Transcript CFO Visit - Iowa State University
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
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Cross-section mode
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Shear profile
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Instability
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Precipitation Type
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Other uses?
Temperature Time-Height
-18 -12 -18 -12
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Click on Overview button in the upper right hand corner of Bufkit GUI to display time-section
Identify Dendritic Growth Zone
Scan Zone for Moisture and Identify Favored Growth Zone Favored Growth Zone
Display Model Omega
Overlay All Variables
“Cross-hair” signature 3”- 4”/hr
Moderate Lift May Fall Outside Dendritic Growth Zone -14ub -1
Snowfall output based on different SLR methods DGZ X 4” actual snow
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Omega bullseye outside Dendritic Growth Zone
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Waldstreicher study correlates cross-hair signature with Advisory and Warning Criteria snowfall
Other operational uses of Bukfit data
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Shear vector in main forcing layer will approximate the orientation of the heavy snow band
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Deep layer unidirectional shear favorable for maintaining frontogenetical circulation with heavy snow band Bufkit Time-Section
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3-8 Km Shear Vector oriented same direction as heavy snow band X actual snow 10.5 “ (Banacos, 2003)
•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
Bourgouin
Technique
Review
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Divide the Temperature Profile into 1 to 4 layers
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Compute the + and - energy (J/kg) in each layer
The Freezing Rain Profile
Thickness method toggle 3 layers
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Bourgouin’s Strengths and Limitations
For Snow Events, Bourgouin Always Assumes Ice Crystals are Present
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Top Down Approach (Microphysics) NOT Addressed
Summary
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A detailed Bufkit analysis should be part of every winter weather decision making process
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Waldstreicher study showed potential in differentiating Warning vs Advisory criteria using cross-hair technique
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Utilize full functionality, including overview mode, precipitation type, shear profiles, instability, SLR’s
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