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An Investigation of the New Years 2010 Lake Effect Snow Event Using Sounding-Based Parameters

Justin Arnott Senior Forecaster WFO Northern Indiana - IWX. An Investigation of the New Years 2010 Lake Effect Snow Event Using Sounding-Based Parameters. 500 hPa Height Anomalies 1/1-5/2010. 500 hPa U Wind Anomalies 1/1-5/2010. Regional Radar Loop. IWX Radar Loop.

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An Investigation of the New Years 2010 Lake Effect Snow Event Using Sounding-Based Parameters

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  1. Justin Arnott Senior Forecaster WFO Northern Indiana - IWX An Investigation of the New Years 2010 Lake Effect Snow Event Using Sounding-Based Parameters

  2. 500 hPa Height Anomalies 1/1-5/2010

  3. 500 hPa U Wind Anomalies 1/1-5/2010

  4. Regional Radar Loop

  5. IWX Radar Loop

  6. Event Total Snowfall

  7. Event Summary • Incredible Persistence • ~5 days of nearly continuous LES • Modest Strength • 24 hour warning snowfall values only seen once • ~1/2 of 5 day snowfall fell in < 12 hrs

  8. Project Goals • Examine Event from a Sounding Perspective • Can we explain the evolution through sounding-derived parameters? • Goal: Similar Sounding tool akin to the BGM model • Possible further refinements? • Examine Event from a Modeling Perspective • Not enough time for this today!

  9. Sounding Variables • BGM Variables • Instability Variables • T850 and delta T • Inversion Height • Low level lapse rates • Moisture Variables • Moisture Depth • Tdd below 900 • Kinematic Variables • Mixed Layer Wind Direction • Mixed Layer Wind Speed • Wind Shear • DGZ Variables (snow:liquid) • DGZ Depth • DGZ Omega • We’ll examine these and try a few more

  10. Data / Methods • RUC Analysis (00hr) soundings • RUC/NAM sounding parameters very similar overall • When: Hourly (144 soundings) • Is increased temporal resolution helpful (vs. BGM tool)? • Where: South Bend, IN (KSBN) • Qualitative results superior to LM2

  11. Data / Methods • Examine 3 interesting periods • Intense single band • Null Event (you’ll see why later!) • Seeder-Feeder Enhancement

  12. Delta T Can you find the 12 hour period with ~1/2 of the event total snow? Perhaps another variable would help? oC Intense Single Band 1’ Seeder Feeder Event 4-6” Null Event 1-3” Dec 31 Jan 1 Jan 2 Jan 3 Jan 4 Jan 5

  13. Inversion Height Dec 31 Jan 1 Jan 2 Jan 3 Jan 4 Jan 5

  14. Bulk Shear (smoothed) Dec 31 Jan 1 Jan 2 Jan 3 Jan 4 Jan 5

  15. Moisture Depth (Tdd < 3C) Dec 31 Jan 1 Jan 2 Jan 3 Jan 4 Jan 5

  16. 700-500 hPa Mean Tdd Dec 31 Jan 1 Jan 2 Jan 3 Jan 4 Jan 5

  17. Max Tdd below 900 hPa Dec 31 Jan 1 Jan 2 Jan 3 Jan 4 Jan 5

  18. Mean ML Wind Speed Dec 31 Jan 1 Jan 2 Jan 3 Jan 4 Jan 5

  19. Depth of DGZ Below Inversion Dec 31 Jan 1 Jan 2 Jan 3 Jan 4 Jan 5

  20. Moist DGZ Depth Dec 31 Jan 1 Jan 2 Jan 3 Jan 4 Jan 5

  21. Summary • Instability/moisture variables define events/null events successfully • T850 ~ On/Off Parameter • T700/Inversion Height suggest potential strength • Moisture variables indicate if potential is realized • Kinematic/DGZ variables less promising • But, should a favorable DGZ result in a strong band? • Apples/Oranges?

  22. Mixed Layer Mean Wind Direction Dec 31 Jan 1 Jan 2 Jan 3 Jan 4 Jan 5

  23. IWX Similar Sounding Approach A 2-step Process • Step 1 - Instantaneous “Radar Match” • Band Location/Orientation (wind direction) • Band appearance (single vs. multiband)/strength (instability/moisture variables) • Step 2 – Snow Accumulation Potential • Residence Time (D wind direction) • Snowfall Rate Potential (Lake Snow Parameter?)

  24. Future Work • Compile 2005-2010 LES Sounding parameters • COMET NAM/Local RUC BUFR Archive • Refine “Important Parameters” and develop matching algorithm • Separate Step 1/Step 2 variables • Deploy Operational Tool for 2010-2011 Season

  25. Acknowledgements • Mark Steinwedel, Nick Greenawalt, Sam Lashley (IWX) for developing IWX 5 year climatology • Dolores Kiessling (COMET) for archived BUFR data • Jeff Logsdon, SOO IWX • IWX Forecasters

  26. References • Evans and Murphy 2008: A proposed methodology for reconciling high-resolution numerical model guidance with pattern recognition to predict lake-effect snow. EJOM. Available from: http://www.nwas.org/ej/2008-EJ2/ • Smith and Boris 2009: The Lake Snow Parameter. Available from: http://www.crh.noaa.gov/apx/?n=lake_snow_parameter

  27. Extra Slides

  28. Max DGZ Omega Dec 31 Jan 1 Jan 2 Jan 3 Jan 4 Jan 5

  29. 850-700 hPa Mean Tdd Dec 31 Jan 1 Jan 2 Jan 3 Jan 4 Jan 5

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