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What idiot is wasting our storm-chasing time talking about a winter storm?

What idiot is wasting our storm-chasing time talking about a winter storm?. The New Year’s Day Storm in Central Minnesota. Robert A. Weisman, Saint Cloud State University raweisman@stcloudstate.edu http://web.stcloudstate.edu/raweisman/ Amanda E. Brandt, NWS Forecast Office, Duluth, MN

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What idiot is wasting our storm-chasing time talking about a winter storm?

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  1. What idiot is wasting our storm-chasing time talking about a winter storm? The New Year’s Day Storm in Central Minnesota Robert A. Weisman, Saint Cloud State University raweisman@stcloudstate.edu http://web.stcloudstate.edu/raweisman/ Amanda E. Brandt, NWS Forecast Office, Duluth, MN Amanda.Brandt@noaa.gov

  2. Storm of 1 January 2005 • Yes, there has been winter somewhere! • 20-31.8 cm (8-12.5 in) of snow in northeastern Minnesota • Record 24 cm (9.5 in) snow at NWS Duluth • Hourly snowfall of 2.5 and 3.5 inches at KDLH in convective bands Snow Depth courtesy of MN State Climatology Office 1/1/05 Storm: 9th Northern Plains Convective Workshop

  3. Storm of 1 January 2005 • Thundersleet in Saint Cloud at 20-22Z • 30 cloud-to-ground lightning strikes • Thundersleet is frequent in cold sector (e.g., Gedzelman 1987) • Not “The Day BeforeThe Day After Tomorrow” • Sleet is significant because: • Icing conditions • It hurts! Radar courtesy of UCAR Archive 1/1/05 Storm: 9th Northern Plains Convective Workshop

  4. Surface Set-up Rather Benign 1/1/05 Storm: 9th Northern Plains Convective Workshop

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  18. Role of Inverted Trough • Inverted trough ahead case (Schumacher, Selzler, Frosig, et al., some century will get published?) • Inverted trough at surface and in the lower troposphere is vertical • IT is “limiting streamline” of warm-air advection • Warm-air advection and lift downstream of IT position • Cold-air advection and sinking upstream of IT position • When the IT goes by, the precipitation ends 1/1/05 Storm: 9th Northern Plains Convective Workshop

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  29. Conclusions • Large-scale • Frontogenesis and warm-air advection to east of IT provided lift • Strong upper-level divergence added by right entrance region to anticyclonically curved jet streak • Convection • Formed just to east of IT near Sioux Falls in warm-air advection area • Warm-air advection at 850 hPa accompanied by high Tds of 6-8oC • Parcels lifted from both warm sector or 850 hPa above surface cold air were unstable until the upper troposphere 1/1/05 Storm: 9th Northern Plains Convective Workshop

  30. More Conclusions • Microphysics • Warm layer at 700-850 hPa, reinforced by convection, kept precipitation as sleet or rain in central and southern Minnesota despite potential for evaporational cooling, cooling by lift • This layer was cold enough only in northeastern Minnesota, allowing heavy snowfall rates 1/1/05 Storm: 9th Northern Plains Convective Workshop

  31. References • Moore, J. T., and G. E. VanKnowe, (Nov.) 1992: The effect of jet streak curvature on kinematic fields. Monthly Weather Review, 120, 2429-2441. • Plymouth State Weather Center • http://vortex.plymouth.edu/u-make.html • Inverted trough references: • Webcast by Phil Schumacher: http://www.meted.ucar.edu/norlat/invtroughs/ • Article • Weisman, R. A., K. G. MacGregor, D. R. Novak, J. L. Selzler, M. L. Spinar, B. C. Thomas, and P. N. Schumacher, (Dec.) 2002: Precipitation regimes during cold-season Central U.S. inverted trough cases. Part I: synoptic climatology and composite study. Weather and Forecasting, 17, 1173-1193. • Co-authors on IT work: G. R. Frosig, J. L. Selzler, K. G. MacGregor, D. R. Novak, M. L. Spinar, B. C. Thomas 1/1/05 Storm: 9th Northern Plains Convective Workshop

  32. Acknowledgments • More on the Storm: • Amanda Brandt’s Winter Storm Summary at http://www.crh.noaa.gov/dlh/snowstorm_Jan1_2005.shtml • This talk will be posted in html at http://web.stcloudstate.edu/raweisman/courses/synguide/tsleet010105.html 1/1/05 Storm: 9th Northern Plains Convective Workshop

  33. Acknowledgments Brad Nelson and Peggy Willenberg for their flaming emails and interest both during and after the storm that inspired further investigation. 1/1/05 Storm: 9th Northern Plains Convective Workshop

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