1. The Inland Extent of Lake Effect Snow (LES) Bands Joseph P. Villani NOAA/NWS Albany, NY Michael L. Jurewicz, Sr. NOAA/NWS Binghamton, NY Jason Krekeler NOAA/NWS State College, PA/State University of NY at Albany

2. Outline Goals Methodology Results A few case studies/examples Summary

3. Goals Identify atmospheric parameters which commonly have the greatest influence on a LES band’s inland extent Infuse research findings into operations Improve forecasts to support NWS Watch/Warning/Advisory program

4. Satellite depiction of developing LES band Well developed band from Lake Ontario to the Hudson Valley Upstream moisture sources

5. Methodology/Data Sources Examined around 25 LES events across the Eastern Great Lakes (Erie/Ontario) during the 2006-2009 time frame – For each event, parameters evaluated at 6-hour intervals (00, 06, 12, and 18 UTC), using mainly 0-hr NAM12 model soundings – Event duration varied from 6 hours to multiple days

6. Methodology/Data Sources Wind regimes stratified by mean flows: – 250-290° for single bands (WSW-ENE oriented) – 300-320° for multi bands (NW-SE oriented) LES bands’ inland extent (miles) calculated from radar mosaics, distance measuring tool Data points: – Locations inside and north/south band Data stratified by location relative to band

7. Example of Data Points Points in and near LES band BUF sounding ALY sounding

8. Parameters 1) Mixed layer (ML) windAvg. direction/speed (deg/kt) 2) Ambient low level moisture Surface dewpoint ( ° C); Max ML dewpoint depression (T dD ) ( ° C) 3) Snow band width/length>= 15 dBZ contour (mi) 4) Niziol instability class Lake–air  T( ° C) at 700/850 hPa 5) Capping inversionInversion height: top of ML (m) 6) Vertical wind shear a. bulk shear (0-1, 0-3 km) Vector difference between wind at top and bottom of layer (kt) 6) Vertical wind shear b. directional/speed Estimated values between surface and top of ML (deg/kt) 7) Low-level convergenceFrom 0-hour 12km NAM 8) Multi-lake connection?Satellite/radar data

9. Strategy to Determine Best Parameters Used statistical correlations in Excel spreadsheet to determine most influential factors driving inland extent – Overall, locations relative to bands made little difference in the correlations (within the bands vs. north or south) A few exceptions

11. 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)

12. Statistical Correlations Also notable correlators in locations outside of the bands: – Points south of the band: Mixed-layer wind speed (0.33) Mixed-layer directional shear (-0.18) – Points north of the band: Surface convergence (0.34) 925 hPa convergence (0.12)

13. Results from Correlations Environments that promote greater inland extent: – Multi-Lake Connection – Conditional instability class – Strong 0-1 km shear, weaker shear in1-3 km layer – High capping inversion height

14. Event Types from Results Event types favorable for inland extent based on strongest correlations – Instability and Multi-Lake Connection (MLC) Niziol Instability Class: – Conditional Instability Lake-850 hPa difference: 12°C to18°C Lake-700 hPa difference: 17°C to 24°C – Moderate-Extreme Instability Lake-850 hPa difference: >18°C Lake-700 hPa difference: >24°C

15. Use these parameters to classify events: – Type A – MLC & Conditional Instability (most favorable type for inland extent) – Type B – MLC & Moderate/Extreme Instability – Type C – No MLC & Moderate/Extreme Instability – Type D – No MLC & Conditional Instability Classifying Event Types

16. Results by Event Type

17. Vertical Wind Profiles of Mixed Layer Type A – greater 0-1 km shear, less above 1 km Other Types – less 0-1 km shear, greater above 0-3 km 0-1 km Z X

18. Type A – Surface – 29Oct2006 18Z

19. Type A Sounding - 29Oct2006 18Z Strong 0-1 km speed shear, weaker 1-3 km Little directional shear in mixed layer High (if any) capping inversion Conditional Instability – Lake temp: 10°C – 850 temp : - 4°C – 700 temp: - 15°C 0°C

20. Broad cyclonic flow associated with Low pressure in Quebec Multi-Lake Connection indicated by visible satellite Type A – Satellite – 29Oct2006 18Z 850 hPa wind Upstream Bands

21. LES band inland extent around 169 mi Type A – Radar – 29Oct2006 18Z 0-1 km bulk shear

22. Type C – Surface – 07Feb2007 18Z

23. Type C Sounding – 07Feb2007 18Z Less 0-1 km speed shear, greater shear in 1-3 km layer More directional shear in mixed layer Extreme Instability – Lake temp: 4°C – 850 temp : -18°C – 700 temp: - 28°C 0°C

24. NO Multi-Lake Connection indicated by visible satellite Well-developed single band, but with little inland extent Type C – Satellite – 07Feb2007 18Z 850 hPa wind No connection with upstream bands

25. LES band inland extent only 34 mi Type C – Radar – 07Feb2007 18Z 0-1 km bulk shear

26. Type A events result in greatest inland extent, often over 100 miles Key factors are: Instability, MLC, Shear – Ideal conditions: Conditional instability MLC Strong mixed layer flow with minimal speed shear between 1-3 km Nearly unidirectional flow through mixed layer Summary

27. Refer to event types when forecasting inland extent – Forecast the event type, which will yield good first guess for inland extent potential Use pattern recognition of favorable surface, 850/700 hPa low tracks in forecasting MLC Use AWIPS forecast application (based on equation derived from correlated parameters), which provides estimate of inland extent Application

28. 850 mb Low center tracks

29. Example of Real-time Application

31. Ongoing/Future Work Infuse forecast applications into operations Develop graphical interface for output from equation Evaluate output from AWIPS forecast application

32. Acknowledgements Jason Krekeler – NOAA/NWS State College, PA/State University of NY at Albany Hannah Attard – State University of NY at Albany

33. 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.

34. 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