1 / 47

Shawn M. Milrad, Department of Geography University of Kansas Eyad H. Atallah and John R. Gyakum

No Visibility, No Warning: A Dynamic Analysis and Associated Impacts of Non-Lake Effect Snow Bursts. Shawn M. Milrad, Department of Geography University of Kansas Eyad H. Atallah and John R. Gyakum Department of Atmospheric and Oceanic Sciences McGill University Montreal, Quebec, Canada

eljah
Download Presentation

Shawn M. Milrad, Department of Geography University of Kansas Eyad H. Atallah and John R. Gyakum

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. No Visibility, No Warning: A Dynamic Analysis and Associated Impacts of Non-Lake Effect Snow Bursts Shawn M. Milrad, Department of Geography University of Kansas Eyad H. Atallah and John R. Gyakum Department of Atmospheric and Oceanic Sciences McGill University Montreal, Quebec, Canada Jennifer F. Smith Environment Canada Dartmouth, Nova Scotia, Canada

  2. Outline • Motivation • Background • Ottawa, Ontario: 28 January 2010 • Case overview • Synoptic-dynamic analysis • Forecasts and warnings • Future work

  3. Motivation Background Ottawa: Overview Dynamics Forecasts Future Work Motivation • The climatology, dynamics and impacts of lake effect snow squalls (bursts) throughout the U.S. have been well-documented • Great Lakes • Wiggins (1950); Niziol (1987); Niziol et al. (1995) • Great Salt Lake • Steenburgh et al. (2000); Steenburgh and Onton (2001) • Lake Champlain • Payer et al. (2007); Laird et al. .(2009) • Other studies have examined events dynamically related to snow bursts • Thundersnow events (synoptic-scale cyclones) • Market et al. (2002); Market et al. (2006); Crowe et al. (2006) • C0ld-season severe weather • Holle and Watson (1996); Schultz (1999); Hunter et al. (2001); Trapp et al. (2001); van den Broeke et al. (2005); Corfidi et al. (2006)

  4. Motivation Background Ottawa: Overview Dynamics Forecasts Future Work Motivation Source: UCAR/COMET

  5. Motivation Background Ottawa: Overview Dynamics Forecasts Future Work Motivation • However, few studies have focused on snow bursts that occur outside lake effect regions • Snow bursts outside of lake effect regions: • Often not associated with a synoptic-scale cyclone • “Cold-season convection” • Can produce rapid-onset whiteout conditions  hazardous to motorists and aviation • Often occur without warning (DeVoir 2004) • Not large enough snow accumulations to meet NWS warning or advisory criteria

  6. Motivation Background Ottawa: Overview Dynamics Forecasts Future Work Ottawa, Ontario: 28 January 2010 (Photos are courtesy of the Ottawa Citizen)

  7. Motivation Background Ottawa: Overview Dynamics Forecasts Future Work Previous Work • Lundstedt et al. (1993): NWS Eastern Region technical bulletin • Development of Wintertime Instability Index (WINDEX) • Low-level lapse rates (instability), boundary layer relative humidity (moisture), 12-hour change in lifted index (instability) • Ever implemented operationally? • Weakness: No criterion directly associated with lift

  8. Motivation Background Ottawa: Overview Dynamics Forecasts Future Work Previous Work • DeVoir (2004) and Nicosia et al. (2009) • Impacts in Pennsylvania • Little to no warning (below advisory/warning criteria) From Nicosia et al. (2009)

  9. Motivation Background Ottawa: Overview Dynamics Forecasts Future Work Previous Work From Nicosia et al. (2009)

  10. Motivation Background Ottawa: Overview Dynamics Forecasts Future Work Previous Work • Nicosia et al. (2009) • Impacts in Pennsylvania

  11. Motivation Background Ottawa: Overview Dynamics Forecasts Future Work Previous Work • Pettegrew et al. (2009): Eastern Iowa/North Central Illinois in 2003 • 4 cm (1.6 in) of snow • > 50 kt winds (exceeds “severe” warning criteria) • Near-whiteout conditions • Arctic front passage  Intense frontogenesis • Convective instability • Steep lapse rates (momentum mixing) • Convection rooted in the boundary layer

  12. Motivation Background Ottawa: Overview Dynamics Forecasts Future Work Previous Work From Pettegrew et al. (2009)

  13. Motivation Background Ottawa: Overview Dynamics Forecasts Future Work Ottawa, Ontario: 28 January 2010 • In association with the passage of an arctic cold front, two intense snow bursts (SB1 and SB2) moved through eastern Ontario and western Quebec • Snow accumulation at Ottawa (CYOW) : 3.6 cm (1.4 in.) BUT • VERY low visibility • Dozens of automobile accidents in the Ottawa region (Ottawa Citizen 2010) • At least one critical injury (13-year old boy) Ottawa, Ontario: 28 January 2010 (Photo courtesy of the Ottawa Citizen) Milrad, S. M., E. H. Atallah, J. R. Gyakum, and J.F. Smith, 2011: A diagnostic examination of the eastern Ontario and western Quebec wintertime convection event of 28 January 2010. Wea. Forecasting, in press.

