TORNADO OUTBREAK IN OKLAHOMA, ARKANSAS,

AND IOWARound One: April 26-27, 2014

Walter Hays, Global Alliance for Disaster Reduction, Vienna,

Virginia, USA 

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

COMMUNITYCOMMUNITY

DATA BASES DATA BASES AND INFORMATIONAND INFORMATION

•SEVERE WINDSTORM HAZARDS•INVENTORY•VULNERABILITY•LOCATION

RISK ASSESSMENTRISK ASSESSMENT

RISK

ACCEPTABLE RISK

UNACCEPTABLE RISK

SEVERE WINDSTORM SEVERE WINDSTORM RISK REDUCTIONRISK REDUCTION

•PREVENTION/MITIGATION•PREPAREDNESS•EMERGENCY RESPONSE•RECOVERY and RECONSTRUCTION• EDUCATIONAL SURGES

POLICY OPTIONSPOLICY OPTIONS

Wind profileWind profile

Storm Hazards:Storm Hazards:-Wind pressure-Surge-Rain-Flood-Waves-Salt water-Missiles-Tornadoes

OceanOcean

Gradient WindGradient Wind

WIND AND WATER PENETRATE BUILDING ENVELOPE

SEVEREWINDSTORMS

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 SEVERE THUNDERSTORM SYSTEM SPAWNS TORNADOES IN TEXAS:SPAWNS TORNADOES IN TEXAS:APRIL 24, 2008APRIL 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 decadeAccompanied by large hailMay 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.