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

The New Year’s Day Storm The New Year’s Day Storm in Central Minnesotain Central Minnesota

Robert A. Weisman, Saint Cloud State Universityraweisman@stcloudstate.eduhttp://web.stcloudstate.edu/raweisman/Amanda E. Brandt, NWS Forecast Office, Duluth, MNAmanda.Brandt@noaa.gov

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Storm of 1 January 2005Storm of 1 January 2005

• Yes, there has been Yes, there has been winter somewhere!winter somewhere!

• 20-31.8 cm (8-12.5 in) 20-31.8 cm (8-12.5 in) of snow in of snow in northeastern northeastern MinnesotaMinnesota

• Record 24 cm (9.5 in) Record 24 cm (9.5 in) snow at NWS Duluth snow at NWS Duluth – Hourly snowfall of 2.5 Hourly snowfall of 2.5

and 3.5 inches at KDLH and 3.5 inches at KDLH in convective bandsin convective bands

Snow Depth courtesy ofMN State Climatology Office

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Storm of 1 January 2005Storm of 1 January 2005

• Thundersleet in Saint Thundersleet in Saint Cloud at 20-22ZCloud at 20-22Z– 30 cloud-to-ground 30 cloud-to-ground

lightning strikeslightning strikes• Thundersleet is Thundersleet is

frequent in cold sector frequent in cold sector (e.g., Gedzelman 1987)(e.g., Gedzelman 1987)– Not Not “The Day Before“The Day Before The The

Day After Tomorrow”Day After Tomorrow”• Sleet is significant Sleet is significant

because:because:– Icing conditionsIcing conditions– It hurts!It hurts!

Radar courtesy ofUCAR Archive

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Surface Set-up Rather BenignSurface Set-up Rather Benign

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Role of Inverted TroughRole of Inverted Trough

• Inverted trough ahead case (Schumacher, Inverted trough ahead case (Schumacher, Selzler, Frosig, et al., some century will get Selzler, Frosig, et al., some century will get published?)published?)– Inverted trough at surface and in the lower Inverted trough at surface and in the lower

troposphere is verticaltroposphere is vertical• IT is “limiting streamline” of warm-air advectionIT is “limiting streamline” of warm-air advection

• Warm-air advection and lift downstream of IT positionWarm-air advection and lift downstream of IT position

• Cold-air advection and sinking upstream of IT positionCold-air advection and sinking upstream of IT position

– When the IT goes by, the precipitation endsWhen the IT goes by, the precipitation ends

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ConclusionsConclusions

• Large-scaleLarge-scale– Frontogenesis and warm-air advection to east of Frontogenesis and warm-air advection to east of

IT provided liftIT provided lift– Strong upper-level divergence added by right Strong upper-level divergence added by right

entrance region to anticyclonically curved jet entrance region to anticyclonically curved jet streakstreak

• ConvectionConvection– Formed just to east of IT near Sioux Falls in Formed just to east of IT near Sioux Falls in

warm-air advection areawarm-air advection area•Warm-air advection at 850 hPa accompanied Warm-air advection at 850 hPa accompanied

by high Tby high Tdds of 6-8s of 6-8ooCC•Parcels lifted from both warm sector or 850 Parcels lifted from both warm sector or 850

hPa above surface cold air were unstable until hPa above surface cold air were unstable until the upper tropospherethe upper troposphere

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More ConclusionsMore Conclusions

• MicrophysicsMicrophysics– Warm layer at 700-850 hPa, reinforced Warm layer at 700-850 hPa, reinforced

by convection, kept precipitation as by convection, kept precipitation as sleet or rain in central and southern sleet or rain in central and southern Minnesota despite potential for Minnesota despite potential for evaporational cooling, cooling by liftevaporational cooling, cooling by lift

– This layer was cold enough only in This layer was cold enough only in northeastern Minnesota, allowing heavy northeastern Minnesota, allowing heavy snowfall ratessnowfall rates

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ReferencesReferences

• Moore, J. T., and G. E. VanKnowe, (Nov.) 1992: The effect of Moore, J. T., and G. E. VanKnowe, (Nov.) 1992: The effect of jet streak curvature on kinematic fields. jet streak curvature on kinematic fields. Monthly Weather Monthly Weather ReviewReview, , 120120, 2429-2441., 2429-2441.

• Plymouth State Weather CenterPlymouth State Weather Center– http://vortex.plymouth.edu/u-make.htmlhttp://vortex.plymouth.edu/u-make.html

• Inverted trough references:Inverted trough references:– Webcast by Phil Schumacher: Webcast by Phil Schumacher:

http://www.meted.ucar.edu/norlat/invtroughs/ http://www.meted.ucar.edu/norlat/invtroughs/ – ArticleArticle

• Weisman, R. A., K. G. MacGregor, D. R. Novak, J. L. Selzler, M. L. Weisman, R. A., K. G. MacGregor, D. R. Novak, J. L. Selzler, M. L. Spinar, B. C. Thomas, and P. N. Schumacher, (Dec.) 2002: Spinar, B. C. Thomas, and P. N. Schumacher, (Dec.) 2002: Precipitation regimes during cold-season Central U.S. inverted Precipitation regimes during cold-season Central U.S. inverted trough cases. Part I: synoptic climatology and composite study. trough cases. Part I: synoptic climatology and composite study. Weather and ForecastingWeather and Forecasting, , 1717, 1173-1193., 1173-1193.

– Co-authors on IT work: G. R. Frosig, J. L. Selzler, K. G. Co-authors on IT work: G. R. Frosig, J. L. Selzler, K. G. MacGregor, D. R. Novak, M. L. Spinar, B. C. Thomas MacGregor, D. R. Novak, M. L. Spinar, B. C. Thomas

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AcknowledgmentsAcknowledgments

• More on the Storm: More on the Storm: – Amanda Brandt’s Winter Storm Amanda Brandt’s Winter Storm

Summary at Summary at http://www.crh.noaa.gov/dlh/snowstormhttp://www.crh.noaa.gov/dlh/snowstorm_Jan1_2005.shtml_Jan1_2005.shtml

– This talk will be posted in html at This talk will be posted in html at http://web.stcloudstate.edu/raweisman/chttp://web.stcloudstate.edu/raweisman/courses/synguide/tsleet010105.htmlourses/synguide/tsleet010105.html

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AcknowledgmentsAcknowledgments

Brad Nelson and Peggy Willenberg for Brad Nelson and Peggy Willenberg for their flaming emails and interest both their flaming emails and interest both during and after the storm that inspired during and after the storm that inspired further investigation.further investigation.