  14. Motivation Background Ottawa: Overview Dynamics Forecasts Future Work Data • Radar Imagery • Environment Canada online historical radar database • Meteograms • Environment Canada and Iowa State University online climate data • For all analyses, t=0 h defined as hour first snow burst (SB1) moved through CYOW • 1800 UTC 28 January

  15. Motivation Background Ottawa: Overview Dynamics Forecasts Future Work Radar Imagery t=-3 h (1510 UTC) t=-2 h (1610 UTC) ***Ottawa International Airport (CYOW): black star*** ***Massena, NY (KMSS): purple star*** ***SB1 (blue arrow),SB2 (red arrow)***

  16. Motivation Background Ottawa: Overview Dynamics Forecasts Future Work Radar Imagery t=-1 h (1710 UTC) t=0 h (1810 UTC) ***Ottawa International Airport (CYOW): black star*** ***Massena, NY (KMSS): purple star***

  17. Motivation Background Ottawa: Overview Dynamics Forecasts Future Work Radar Imagery t=+1 h (1910 UTC) t=+2 h (2010 UTC) ***Ottawa International Airport (CYOW): black star*** ***Massena, NY (KMSS): purple star***

  18. Motivation Background Ottawa: Overview Dynamics Forecasts Future Work Case Overview: Meteograms Ottawa, ON (CYOW): 28 January 2010

  19. Motivation Background Ottawa: Overview Dynamics Forecasts Future Work Case Overview: Meteograms Massena, NY (KMSS): 28 January 2010

  20. Motivation Background Ottawa: OverviewDynamics Forecasts Future Work Dynamic Analysis: Strategy • Snow bursts are essentially a form of wintertime moist convection • Use “ingredients-based” methodology for moist convection • Doswell et al. (1996); Schultz and Schumacher (1999); Wetzel and Martin (2001) • Three main ingredients • Lift (synoptic-scale and mesoscale)** • Moisture • Instability** • Convective (CI): (dθe/dz) < 0 • Conditional Symmetric (CSI): MPV*g < 0

  21. Motivation Background Ottawa: OverviewDynamics Forecasts Future Work Data • National Centers for Environmental Prediction (NCEP) North American Regional Reanalysis (NARR) • 32 km horizontal resolution • 3-hourly • For all analyses, t=0 h defined as hour first snow burst (SB1) moved through CYOW • 1800 UTC 28 January

  22. Motivation Background Ottawa: OverviewDynamics Forecasts Future Work Lift: Synoptic-scale 850-500 hPa Q-vector divergence (shaded, cool colors convergent), SLP (hPa, solid), 1000-500 hPa thickness (dam, dashed) t=-18 h (0000 UTC) t=-12 h (0600 UTC)

  23. Motivation Background Ottawa: OverviewDynamics Forecasts Future Work Lift: Synoptic-scale 850-500 hPa Q-vector divergence (shaded, cool colors convergent), SLP (hPa, solid), 1000-500 hPa thickness (dam, dashed) t=-6 h (1200 UTC) t=-3 h (1500 UTC)

  24. Motivation Background Ottawa: OverviewDynamics Forecasts Future Work Lift: Synoptic-scale 850-500 hPa Q-vector divergence (shaded, cool colors convergent), SLP (hPa, solid), 1000-500 hPa thickness (dam, dashed) t=0 h (1800 UTC) t=+3 h (2100 UTC)

  25. Motivation Background Ottawa: OverviewDynamics Forecasts Future Work Lift: Synoptic-scale θ on the dynamic tropopause (2 PVU surface, K, shaded), 10 m winds (knots, barbs), and coupling index (θDT – θe850) (contoured every 4 K from 0 to +16) t=-18 h (0000 UTC) t=-12 h (0600 UTC)

