Tuesday, 21 July 2015

Hail and Snow - what's the difference? and some Rainy Day activities

Cold weather is sweeping across New Zealand in waves this winter. Children who have never seen or touched snow before have had the chance to build snow people and have snow fights. And discover that while it might be fun in its snow form, it soon melts and turns into wet slush.

I had to walk up into the hills to the snow. But down where I live near sea level we've had hail which lay on the ground long enough, it almost looked like snow.

What, I wondered, is the difference between hail and snow?

My search led me to many complicated explanations. I understand why scientists want to give as much detail as possible and explain a phenomenon as accurately as possible, but, for young children, a simple explanation is what's required.

Here's a simple explanation:

HAIL is frozen rain drops
SNOW is made up of ice crystals 

And here's a slightly more complicated version:
Hail is formed in rain clouds that get very cold, so the rain drops turn to ice.
Snow is formed when water vapour (think of how you can see your breath on a cold morning) in clouds freezes so quickly that it goes straight from vapour to ice crystals without turning into water first. (Usually water vapour cools and turns into water and then cools more to turn into ice.) This is how ice crystals form. The temperature below the cloud (and on the ground) needs to be cold enough that the snow doesn't melt before it reaches the ground.

My search took me to lots of sites to find ones that were clear and easy to follow.
A good site aimed at children is Severe Weather 101.
I also like this student's attempt at explaining it on You Tube by Izzy M. Why does it rain, hail, sleet and snow?
Here is a more technical answer on You Tube: MetOffice UK

On the way I learned that there are many different names for precipitation - wet stuff that comes from clouds.
rain, sleet, snow, 
drizzle, powder snow, 
firn, blizzard, shower,
soft hail, 
snow pellets, 

There are sayings too, which try to describe the kind of rain or snow like:
raining cats and dogs,
teeming down
biting rain

A couple of my own descriptions are:
horizontal rain (rain in strong wind coming in at an angle)
tramping rain (heavy rain that would make noise on a hut roof)

Some rainy/snowy day activities
Next time it rains, hails or snows, invent your own names and phrases to describe the kind of precipitation. Create a precipitation picture dictionary.
Make paper snowflake patterns and stick them on the window. Snow flakes always have 6 points.
Create your own video explanation for rain or snow.
Play in the snow.
Cut a hailstone in half and look at it through a magnifying glass.