Chapter 10 Study Guide

ordinary cell thunderstorm

A thunderstorm produced by local convection within a conditionally unstable air mass, often in low wind shear.

cumulus stage

The initial stage of an ordinary thunderstorm where rising warm, humid air develops into a cumulus cloud.

mature stage

The second stage characterized by heavy showers, lightning, thunder, and violent vertical motions inside cumulonimbus clouds.

dissipating stage

The final stage of an ordinary cell thunderstorm when downdrafts exist throughout the cloud.

multicell thunderstorm

Thunderstorms often in a line, with each cell at a different stage of its life cycle.

overshooting top

A feature in a mature thunderstorm where strong convection causes the upper part of the cloud to rise above the anvil top.

gust front

The boundary that separates a cold downdraft of a thunderstorm from warm, humid surface air.

straight-line winds

Strong winds produced by a thunderstorm's downdraft that flow outward away from the storm.

shelf cloud

A dense, arch-shaped cloud that forms along the leading edge of a thunderstorm's gust front.

roll cloud

A dense, roll-shaped cloud that spins about a horizontal axis behind the gust front.

outflow boundary

A surface boundary separating cooler, denser air from warmer, less dense air originating from a thunderstorm.

downburst

A powerful downdraft resulting in a strong downward burst of wind, often associated with thunderstorms.

Microburst

A localized downdraft less than 4 km wide that occurs beneath thunderstorms.

heat burst

A sudden increase in surface air temperature often accompanied by extreme drying, related to a thunderstorm downdraft.

squall line

A line of thunderstorms forming along a cold front or ahead of it.

bow echo

A radar indication of a line of thunderstorms shaped like a bow, often associated with damaging winds.

Derecho

Strong, damaging, straight-line winds associated with a cluster of severe thunderstorms.

mesoscale convective complexes (MCCs)

Large organized convective weather systems comprising multiple thunderstorms.

Supercell

A severe thunderstorm that features a single rotating updraft allowing it to persist for several hours.

Mesocyclone

A vertical column of rotating air within a supercell thunderstorm.

wall cloud

An area of rotating clouds beneath a supercell from which a funnel cloud may appear.

Pyrocumulonimbus

A thunderstorm cloud that develops within the updraft above an intense wildfire.

flash floods

Floods that rise and fall rapidly with little or no advance warning, usually from intense rainfall.

Lightning

A visible electrical discharge produced by thunderstorms.

Thunder

Sound from rapidly expanding gases along the channel of a lightning discharge.

sonic boom

A loud explosive sound caused by a shock wave from an object traveling at or above the speed of sound.

stepped leader

The initial discharge of electrons towards the ground in a lightning stroke.

return stroke

The luminous upward stroke from the ground to the base of a cloud.

dart leader

The discharge of electrons that proceeds towards the ground along the ionized channel of the initial lightning stroke.

heat lightning

Distant lightning that illuminates the sky but is too far for its thunder to be heard.

dry lightning

Lightning that occurs with thunderstorms producing little to no precipitation at the surface.

St. Elmo’s fire

A bright electric discharge seen from pointed objects in a strong electric field.

Tornado

A rapidly rotating column of air extending from a thunderstorm to the ground, characterized by a funnel shape.

funnel cloud

A funnel-shaped cloud that extends from the base of a cumuliform cloud, not in contact with the ground.

Tornado Alley

Region in the Great Plains of the U.S. known for high tornado frequency.

Dixie Alley

Region in the southern U.S. known for frequent tornado activity.

suction vortices

Small, rapidly rotating whirls within large tornadoes.

tornado watch

A forecast alerting the public that tornadoes may develop in a specified area.

tornado warning

A warning issued when a tornado has been observed or indicated by radar.

tornado emergency

A warning indicating a particularly strong tornado posing major damage or loss of life potential.

Fujita Tornado Damage Scale

A scale for classifying tornadoes based on the damage they cause.

Enhanced Fujita Scale (EF Scale)

A modified scale assessing tornado intensity based on damage caused.

tornado outbreak

A series of tornadoes forming within a specified region, often causing widespread damage.

supercell tornadoes

Tornadoes that occur within supercell thunderstorms containing well-developed mesocyclones.

hook echo

Radar indication of a hook shape suggesting the presence of a tornado.

Tornadogenesis

The process by which a tornado forms.

non supercell tornadoes

Tornadoes occurring with clouds not containing a mid-level mesocyclone, such as landspouts.

Gustnadoes

Weak tornadoes formed from a thunderstorm's outflow along the gust front.

Landspout

A weak non supercell tornado originating from a cloud in its growth stage.

Waterspout

A column of rotating wind over water, resembling a tornado.

NEXRAD

Next Generation Weather Radar, primarily the WSR 88-D Doppler radar.

What are the three ingredients needed for thunderstorm development?

Moisture, instability, and a lifting mechanism.

What is an ordinary thunderstorm?

A localized storm with a single updraft, lasting less than an hour.

What is a multicell thunderstorm?

Thunderstorms made of multiple cells allowing development of new updrafts.

What is a supercell?

A highly organized thunderstorm with a rotating updraft called a mesocyclone.

What is wind shear?

The change in wind speed and direction with altitude that can create rotation.

What is the EF scale?

A scale used to classify tornado intensity based on damage.

What is the difference between tornado watch and tornado warning?

A watch indicates favorable conditions for tornado development; a warning indicates the presence of a tornado.