  26. Motivation Background Ottawa: OverviewDynamics Forecasts Future Work Lift: Synoptic-scale θ on the dynamic tropopause (2 PVU surface, K, shaded), 10 m winds (knots, barbs), and coupling index (θDT – θe850) (contoured every 4 K from 0 to +16) t=-6 h (1200 UTC) t=-3 h (1500 UTC)

  27. Motivation Background Ottawa: OverviewDynamics Forecasts Future Work Lift: Synoptic-scale θ on the dynamic tropopause (2 PVU surface, K, shaded), 10 m winds (knots, barbs), and coupling index (θDT – θe850) (contoured every 4 K from 0 to +16) t=0 h (1800 UTC) t=+3 h (2100 UTC)

  28. Motivation Background Ottawa: OverviewDynamics Forecasts Future Work Lift: Mesoscale 925 hPa frontogenesis (K (100 km)-1 (3 h)-1), shaded), 925-700 hPa lapse rate (K km-1, blue solid contours starting at -8 with an interval of .5), 1000-500 hPa thickness (dam, dashed), and 10 m wind (knots, barbs). t=-18 h (0000 UTC) t=-12 h (0600 UTC)

  29. Motivation Background Ottawa: OverviewDynamics Forecasts Future Work Lift: Mesoscale 925 hPa frontogenesis (K (100 km)-1 (3 h)-1), shaded), 925-700 hPa lapse rate (K km-1, blue solid contours starting at -8 with an interval of .5), 1000-500 hPa thickness (dam, dashed), and 10 m wind (knots, barbs). t=-6 h (1200 UTC) t=-3 h (1500 UTC)

  30. Motivation Background Ottawa: OverviewDynamics Forecasts Future Work Lift: Mesoscale 925 hPa frontogenesis (K (100 km)-1 (3 h)-1), shaded), 925-700 hPa lapse rate (K km-1, blue solid contours starting at -8 with an interval of .5), 1000-500 hPa thickness (dam, dashed), and 10 m wind (knots, barbs). t=0 h (1800 UTC) t=+3 h (2100 UTC)

  31. Motivation Background Ottawa: OverviewDynamics Forecasts Future Work Instability: CI and CSI Saturated equivalent geostrophic potential vorticity (MPV*g, m2 s−1 K kg−1,shaded for negative values) and θe (K, solid contours). t=-18 h (0000 UTC) t=-12 h (0600 UTC)

  32. Motivation Background Ottawa: OverviewDynamics Forecasts Future Work Instability: CI and CSI Saturated equivalent geostrophic potential vorticity (MPV*g, m2 s−1 K kg−1,shaded for negative values) and θe (K, solid contours). t=-6 h (1200 UTC) t=-3 h (1500 UTC)

  33. Motivation Background Ottawa: OverviewDynamics Forecasts Future Work Instability: CI and CSI Saturated equivalent geostrophic potential vorticity (MPV*g, m2 s−1 K kg−1, shaded for negative values) and θe (K, solid contours). t=0 h (1800 UTC) t=+3 h (2100 UTC)

  34. Motivation Background Ottawa: OverviewDynamics Forecasts Future Work Instability: MAUL • Bryan and Fritsch (2000) argued that a sixth static stability state exists • Moist absolutely unstable (γs > Γs) • Occurrences of this sixth state are called Moist Absolutely Unstable Layers (MAULs) • Short-lived • Rare: 1.1% of 100,000 soundings in Bryan and Fritsch (2000) • Often shallow; deep MAULs are defined as at least 100 mb in depth with a dewpoint depression of <= 1˚C throughout • Occur in close proximity to moist convection • Indications of (and caused by) intense mesoscale vertical motion

  35. Motivation Background Ottawa: OverviewDynamics Forecasts Future Work Instability: MAUL NARR soundings for Ottawa (CYOW) t=-18 h (0000 UTC) t=-12 h (0600 UTC)

  36. Motivation Background Ottawa: OverviewDynamics Forecasts Future Work Instability: MAUL NARR soundings for Ottawa (CYOW) t=-6 h (1200 UTC) t=-3 h (1500 UTC)

  37. Motivation Background Ottawa: OverviewDynamics Forecasts Future Work Instability: MAUL NARR soundings for Ottawa (CYOW) t=0 h (1800 UTC) t=+3 h (2100 UTC)

  38. Motivation Background Ottawa: OverviewDynamics Forecasts Future Work Conclusions: Dynamics • Dynamics • Synoptic-scale forcing for ascent • Arctic front • Mesoscale ascent-focusing mechanism • Mesoscale forcing for ascent (frontogenesis) • Just enough moisture to create a problem • Thermodynamics • Very unstable, however you slice it • Very steep low-level lapse rates • Convective instability (CI) • Conditional Symmetric Instability (CSI) • Soundings: Deep (300-400 hPa) Moist Absolutely Unstable Layer (MAUL)

