1. A Multiscale Analysis of Major Transition Season Northeast Snowstorms Rebecca Steeves, Andrea L. Lang, and Daniel Keyser Department of Atmospheric and Environmental Sciences University at Albany Northeast Regional Operational Workshop XVI 4 November 2015 Supported by the NOAA Collaboration Science, Technology, and Applied Research Program (NA13NWS4680004)

2. Investigate major transition season snowstorms in the northeast U.S. that result in widespread socioeconomic disruption and that are difficult to forecast Overview

3. Motivation Major transition season snowstorms have the potential to produce widespread socioeconomic disruption Infrastructure damage Transportation delays Power outages Heavy wet snow occurring in major transition season events can be especially damaging when trees are in full leaf Damage in Belmont, MA, from the 28–30 October 2011 snowstorm. Source: Washington Post

4. Objectives Project research focuses on documenting: Synoptic-to-mesoscale atmospheric conditions occurring prior to and during major transition season Northeast snowstorms, with emphasis on the formation and maintenance of regions of lower- tropospheric cold air that coincide with areas of heavy snowfall

5. Objectives Project research focuses on documenting: Synoptic-scale atmospheric conditions occurring prior to and during major transition season Northeast snowstorms, with emphasis on the role of tropical moisture transport occurring within atmospheric rivers (ARs) in the formation and evolution of this class of snowstorms

6. Motivation Understand the ingredients of major transition season Northeast snowstorms from a Lagrangian perspective What is the source region of the cold air at the surface? What is the source region of moist parcels in areas of heavy snowfall?

7. Datasets General: Quantum Geographic Information System (QGIS) NWS GIS - AWIPS Shapefile Database Event compilation: NY State Department of Environmental Conservation NOAA/NCDC Storm Data (SD) Monthly Publications PA Tourism Office

8. Datasets Snowfall accumulation maps: Global Multi-resolution Terrain Elevation Data 2010 NCDC GHCN Daily Summaries Case studies: NEXRAD Iowa Environmental Mesonet ASOS NCEP CFSR global reanalysis (Saha et al. 2010) 6-h time interval 0.5° grid spacing 1979–present

9. Methodology Defined and compiled list of major transition season Northeast snowstorms Categorized distinctive types of lower-tropospheric cold air that coincide with areas of heavy snowfall Selected a fall event and a spring event that illustrate the following types: A cold pool type for the 28–30 October 2011 event A baroclinic zone type for the 8–9 March 2005 event

10. Methodology Calculated 72-h kinematic backward trajectories using CFSR Diagnosed evolution of selected thermodynamic quantities Identified source regions of moist parcels Applied the objective AR identification algorithm of Lavers and Villarini (2015)

11. Objective Definition To be objectively defined as a major transition season Northeast snowstorm, an event in SD must have at least three separate county warning areas (CWA) report: “Heavy Snow” (HS) “Winter Storm”(WS) “Blizzard” (B) A combination of any of the three WS and B must meet 12-h snow warning criterion for the reporting CWA Northeast domain outlined in dark black with thin black CWA borders

12. 28–30 October 2011 Event 1000–850-hPa thickness (shaded, dam) and MSLP (contoured, hPa) Approximately 3 million power outages Significant travel disruptions Emergencies declared in multiple states Indirect fatalities 0000 UTC 30 October 2011 Snowfall accumulation (shaded, in.) map displayed over terrain for the 28–30 October 2011 event produced from NCDC GHCN Daily Summaries

13. 0000 UTC 28 October 2011 250-hPa wind speed (shaded, m s − 1 ) and 500- hPa geopotential height (contoured, dam) at 0000 UTC 28 October 2011 Precipitable water (shaded, mm) and MSLP (contoured, hPa) at 0000 UTC 28 October 2011

14. 1200 UTC 28 October 2011 250-hPa wind speed (shaded, m s − 1 ) and 500- hPa geopotential height (contoured, dam) at 1200 UTC 28 October 2011 Precipitable water (shaded, mm) and MSLP (contoured, hPa) at 1200 UTC 28 October 2011

