Forecasting the Inland Extent of Lake-Effect Snow (les) Bands: Application and Verification for Winter 2010-2011


НазваForecasting the Inland Extent of Lake-Effect Snow (les) Bands: Application and Verification for Winter 2010-2011
Дата конвертації20.04.2013
Розмір445 b.
ТипПрезентации


Forecasting the Inland Extent of Lake-Effect Snow (LES) Bands: Application and Verification for Winter 2010-2011

Joseph P. Villani

NOAA/NWS Albany, NY

Michael L. Jurewicz, Sr.

NOAA/NWS Binghamton, NY

Jason Krekeler

NOAA/NWS State College, PA

Outline

  • Introduction

  • Forecast Application

  • Verification of App.

  • A few case studies

  • Composite Plots

  • Future Work



Introduction

  • Determine atmospheric parameters which commonly have the greatest influence on a LES band’s inland extent

  • Examined over 20 LES events across the Eastern Great Lakes (Erie/Ontario) during 2006-2009 winter seasons

    • For each event, parameters evaluated at 6-hour intervals (00, 06, 12, and 18 UTC), using mainly 0-hr NAM12 model soundings


Introduction

  • Wind regimes stratified by mean flows:

    • 250-290° for single bands
    • 300-320° for multi bands
  • LES bands’ inland extent (miles) calculated from radar mosaics, distance measuring tool

  • Data points:

    • Locations inside and north/south band


Parameters



Strategy to Determine Best Parameters

  • Used statistical correlations in Excel spreadsheet to determine most influential factors driving inland extent of LES bands

  • Values for the best correlated parameters statistically significant to the 99.95% level with N > 500



Statistical Correlations

  • Best correlators to inland extent (all points together): ALY events

    • 850 hPa Lake-air ∆T (-0.63)
    • Multi-lake connection present (0.59)
    • Capping inversion height (0.53)
    • 0-1 km bulk shear (0.44)


Results from Correlations

  • Environments that promote greater inland extent (IE):

    • Multi-Lake Connection (from upstream lakes)
    • Conditional instability class
    • Strong 0-1 km shear, weaker shear in1-3 km layer
    • High capping inversion height


Favorable Environment far-reaching IE

  • MLC present (not shown)

  • Strong 0-1 km shear; little shear in 1-3 km layer

  • High capping inversion height over 3 km



AWIPS Forecast Application

  • Equation developed to determine inland extent of lake effect snow bands based on most strongly correlated parameters

  • Forecast application based on equation created for use in NWS AWIPS software

  • Application integrated on experimental basis at Albany and Binghamton NWS offices



Example of Forecast Application



Multi-Lake Connection (MLC)

  • Use pattern recognition for favorable surface, 850/700 hPa low center tracks in forecasting MLC

  • 850 hPa low center tracks



Verification of Application

  • 10 event times verified via radar with >15 dBZ

    • Avg error = 10 miles
    • Excluding two narrow/multi-band/NW flow events
    • Avg error = 4 miles
    • Avg bias = (-7) miles (under-forecasting IE)
    • Avg bias = (1) miles (excluding the two outliers)
    • Avg bias = (-35) miles (for 2 outliers)
    • Need more events to support verification


Example of single-band event

  • 27 November 2010

    • Single band event – extensive IE
    • MLC Present
    • IE forecast from application:
    • 1100 UTC = 94 miles
      • Verification = 92 miles
    • 1600 UTC = 90 miles
      • Verification = 100 miles


27 November 2010 – 1600 UTC

  • MLC present from Georgian Bay

  • Well-developed single band depicted by satellite



27 November 2010 – 1200 UTC

  • MLC present

  • Strong 0-1 km shear; little shear in 1-3 km layer

  • High capping inversion height over 3 km



27 November 2010 – 1100 UTC

  • IE Forecast from application = 94 miles

  • Actual IE = 92 miles

  • Good performance of app.



Example of single-band event

  • 02 December 2010

    • Single band event – IE not extensive
    • No MLC Present
    • IE forecast from application:
    • 1400 UTC = 46 miles
      • Verification = 45 miles
    • 1500 UTC = 43 miles
      • Verification = 37 miles


02 December 2010 – 1400 UTC

  • No MLC present (not shown)

  • Modest 0-1 km shear; greater shear in 1-3 km layer

  • Lower capping inversion height



02 December 2010 – 1400 UTC

  • IE Forecast from application = 46 miles

  • Actual IE = 45 miles

  • Good performance of app.



Example of multi band event

  • 08 December 2010

    • Multi band event – IE extensive
    • MLC Present
    • IE forecast from application:
    • 2100 UTC = 67 miles
      • Verification = 120 miles


08 December 2010 – 2100 UTC

  • IE Forecast from application = 67 miles

  • Actual IE = 120 miles

  • Poor performance of app.



Example of single-band event

  • 16 January 2011

    • Single band event – IE extensive
    • MLC Present
    • IE forecast from application:
    • 0200 UTC = 92 miles
      • Verification = 87 miles
    • 0600 UTC = 103 miles
      • Verification = 104 miles


16 January 2011 – 0200 UTC

  • IE Forecast from application = 92 miles

  • Actual IE = 87 miles

  • Good performance of app.



Composite Plots using NARR

  • Composite maps of surface pressure and 500/700/850 hPa mean geopotential height plotted for far-reaching IE of LES bands

  • Plus favorable environments with:

    • Multi-Lake Connection (from upstream lakes)
    • Conditional instability class
    • Strong 0-1 km shear, weaker shear in1-3 km layer
    • High capping inversion height






Composite Plots using NARR

  • Plots obtained from NOAA’s Earth System Research Laboratory (ESRL) using North American Regional Reanalysis (NARR)

  • Favorable positions for low centers generally in South-Central Quebec for far-reaching IE of LES bands into Albany forecast area



Conclusions

  • In general, application represented IE well for well-developed single bands in W to WSW flow.

  • Application under-forecasted IE (significantly at times) for narrow multi-bands in NW flow

  • Additional changes may be needed for multi-band events



Ongoing/Future Work

  • Solidify operational functionality of application through additional real-time events

  • Develop graphical representation of the inland extent of snow bands, compare to models



Acknowledgements

  • Jason Krekeler

    • NOAA/NWS State College, PA/State University of NY at Albany
  • Vasil Koleci

    • NOAA/NWS Albany, NY
  • Hannah Attard

    • State University of NY at Albany


References

  • Niziol, Thomas, 1987: Operational Forecasting of Lake Effect Snowfall in Western and Central New York. Weather and Forecasting.

  • Niziol, et al., 1995: Winter Weather Forecasting throughout the Eastern United States – Part IV: Lake Effect Snow. Weather and Forecasting.



Questions?

Joe.Villani@noaa.gov

Michael.Jurewicz@noaa.gov

Jason.Krekeler@noaa.gov

www.weather.gov/aly

www.weather.gov/bgm

www.weather.gov/ctp


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