Chapter 10: Tornadoes and Thunderstorms

"Describe the characteristics of thunderstorms."

"Thunderstorms are storms that contain lightning and thunder, formed by rising air. Severe thunderstorms can produce large hail, wind gusts of 50 knots or more, or tornadoes."

"Define the stages of ordinary cell thunderstorms."

"Stage 1 is the cumulus or growth stage where warm, humid air rises and forms cumulus clouds. Stage 2 is the mature stage where downdrafts and updrafts create a cell. Stage 3 is the dissipating stage where strong downdrafts overpower updrafts, cutting off the storm's fuel supply."

"How do multicell thunderstorms differ from ordinary cell thunderstorms?"

"Multicell thunderstorms consist of multiple cells in various stages of development, can last for hours, and produce severe weather, including strong winds, large hail, flash floods, and tornadoes."

"What triggers the formation of thunderstorms?"

"Thunderstorms can be triggered by random turbulent eddies, unequal heating at the surface, terrain lifting of air, diverging upper-level winds with converging surface winds, and large-scale uplift along mountain boundaries."

"Explain the term 'gust front' in the context of thunderstorms."

"A gust front is the leading edge of cold out-flowing air from a thunderstorm, which can lead to straight-line winds."

"What is a squall line and where is it typically found?"

"A squall line is a line of thunderstorms typically found forming directly along a cold front."

"Describe the dissipating stage of a thunderstorm."

"The dissipating stage usually begins 15 to 30 minutes after the mature stage, where strong downdrafts overpower updrafts, cutting off the storm's fuel supply."

"What is a micro-burst?"

"A micro-burst is a localized downburst with winds extending 4 km or less."

"How does intense wind shear affect multicell thunderstorms?"

"Intense wind shear causes the storm to tilt, allowing the updraft to ride up and over the downdraft, which can lead to severe weather conditions."

"What are the conditions necessary for the formation of ordinary cell thunderstorms?"

"Ordinary cell thunderstorms form in areas of limited vertical wind shear and typically occur in warm, humid air masses away from significant weather fronts."

"What is the significance of the overshooting tip in thunderstorms?"

"An overshooting tip occurs when rising air intrudes into the stable stratosphere, indicating strong updrafts and severe storm conditions."

"Identify the date and name of a significant tornado event mentioned in the content."

"The Tri-state Tornado occurred on March 18, 1925."

"Describe a Bow Echo."

"A Bow Echo is a bow-shaped squall line that has the strongest winds near the center of the bow."

"Define a Derecho."

"A Derecho is characterized by straight line winds gusting to more than 58 mph with persistence."

"What is a Mesoscale Convective System (MCS)?"

"A Mesoscale Convective System (MCS) is a long-lasting complex of thunderstorms."

"Explain the formation of a Mesoscale Convective Complex."

"A Mesoscale Convective Complex forms when a number of individual multicell thunderstorms grow in size and organize into a large circular convective weather system."

"How do Supercell Thunderstorms differ from regular thunderstorms?"

"Supercell Thunderstorms are long-lasting storms with a single violently rotating updraft and strong vertical wind shear, producing the most severe weather."

"Identify the types of Supercell Thunderstorms."

"The types of Supercell Thunderstorms include Classic, HP (high precipitation), and LP (low precipitation)."

"What is a Mesocyclone?"

"A Mesocyclone is a rotating air column associated with an updraft in a thunderstorm."

"Describe a Wall Cloud."

"A Wall Cloud is a rotating cloud formed by humid low-level air being drawn into the updraft of a thunderstorm."

"How do thunderstorms contribute to flooding?"

"Thunderstorms can cause flash floods when water rises rapidly with little or no advance warning, often due to stalled or slow-moving storms."

"What is the estimated number of thunderstorms occurring daily worldwide?"

"It is estimated that there are about 50,000 thunderstorms occurring daily throughout the world."

"Explain the conditions conducive to thunderstorm formation in equatorial regions."

"The combination of warmth and moisture in equatorial landmasses makes them most conducive to thunderstorm formation."

"How does heat energy from thunderstorms affect the environment?"

"Heat energy liberated from thunderstorms helps distribute heat poleward."

"What is lightning?"

"Lightning is a discharge of electricity that usually occurs from mature storms and can travel within a cloud, between clouds, or from a cloud to the surrounding air."

"Describe the phenomenon of thunder."