  39. Motivation Background Ottawa: Overview Dynamics Forecasts Future Work Forecasts: The problem • From limited research (a few case studies), the models appear to do a decent job in predicting these events • Probably as accurate as warm-season squall line forecasts • The real problem is that despite the high impact of snow burst events, they often do NOT meet warning or advisory criteria • Snow accumulations too low • Winds not high enough for severe criteria • Not the season for “convection” • Not in lake effect regions

  40. Motivation Background Ottawa: Overview Dynamics Forecasts Future Work Forecasts: The problem • NWS winter weather advisory: “A Winter Weather Advisory will be issued when 2 to 4 inches of snow, alone or in combination with sleet and freezing rain, is expected to cause a significant inconvenience, but not serious enough to warrant a warning.” • NWS Blizzard Warning: “A Blizzard Warning means that the following conditions are occurring or expected within the next 12 to 18 hours.1) Snow and/or blowing snow reducing visibility to 1/4 mile or less for 3 hours or longer AND 2)  Sustained winds of 35 mph or greater or frequent gusts to 35 mph or greater.” • Environment Canada Snowsquall Warning: “When, to the lee of the Great Lakes or other large lakes, snow squalls are expected and 15 cm or more of snow is likely to fall within 12 hours, OR the visibility is likely to be near zero for four or more hours, even without warning level accumulations of snow.”

  41. Motivation Background Ottawa: Overview Dynamics Forecasts Future Work Forecasts: The problem

  42. Motivation Background Ottawa: Overview Dynamics Forecasts Future Work Forecasts: Ottawa Case • The Environment Canada Ontario Storm Prediction Center • Accurately called for 2-4 cm of snow throughout much of eastern Ontario on the day of the snow bursts • However, the forecast implied gradual “flurries over the course of the day.” • A special weather statement was issued for CYOW twenty minutes before the first snow burst hit the city • “Narrow but intense bands of snow are moving through southeastern Ontario…Because of the short duration, snowfall accumulations are not expected to be significant, however visibilities may be reduced to a few hundred metres or less at times” • But did anyone actually see the special weather statement? • http://www.weatheroffice.gc.ca/canada_e.html

  43. Motivation Background Ottawa: Overview Dynamics Forecasts Future Work Forecasts: Ottawa Case • Shortly after both squalls were evident on radar and moving through eastern Ontario, the Quebec Storm Prediction Centre (QSPC) issued a ‘snowsquall warning’ for western Quebec. • Forecaster judgment supersedes warning criteria? t=+2 h (2010 UTC) t=+1 h (1910 UTC)

  44. Motivation Background Ottawa: Overview Dynamics Forecasts Future Work Forecasts: Potential Solutions • DeVoir (2004) pointed out that for the United States, no warning or advisory exists that is specific to a high-impact, but short-duration and low-precipitation event such as the Ottawa snow bursts • But what do you do? • New warning/advisory • Issue a “winter weather advisory” etc. even if criteria is not met • Change current advisory/warning criteria • Special weather statements: Are these well enough disseminated? • How do you get the message out? • NWS State College: PENNDOT cooperation (Nicosia et al. 2009) • Contact emergency managers? • Radio/Weather radio? • Text messages?

  45. Motivation Background Ottawa: Overview Dynamics Forecasts Future Work Future Work • Important questions: • What is the frequency of occurrence of snow burst events? • Are they more prevalent in certain regions? • What are the favorable large-scale meteorological conditions? • What are the favored instability regimes? • Predictability • Objectives: • Assemble an event climatology at representative stations in the northern U.S. and southern Canada • Dynamic analysis and synoptic typing • Index and forecast decision tree development

  46. Motivation Background Ottawa: Overview Dynamics Forecasts Future Work Future Work • Objectives: • Assemble an event climatology at representative stations in the northern U.S. and southern Canada • Surface observations • Radar data • Dynamic analysis and synoptic typing • Group similar events using different sets of dynamic parameters or thresholds • Composite analysis of groups • Case studies • Index and forecast decision tree development • Update to/revamping of WINDEX • Lake-effect snow decision tree (Niziol et al. 1987) • Disseminate to operational community

  47. Motivation Background Ottawa: Overview Dynamics Forecasts Future Work

More Related