Extreme Weather and Extreme Weather and Climate EventsClimate Events

Blizzards, Thunderstorms, Hurricanes, Blizzards, Thunderstorms, Hurricanes, Floods, and DroughtFloods, and Drought

Why Look at Extreme Events?Why Look at Extreme Events?

Can harm human and natural systems both Can harm human and natural systems both during and after eventduring and after event

Economic lossesEconomic losses Occurrence may be affected by human Occurrence may be affected by human

activity according to various studies, activity according to various studies, including IPCC, 2001including IPCC, 2001

BlizzardsBlizzards A strong winter storm with cold temperatures, A strong winter storm with cold temperatures,

strong winds, and intense falling or blowing snowstrong winds, and intense falling or blowing snow Rarely experienced in US below ~ 35Rarely experienced in US below ~ 35°N°N TypesTypes

– Longwave cycloneLongwave cyclone: low pressure centers both at surface : low pressure centers both at surface and in upper atmosphere; move very slowly; affect and in upper atmosphere; move very slowly; affect northern portions of US; northern portions of US; usuallyusually in spring in spring

– Trough cycloneTrough cyclone: develops in association with trough in : develops in association with trough in jet stream; then upper-air features strengthen low jet stream; then upper-air features strengthen low pressure at surface; move faster; typically along eastern pressure at surface; move faster; typically along eastern coast of US (nor’easters); any time during wintercoast of US (nor’easters); any time during winter

Features Associated Features Associated with Blizzardswith Blizzards

Low pressure, frontsLow pressure, fronts Cold temperatures (usually < Cold temperatures (usually <

2020°C (-6°F))°C (-6°F)) Strong winds (Strong winds (>> 35 mph) 35 mph) Intense falling or blowing Intense falling or blowing

snowsnow Sleet and freezing rain south Sleet and freezing rain south

of snowof snow Sometimes rain even farther Sometimes rain even farther

southsouth Low visibility due to Low visibility due to

falling/blowing snowfalling/blowing snow ““Whiteout” conditionsWhiteout” conditions

Problems Associated Problems Associated with Blizzardswith Blizzards

Economic loss – Economic loss – businesses closedbusinesses closed

Death – due to exposure, Death – due to exposure, accidents, etc.accidents, etc.

Other health problems – Other health problems – hypothermia, frostbitehypothermia, frostbite

Utility complicationsUtility complications Structural damage – Structural damage –

weight of snowweight of snow Travel inconvenience – Travel inconvenience –

closed airports, closed closed airports, closed highways, accidentshighways, accidents

A Few ExamplesA Few Examples Montana (March 1969)Montana (March 1969)

– 20+” (45+cm) of snow20+” (45+cm) of snow– Trough cycloneTrough cyclone

Eastern US (January 1978)Eastern US (January 1978)– Lowest central pressure = 958 mb, winds to ~ 90 mph, almost 100 Lowest central pressure = 958 mb, winds to ~ 90 mph, almost 100

deathsdeaths– Longwave cycloneLongwave cyclone

Storm of the Century – eastern US (March 1993)Storm of the Century – eastern US (March 1993)– Lowest central pressure = 960 mb, up to 56” of snow (Tenn.), 24” in Lowest central pressure = 960 mb, up to 56” of snow (Tenn.), 24” in

Mtn. City, Georgia, winds > 75 mphMtn. City, Georgia, winds > 75 mph– Every major East Coast airport closed, 3 million customers with no Every major East Coast airport closed, 3 million customers with no

electricity, roofs collapseselectricity, roofs collapses– In Florida – 27 tornadoes, 3 m storm surgeIn Florida – 27 tornadoes, 3 m storm surge– In total, ~ 270 deaths and > $3 billion in damageIn total, ~ 270 deaths and > $3 billion in damage

ThunderstormsThunderstorms

A strong local storm that A strong local storm that contains intense updrafts contains intense updrafts and downdrafts, lightning, and downdrafts, lightning, and thunderand thunder

Capable of producing Capable of producing flooding, strong winds, flooding, strong winds, hail, and tornadoeshail, and tornadoes

SevereSevere if produces any/all if produces any/all of followingof following– Hail Hail >> 0.75” (1.9 cm) 0.75” (1.9 cm)– Wind Wind >> 57 mph (50 knots, 57 mph (50 knots,

92 km/hr)92 km/hr)– TornadoTornado

Some Features in ThunderstormsSome Features in Thunderstorms Overshooting topOvershooting top – intense updrafts push cloud into – intense updrafts push cloud into

stratosphere (top > 70 000 ft)stratosphere (top > 70 000 ft) HailHail – chunks of ice that grow inside a storm due to – chunks of ice that grow inside a storm due to

internal circulation; most common in Great Plainsinternal circulation; most common in Great Plains MicroburstMicroburst – strong winds at surface produced when – strong winds at surface produced when

precip pulls air with it (leading edge at surface called precip pulls air with it (leading edge at surface called gust frontgust front))

LightningLightning – series of huge “sparks” caused by differing – series of huge “sparks” caused by differing electrical chargeselectrical charges

ThunderThunder – sound waves produced by rapid expansion of – sound waves produced by rapid expansion of air due to heat from lightningair due to heat from lightning

TornadoesTornadoes......

