A Historical Look at Tornadoes: Damage and Death Harold E. Brooks NOAA/National Severe Storms Laboratory Norman, Oklahoma

Impacts of tornadoes on society What happens in an “average” year? –~40 deaths –~$400M in damage Looking backwards and forwards –Historical trends –Implications for the future

Adjusting historical tornado damage Damage numbers go up –Inflation, acquisition of things, population Adjust for inflation, total wealth (1997) Consumer Price Index Current-Cost Net Stock of Fixed Reproducible Tangible Wealth ( )-“Stuff” $25,000,000,000,000 in 1997

Adjusting stuff outside of period Pure inflation (gap between curves stays same) Stuff grows with GNP

Inflation adjusted top ten Worcester, MA 9 June Conyers, GA 31 Mar Xenia, OH 3 Apr Saint Louis, MO 26 May Windsor Locks, CT 3 Oct Topeka, KS 8 June Lubbock, TX 11 May Omaha, NE 6 May Wichita Falls, TX 10 Apr Oklahoma City, OK 3 May 1999 Adjusted Value Raw Value ($M) PlaceDate

Stuff-adjusted Big Ten 11Oklahoma City 909(963) 10-4 all range from –Lorain-Sandusky (28 June 1924), Lubbock, Gainesville, GA (6 April 1936), Topeka, Omaha, Worcester, Wichita Falls 3Tri-State (1925, raw-16)1392 2St. Louis (1927, raw-22) St. Louis (1896, raw-12)2916 (2167)

Summary of Adjustments Big damage-combination of meteorological event and civilization Inflation still shows some era bias Saint Louis 1896 –Destroyed ~ % of national wealth –Comparable to Dallas-Fort Worth study

Tornado deaths First recorded death –1680 in Cambridge, Massachusetts Total of 19,814 (as of 23 April 2001) When do they occur? How have they changed through time?

Problems with death tolls Poor counting –Cultural biases (e.g., Natchez 1840) –Who was there (e.g., Saint Louis 1896)? “Indirect” fatalities –Big problem with hurricanes –At least 5 in Oklahoma City –None, apparently, in Plainfield (1991)

How has the decrease happened? Causes can’t be deconvolved Changes –Number of tornadoes –Frequency of “big deaths” –Number in big events “95 th percentile” killer

How has the decrease happened? Fewer fatal tornadoes –40/year in 1920s, 1930s –20/year in 1980s, 1990s –Increase in time between fatal tornadoes “High death” tornadoes are smaller –36-fatality tornadoes occurred once/year in 1920s, 1930s –95 th percentile death toll dropped from to 10-15

Putting death and damage together Consider deaths per damage amount –Inflation –Wealth

3 May 1999 Oklahoma City 36 deaths, 11 in mobile homes –>7000 permanent homes, 100 mobile homes Estimating the death toll before warnings? –Rate used to be ~15x today, so ~540 –Inflation-adjustment, ~700 –Wealth-adjustment, ~250 What happened?

Mobile Homes Previously –20x rate of deaths compared to permanent –Big increase in Oklahoma City What might the future hold?

Final Thoughts $1B tornadoes occur ~1/decade in US ~$3B tornado is “practically” worst case Can’t identify causes of decline in deaths Mobile home problem Big disaster situations? Education and communication