Module 9 Thunderstorms Flashcards
How many thunderstorms form on Earth approximately every day?
About 44,000 thunderstorms.
What is the primary cause of thunderstorm formation?
Moist, unstable air being lifted vertically.
What initiates the vertical lifting of air that leads to thunderstorms?
Heating of the Earth’s surface.
What happens to moisture as it evaporates from the surface?
It increases humidity, causing air mass instability.
What are the two common triggers for thunderstorms?
- Orographic lifting of wind
- Collision of two fronts
What is the first stage in the development of a thunderstorm?
Cumulus/Developing Stage.
What type of cloud forms during the cumulus stage?
Cumulus or towering cumulus cloud.
What occurs as water droplets coalesce in the cumulus stage?
They eventually fall as precipitation.
What characterizes the mature stage of a thunderstorm?
Cloud becomes a cumulonimbus cloud rising 5–10 miles high.
What stops the rising of a thunderstorm cloud during the mature stage?
When the cooling air temperature equals the surrounding air temperature.
What happens to air when precipitation begins to fall?
It cools the air due to evaporation, creating downdrafts.
What indicates a mature thunderstorm?
Equal amounts of air rising in updrafts and sinking in downdrafts.
What shape may the top of a mature thunderstorm cloud take?
Anvil shape.
How quickly can thunderstorms form, grow, and dissipate?
In under thirty minutes.
What are the criteria for a thunderstorm to be classified as severe?
- Tornadoes
- Large hail (larger than three-quarters of an inch)
- Winds greater than 58 mph
What is a characteristic of severe thunderstorms?
Fast-rising, warm air that overshoots the anvil top.
What is a supercell?
A severe, long-lasting thunderstorm with strong updrafts.
What can updrafts of 70 mph in supercells carry?
Hail.
What is a downburst?
A rapid fall of cold air through a supercell that bursts out from the storm.
What is the difference between a macroburst and a microburst?
- Macroburst: Exceeds 2.5 miles in diameter, winds up to 124 mph
- Microburst: Less than 2.5 miles in diameter, winds up to 155 mph
What causes lightning in a cumulonimbus cloud?
Friction of updrafts and downdrafts producing static electricity.
What are the charged particles involved in lightning formation?
- Step leader (negative ions seeking ground)
- Streamers (positive ions moving up)
What temperature is reached during a lightning flash?
Between 28,000°C and 30,000°C.
Why do we hear thunder after seeing lightning?
Lightning travels at the speed of light, while sound travels much slower.
