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. 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. The peak tornado season is late winter through midsummer. But tornadoes can happen any time of the year when the atmospheric conditions are right. Lessons learned from tornadoes. Timely communication of critical inform-ation in the form of watches and warnings is essential for safety. Presentation courtesy of Dr. Walter Hays, Global Alliance for Disaster Reduction

1. TORNADO OUTBREAK
IN OKLAHOMA, ARKANSAS, AND IOWA
April 26-27, 2014

2. 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.

3. THE FORECAST: APRIL 14

4. ACTUAL: APRIL 26-27

5. 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.

6. Some of the tornadoes were
rated as EF-3, which have
wind fields of at least
246 kph (136 mph).

7. VILONIA, ARKANSAS (ALSO
HIT BY TORNADOES IN 2011)

8. 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

9. “ROUND TWO”
MONDAY, APRIL 28
Millions of people braced for more severe
weather as at least three tornadoes struck
Mississippi on Monday afternoon .

10. TUEPLO, MISSISSIPPI:
APRIL 28

11. INITIAL IMPACT REPORTS
• A tornado hit Tupelo and
tracked northward, causing
"significant property damage,
but no deaths" Tueplo Mayor
Jason Shelton said.

12. BACKGROUND
SEVERE WINDSTORMS--
TORNADOES

13. UNDERSTANDING AND
PREPARING FOR
TORNADOES
A PRIMER OF KNOWLEDGE THAT
CAN MULTIPLY AND SPILL OVER
FOR THE BENEFIT OF MILLIONS

14. THE PHYSICS OF SEVERE
WINDSTORMS
SEVERE WINDSTORMS:
TORNADOES

15. 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

16. 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

17. BASIC PRINCIPLES OF PHYSICS
UNDERPINNING WINDSTORMS
• HEAT AND
HEAT FLOW
• PRESSURE
AND
PRESSURE
FLOW
• GRAVITY
FIELD
• KINETIC
ENERGY
• POTENTIAL
ENERGY

18. SEVERE WINDSTORMS
TORNADOES
OCCUR OVER LAND AS THE
RESULT OF COLLISIONS OF
COLD AND WARM AIR MASSES

20. 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.

21. 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.

22. MAP OF TORNADO ALLEY

23. 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.

24. 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.

25. PHYSICS OF A TORNADO

26. 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

27. HISTORIC OCCURRENCES

28. THIRTY TO FORTY
TORNADOES STRIKE FIVE
SOUTHERN STATES
Mississippi, Alabama, Arkansas, Kentucky,
and Tennessee impacted
54 dead
FEBRUARY 5, 2008

29. LOCATION MAP

30. 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.

31. 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.

32. A TORNADO TOUCHES DOWN
NEAR ATKINS, ARKANSAS

33. DEVASTATION NEAR ATKINS,
ARKANSAS

34. DEVASTATION NEAR ATKINS,
ARKANSAS

35. DEVASTATION NEAR ATKINS,
ARKANSAS

36. COLLAPSE OF WAREHOUSE IN
SOUTH HAVEN, MS

37. COLLAPSE OF WALL IN SHOPPING
MALL: MEMPHIS, TN

38. A FIRE BROKE OUT IN A NATURAL
GAS PUMPING STATION:
HARTSVILLE, TN

39. SEVERE THUNDERSTORM SYSTEM
SPAWNS TORNADOES IN TEXAS:
APRIL 24, 2008

40. A SUPERCELL

41. THE FUNNEL

42. 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)

43. IMPACTS IN WEST AND
NORTH TEXAS
•HEAVY RAIN FALL CAUSED
POWER OUTAGES AND MINOR
FLOODING
•BASEBALL-SIZED HAIL

44. WIND DAMAGE

45. TORNADOES STRIKE IOWA
AND MINNESOTA
Continuation of deadliest
tornado season in a decade
Accompanied by large hail
May 25, 2008

47. HUGO, MINNESOTA: DEBRIS
MARKS STORM'S PATH

48. PARKERSBURG, IOWA: DAMAGE

49. PARKERSBURG, IOWA: LOOKING
FOR SURVIVORS

50. LESSONS LEARNED FROM
TORNADOES
• RECOVERY
USUALLY
TAKES LONGER
AND COSTS
MORE THAN
EXPECTED.

51. 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.

52. LESSONS LEARNED FROM
TORNADOES
• TIMELY COMMUN-
ICATION OF
CRITICAL INFORM-
ATION IN THE FORM
OF WATCHES AND
WARNINGS IS
ESSENTIAL FOR
SAFETY.

53. LESSONS LEARNED FROM ALL
TORNADOES
• HIGH VELOCITY
WIND LIFTS THE
ROOFS OFF OF
BUILDINGS AND
IS A KILLER IN
TORNADOES.

54. LESSONS LEARNED FROM ALL
SEVERE WINDSTORMS
• HIGH VELOCITY
WIND AND
PRESSURE
CHANGES CAUSE
BUILDINGS WITH
INADEQUATE
ENGINEERING
DESIGN TO
COLLAPSE.

55. 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.

56. PUBLIC POLICIES INTEGRATE
TECHNICAL AND POLITICAL
SOLUTIONS
FOR THE LONG-TERM BENEFIT
OF THE PEOPLE.