1. Thunderstorms

2. How Thunderstorms Form
Must be an abundance of moisture in lower atmosphere
Must be something that lifts the moisture
The portion of the atmosphere through which the cloud grows must be unstable

3. Limits to Growth
If the previous 3 conditions are met storms will continue to grow until stable air is hit
Typical storms last about 30 minutes

4. Air mass T-storms Forms because of unequal heating of Earth’s surface
most common in mid-afternoon
2 common types
Mountain t-storms – orographic lifting
Sea-breeze – temp differences between water and land

5. Frontal T-storms Normally produced by oncoming cold fronts
Can last longer into the night

6. Stages of Development
Cumulus Stage
Mature Stage
Dissipation Stage

7. Cumulus Stage air begins to rise vertically
this creates an updraft, which transports moisture to the upper levels of the clouds
the moisture condenses into visible cloud droplets and releases latent heat
these water droplets will form precipitation which begins the next stage

8. Mature Stage
precipitation in the cloud forms at high, cool levels of the atmosphere
as precipitation falls, it cools the air around it
newly cooled air is more dense so it sinks rapidly to the ground along with precip and causes downdrafts
updrafts and downdrafts form a convection cell that produces the strong winds normally found with t-storms

9. Dissipation Stage production of downdrafts is the storms undoing
the convection cell can only exist with warm, moist air
once the warm, moist air runs out the updrafts stop slowly