A Few ExamplesA Few Examples Tri-State Outbreak (March Tri-State Outbreak (March

18, 1925)18, 1925)– Missouri, Illinois, and IndianaMissouri, Illinois, and Indiana– 7 tornadoes over ~ 440 mi 7 tornadoes over ~ 440 mi

(700km), 695 deaths(700km), 695 deaths Palm Sunday Outbreak Palm Sunday Outbreak

(1965)(1965)– Midwest USMidwest US– 30 tornadoes in 5 states, 256 30 tornadoes in 5 states, 256

deathsdeaths Topeka, KS (June 8, 1966)Topeka, KS (June 8, 1966)

– 16 deaths, hundreds of houses 16 deaths, hundreds of houses destroyed or damaged, destroyed or damaged, Washburn University badly Washburn University badly damageddamaged

A Few More ExamplesA Few More Examples

Lubbock, TX (May 11, 1970)Lubbock, TX (May 11, 1970)– 26 deaths, > $100 million in damage26 deaths, > $100 million in damage– Weather observer recordsWeather observer records

April 3-4 Outbreak (1974)April 3-4 Outbreak (1974)– 13 states (central AL to s. MI, central IL to central VA)13 states (central AL to s. MI, central IL to central VA)– 16 hrs, 148 tornadoes, 307 deaths, > 6000 injuries, 16 hrs, 148 tornadoes, 307 deaths, > 6000 injuries,

approximately $600 million in damageapproximately $600 million in damage Central Oklahoma Outbreak (May 3, 1999)Central Oklahoma Outbreak (May 3, 1999)

– ~ 74 tornadoes through Oklahoma~ 74 tornadoes through Oklahoma– In OKC, estimated$1.2 billion in damage, 41 deaths, In OKC, estimated$1.2 billion in damage, 41 deaths,

675+ injuries (winds estimated at 300 mph)675+ injuries (winds estimated at 300 mph)

FloodsFloods Condition in which Condition in which

water cannot be drained water cannot be drained adequately by (1) stream adequately by (1) stream discharge to prevent discharge to prevent overflow of channel overflow of channel banks or (2) infiltration, banks or (2) infiltration, runoff, or evaporation to runoff, or evaporation to prevent excessive prevent excessive “ponding” on the surface“ponding” on the surface

North Atlantic region North Atlantic region most prone region in USmost prone region in US

Causes of FloodsCauses of Floods Excessive precip over brief period (flash flood) or extended Excessive precip over brief period (flash flood) or extended

period (as in a hurricane)period (as in a hurricane) Moderate precip over extended period (slow moving Moderate precip over extended period (slow moving

cyclone, repeated passing of cyclones, stationary front, cyclone, repeated passing of cyclones, stationary front, “training” of thunderstorms)“training” of thunderstorms)

Snowmelt (in spring, combined with rain)Snowmelt (in spring, combined with rain) Dam or levee breakageDam or levee breakage

Rillito River (July 2006)Rillito River (July 2006)

Rillito River (July 2006)Rillito River (July 2006)

Problems Associated with FloodsProblems Associated with Floods

Water supplyWater supply Agricultural and other Agricultural and other

economic losseseconomic losses Water-born diseasesWater-born diseases Human and animal Human and animal

deaths (drowning, deaths (drowning, electrocution)electrocution)

Travel inconveniencesTravel inconveniences FireFire

A Few ExamplesA Few Examples Much of East Coast (1972) – AgnesMuch of East Coast (1972) – Agnes Big Thompson Canyon (1976)Big Thompson Canyon (1976)

– Due to thunderstorm (12” (30.5cm) in 4 hours!)Due to thunderstorm (12” (30.5cm) in 4 hours!)– 135 deaths, $35.5 million in property damage135 deaths, $35.5 million in property damage

Mississippi River, a.k.a. The Great Flood (1993)Mississippi River, a.k.a. The Great Flood (1993)– Due to repeated passing of cyclonesDue to repeated passing of cyclones– 50 deaths, 70,000 evacuated, $12 billion in property 50 deaths, 70,000 evacuated, $12 billion in property

damagedamage California (summer 2004)California (summer 2004)

– Due to levee breakageDue to levee breakage

DroughtDrought Definition varies depending on agricultural or Definition varies depending on agricultural or

hydrological considerationshydrological considerations Deficiency of water normally obtained from precipDeficiency of water normally obtained from precip Various monitors exist, one of which is the Palmer Various monitors exist, one of which is the Palmer

Drought Severity Index (PDSI) – updates available Drought Severity Index (PDSI) – updates available on Interneton Internet

CausesCauses– Weather/climate-relatedWeather/climate-related

» Lack of rainfallLack of rainfall» Strong windsStrong winds» TeleconnectionsTeleconnections

Drought (cont’d)Drought (cont’d) Causes (cont’d)Causes (cont’d)

– Human-induced aggravationHuman-induced aggravation» Poor farming practicesPoor farming practices» Increased populationIncreased population» Expansion of civilizationExpansion of civilization» Removal of vegetationRemoval of vegetation» Excessive water usageExcessive water usage

Associated problemsAssociated problems– Water supplyWater supply– Agricultural and other economic lossesAgricultural and other economic losses– Landscape changesLandscape changes– DeathDeath– FireFire– Dust stormsDust storms

A Few ExamplesA Few Examples The Dust Bowl (1930s)The Dust Bowl (1930s) Western and central US (early Western and central US (early

to mid-1950s)to mid-1950s) Northeastern US (early 1960s)Northeastern US (early 1960s) Sahelian Drought (1968-1974)Sahelian Drought (1968-1974) California (1976-1977)California (1976-1977) Northeastern US (late ’90s to Northeastern US (late ’90s to

early 2000s)early 2000s) Much of western US (~2000 to Much of western US (~2000 to

present)present)