Thunderstorms How Thunderstorms Form 1 Must be an

Thunderstorms

How Thunderstorms Form 1. Must be an abundance of moisture in lower atmosphere 2. Must be something that lifts the moisture 3. The portion of the atmosphere through which the cloud grows must be unstable

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

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

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

Stages of Development 1. Cumulus Stage 2. Mature Stage 3. Dissipation Stage

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

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

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