10: Thunderstorms
- Page ID
- 46836
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A thunderstorm is a rainstorm accompanied by thunder and lightning. Figure \(\PageIndex{1}\) depicts lightning and dark clouds during a thunderstorm in northern Sicily. Thunderstorms are deep convective clouds that have a significant vertical extent all the way from the boundary layer to the tropopause. Thunderstorms often bring severe weather, including heavy rain, hail, lightning, damaging winds, and occasionally tornadoes. Thunderstorms are sometimes thought to be synonymous with cumulonimbus clouds, though not all cumulonimbus clouds are thunderstorms.
Figure \(\PageIndex{1}\): Lightning strikes the water from a thunderstorm in Northern Sicily. (CC BY-SA 2.0; Gerlos via Wikimedia Commons).
The primary energy driving thunderstorms is the conversion of warm, moist air into clouds and precipitation, which releases significant latent heat during condensation. Over land, thunderstorms occur most frequently in the late afternoon and early evening. Storms are most likely to occur soon after the warmest surface temperatures, which help warm air parcels gain the initial buoyancy needed to begin rising. Thunderstorms can last anywhere from less than an hour to more than 12 hours. Due to their rapid growth, relatively small size (mesoscale), and sensitivity to environmental conditions, it is challenging to predict a storm's exact time and location. Typically, a forecast will say there is a chance of thunderstorms over an area—meaning that although conditions are conducive for a storm, the forecasters don’t know precisely where or when it will occur.
By the end of this chapter, you should be able to:
- Name and label parts of a thunderstorm.
- Describe the importance of updraft, downdraft, and windshear for a thunderstorm.
- Identify a few types of thunderstorms (airmass, MCC, squall line, supercell, etc.).
- Discuss a few favorable conditions for thunderstorm formation.
- 10.1: Thunderstorms formation and types
- This page covers the formation and development of thunderstorms, highlighting the importance of wind speed and direction with altitude, particularly wind shear, which helps prolong their lifespan. It outlines the life cycle of thunderstorms and distinguishes between airmass and severe thunderstorms, the latter needing wind shear and often resulting in complex structures like squall lines and supercells.
- 10.2: Precipitation during Thunderstorms
- This page discusses thunderstorms, highlighting their deep convective clouds that generate intense rainfall, with rates up to 1000 mm per hour. It explains the coexistence of ice crystals and droplets, leading to phenomena like graupel and hail. Graupel is formed from supercooled droplets, while hailstones develop through droplet accretion, necessitating strong updrafts.
- 10.3: Winds during thunderstorms
- This page explains gust fronts in thunderstorms, emphasizing the impact of downdrafts that create boundaries between cold and warm air. It details how gust fronts lead to temperature drops and wind shifts. The page also covers downbursts and microbursts, highlighting their significance as intense downdrafts capable of causing substantial wind damage to structures and aircraft, despite their small size.
- 10.4: Lightning and Thunder
- This page explains lightning as an electrical discharge in thunderstorms, mostly occurring within clouds, with only 20% reaching the ground. It heats the air to 30,000°C, creating thunder, which can be timed from the flash. Lightning results from charge separation in clouds, due to interactions between graupel, hail, and supercooled droplets. Thunderstorms need these ice phase processes for both lightning and thunder.
- 10.5: Tornadoes
- This page discusses supercell storms as rotating thunderstorms capable of producing tornadoes due to wind shear. It emphasizes the complexities of tornado forecasting, which involves issuing Watches and Warnings based on atmospheric conditions and recognizing radar signatures like hook echoes. Tornadoes are classified using the Enhanced Fujita scale based on damage.
- 10.6: Keeping Yourself Safe
- This page focuses on storm hazards, stressing the seriousness of severe weather's unpredictability. It outlines key safety measures like avoiding flooded areas and seeking shelter during storms. The chapter promotes proactive emergency planning due to the limited time for reactions. Additionally, it encourages readers to think about storm logistics, including the impacts of hail and lightning distances, underscoring the necessity for preparedness against severe weather events.
- 10.7: Exercises
- Some exercises to review the topics covered in this chapter.
Thumbnail: Lightning during a thunderstorm. Thunderstorm by Gerlos is licensed under CC BY-ND 2.0