15. 0000 UTC 29 October 2011 250-hPa wind speed (shaded, m s − 1 ) and 500- hPa geopotential height (contoured, dam) at 0000 UTC 29 October 2011 Precipitable water (shaded, mm) and MSLP (contoured, hPa) at 0000 UTC 29 October 2011

16. 1200 UTC 29 October 2011 250-hPa wind speed (shaded, m s − 1 ) and 500- hPa geopotential height (contoured, dam) at 1200 UTC 29 October 2011 Precipitable water (shaded, mm) and MSLP (contoured, hPa) at 1200 UTC 29 October 2011

17. 0000 UTC 30 October 2011 250-hPa wind speed (shaded, m s − 1 ) and 500- hPa geopotential height (contoured, dam) at 0000 UTC 30 October 2011 Precipitable water (shaded, mm) and MSLP (contoured, hPa) at 0000 UTC 30 October 2011

18. 1200 UTC 30 October 2011 250-hPa wind speed (shaded, m s − 1 ) and 500- hPa geopotential height (contoured, dam) at 1200 UTC 30 October 2011 Precipitable water (shaded, mm) and MSLP (contoured, hPa) at 1200 UTC 30 October 2011

19. 1000–850-hPa thickness (shaded, dam) and MSLP (contoured, hPa) at 0000 UTC 30 October 2011 Snowfall accumulation (shaded, in.) map displayed over terrain for the 28–30 October 2011 event produced from NCDC GHCN Daily Summaries 1000–850-hPa thickness values support snowfall 0000 UTC 30 October 2011 Cold pool coincident with snowfall accumulation ≥ 20 in.

20. 1000–850-hPa thickness (shaded, dam) and MSLP (contoured, hPa) at 0000 UTC 30 October 2011 0000 UTC 30 October 2011 A A’ A Snowfall accumulation (shaded, in.) map displayed over terrain for the 28–30 October 2011 event produced from NCDC GHCN Daily Summaries Cold pool coincident with snowfall accumulation ≥ 20 in. 1000–850-hPa thickness values support snowfall

21. 0000 UTC 30 October 2011 A A’ A 1000–850-hPa thickness (shaded, dam) and MSLP (contoured, hPa) at 0000 UTC 30 October 2011 (above) Cross section along 43°N of θ (shaded, K) and temperature (contoured, °C) at 0000 UTC 30 October 2011 (right) e

22. 1000–850-hPa thickness (shaded, dam) and MSLP (contoured, hPa) at 0000 UTC 30 October 2011 (above) Cross section along 43°N of θ (shaded, K) and temperature (contoured, °C) at 0000 UTC 30 October 2011 (right) e 0000 UTC 30 October 2011 A A’

23. 1000–850-hPa thickness (shaded, dam) and MSLP (contoured, hPa) at 0000 UTC 30 October 2011 (above) Cross section along 43°N of θ (shaded, K) and temperature (contoured, °C) at 0000 UTC 30 October 2011 (right) e 0000 UTC 30 October 2011 Level selection based on Fuhrmann and Konrad (2013) A A’ 975-hPa

24. 850-hPa 1000–850-hPa thickness (shaded, dam) and MSLP (contoured, hPa) at 0000 UTC 30 October 2011 (above) Cross section along 43°N of θ (shaded, K) and temperature (contoured, °C) at 0000 UTC 30 October 2011 (right) e 0000 UTC 30 October 2011 Level selection based on Fuhrmann and Konrad (2013) A A’ 975-hPa

25. 500-hPa–600-hPa DGZ 850-hPa 1000–850-hPa thickness (shaded, dam) and MSLP (contoured, hPa) at 0000 UTC 30 October 2011 (above) Cross section along 43°N of θ (shaded, K) and temperature (contoured, °C) at 0000 UTC 30 October 2011 (right) e 0000 UTC 30 October 2011 Level selection based on Fuhrmann and Konrad (2013) A A’ 975-hPa

26. 72-h Backward Trajectories (975 hPa) 72-h backward trajectories for 975 hPa (blue) ending at 0000 UTC 30 October 2011 with representative trajectories bolded (above) and corresponding time series (right) for the representative trajectories

