1. EL NIÑO-SOUTHERN OSCILLATION’S EFFECT ON AMERICAN TORNADOS Jake Mittelman April 24 2012

2. Overview  ENSO  Tornados  Data  Hypothesis  Periodogram  Correlations  Bootstrap  Jacknife Title Source: http://en.wikipedia.org/wiki/Tornado Image Source: http://dailypicksandflicks.com/wp-content/uploads/2012/04/Dallas-Tornado-Throwing-Semi-Trucks-and-Trailers.jpg

3. El Niño-Southern Oscillation  Quasiperiodic  Tropical Pacific Ocean  Variations in SST  El Nino – Warm Phase  La Nina – Cool Phase Image Source: http://en.wikipedia.org/wiki/El_Ni%C3%B1o-Southern_Oscillation

4. ENSO

5. Image Source: http://en.wikipedia.org/wiki/El_Ni%C3%B1o-Southern_Oscillation El Nino La Nina

6. Tornados  Severe Weather  Instability  Wind Shear  Lifting  Moisture  Moisture  Tornados more likely with low LCL  Can increase instability Image Source: http://en.wikipedia.org/wiki/File:Binger_Oklahoma_Tornado.jpg

7. Hypothesis  Whole U.S.  Little to no correlation  Southeast  Positive Correlation with El Nino  Negative Correlation with La Nina (Winter)  Midwest  Positive Correlation with La Nina Image Source: http://en.wikipedia.org/wiki/File:Dimmit_Sequence.jpg

8. Nino 3.4 Index  1950-2007  Middle Ocean  NCAR CGD’s Climate Analysis Section  Compute area averaged total SST from Niño 3.4 region.  Compute monthly climatology (1950-1979) for area averaged total SST from Niño 3.4 region, and subtract climatology from area averaged total SST time series to obtain anomalies.  Smooth the anomalies with a 5-month running mean.  Normalize the smoothed N3.4 by its standard deviation over the climatological period 1950- 1979. Image Source: http://en.wikipedia.org/wiki/File:Enso-index-map.png

9. Nino 3.4 Index

10. Tornado Data Initial Problem  Severe Weather Database from SPC  1950-2007  EF0-EF5

11. LSQR On Tornado

12. Pearson Correlation Coefficients  Strength of Linear Dependence  Nino 3.4 & Tornado (all)  r =.0411

13. Correlation By Year

14. States  No Correlation

15. Southeast (MS, AR, LA, GA, SC, FL, TN, MS, AR, LA, SC, GA, FL, TN)  No Correlation

16. El Nino and La Nina Correlations  Southeast  La Nina r = 0  El Nino r = 0  Midwest (IL, IN, IA, KS, MI, MO, NE, ND, OH, SD, WI)  La Nina r =.11  El Nino r = -.06  Total r =.02  Total  La Nina r =.13  El Nino r = 0

17. Periodograms

18. CPSD

19. Coherence

20. Bootstrap  Tends to be overly optimistic  Seasons  Still Working On  Summer r =.15

21. Bootstrap

22. Jackknife

23. Other Research  Cook, A. R., Schaefer, J.T. 2007  Used Tornado Days  Problem: Not a lot of Data – Total ~220 Days  Found Jet Stream Movement Had Effect  Used Trends  Bove, Mark 1999  Boostrap Method to Increase Data  Most Places Show No Change  Knowles, J., Pielke, R. 1993  Used 7 El Nino and 5 La Nina Events  Found Little Difference in Number  But Found El Nino to have Weaker Tornado Outbreaks

24. More I can Do  Take out More Neutral ENSO Months  Create Smaller Areas  Look at Numbers not Linear Correlations Image Source: http://en.wikipedia.org/wiki/Tornado

25. Conclusion  No Correlation Overall  Number of Tornados and ENSO Phase  Go More Into Year  ENSO still can have an effect  Tornado Strength  Number per Outbreak  Location Image Source: http://uncyclopedia.wikia.com/wiki/File:Animated_tornado.gif

26. Any Questions? Image Source: http://www.google.com/imgres?imgurl=http://a.abcnews.com/images/US/Severe_Weather_110427_wg.jpg