Chapter 10: Chapter 10: Thunderstorms Thunderstorms and tornadoesand tornadoes

ThunderstormsThunderstorms TornadoesTornadoes Tornadic thunderstormsTornadic thunderstorms Severe weather and doppler radarSevere weather and doppler radar

ThunderstormsThunderstorms

Ordinary cell Ordinary cell thunderstormsthunderstorms

cumulus stagecumulus stage mature stagemature stage dissipating stagedissipating stage

• Ordinary cell thunderstorms are sometimes calledOrdinary cell thunderstorms are sometimes called‘air mass thunderstorms’, because they form in ‘air mass thunderstorms’, because they form in conditionally unstable air masses and are not necessarilyconditionally unstable air masses and are not necessarilyassociated with fronts or severe weatherassociated with fronts or severe weather

Severe thunderstorms Severe thunderstorms and the supercelland the supercell

multicell stormsmulticell storms supercellsupercell

Squall lines and Squall lines and mesoscale convective mesoscale convective

complexescomplexes multicell thunderstormmulticell thunderstorm squall linesquall line mesoscale convective complexmesoscale convective complex

Dryline thunderstormsDryline thunderstorms

drylinedryline

• these storms occur frequently in the southernthese storms occur frequently in the southernGreat Plains of the US Great Plains of the US

Gust fronts, microbursts Gust fronts, microbursts and derechoesand derechoes

gust frontgust front shelf cloud and roll cloudshelf cloud and roll cloud outflow boundaryoutflow boundary downbursts and microburstsdownbursts and microbursts derechoderecho

• Microbursts present a severe hazard to aircraft, Microbursts present a severe hazard to aircraft, especially during takeoff and landingespecially during takeoff and landing

• Several airports have installed microburst detection instrumentsSeveral airports have installed microburst detection instruments

Floods and flash floodsFloods and flash floods

flash floodsflash floods

Distribution of Distribution of thunderstormsthunderstorms

combination of warmth and moisturecombination of warmth and moisture geographical placementgeographical placement

• “ “Tornado Alley” is home to most of the world’s tornadoes Tornado Alley” is home to most of the world’s tornadoes

Lightning and thunderLightning and thunder

lightninglightning thunderthunder

• According to the Guinness Book of World Records,According to the Guinness Book of World Records,Roy Sullivan holds the world’s record for being struckRoy Sullivan holds the world’s record for being struckby lightning seven times between 1942 and his deathby lightning seven times between 1942 and his deathin 1983. in 1983.

Electrification of cloudsElectrification of clouds

electrical charges in cloudselectrical charges in clouds relationships of updrafts and relationships of updrafts and

downdrafts to electrical chargesdowndrafts to electrical charges

The lightning strokeThe lightning stroke

cloud-to-ground lightningcloud-to-ground lightning stepped leaderstepped leader return strokereturn stroke dart leaderdart leader

Types of lightningTypes of lightning

forked lightningforked lightning ribbon lightningribbon lightning dry lightningdry lightning heat lightningheat lightning St. Elmo’s fireSt. Elmo’s fire

• “ “heat lightning” isn’t really any different thanheat lightning” isn’t really any different thanordinary lightning ordinary lightning

Lightning detection and Lightning detection and suppressionsuppression

lightning direction-finderlightning direction-finder

TornadoesTornadoes

Tornado life cyclesTornado life cycles

tornadotornado funnel cloudfunnel cloud dust-whirl stagedust-whirl stage mature stagemature stage

Tornado outbreaksTornado outbreaks

tornado familiestornado families tornado outbreakstornado outbreaks

• Much ground-breaking research on tornadoes wasMuch ground-breaking research on tornadoes wasconducted by Professor Ted Fujita of the Universityconducted by Professor Ted Fujita of the Universityof Chicago. The “F-scale” of tornado intensity wasof Chicago. The “F-scale” of tornado intensity wasnamed after him. named after him.

Tornado occurrenceTornado occurrence

tornado alleytornado alley time of daytime of day times of yeartimes of year

Tornado windsTornado winds

multi-vortex tornadoesmulti-vortex tornadoes suction vorticessuction vortices

Seeking shelterSeeking shelter

tornado watchtornado watch tornado warningtornado warning

• It’s always a good idea to know what to do if a It’s always a good idea to know what to do if a tornado watch or warning is issued for your area tornado watch or warning is issued for your area

The Fujita scaleThe Fujita scale

tornado classification based on tornado classification based on damagedamage

Tornadic Tornadic thunderstormsthunderstorms

Supercell tornadoesSupercell tornadoes

mesocyclonesmesocyclones bounded weak echo regionbounded weak echo region hook echohook echo rotating cloudsrotating clouds wall cloudwall cloud

• A rotating wall cloud is an unforgettable sight - justA rotating wall cloud is an unforgettable sight - justask a successful storm chaser ask a successful storm chaser

Nonsupercell tornadoesNonsupercell tornadoes

gustnadoesgustnadoes landspoutslandspouts cold air funnelscold air funnels

Severe weather Severe weather and Doppler radarand Doppler radar

Severe weather and Severe weather and Doppler radarDoppler radar

Doppler shiftDoppler shift tornado vortex signaturetornado vortex signature Doppler lidarDoppler lidar NEXRADNEXRAD waterspoutwaterspout

• Many cities in the US have multiple Doppler radars,Many cities in the US have multiple Doppler radars,operated by television station weather centers operated by television station weather centers