El%20Ni

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El Niño-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-c
ontent/uploads/2012/04/Dallas-Tornado-Throwing-Sem
i-Trucks-and-Trailers.jpg
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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_NiC
3B1o-Southern_Oscillation
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ENSO
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El Nino
La Nina
Image Source http//en.wikipedia.org/wiki/El_NiC
3B1o-Southern_Oscillation
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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/FileBi
nger_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/FileDi
mmit_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 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/FileEn
so-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/F
ileAnimated_tornado.gif
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Any Questions?
Image Source http//www.google.com/imgres?imgurl
http//a.abcnews.com/images/US/Severe_Weather_1104
27_wg.jpg