CFO%20Visit

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

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Temperature Time-Height

• Click on Overview button in the upper right hand
  corner of Bufkit GUI to display time-section

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-18
-12
-12
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Identify Dendritic Growth Zone
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Scan Zone for Moisture and Identify Favored
Growth Zone
Favored Growth Zone
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Display Model Omega
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Overlay All Variables
3- 4/hr
Cross-hair signature
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Moderate Lift May Fall Outside Dendritic Growth
Zone
-14ub-1
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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
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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)
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• 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
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Bourgouin Technique Review

• Divide the Temperature Profile into 1 to 4 layers
• Compute the and - energy (J/kg) in each layer

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The Freezing Rain Profile
3 layers
Thickness method toggle
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Bourgouins Strengths and Limitations

• For Snow Events, Bourgouin Always Assumes Ice
  Crystals are Present
• Top Down Approach (Microphysics) NOT Addressed

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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, SLRs

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Any questions?ask Chris Karstens
Bufkit Resources
http//www.meteor.iastate.edu/ckarsten/bufkit/buf
kit.html
http//www.wdtb.noaa.gov/tools/BUFKIT/index.html
Rich.Kinney_at_noaa.gov