Cumulus Clouds and Thunderstorms

Cumulus Clouds

• puffy, “popcorn-like” clouds
• cumulus humilis (humble):
  • fair weather
  • small
• cumulus congestus (heap):
  • towering cumulus clouds
  • heating causes vertical updrafts
  • air parcels cool as they rise
  • excess water vapor condenses
  • latent heat released
  • causes more updrafts

Thunderstorms

• cumulonimbus:
  • thunderstorm cloud
  • very large (tall), thick clouds
• thunderstorm = cumulonimbus clouds with lightning and thunder (and commonly rain)
• top of cloud is near top of troposphere
• base of cloud is near the ground
• strong updrafts and downdrafts (turbulent)
• looks like a mushroom or an anvil (well-developed)
  • anvil can be 10s of mile in diameter
• if very strong updrafts, then the dome of the cloud overshoots above the anvil
• storm energy from temperature and humidity

Thunderstorm Occurrence

• more commonly occur in:
  • tropical locations: abundant sunshine (heat) and moisture
  • late afternoons in the summer: most surface heating
• also in regions with convergent winds and/or lifting
  • mountains
  • land/sea boundary

Thunderstorm Fuel

• need constant inflow of warm, moist air or they die out
• most thunderstorms use up fuel (warm, moist air) and choke on their exhaust (cool, dry air)
• last only a half hour to an hour

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