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The Inland Extent of Lake-Effect Snow (LES) Bands

The Inland Extent of Lake-Effect Snow (LES) Bands . Joe Villani NOAA/NWS Albany, NY Michael L. Jurewicz, Sr. NOAA/NWS Binghamton, NY Jason Krekeler State Univ. of NY, Albany, NY 18 th GLOMW, Toronto, Ontario March 22-24, 2010. Outline. Motivation Goals Methodology Results

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The Inland Extent of Lake-Effect Snow (LES) Bands

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  1. The Inland Extent of Lake-Effect Snow (LES) Bands Joe Villani NOAA/NWS Albany, NY Michael L. Jurewicz, Sr. NOAA/NWS Binghamton, NY Jason Krekeler State Univ. of NY, Albany, NY 18th GLOMW, Toronto, Ontario March 22-24, 2010

  2. Outline • Motivation • Goals • Methodology • Results • Case Studies • Ongoing / Future Work

  3. Motivation • Considerable research has been devoted to LES processes and forecast issues over the last 2-3 decades • However, among these, comparatively little attention has been given to inland extent

  4. Goals • To identify atmospheric parameters that commonly have the most influence on a LES band’s inland penetration • Use these results in the forecast process to improve: • The quality/detail of information given to the public (nowcasting) • The NWS Watch/Warning/Advisory program

  5. Satellite Depiction of an Intense Band all the way to Albany, NY Upstream moisture sources Well developed single band from Lake Ontario to the Hudson Valley

  6. Methodology/Data Sources • Examined 20 LES events across the Eastern Great Lakes (Erie/Ontario) during the 2007-2010 time frame • For each event, parameters were evaluated at 6-hour intervals (00, 06, 12, and 18 UTC), using the NAM12 and RUC models, as well as BUF/ALY soundings • Events averaged 24-30 hours in length • Wind regimes varied from a mean flow of 250-260 (WSW-ENE oriented bands) to 300-320 (NW-SE oriented bands)

  7. Methodology (Continued) • LES bands’ inland penetrations (miles) calculated from radar mosaics, and a distance measuring application • Data points • Locations both inside bands and on their peripheries were used (north, south, and just downstream of the band) • Data stratified based on location relative to band

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

  9. Parameters

  10. Strategy to Determine “Best” Parameters • Used statistical correlations to determine the most influential factors for inland extent • Overall, locations relative to bands made little difference in the correlations (within the bands vs. north or south) • A few notable exceptions

  11. Statistics • Best correlators to inland extent (all points together): • Multi-lake connection (0.75) • 850/700 mb Lake-air differentials (-0.65) • Mixed-layer speed shear (0.27) • Mixed-layer directional shear (-0.23)

  12. Results (Continued) • Also a few healthy correlators in locations outside of the bands: • Points south of the band: • Height of capping inversion (-0.4) • Mixed-layer speed shear (0.35) • Points north of the band: • Mixed-layer directional shear (-0.4) • Surface winds (0.3)

  13. Brief Case Study Examples • Both events featured 260-270 mean flow single bands • 8 January 2009 • Only small inland penetration • 16 January 2009 • Much greater inland extent

  14. 8 January – Radar + 1 km Shear Strong mixed-layer flow - 30 to 40 kt

  15. 8 January – BUF Sounding - Lake to 850 mb Delta T of 13C - Lake to 700 mb Delta T of 22C - Only conditionally unstable LR’s

  16. 16 January – Radar + 1 km Shear Weaker mixed-layer flow - 10-20 kt Strong mixed-layer flow – 30 to 40 kt

  17. 16 January – BUF Sounding - Lake to 850 mb Delta T of 26C - Lake to 700 mb Delta T of 37C - Much steeper LR’s

  18. Take-Home Points • Environments that promoted greater inland extent of LES bands seemed to feature these characteristics: • Strong, well aligned flow in the mixed layer (especially north of the band) • Only conditional terrestrial instability • Moderately to extremely unstable cases tended to produce disorganized/cellular structures, confined closer to the shoreline

  19. More Summary Points • South of the band: • Stable, sheared environments seemed favorable for inland extent • Cold low-level inflow into the band • Lower cap/EL • Multi-Lake connection (MLC) is another factor that strongly related to inland extent

  20. Ongoing / Future Work • Further develop an algorithm/equation that provides an estimate of inland extent, based on favorably correlated parameters • To be used in cases where LES band development seems likely • Has already been tested on some of our cases, with favorable results • Individual/composite plots for MLC patterns • MSLP/850/700 low tracks • Based on flow regimes

  21. Present/Future Work (Continued) • Perhaps better delineate significant thresholds for strongly correlated parameters • Single banded vs. Multi-banded cases

  22. The End Questions ??

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