"Thunder is a booming sound wave caused by the explosive expansion of air due to heat from lightning."

"How can one estimate the distance of lightning strikes?"

"Counting the seconds between seeing lightning and hearing thunder can provide a good estimate of the distance."

"What factors can affect the timing of thunder after lightning?"

"Air moisture and terrain can affect the timing of thunder after a lightning strike."

"Explain the process of electrification of clouds."

"Electrification of clouds occurs through interactions between different types and temperatures of cloud particles, creating regions of positive and negative charge."

"What is a Stepped Leader in lightning?"

"A Stepped Leader is a localized electric potential gradient that forms at the cloud base during a lightning strike."

"Define the Return Stroke in lightning."

"The Return Stroke is the ground to cloud stroke that follows the path of the Stepped Leader."

"What is a Dart Leader?"

"A Dart Leader is a single cloud to ground stroke that follows a Stepped Leader path, followed by a Return Stroke."

"How does a Stepped Leader sense charges on the ground?"

"The Stepped Leader does not sense the actual charges on the ground as it emerges from the cloud; it only senses charges within about 50 meters of its tip."

"Identify the types of lightning."

"One type of lightning is Forked lightning."

"Describe the appearance of lightning when it appears as a ball."

"Lightning appears as a luminous sphere floating in the air or slowly darting about."

"How does ribbon lightning form?"

"Ribbon lightning occurs when wind moves the ionized channel between strokes."

"Define sheet lightning."

"Sheet lightning is a flash that occurs inside a cloud or is obscured by other clouds, making it appear as a luminous white sheet."

"What is heat lightning and when does it typically occur?"

"Heat lightning is named for its occurrence on hot summer nights, where light from distant electrical storms is refracted through the atmosphere."

"Explain dry lightning and its impact."

"Dry lightning occurs from thunderstorms that do not produce rain and is responsible for starting many forest fires."

"What is St. Elmo’s Fire?"

"St. Elmo’s Fire is an electrical potential appearing as a luminous greenish or bluish halo, indicating a continuous spark (corona) discharge."

"How do lightning detection systems work?"

"Lightning detection systems use finders to detect radio waves produced by lightning, with webs of detectors pinpointing locations."

"What role do satellites play in lightning detection?"

"Satellites continuously detect all forms of lightning over land and over water."

"Describe a tornado."

"A tornado is a rapidly rotating column of air that blows around a small area of intense low pressure with circulation that reaches the ground."

"What is a funnel cloud?"

"A funnel cloud is a visible funnel that does not touch the ground."

"Outline the life cycle stages of a tornado."

"The life cycle stages of a tornado include the dust-whirl stage, mature stage, and decay stage."

"Where in the US are tornadoes most commonly experienced?"

"The US experiences most tornadoes in areas known as Tornado Alley and Dixie Alley."

"What is Tornado Alley?"

"Tornado Alley is a region in the central plains from Texas to Nebraska known for frequent tornado occurrences."

"Identify the characteristics of tornado winds."

"Tornado winds are measured by Doppler radar and can include multi-vortex tornadoes, which are violent tornadoes containing smaller wheels that rotate within them."

"What should you do when seeking shelter from a tornado?"

"When seeking shelter from a tornado, go to a basement, storm shelter, or small room, and do not try to overturn."

"Differentiate between a tornado watch and a tornado warning."

"A tornado watch indicates that tornadoes are likely, while a tornado warning means that a tornado is on the ground."

"What is the Enhanced Fujita Scale used for?"

"The Enhanced Fujita Scale attempts to provide a wide range of criteria for estimating the intensity of a tornado."

"Describe the basic requirements for tornado formation."

"A conditionally unstable atmosphere and a supercell thunderstorm are required for tornado formation."

"What is a tornado outbreak?"

"A tornado outbreak refers to a large number of tornadoes occurring in a specific area over a short period of time."

"How are tornadoes assessed for damage?"

"Tornadoes are assessed for damage using a set of 28 damage indicators."

"Define a supercell thunderstorm."

"A supercell thunderstorm is a highly organized thunderstorm characterized by a rotating updraft, which can lead to the formation of tornadoes."

"Explain the significance of a conditionally unstable atmosphere in tornado formation."

"A conditionally unstable atmosphere provides the necessary conditions for strong updrafts, which can lead to the development of supercell thunderstorms and potentially tornadoes."