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National Weather Service Des Moines IA

Using Bufkit to Diagnose Winter Weather. Central Iowa NWA 12-5-07. National Weather Service Des Moines IA. The views expressed are those of the author and do not necessarily represent those of the National Weather Service. Outline Cross-section mode Shear profile Instability

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National Weather Service Des Moines IA

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  1. Using Bufkit to Diagnose Winter Weather Central Iowa NWA 12-5-07 National Weather Service Des Moines IA The views expressed are those of the author and do not necessarily represent those of the National Weather Service.

  2. Outline • Cross-section mode • Shear profile • Instability • Precipitation Type • Other uses?

  3. Temperature Time-Height • Click on Overview button in the upper right hand corner of Bufkit GUI to display time-section -18 -18 -12 -12

  4. Identify Dendritic Growth Zone

  5. Scan Zone for Moisture andIdentify Favored Growth Zone Favored Growth Zone

  6. Display Model Omega

  7. Overlay All Variables 3”- 4”/hr “Cross-hair” signature

  8. Moderate Lift May Fall Outside Dendritic Growth Zone -14ub-1

  9. Snowfall output based on different SLR methods • Omega bullseye outside Dendritic Growth Zone • Waldstreicher study correlates cross-hair signature with Advisory and Warning Criteria snowfall DGZ X 4” actual snow

  10. Other operational uses of Bukfit data • Shear vector in main forcing layer will approximate the orientation of the heavy snow band • Deep layer unidirectional shear favorable for maintaining frontogenetical circulation with heavy snow band Bufkit Time-Section • 3-8 Km Shear Vector oriented same direction as heavy snow band X actual snow 10.5 “ (Banacos, 2003)

  11. Near neutral or unstable lapse rates (with respect to a moist adiabat) implies multiple narrow and intense (maybe 5-10 km or so in width) bands. Note elevated instability layer

  12. Bourgouin Technique Review • Divide the Temperature Profile into 1 to 4 layers • Compute the + and - energy (J/kg) in each layer

  13. The Freezing Rain Profile 3 layers Thickness method toggle

  14. Bourgouin’s Strengths and Limitations • For Snow Events, Bourgouin Always Assumes Ice Crystals are Present • Top Down Approach (Microphysics) NOT Addressed

  15. Summary • A detailed Bufkit analysis should be part of every winter weather decision making process • Waldstreicher study showed potential in differentiating Warning vs Advisory criteria using cross-hair technique • Utilize full functionality, including overview mode, precipitation type, shear profiles, instability, SLR’s

  16. Any questions?…ask Chris Karstens Bufkit Resources: http://www.meteor.iastate.edu/~ckarsten/bufkit/bufkit.html http://www.wdtb.noaa.gov/tools/BUFKIT/index.html Rich.Kinney@noaa.gov

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