TORNADO OUTBREAK

IN OKLAHOMA, ARKANSAS, AND IOWA

April 26-27, 2014

The most destructive tornado

outbreak of 2014 killed at least

18 people in three states and

hammered the suburbs of

Little Rock, Arkansas over a

200-mile-long path.

THE FORECAST: APRIL 14

ACTUAL: APRIL 26-27

In all, at least 31 tornadoes

were recorded. They formed

late in the day, and were

especially destructive in

Arkansas because they

struck as night fell.

Some of the tornadoes were

rated as EF-3, which have

wind fields of at least

246 kph (136 mph).

VILONIA, ARKANSAS (ALSO

HIT BY TORNADOES IN 2011)

IMPACTS

• Faulkner County, Ark., particularly the

suburbs of Mayflower and Vilonia, was

the hardest hit on Sunday, with as

many as 18 people dead, including two

children

• At least 150 homes destroyed.

• Two highways closed; 20,000 power

outages

“ROUND TWO”

MONDAY, APRIL 28

Millions of people braced for more severe

weather as at least three tornadoes struck

Mississippi on Monday afternoon .

TUEPLO, MISSISSIPPI:

APRIL 28

INITIAL IMPACT REPORTS

• A tornado hit Tupelo and

tracked northward, causing

"significant property damage,

but no deaths" Tueplo Mayor

Jason Shelton said.

BACKGROUND

SEVERE WINDSTORMS--

TORNADOES

UNDERSTANDING AND

PREPARING FOR

TORNADOES

A PRIMER OF KNOWLEDGE THAT

CAN MULTIPLY AND SPILL OVER

FOR THE BENEFIT OF MILLIONS

THE PHYSICS OF SEVERE

WINDSTORMS

SEVERE WINDSTORMS:

TORNADOES

COMMUNITY

DATA BASES

AND INFORMATION

•SEVERE WINDSTORM

HAZARDS

•INVENTORY

•VULNERABILITY

•LOCATION

RISK ASSESSMENT

RISK

ACCEPTABLE RISK

UNACCEPTABLE RISK

SEVERE WINDSTORM

RISK REDUCTION

•PREVENTION/MITIGATION

•PREPAREDNESS

•EMERGENCY RESPONSE

•RECOVERY and

RECONSTRUCTION

• EDUCATIONAL SURGES

POLICY OPTIONS

Wind profile

Storm Hazards:-Wind pressure

-Surge

-Rain

-Flood

-Waves

-Salt water

-Missiles

-Tornadoes

Ocean

Gradient Wind

WIND AND WATER

PENETRATE BUILDING

ENVELOPE

SEVERE

WINDSTORMS

UPLIFT OF ROOF SYSTEM

FLYING DEBRIS PENETRATES

WINDOWS

HEAVY PRECIPITATION

IRREGULARITIES IN

ELEVATION AND PLAN

POOR WORKMANSHIP

IGNORING NON-STRUCTURAL

ELEMENTS

CAUSES

OF RISK

CASE HISTORIES

BASIC PRINCIPLES OF PHYSICS

UNDERPINNING WINDSTORMS

• HEAT AND

HEAT FLOW

• PRESSURE

AND

PRESSURE

FLOW

• GRAVITY

FIELD

• KINETIC

ENERGY

• POTENTIAL

ENERGY

SEVERE WINDSTORMS

TORNADOES

OCCUR OVER LAND AS THE

RESULT OF COLLISIONS OF

COLD AND WARM AIR MASSES

TORNADOE SEASON

• The peak tornado season is

late winter through

midsummer,….

• But tornadoes can happen any

time of the year when the

atmospheric conditions are

right.

TORNADO ALLEY

• ALTHOUGH TORNADOES HAVE

OCCURRED IN EVERY STATE, THEY

OCCUR MOST FREQUENTLY IN

“TORNADO ALLEY,” WHICH INCLUDES

PARTS OF: TEXAS, OKLAHOMA,

ARKANSAS, TENNESSEE, NEBRASKA,

KANSAS, MISSOURI, ILLINOIS, AND

IOWA.

MAP OF TORNADO ALLEY

THE PHYSICS OF

TORNADOES

• TORNADOES ARE CAUSED BY THE

COLLISION OF DESCENDING COLD

AIR MASSESS COMING FROM THE

NORTH AND ASCENDING WARM AIR

MASSES COMING FROM THE SOUTH.

