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Bailey Wright
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Tornadoes are formed when the vertical wind shear, vertical vorticity, and stream line vorticity conditions are favorable. ◦ Storms and frontal systems develop rapidly when moisture and warm air is drawn off the Gulf of Mexico. Objectives ◦ Determine whether the sea surface temperature in the Caribbean affects the frequency of tornado occurrences in the US. ◦ Determine whether there are oscillations in the number of tornadoes per year in the US. Data ◦ Tornado History Project http://www.tornadohistoryproject.com http://www.tornadohistoryproject.com ◦ Caribbean SST Index http://www.esrl.noaa.gov/psd/data/correlation/CAR.data http://www.esrl.noaa.gov/psd/data/correlation/CAR.data
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Linearly Increasing Trends: US Tornadoes 15.4 Tornadoes each year SST Index 0.0029 Index each year
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Phase lag at f=0.121 is 149.6 degrees 4.9 months Phase lag at f=0.31 is -111 degrees -3.7 months
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Periods of 8.26 and 3.23 years
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Green- Least Squares Regression Y = 349.65X + 894.21 Increase of 1.01 per year Red- 95% Confidence Interval Blue- Reduced Major Axis Regression Y = 1993.8X + 844.95 Increase of 5.78 per year Black- Data Correlation Coefficient = 0.1754 95% Confidence Interval -0.0869<r<0.4149
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Critical Value = 7.815 Chi Square Value =3.385 We do not reject the null hypothesis that the residuals are normally distributed
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Low Average High RP 1988-0.2290.6711 19890.34930.4974 1990-0.66780.1472 19910.43430.3895 20040.10150.8483 20080.74330.0904
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The two variables show a relationship at periods of 8.26 and 3.23 years The phase lags between the two variables occur around 4.9 months and -3.7 months ◦ Reduces the possibility of a cause and effect relationship between the two variables Overall, low correlation between the two ◦ Other variables most likely have a stronger influence on tornado frequency Possible problems ◦ “Observed” Tornado data ◦ Seasonal Periodicities If the study was completed again, it would be interesting to look at overall monthly, rather than yearly, occurrences.
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