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2’ By Morning: Synoptic & Frontogenetic Aspects of the 6-7 March 2011 Snowfall

INTRODUCTION | RESULTS | CONCLUSION. INTRODUCTION | SNOWFALL | SYNOPTIC | RADAR | MESOSCALE | DISCUSSION. 2’ By Morning: Synoptic & Frontogenetic Aspects of the 6-7 March 2011 Snowfall. P ETER C. B ANACOS WFO BURLINGTON, VT BTV Winter Weather Workshop – 10 December 2013.

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2’ By Morning: Synoptic & Frontogenetic Aspects of the 6-7 March 2011 Snowfall

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  1. INTRODUCTION | RESULTS | CONCLUSION INTRODUCTION | SNOWFALL | SYNOPTIC | RADAR | MESOSCALE | DISCUSSION 2’ By Morning: Synoptic & Frontogenetic Aspects of the 6-7 March 2011 Snowfall PETER C. BANACOS WFO BURLINGTON, VT BTV Winter Weather Workshop – 10 December 2013

  2. INTRODUCTION | SNOWFALL | SYNOPTIC | MESOSCALE | CONCLUSION INTRODUCTION | SNOWFALL | SYNOPTIC | RADAR | MESOSCALE | DISCUSSION 6-7 March 2011 - By the Numbers • 25.8": Storm total snowfall, the 3rd greatest on record at BTV. • (#1:33.1", 2-3 Jan 2010; #2:29.8", 25-28 Dec 1969) • 2.05": The liquid equivalent precipitation at BTV, following the changeover to frozen precipitation at 1529 UTC on 6 March through the end of the storm on 7 March. • 1: Greatest March snowfall on record at BTV. • 2: The storm pushed the 2010-11 season into 2nd place all-time for • snowfall at BTV. The season ended with 128.4" of snowfall, behind only • the 145.4" that fell in 1970-71). • 51: Temperature in oF at Worcester, MA while heavy snow was occurring in • Vermont (intense low-level temperature gradient).

  3. INTRODUCTION | RESULTS | CONCLUSION INTRODUCTION | SNOWFALL | SYNOPTIC | MESOSCALE | CONCLUSION INTRODUCTION | SNOWFALL | SYNOPTIC | RADAR | MESOSCALE | DISCUSSION 6-7 March 2011: Storm Total Snowfall (in.) CSTAR

  4. INTRODUCTION | RESULTS | CONCLUSION INTRODUCTION | SNOWFALL | SYNOPTIC | MESOSCALE | CONCLUSION INTRODUCTION | SNOWFALL | SYNOPTIC | RADAR | MESOSCALE | DISCUSSION 6-7 March 2011: Storm Total Snowfall (in.) ≥20” RAIN Inches of Depth (NOHRSC)

  5. INTRODUCTION | SNOWFALL | SYNOPTIC | RADAR | MESOSCALE | DISCUSSION C/100km NARR: 925mb heights, winds, temps, T-gradient (color filled). Loop from 06/09Z through 07/18Z.

  6. INTRODUCTION | RESULTS | CONCLUSION INTRODUCTION | SNOWFALL | SYNOPTIC | RADAR | MESOSCALE | DISCUSSION Cold Frontal PassageBurlington, VT (BTV) and Montpelier, VT (MPV) Meteograms = Time Frame of Heaviest Snowfall

  7. INTRODUCTION | SNOWFALL | SYNOPTIC | MESOSCALE | CONCLUSION INTRODUCTION | SNOWFALL |SYNOPTIC| RADAR | MESOSCALE | DISCUSSION The snow was preceded by Ice Jam Flooding Dishmill Brook, East Burke, VT There were several reports of ice jam flooding along the Passumpsic, Missisquoi, Winooski, and Ausable rivers with some Decision Support activities. Focus on hydro and weekend resulted in limited messaging concerning magnitude of snow event on Sunday night into Monday morning. It was unusual to have ice jam flooding followed by a major snowstorm!

  8. INTRODUCTION | SNOWFALL | SYNOPTIC | MESOSCALE | CONCLUSION INTRODUCTION | SNOWFALL |SYNOPTIC| RADAR | MESOSCALE | DISCUSSION Ausable Forks (ASFN6) Hydrograph Flash Flood Warning 3/6/11 (2300-0340 UTC) The most serious flooding occurred in the village of Ausable Forks, NY where a jam produced flash flooding and forced evacuations in the village.

