EOSC 114 Mod 5 Glossary

Storms

thunderstorm

a cumulonimbus cloud/storm containing lightning and thunder, with strong updrafts and downdrafts

cumulonimbus

the cloud type associated with thunderstorms

updraft

rising air within a storm

downdraft

sinking air within a storm

anvil

the broad, flattened upper part of a mature thunderstorm cloud

overshooting top

a dome of cloud that rises above the anvil because of an exceptionally strong updraft

flanking line

a line of developing clouds on the side of a thunderstorm, associated with storm inflow and development

wall cloud

a lowered cloud base beneath a thunderstorm, often associated with strong rotation and tornado formation

funnel cloud

a visible funnel-shaped cloud extending downward from a thunderstorm; it becomes a tornado when it reaches the ground

mammatus clouds

pouch-like clouds on the underside of a thunderstorm anvil

striations

visible bands or lines in a thunderstorm cloud associated with its structure and airflow

lightning

a large electrical discharge in the atmosphere

thunder

the sound produced by the rapid heating and expansion of air around a lightning channel

lightning-safety crouch

a last-resort position in the open with feet together and hands over the ears when no shelter is available

multicell thunderstorm

a thunderstorm containing multiple cells at different stages of development

thunderstorm cell

an individual convective unit within a thunderstorm that develops and evolves over roughly 15–30 minutes

squall line

a line of thunderstorms, often forming along a cold front

supercell

a large, rotating single-cell thunderstorm capable of producing severe weather including tornadoes, large hail, heavy rain, lightning, and strong winds

mesocyclone

a rotating thunderstorm circulation associated with a supercell

low-precipitation (LP) supercell

a supercell with relatively little precipitation; can produce large amounts of hail

classic supercell

a supercell with a rainy downdraft and a relatively rain-free updraft

high-precipitation (HP) supercell

a supercell whose updraft is largely surrounded by precipitation

downpour

an extremely large rainfall rate that can produce flooding

flash flood

rapid flooding caused by intense rainfall over a short period

downburst

a strong downdraft that spreads outward after reaching the ground and produces damaging winds

microburst

a relatively small downburst, about 1 km in diameter

gust front

the leading edge of cool air spreading outward from a thunderstorm downdraft

haboob

a dust storm produced when strong outflow winds lift dust from the ground

hail

balls or lumps of ice produced within thunderstorms

latent heat

energy stored or released when water changes phase; condensation releases latent heat into the atmosphere

sensible heat

heat associated with temperature that can directly warm the surrounding air

humidity

the amount of water vapor in the air

saturation

the condition in which air contains the maximum water vapour possible at a given temperature

condensation

the change of water vapour into liquid water, releasing latent heat

adiabatic cooling

cooling of rising air caused by expansion as pressure decreases, without heat being exchanged with the surroundings

advection

horizontal transport of air or another atmospheric property by wind

buoyancy

the tendency of relatively warm/light air to rise and relatively cold/dense air to sink

pressure-gradient force (PGF)

a force caused by differences in atmospheric pressure that drives air from high toward low pressure

continuity

the atmospheric principle linking vertical and horizontal air motions so that air mass is conserved within circulations

Coriolis effect

the apparent deflection of moving air caused by Earth's rotation

hurricane

a tropical cyclone with sufficiently strong winds; also called a typhoon or tropical cyclone

tropical cyclone

the general term for a rotating low-pressure storm system that forms over warm tropical/subtropical oceans

eye

the relatively calm, clear, low-pressure centre of a hurricane

eyewall

the ring of thunderstorms surrounding the hurricane eye where the strongest winds occur

spiral rainbands

curved bands of thunderstorms extending outward from a hurricane's eyewall

warm core

a region of relatively warm air in the centre of a hurricane produced by storm processes

Saffir-Simpson Hurricane Wind Scale

a scale that categorizes hurricanes according to their sustained wind speed

storm surge

an abnormal rise of coastal water caused primarily by hurricane winds and low pressure

coastal flooding

flooding of coastal areas caused by elevated water levels, including storm surge

hurricane forecasting

predicting the future track, intensity, and hazards of hurricanes using observations and numerical models

hurricane watch

an indication that hurricane conditions are possible in the specified area

hurricane warning

an indication that hurricane conditions are expected or occurring in the specified area

tornado

a violently rotating column of air extending from a thunderstorm toward the ground

Enhanced Fujita (EF) scale

a scale used to classify tornado intensity based primarily on damage indicators

tornado watch

an alert that conditions are favourable for tornadoes to develop

tornado warning

an alert issued when a tornado has been detected or is strongly indicated and immediate shelter is required