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Twister Tracking: Analysis of Weather Events in Indiana

2014 Indiana GIS Conference May 8, 2014. Twister Tracking: Analysis of Weather Events in Indiana. Olivia Kellner Ph.D. Candidate, Purdue University Climate Specialist, Indiana State Climate Office. Photos: Doyle McIntosh.

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Twister Tracking: Analysis of Weather Events in Indiana

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  1. 2014 Indiana GIS Conference May 8, 2014 Twister Tracking: Analysis of Weather Events in Indiana Olivia Kellner Ph.D. Candidate, Purdue University Climate Specialist, Indiana State Climate Office Photos: Doyle McIntosh

  2. Land-surface Heterogeneity in Tornado Climatology? An Illustrative Analysis over Indiana 1950-2012 Presentation Outline: • Founding science and hypothesis • Data • Climatology • Methods • Findings • Geospatial Analysis • Methods • Maps • Findings • Conclusions http://www.crh.noaa.gov/ilx/events/may302004/040530_rpts.gif http://www.srh.noaa.gov/ohx/?n=april31974_40thanniversary Kellner, O. and D. Niyogi, 2013, Land-surface Heterogeneity Signature in Tornado Climatology? An Illustrative Analysis over Indiana 1950-2012, Earth Interactions, e-view, doi: http://dx.doi.org/10/1175/2013EI000548.1. http://www.angelfire.com/theforce/storm_chasingf5/Historical%20and%20Major%20Tornado%20Outbreaks%20the%20one.htm

  3. Founding science:  Land-surface heterogeneity: where the land cover or land use is not uniform across an area  Leads to a heterogeneous boundary layer in terms of temperature, dew points, vertical velocities, and winds  Can these surface discontinuities modify the boundary layer enough to impact storm dynamics and evolution? Mahmood et al., 2011 Fig. 5. Inner domain average modeled (a) relative humidity, (b) dew point temperature, (c) ground temperature, (d) two-meter temperature, and (e) planetary boundary layer height for control, bare soil, grassland, and forest. Mahfouf et al., 1987

  4. Convective weather and land surface heterogeneity: physiographic boundaries, land use changes, & urban areas From Brown and Arnold, 1998: Figure 6. Spatial distribution for all convective cloud masses(dots, both initial and vertically enhanced) for 34 weak synoptic flow days, July–August, 1986–1991, in the aggregate. From Changnon et al., 1991 Journal of Applied Meteorology

  5. Convective weather & land surface heterogeneity From Brown and McCann, 2004

  6. Hypothesis • Indiana’s land surface, rich with physiographic boundaries, land-surface heterogeneity, topography, and distinct, isolated urban regions may influence the evolution of convective weather (specifically tornado touchdown locations). http://media.wfyi.org/NaturalHeritage/learn/regions.html https://ou-gisapplications.wikispaces.com/Indiana+Land+Use http://pubs.usgs.gov/of/2004/1451/rupp/

  7. Storm and Geospatial Data Sources Climatology Geospatial Data • Storm Prediction Center (SPC) Storm reports, available in their Severe Weather Database Files • Inclusive of • Date • Time • Touchdown in lat/long • County • F-scale • Injuries • Fatalities • SPC SVRGIS webpage: http://www.spc.noaa.gov/gis/svrgis/ • Tornado touchdown points • States • Cities • Counties • Population Density (2010 raster file, density per square kilometer) • Land cover: U.S.G.S Enhanced Historical Land-use and Land-cover Data sets • DEM: Ball State University

  8. Climatology Development • Implementation of .csv files of storm data into Excel • Sort data by: • Date • Time • F-scale • Compute tornado days and climatological data by parameters investigated • Month • Year • F-scale • Weak (F0-F1) and Strong (F2-F5) • Increase/decrease in annual tornado days • Also investigated antecedent rainfall at 1, 3, and 6 month periods and ENSO phase to annual number of tornado days

  9. Climatology • Most active time of day • weak tornadoes: 4-7pm LST; • strong tornadoes: 2-4pm and 5-8pm LST; • all tornadoes 4-8pm LST • Majority of Indiana’s tornadoes are weak tornadoes (50%) • 30-year moving averages show no increase or decrease in annual tornado days • 30-year moving averages by climate division show an increase in annual tornado days in southern most climate divisions from 1 day a year to 3 days a year • ENSO: rate at which ENSO changes phase appears to relate to more active seasons in Indiana • Weak relationship between 6-month antecedent drought conditions and number of tornado days This shift is a result of the windshear environment more common with strong tornadoes

  10. Geospatial Analysis Dr. T. T. Fujita, University of Chicago

  11. Methods • Spatial analyst tools: • Kernel density • Map algebra • Slope calculator • Conversion tools • Analysis tools: • Buffer • “Select features within”

  12. Investigate the potential impacts of: • Changes in elevation • Change in slope of 5 degrees or more over a distance of ~100 meters • Change in land cover • 6 classes • Forest • Urban • Agriculture • Barren • Wetlands/water bodies • Range land • Urban areas • City centroids • Urban area shapefiles • Population density • People per square kilometer

  13. Elevation & Tornado Touchdown Points Is this happening here in Indiana? http://pubs.usgs.gov/of/2004/1451/rupp/ http://jasonahsenmacher.wordpress.com/category/terrain/

  14. Urban Areas, City Centroids, &Tornado Touchdown Points ~9 miles ~1 mile Tornado “rings” ? ~Noted by Fujita in other cities such as Chicago in early 1970s

  15. Land-use, Land-cover change & Tornado Touchdown Points

  16. Population &Tornado Touchdown Points Correlation: -0.79 -0.79 -0.80 -0.80 An indirect relationship: higher percentage of tornado touchdown points in land area with lower populations However, the spatial distribution close to major cities towns suggest a population bias…

  17. El Niño vs. La Niña Years • Spatially different patterns -> La Niña more concentrated touchdown locations • In terms of climatology, no year has a greater risk for more tornadoes • Transition between phases appears to contribute to active and less active tornado years

  18. Conclusions • Meteorology &climatology are very cartographically intensive sciences (forecasters constantly look at &analyze maps)! • Sadly, a gap between those that know meteorology & the benefits of geospatial analysis is present • Indiana tornado days have not increased or decreased through time • Note that tornado days are not the same as tornadoes! • Any given day can have 1 – 20+ tornadoes • Several land surface relationships may be occurring • topography • physiographic regions • land use : 42 % & 64% touched down within 1 km of forest & urban land areas, respectively • All tornadoes: 43% & 61% touched down within 1 km of forest and urban, respectively • Supports land-surface heterogeneity hypotheses: • Boundaries of temperature, dewpoints, CAPE, vertical velocities , & surface roughness when transitioning from one land use to another

  19. Thank you! - Questions?!?! • Special thanks to Dr. David L. Arnold & Tim Samaras for inspiration and devotion to novel, challenging research seeking to unravel the unsolved mysteries of severe weather & tornadoes • NWS Indianapolis for continued support • Dev Niyogi & the Indiana State Climate Office Email: okellner@purdue.edu

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