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.

Using Bufkit to Diagnose Winter Weather

Central Iowa NWA

12-5-07

Outline

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

Temperature Time-HeightTemperature Time-Height

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

-18 -18

-12-12

Identify Dendritic Growth ZoneIdentify Dendritic Growth Zone

Scan Zone for Moisture and Identify Favored Growth Zone

Scan Zone for Moisture and Identify Favored Growth Zone

Favored Growth Zone

Display Model OmegaDisplay Model Omega

Overlay All VariablesOverlay All Variables

3”- 4”/hr

“Cross-hair” signature

Moderate Lift May Fall Outside Dendritic Growth Zone

Moderate Lift May Fall Outside Dendritic Growth Zone

-14ub-1

4” actual snow

X

•Omega bullseye outside Dendritic Growth Zone

DGZ•Waldstreicher study correlates cross-hair signature with Advisory and Warning Criteria snowfall

Snowfall output

based on different

SLR methods

Bufkit Time-SectionBufkit Time-Section

•3-8 Km Shear Vector oriented same direction as heavy snow band

X

(Banacos, 2003)

actual snow 10.5 “actual snow 10.5 “

•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

Other operational uses of Bukfit data

Note elevated instability layer

•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.

Bourgouin Technique ReviewBourgouin Technique Review

• Divide the Temperature Profile into 1 to 4 layers

• Compute the + and - energy (J/kg) in each layer

• Divide the Temperature Profile into 1 to 4 layers

• Compute the + and - energy (J/kg) in each layer

The Freezing Rain ProfileThe Freezing Rain Profile

3 layers

Thickness method toggle

Bourgouin’s Strengths and Limitations

Bourgouin’s Strengths and Limitations

• For Snow Events, Bourgouin Always Assumes Ice Crystals are Present

• Top Down Approach (Microphysics) NOT Addressed

• For Snow Events, Bourgouin Always Assumes Ice Crystals are Present

• Top Down Approach (Microphysics) NOT Addressed

SummarySummary

• 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

• 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

Any questions?…ask Chris Karstens

Any questions?…ask Chris Karstens

Rich.Kinney@noaa.gov

http://www.wdtb.noaa.gov/tools/BUFKIT/index.html

Bufkit Resources:http://www.meteor.iastate.edu/~ckarsten/bufkit/bufkit.html