Tornadoes are caused by collisions of cold descending and warm ascending air masses. The main tornado season in the USA is late winter through midsummer. However, tornadoes can occur anytime conditions are right. Past tornado disasters have caused extensive damage and loss of life. Examples from 2008 are described, including tornado outbreaks in several southern states that killed 54 people, and tornadoes in Iowa and Minnesota that struck during the deadliest season in a decade. While the Midwest experiences fewer tornadoes than regions like Tornado Alley, its tornadoes are more likely to occur at night and in colder months. Lessons from past disasters emphasize the importance of early warning, wind-engineered buildings, safe rooms, timely emergency response,

1. LEARNING FROM GLOBAL
DISASTER LABORATORIES
PART 5: TORNADOES

2. TORNADOES
Caused by the
collision of
descending
cold and
ascending
warm air
masses

3. “THE TORNADO SEASON”
• The “tornado season” is late winter
through midsummer,….
• But tornadoes can happen any time of
the year and in any state when the
atmospheric conditions are right.
• Unusual numbers of tornadoes are a
consequence of La Nina, the cooling of
the Pacific Ocean, which can cause
global changes in weather patterns.

4. A SUPER STORM CELL CAN
SPAWN MANY TORNADOES

5. WINDS CAN REACH 500 KPH
(300 MPH) AT “TOUCH DOWN”

6. NATIONS THAT NEED TO BECOME
TORNADO DISASTER RESILIENT
• USA (especially in the states
identified as “Tornado Alley”)
• AUSTRALIA (rare, but
occasionally)

7. TORNADO ALLEY

8. TORNADO RISK MAP

9. WIND AND WATER
PENETRATE BUILDING
ENVELOPE
TORNADOES
UPLIFT OF ROOF SYSTEM
FLYING DEBRIS (all sizes and
shapes)
REGIONAL STORM CELLS
HEAVY PRECIPITATION AND
HAIL STONES
NO WARNING
(MUDFLOWS)
NO SAFE “SAFE HAVENS”
CAUSES
OF RISK
GLOBAL
DISASTER
LABORATORIES

10. TYPICAL SOCIOECONOMIC
IMPACTS
• Little or no warning; no time for
effective evacuation
• Downed trees
• Power outages
• Damaged cars and trucks
• Roofs ripped off; buildings
destroyed

11. TYPICAL SOCIOECONOMIC
IMPACTS
• Houses, businesses,
warehouses, shopping malls,
schools, and hospitals
damaged and/or destroyed
• Major roads blocked by debris
• Airports and train stations
closed

12. WE CONTINUE TO OPERATE WITH
A FLAWED PREMISE:
TORNADO DISASTERS, WHICH ARE
SEASONAL EVENTS THAT OCCUR
ANNUALLY IN THE UNITED
STATES ARE WELL UNDERSTOOD;
THEREFORE TORNADO DISASTER
RESILIENCE IS SHOULD BE
RELATIVELY EASY.

13. FACT: TORNADO DISASTERS ARE
COMPLEX, MAKING TORNADO
DISASTER RESILIENCE A VERY
ELUSIVE GOAL TO ACHIEVE

14. EXAMPLES OF PAST
TORNADO DISASTERS

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

16. MAP

17. A TORNADO TOUCHES DOWN
NEAR ATKINS, ARKANSAS

18. DEVASTATION NEAR ATKINS,
ARKANSAS

19. DEVASTATION NEAR ATKINS,
ARKANSAS

21. COLLAPSE OF WAREHOUSE IN
SOUTH HAVEN, MISS.

23. COLLAPSE OF SHOPPING MALL:
MEMPHIS, TN

24. FIRE IN A NATURAL GAS PUMPING
STATION: HARTSVILLE, TN

25. SUPER STORM CELL SPAWNS
TORNADOES; TX: APRIL 2008

26. IMPACTS
•WIND AND HAIL DAMAGE NEAR
FT WORTH, TX ESTIMATED AT
$35 MILLION
• POWER OUTAGES

27. TORNADOES STRIKE IOWA
AND MINNESOTA
Continuation of the deadliest
tornado season in a decade
May 25, 2008

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

30. PARKERSBURG, IOWA: DAMAGE

31. PARKERSBURG, IOWA: SEARCH
AND RESCUE

32. STORMS IN THE
MID-WESTERN USA
Occur Late Winter through
Spring, Every Year

33.  Although far from the so-called
"Tornado Alley," a region that falls
generally in the southern plains of
Texas, Okla. and Kan., the greater
Midwest also experiences a large
number of tornadoes each year.

34.  A major difference is that
Midwestern tornadoes are
more likely to form late at
night and in colder months
than those in “Tornado
Alley.”

35. . For example, Indiana
experiences only about 20
tornadoes a year, compared
to about 52 in Oklahoma. and
124 in Texas.

38. LESSON: THE TIMING OF
ANTICIPATORY ACTIONS IS VITAL
• The people who know: 1) what to
expect (e.g., high-velocity winds,
rain, hail), 2) where and when the
toudh down will happen, and 3)
what they should (and should not)
do to prepare will survive.

39. LESSON: TIMELY EARLY WARNING
AND EVACUATION SAVES LIVES
• The people who know that they may
have little or no warning and still
can get out of harm’s way will
survive.

40. LESSON: WIND ENGINEERED
BUILDINGS SAVE LIVES
• Buildings with roof systems and
facads engineered to withstand a
tornado’s high velocity winds will
protect occupants and users from
death and injury.

41. WHEN IMPLEMENTED, THE
TORNADO “SAFE ROOM” IS A
RECENT INNOVATION THAT IS MORE
EFFECTIVE THAN THE WELL KNOWN
CELLAR IN SAVING LIVES

43. LESSON: EMERGENCY RESPONSE
SAVES LIVES AND PROTECTS
• The timing of emergency response
operations is vitally important for
search and rescue and provision of
emergency services to save lives
and protect property.

44. LESSON: EMERGENCY MEDICAL
PREPAREDNESS SAVES LIVES
• The local community’s capacity for
emergency health care offsets the
crisis caused by damaged hospitals
and medical facilities, lack of clean
drinking water, food, and medicine,
and high levels of morbidity and
mortality.