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
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
