanilla-dippin-dots

(thank you to www.dippindots.com for the image above)

 

 

If you ever have any questions about winter weather of any type, or any other weather question, email me: dmazza@wcmh.com

-Dave

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s