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A Comparison of Iowa Flash Flood Events and Eight Common Features of Excessive Rainfall for 2006-2011

Brittany Konradi 1 Mentors: Melinda Beerends 2 and Dr. Kristie Franz 1 Iowa State University 1 , NWS Des Moines 2. A Comparison of Iowa Flash Flood Events and Eight Common Features of Excessive Rainfall for 2006-2011. Outline. Background Information Methodology Analysis and Results

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A Comparison of Iowa Flash Flood Events and Eight Common Features of Excessive Rainfall for 2006-2011

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  1. Brittany Konradi1 Mentors: Melinda Beerends2 and Dr. Kristie Franz1 Iowa State University1, NWS Des Moines2 A Comparison of Iowa Flash Flood Events and Eight Common Features of Excessive Rainfall for 2006-2011

  2. Outline • Background Information • Methodology • Analysis and Results • Conclusions • Future Work

  3. Background • Flash flood occurs within 6 hours of a causative event • Flood forecasts • Flash flood guidance (FFG) software from local river forecast center (RFC) • Soil conditions, estimated precipitation, river levels, and terrain • Current variable checklist is small • Improve checklist

  4. Motivation • Second-most deadly weather event in the United States • First is heat-related events • Damages and fatalities are increasing • Antecedent environmental conditions and location

  5. Hypothesis • When environmental and antecedent conditions meet the criteria of Maddox et al. (1979), a flash flood event will occur in Iowa.  

  6. Data • Archived data • Iowa Environmental Mesonet • Storm Prediction Center • NCDC (National Climatic Data Center) StormData • Wunderground • University of Wyoming soundings • AWIPS (Advanced Weather Interactive Processing System)

  7. Case Selection • Watches, Warnings, and LSRs • Ice jams • 1. Watch and warning issued, and flash flood reported • 2. Watch issued, and no flash flood reported • 3. No watch issued, and flash flood reported

  8. Cases

  9. Maddox et al. (1979) • Eight criteria • Associated with convective storms. • Surface dew points are high. • High moisture content is present throughout the layer • Weak to moderate vertical wind shear throughout the layer • Repeatedly move over the same area • Weak, mid-tropospheric, meso-α scale trough • Meso-α scale = 200-2000 km (squall lines, MCSs, tropical cyclones) • Very near the mid-tropospheric, large-scale ridge position • Occurs during the nighttime hours

  10. Results: Convective (#1) and Motion (#5) • Lightning strikes and slow motion • Case 1 (10/14/2007) • Case 3 (5/10/2008)

  11. Results: Dew Point (#2) • Threshold: Climatological average

  12. Results: Moisture (#3) • High moisture throughout layer • Moisture transport vectors, Θe, and precipitablewater • Equivalent potential temperature = total moisture and heat • Case 1 • Case 3

  13. Results: Precipitable Water (#3) • Threshold: Climatological average

  14. Results: Shear (#4) • Threshold: Weak to Moderate shear • Slower storm motion

  15. Results: Shear (#4) • Threshold: • Veering near surface • Uni-directional aloft • Increasing in magnitude with height • Case 1 (left) • Ideal Maddox (middle) • Case 3 (right)

  16. Results: Set-up (#6, #7) • Thresholds: • Weak, mid-tropospheric, meso-α scale trough • 500 mbanalysis • Mid-tropospheric, large-scale ridge position • Maddox et al (1979) ideal set-up • Double jet streaks • Strong moisture axis at all levels • Developing cyclone

  17. Results: Set-up • Case 1 • SW trough • Large-scale ridge 300 mb 500 mb Surface 850 mb

  18. Results: Set-up • Case 3 • Short-wave trough • Large-scale trough 500 mb 300 mb 850 mb Surface

  19. Results: Nighttime event (#8) • Nighttime event • 3Z to 12 Z • Low-level jet

  20. Results: Antecedent Precipitation

  21. Results: Criteria Comparison

  22. Conclusion • Moisture and forcing • Cyclone maturity and weak to moderate shear • Flood events meet more criteria

  23. Future Work • More cases • Only spring and fall events • Freezing level • Winds increase with height in radiosonde • LLJ influence

  24. References • Ashley, S. T. and W. S. Ashley, 2008: Flood Fatalities in the United States. J. Appl. Meteor. Climatol., 47, 805–818. • Ashley, W. S., 2007: Spatial and Temporal Analysis of Tornado Fatalities in the United States: 1880–2005. Wea. Forecasting, 22, 1214–1228. • Doswell, C. A., H. E. Brooks, and R. A. • Maddox, 1996: Flash Flood Forecasting: An Ingredients-Based Methodology. Wea. Forecasting, 11, 560–581. • European Space Agency, cited 2009: SMOS Scientific Objectives. [Available online at http://www.esa.int/esaLP/ESAS7C2VMOC_LPsmos_0.html.] • Funk, Theodore W., 1991: Forecasting Techniques Utilized by the Forecast Branch of the National Meteorological Center During a Major Convective Rainfall Event. Wea. Forecasting, 6, 548–564. • Junker, N. W., R. S. Schneider, and S. L. Fauver, 1999: A Study of Heavy Rainfall Events during the Great Midwest Flood of 1993. Wea. Forecasting, 14, 701–712. • Maddox, R. A., C. F. Chappell, and L. R. Hoxit, 1979: Synoptic and Meso-α Scale Aspects of Flash Flood Events1. Bull. Amer. Meteor. Soc., 60, 115–123. • Morss, Rebecca E., 2010: Interactions among Flood Predictions, Decisions, and Outcomes: Synthesis of Three Cases. Natural Hazards Review,11, 3, 83. • WFO DMX Station Duty Manual, Vol. 1, Section 5.2, 2011. • Roebber, P. J., and J. Eise, 2001: The 21 June 1997 Flood: Storm-Scale Simulations and Implications for Operational Forecasting. Wea. Forecasting, 16, 197–218

  25. Acknowledgements • Mindy Beerends • Kristie Franz

  26. Questions? Vortex Insurance Agency cited 2009. [Available online at http://www.vortexinsuranceagency.com/AboutUs/InsuranceOrDerivative.aspx.]

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