THE PHYSICS OF

TORNADOES

• THE COLLISION CREATES A FUNNEL

OF HIGH-VELOCITY WIND THAT IS

VERY DESTRUCTIVE AS IT

“TOUCHES DOWN” ONE OR MORE

TIMES ALONG A LONG, NARROW

(TYPICALLY 10-100 M) PATH.

PHYSICS OF A TORNADO

HAZARDS OF A TORNADO

(AKA POTENTIAL DISASTER AGENTS)

• WIND: SPEEDS CAN REACH 500 KM/HR

(300 MI/HR)

• THUNDER, LIGHTNING, AND HEAVY

PRECIPITATION E EXTREME

• HAIL CAN BE VERY DAMAGING

HISTORIC OCCURRENCES

THIRTY TO FORTY

TORNADOES STRIKE FIVE

SOUTHERN STATES

Mississippi, Alabama, Arkansas, Kentucky, and Tennessee impacted

54 dead

FEBRUARY 5, 2008

LOCATION MAP

TORNADOE SEASON

AFFECTED BY LA NINA

• This tornado outbreak could be

a consequence of La Nina, the

cooling of the Pacific Ocean,

which can cause changes in

weather patterns around they

world.

WARNING

• The people had ample warning

to get out of harm’s way and

take cover, …

• In spite of the fact that some of

the warning sirens did not

work.

A TORNADO TOUCHES DOWN

NEAR ATKINS, ARKANSAS

DEVASTATION NEAR ATKINS,

ARKANSAS

DEVASTATION NEAR ATKINS,

ARKANSAS

DEVASTATION NEAR ATKINS,

ARKANSAS

COLLAPSE OF WAREHOUSE IN

SOUTH HAVEN, MS

COLLAPSE OF WALL IN SHOPPING

MALL: MEMPHIS, TN

A FIRE BROKE OUT IN A NATURAL

GAS PUMPING STATION:

HARTSVILLE, TN

SEVERE THUNDERSTORM SYSTEM

SPAWNS TORNADOES IN TEXAS:

APRIL 24, 2008

A SUPERCELL

THE FUNNEL

IMPACTS IN WEST AND

NORTH TEXAS

•WORST DAMAGE NEAR FT WORTH,

TX WITH LOSSES ESTIMATED AT $35

MILLION

•WIND SPEED REACHED 116 KM/HR

(70 MI HR)

IMPACTS IN WEST AND

NORTH TEXAS

•HEAVY RAIN FALL CAUSED

POWER OUTAGES AND MINOR

FLOODING

•BASEBALL-SIZED HAIL

WIND DAMAGE

TORNADOES STRIKE IOWA

AND MINNESOTA

Continuation of deadliest tornado season in a decade

Accompanied by large hail

May 25, 2008

HUGO, MINNESOTA: DEBRIS

MARKS STORM'S PATH

PARKERSBURG, IOWA: DAMAGE

PARKERSBURG, IOWA: LOOKING

FOR SURVIVORS

LESSONS LEARNED FROM

TORNADOES

• RECOVERY

USUALLY

TAKES LONGER

AND COSTS

MORE THAN

EXPECTED.

LESSONS LEARNED FROM

TORNADOES

• EVACUATION IS NOT

TO THE STREET; IT

IS TO THE

BASEMENT OR THE

“SAFE ROOM”

BECAUSE THE

WARNING IS EITHER

VERY SHORT OR

NON-EXISTANT.

LESSONS LEARNED FROM

TORNADOES

• TIMELY COMMUN-

ICATION OF

CRITICAL INFORM-

ATION IN THE FORM

OF WATCHES AND

WARNINGS IS

ESSENTIAL FOR

SAFETY.

LESSONS LEARNED FROM ALL

TORNADOES

• HIGH VELOCITY

WIND LIFTS THE

ROOFS OFF OF

BUILDINGS AND

IS A KILLER IN

TORNADOES.

LESSONS LEARNED FROM ALL

SEVERE WINDSTORMS

• HIGH VELOCITY

WIND AND

PRESSURE

CHANGES CAUSE

BUILDINGS WITH

INADEQUATE

ENGINEERING

DESIGN TO

COLLAPSE.

RISK ASSESSMENT INTEGRATES

RESEARCH AND SCIENTIFIC

KNOWLEDGE GAINED FROM

“DISASTER LABORATORIES,” WITH

EMERGING TECHNOLOGIES INTO

POLICY TO BE IMPLEMENTED IN THE

COMMUNITY’S POLITICAL PROCESS.

PUBLIC POLICIES INTEGRATE

TECHNICAL AND POLITICAL

SOLUTIONS

FOR THE LONG-TERM BENEFIT

OF THE PEOPLE.