Hail forms in cumulonimbus clouds through the following process: 1) Warm air near the ground rises into the atmosphere and cools, causing water vapor to condense into clouds. 2) Strong updrafts in cumulonimbus clouds contain supercooled water droplets that freeze upon colliding with condensation nuclei, starting the growth of hailstones. 3) As hailstones fall through the cloud, they accumulate more frozen water on contact with supercooled droplets, growing in size until they fall to the ground as hail.

1. Formation of Hail in
Cumulonimbus Clouds
By Sarah Allen
**Audio explanations can be found on
slides 2 and 4**

2. Formation of Cumulonimbus Cloud
• The sun heats the ground over the course of
daylight hours, also heating the air close to the
ground
• That air then rises because it is less dense than
the cold air above it
• The air cools as it rises, lowering its ability to hold
water vapor
• When the dew point is reached, the vapor
condenses and forms puffy clouds
• That condensation releases heat, causing the air’s
rise to accelerate
• Cumulonimbus clouds contain a lot of energy,
contained in updrafts and downdrafts

3. Cumulonimbus Cloud
P
i
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4. Formation of Hail
• Hail forms in the cloud’s main updraft out of super
cooled water
-super cooled water is water which exists as a
liquid, but is bellow 273 K
• the super cooled water freezes when it encounters
condensation nuclei- small particles in the cloud
-example: salt, dirt, etc.
• the now frozen water is dragged down by gravity,
colliding with more super cooled water which will
freeze upon collision, increasing the size of the hail
• The hail will grow in size until it leaves the cloud and
falls to earth, causing a cold downdraft

5. Hail Formation within the Cloud
Image from NASA- http://scijinks.jpl.nasa.gov/review/rain/hail-formation-large.jpg

6. The Product: Hail

7. Sources
http://weather.ou.edu/~edavis/clouds.html
http://www.ucar.edu/communications/factshee
ts/Hail.html
http://scijinks.jpl.nasa.gov/review/rain/hail-formation-
large.jpg
http://stormgasm.com/4-17-
02LPday/tom%20pics/hail.jpg