When we combine what we know about air masses, fronts and air pressure, we start to see how thunderstorms form.

1. Winds and Thunderstorms Kella Randolph M. Ed.
https://3.bp.blogspot.com/Gc30eS8IpF0/W6lMQNAEYzI/AAAAAAAAnho/tEmBgJXam0kR
Ym3QhwW4U7zQogkFqxNTACLcBGAs/s1600/Horrifying%2BStorm%2BFootage%2BDepict
s%2B%2527Cloud%2BTsunamis%2527%2B1.jpg

2. How do
thunderstorms
form?
• When we combine what
we know about air masses,
fronts and air pressure, we
start to see how
thunderstorms form.
https://62e528761d0685343e1cf3d1b99a743ffa4142d9d7f1978d9686.ssl.cf2.rackcdn.com/files/674
48/area14mp/image-20141217-19873-18m13c8.jpg

3. Fronts
• The front is where the cooler and more dense air moves
toward and below a warmer air mass. The warmer air mass is
forced up into the atmosphere creating storms. The area
known as “tornado alley” is where cold dry air from the
northwest collides with warm moist air coming up from the
Gulf of Mexico.
http://www.severe-weather.eu/wp-
content/gallery/satelite-images/satelit_3jul2017.png
https://upload.wikimedia.org/wikipedia/commons/thumb/4/43/Tornado_Alley_Diagram.svg/
1200px-Tornado_Alley_Diagram.svg.png

4. Change in air
pressure creates
wind.
• The difference in air pressure at a cold
front changes quickly. This large change
in pressure means a stronger wind
https://upload.wikimedia.org/wikipedia/commons/thumb/e/e9/Wind_circulation.svg/433px-Wind_circulation.svg.png
https://cdn.pixabay.com/photo/2017/09/05/21/42/plant-2719255_960_720.jpg

5. Creating
precipitation
The rising air will cool and will produce
clouds and precipitation.
https://i.imgur.com/F3kMnuB.jpg

6. Making fair
weather
Warm air that sinks will cause
the clouds to dissipate and
therefore produce fair
weather.
Image:
https://c.pxhere.com/photos/29/b7/airplane_aviation_
blue_celebration_chute_cloud_demonstration_descend
-819858.jpg!d

7. What causes
disturbances?
• Where the colder, denser air
meets the thinner, warmer air is
where we find the strongest winds
and disturbances.
• Image:
https://tinylessonsblog.files.wordpress.com/2013/05/thunder-
cloud.jpg

8. Temperature and air
pressure rising
• As the temperature gradient increases, the pressure
gradient increases. The stronger these changes, the stronger
the winds. Weather happens in the troposphere because the
air is warmer near the surface of the earth.
https://s3-us-west-2.amazonaws.com/courses-images-archive-read-
only/wpcontent/uploads/sites/682/2015/07/22230118/201412291419878707620376_ecaef30536692518d738ce07b6bd
e8fb-201412291419879341807763.png
https://opentextbc.ca/chemistry/wp-content/uploads/sites/150/2016/05/CNX_Chem_09_02_Amontons2.jpg

9. Oceans have a lot to
do with weather.
• We have to take the oceans into account when studying
storm formation. Warm waters add a lot of moisture to the
atmosphere. This is why it rains often in the south east.
• Image left: https://62e528761d0685343e1c-
f3d1b99a743ffa4142d9d7f1978d9686.ssl.cf2.rackcdn.com/files/108763/width754/image-20160120-26105-18vrtq0.jpg
• Image right: http://www.arttel.co.nz/wiki/lib/exe/fetch.php/living_in_new_zealand:walker_circulation.jpg

10. Unstable air masses
If an air mass is given a nudge to move up or
down, it is considered unstable. These are
most often a warm moist air mass near the
surface and cold dry air above that are
pushed to move in opposite directions.
Image: http://www.free-online-private-pilot-ground-
school.com/images/occluded-front.gif

11. Why does warm air
rise?
• What causes the warm air to rise? The sun warms the air near the ground.
This warm air becomes less dense and begins to rise. This is the main source
of lift for warm air masses.
http://www.thunderboltkids.co.za/Grade4/03-energy-and-change/images/gd-0005.jpg

12. Water vapor
condenses at higher
altitudes.
• When the warm, moist air rises, it will cool at higher altitudes.
When it cools enough, the water vapor will condense forming
rain clouds.
https://www.e-education.psu.edu/meteo3/sites/www.e-
education.psu.edu.meteo3/files/images/lesson6/ccn_graphic0605.jpg
https://bio4esobil2011.files.wordpress.com/2012/05/water-cycle-i.jpg

13. Lightening
It wouldn’t be a proper thunderstorm
without lightning. Lightening is a spark of
electricity between the clouds.
With the unstable air moving, positive and
negative charges build up, and a quick
discharge of electricity is released - lightning.
Each lightening flash balances the charge,
until they build back up.
https://i.stack.imgur.com/5d63b.jpg

14. Thunder
• Every time there is lightning, there is thunder. When
lightning happens, there is immense heat - 18,000 degrees
Fahrenheit. The temperature rises so quickly that it causes
the air to expand creating a sound wave - thunder.
https://upload.wikimedia.org/wikipedia/commons/thumb/7/71/Thunder_diagram.png/400px-Thunder_diagram.png
https://static.pexels.com/photos/680940/pexels-photo-
680940.jpeg

15. https://3.bp.blogspot.com/-
Gc30eS8IpF0/W6lMQNAEYzI/AAAAAAAAnho/tEmBgJXam0kRYm3QhwW4U7zQogkFqxNTACLcBGAs/s1600/Horrifying%2BStorm%2BFootage%2BDepicts%2B%2527Cloud%2BTsunamis%2527%2B1.jpg