Chapter 10: Tornadoes, Lightning, Heat, and Cold

What percent of yearly death is due to damage from natural disasters

75%

Most people killed by _ than by earthquakes, volcanoes, mass movements combined

Severe weather

What years are tied for being most destructive

2011 and 2017

Human bodies maintain what temp

37 C

Hypothermia occurs when body temp drops below

35 C

Wind chills do what to the body

Strip heat

Most hypothermia deaths due to

Outdoor reaction and disabled vehicles

When precipitation falls as snowflakes or ice particles it falls through

Warmer air and melts as rain

Snowflakes will continue as rain or

• Refreeze into tiny ice particles or sleet

• Supercool and freeze upon impact (freezing rain)

• Refreeze into snow and accumulate on ground

Explain blizzards

• Strong cold winds

• 56km/hr

• Blowing/falling snow

• Visibility < 400 meters

• Cyclone may travel slowly through winds are fast

What happened in Northeastern Unites States, 6 to 8 January 1996

• Record snowfall

• Wind exceeded 80 km/hr

• Killed 154 people

• Followed by warm weather, heavy rains, and destructive flooding with 187 deaths

Blizzards are often winter’s _ storms

Deadliest

Fatalities from blizzards occur from what 4 things

• Heart attacks while shovelling snow and pushing stuck cars

• When automobiles slide and collide

• When people slip on ice and fall

• When people get disoriented or lost and freeze

What city do most blizzards occur per year in Canada

St. John’s

What are ice stomrs

• Large volume of supercooled rain that freezes on impact (freezing rain)

What damage occurs during ice storms

Add mass to trees, power lines, and roofs causing them to collapse

Where was the severe ice storm from the 5th-9th January 1998

New England (Canada)

• Most costly Canadian natural disaster

Describe the aftermath of the New England ice storm

• 130 major power transmission towers, 30,000 wooden utility poles destroyed

• People without power for up to 4 weeks

Ice storms with freezing rain occurs mostly in _ Canada

Eastern

What Canadian city has the most number of hours of freezing rain per year

St. John’s

Explain the St. Lawrence River Valley ice storm

• Electrical pylons designed to withstand thickness started to collapse interrupting the regional transport of electricity

• Sporadic blackouts: 3.5 million people without electricity mid-winter

• Treacherous driving conditions made it impossible for people to leave their homes

Describe the 2013 Toronto ice storm

• Paralyzed the city from 20th-22nd of December

• Covered an extensive corridor from the American Midwest to Cap Breton Island Nova Scotia

Describe thunderstorms

• Tall, buoyant clouds of rising moist air

• Lightning and thunder

• Rain, wind, and hail

Thunderstorms: air temp _ with altitude causing what

Decreases, unstable airflow

_ forms cumulus clouds, heat released to power what

Condensation, power severe weather

_ clouds can build up to 20km high

Cumolonimbus

Thunderstorms develop by three mechanisms

1. convection

2. Fronts

3. Orographic

Convection

Surface heated air rises buoyantly (less dense), clouds form locally

Fronts

Air masses collide at fronts, warmer air rises forming clouds

Orographic

Air mass flows up at steep slope, expands and cools increasing its relative humidity to forming clouds

Thunderstorms are most common during

Afternoons and evenings

Thunderstorms occur year round in the

Tropics (summer in midlatitudes)

_ produces downdraft

Heavy rain

_updraft and _downdraft side-by-side

warm, cool

Downdraft and rain evaporation _ at surface and_ updraft

absorbs heat, extinguishes

• Storm ends

Thunderstorms categorized as severe when

• winds > 93 kph

• Hail diameter > 25 mm

Thunderstorms commonly from at long

Frontal collisions

• allow up and down drafts simultaneously

Much smaller _ with high wind speeds occur within larger systems

Cyclonic thunderstorms

Thunderstorms in Canada: distribution of lightening activity shows a _ pattern

Non-uniformative

_has the most thunderstorms and _ has the fewest

Southern Ontario, Arctic

_ are violent severe thunderstorms with huge updraft

Supercell thunderstorms

Describe a supercell thunderstorm

• 20 to 50 km rotating mass or mesocyclone

• Vortex is rotating updraft about vertical axis

• Rain and hail fall at leading edge

• Potentially powerful tornadoes spin off trailing edge

Thunderstorms most common in

Florida where Atlantic and Gulf of Mexico warm, moist air masses meet

Thunderstorms are also common in

Central and southern U.S. states

Thunderstorms can be major supplier of

Water to area

• Heavy rain and flash floods

Hail: layered ice balls dropped from storms with

• Buoyant rising, hot, moist air

• upper-level cold air (creating large temp contrasts)

• Strong updrafts (keeping hailstones aloft while adding layers)

Tornadoes have the highest _ of any weather phenomenon

Wind speeds

Tornadoes commonly move from _to _

Southwest to northwest

What year was the second deadliest tornado year

2011

Three air masses moving in different directions meet and give _ to thunderstorms

Shear

What are the three air masses

• Warm, humid, low Gulf of Mexico air

• Cold, dry, mid-altitude Rocky Mountain air

• Fast, high-altitude jet stream winds

Tilt of supercell moves warm updraft to center of storm providing rotation that

Spins off

Tornadoes are formed below main mass of

Mesocyclone

Wall clouds are where _ can emerge

Powerful tornadoes

Hook echo

high reflectivity area in radar image shaped like a hook, indicator of tornado potential

Where is the tornado capital of the world called tornado alley

Interior U.S.

Air masses _ and spin out tornadoes that usually travel with jet stream northeast

collide

F scale is

Wind damage scale (F0-F5) estimating wind speed from damage to structures and trees

Tornado deaths occur from

• Wind blowing away buildings/trees

• Wind-blown debris impacts

• Winds remove roofs, lift out contents

Lightening is influenced by

Topography, rainfall, and temperature

Flow of electrical current

Top of clouds have excess positive charges seeking balance with the bottom of the clouds’ excess negative charges

Charge imbalance

From freezing and shattering of super-cooled water drops — charge seperations distributed by updrafts and downdrafts during early cloud buildup

Lightning moves from

• Cloud to ground

• Ground to cloud

• Cloud to cloud

Stepped leader

Discharge begins within cloud, initiates downward stream of electrons

Lightning strikes up to _ from thundercloud

15 km

Risk extends wherever _ can be heard

Thunder

How to avoid lightning

• Get inside house

• Get inside car

• If outside, move to low place

• Remove electronic devices

• Do not touch anything

Heat waves are _ killers

Invisible and silent

Signs of exhaustion/stroke

• high body temp

• Confusion, staggering, strange behaviour

• Fainting

• Dry skin with rapid or slow pulse

Heat wave in July 1995 occurred in

Chicago

Urban heat island

Cities are warmer than surrounding hinterlands, up to 10 degrees C at night