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EL NIO-SOUTHERN OSCILLATIONS EFFECT ON AMERICAN TORNADOS Jake Mittelman April 24 2012

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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

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El Nio-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

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ENSO

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

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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

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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

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Nino 3.4 Index 1950-2007 Middle Ocean NCAR CGDs Climate Analysis Section Compute area averaged total SST from Nio 3.4 region. Compute monthly climatology (1950-1979) for area averaged total SST from Nio 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

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Nino 3.4 Index

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

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LSQR On Tornado

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

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Correlation By Year

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States No Correlation

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

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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

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Periodograms

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CPSD

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Coherence

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

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Bootstrap

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Jackknife

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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

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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

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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

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