  9. INTRODUCTION | RESULTS | CONCLUSION INTRODUCTION | SNOWFALL | SYNOPTIC | RADAR | MESOSCALE | DISCUSSION

  10. INTRODUCTION | RESULTS | CONCLUSION INTRODUCTION | SNOWFALL | SYNOPTIC | RADAR | MESOSCALE | DISCUSSION CPV Convergence

  11. INTRODUCTION | RESULTS | CONCLUSION INTRODUCTION | SNOWFALL | SYNOPTIC | RADAR | MESOSCALE | DISCUSSION Synoptic Composite 300mb Potential Vorticity, Isotachs, Divergence925mb Heights and Temperature RIGHT ENTRANCE REGION

  12. INTRODUCTION | RESULTS | CONCLUSION INTRODUCTION | SNOWFALL | SYNOPTIC | RADAR | MESOSCALE | DISCUSSION Synoptic Composite Synoptic Composite Loop 06/09Z through 07/18Z 300mb Potential Vorticity, Isotachs, Divergence925mb Heights and Temperature

  13. INTRODUCTION | RESULTS | CONCLUSION INTRODUCTION | SNOWFALL | SYNOPTIC | RADAR | MESOSCALE | DISCUSSION 850-700mb Temperature Advection Loop 06/09Z through 07/18Z

  14. INTRODUCTION | RESULTS | CONCLUSION INTRODUCTION | SNOWFALL | SYNOPTIC | RADAR | MESOSCALE | DISCUSSION 850mb Moisture Transport & Theta-e Precipitable Water

  15. INTRODUCTION | RESULTS | CONCLUSION INTRODUCTION | SNOWFALL | SYNOPTIC | RADAR | MESOSCALE | DISCUSSION Mosaic Composite Reflectivity 00-16 UTC 7 March 2011

  16. INTRODUCTION | RESULTS | CONCLUSION INTRODUCTION | SNOWFALL | SYNOPTIC | RADAR | MESOSCALE | DISCUSSION 850-700mb Layer Deformation & Streamlines 850-700mb Layer Petterssen Frontogenesis & Streamlines RUC-40km Loop from 07/03 UTC through 07/21 UTC.

  17. INTRODUCTION | RESULTS | CONCLUSION INTRODUCTION | SNOWFALL | SYNOPTIC | RADAR | MESOSCALE | DISCUSSION Frontogenesis (Definition) (S. Petterssen 1936) • The 2-D scalar frontogenesis function (F ) – quantifies the change in horizontal (potential) temperature gradient following an air parcel: • Conceptually, the local change in horizontal temperature gradient near an existing front, baroclinic zone, or feature as it moves. F > 0 , frontogenesis F < 0, frontolysis

  18. INTRODUCTION | RESULTS | CONCLUSION INTRODUCTION | SNOWFALL | SYNOPTIC | RADAR | MESOSCALE | DISCUSSION Frontogenesis • The frontogenetic forcing has major implications on vertical motion and precipitation rates, as occurred on 6-7 March 2011. • Important to understand the kinematics and dynamics associated with frontogenesis.

  19. INTRODUCTION | RESULTS | CONCLUSION INTRODUCTION | SNOWFALL | SYNOPTIC | RADAR | MESOSCALE | DISCUSSION Horizontal Deformation With deformation, the orientation matters with respect to isotherms matters, but usually frontogenetic near/north of cyclones. F > 0 COL = calm winds Deformation usually gets the frontogenetic process started, which makes it a useful diagnostic.

  20. INTRODUCTION | RESULTS | CONCLUSION INTRODUCTION | SNOWFALL | SYNOPTIC | RADAR | MESOSCALE | DISCUSSION Horizontal Divergence Divergence Convergence F < 0 F > 0 Convergence generally increases as frontogenetic circulation gets organized.

  21. INTRODUCTION | RESULTS | CONCLUSION INTRODUCTION | SNOWFALL | SYNOPTIC | RADAR | MESOSCALE | DISCUSSION Vorticity F > 0 F = 0 Not that important in this context – can rotate the isotherms but not push them together or pull them apart.

  22. INTRODUCTION | SNOWFALL | SYNOPTIC | RADAR | MESOSCALE | DISCUSSION Dynamics of Frontogenesis (vertical circulation)

  23. INTRODUCTION | SNOWFALL | SYNOPTIC | RADAR | MESOSCALE | DISCUSSION Dynamics of Frontogenesis (cont.) Ageostrophic circulation develops as a response to increasing temperature gradient.

  24. INTRODUCTION | SNOWFALL | SYNOPTIC | RADAR | MESOSCALE | DISCUSSION Final Stage • When we talk about frontogenesis forcing, it’s the resulting ageostrophic circulation we are most interested in for precipitation forecasting.

  25. INTRODUCTION | RESULTS | CONCLUSION INTRODUCTION | SNOWFALL | SYNOPTIC | MESOSCALE | CONCLUSION INTRODUCTION | SNOWFALL | SYNOPTIC | RADAR | MESOSCALE | DISCUSSION Some Thoughts on This Case: • Not typical: Warm temps (upper 40s) and ice jam flooding with DSS activities preceded the our #3 snowstorm at BTV. Proved difficult to shift our/media focus to impeding historic snowfall from the ice jam flooding. • Strong frontal-scale forcing: 850-700mb deformation & frontogenesis, helpful to determine heaviest snowfall and mesoscale banded elements. Combined with rich moisture: 2-3”/hr snowfall rates. Examine these diagnostics when strong baroclinitiy is present. • Sunday Night: Mesoscale details weren’t known on Friday. Over a weekend, probably need to contact EMs/State Police via phoneto ensure comprehensive message is communicated. Never hurts to make a few extra calls for a major event. Didn’t have extra staffing in place (except for 2 hours on the midnight shift 3/7). Need to multitask a bit more and/or extra staffing to communicate key points.

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