27. 72-h Backward Trajectories (850 hPa) 72-h backward trajectories for 975 hPa (blue) and 850 hPa (green) ending at 0000 UTC 30 October 2011 with representative trajectories bolded (above) and corresponding time series (right) for the representative trajectories

28. 72-h Backward Trajectories (DGZ) 72-h backward trajectories for 975 hPa (blue), 850 hPa (green), and DGZ (red) ending at 0000 UTC 30 October 2011 with representative trajectories bolded (above) and corresponding time series (right) for the representative trajectories

29. AR objectively identified at 1200 UTC 30 October 2011 Precipitation is only occurring over coastal Maine at this time Vertically integrated water vapor transport (IVT; shaded, kg m − 1 s − 1 ), IVT vectors, MSLP (contoured, hPa), and AR axis (blue line) at 1200 UTC 30 October 2011 Atmospheric River: 1200 UTC 30 Oct 2011

30. DGZ trajectories and AR trajectories originate in different locations DGZ trajectories originate over the southeastern U.S. and western North Atlantic, and AR trajectories originate in the subtropics IVT magnitude (shaded, kg m − 1 s − 1 ), MSLP (contoured, hPa), AR axis (black line), and 72-h backward trajectories (red) at 1200 UTC 30 October 2011 Atmospheric River: 1200 UTC 30 Oct 2011

31. The configuration of the trajectories ending over Concord, NH, and the occurrence of heavy snowfall suggest cold pool formation and maintenance through diabatic cooling The objective AR identification algorithm and trajectory analysis reveal that an AR did not contribute to the heavy snowfall in Concord, NH An AR was objectively identified at 1200 UTC 30 October 2011 DGZ trajectories and AR trajectories originate in different locations 28–30 October 2011 Event Summary

32. 8–9 March 2005 Event 1000–850-hPa thickness (shaded, dam) and MSLP (contoured, hPa) at 0000 UTC 9 March 2005 0000 UTC 9 March 2005 Snowfall accumulation (shaded, in.) map displayed over terrain for the 8–9 March 2005 event produced from NCDC GHCN Daily Summaries Flash freeze due to ~11°C temperature change in 3 h occurred in CT Nearly 70,000 power outages Many forms of travel disruption

33. 250-hPa wind speed (shaded, m s − 1 ) and 500- hPa geopotential height (contoured, dam) at 0000 UTC 7 March 2005 Precipitable water (shaded, mm) and MSLP (contoured, hPa) at 0000 UTC 7 March 2005 0000 UTC 7 March 2005

34. 1200 UTC 7 March 2005 250-hPa wind speed (shaded, m s − 1 ) and 500- hPa geopotential height (contoured, dam) at 1200 UTC 7 March 2005 Precipitable water (shaded, mm) and MSLP (contoured, hPa) at 1200 UTC 7 March 2005

35. 0000 UTC 8 March 2005 250-hPa wind speed (shaded, m s − 1 ) and 500- hPa geopotential height (contoured, dam) at 0000 UTC 8 March 2005 Precipitable water (shaded, mm) and MSLP (contoured, hPa) at 0000 UTC 8 March 2005

36. 1200 UTC 8 March 2005 250-hPa wind speed (shaded, m s − 1 ) and 500- hPa geopotential height (contoured, dam) at 1200 UTC 8 March 2005 Precipitable water (shaded, mm) and MSLP (contoured, hPa) at 1200 UTC 8 March 2005

37. 0000 UTC 9 March 2005 250-hPa wind speed (shaded, m s − 1 ) and 500- hPa geopotential height (contoured, dam) at 0000 UTC 9 March 2005 Precipitable water (shaded, mm) and MSLP (contoured, hPa) at 0000 UTC 9 March 2005

38. 1200 UTC 9 March 2005 250-hPa wind speed (shaded, m s − 1 ) and 500- hPa geopotential height (contoured, dam) at 1200 UTC 9 March 2005 Precipitable water (shaded, mm) and MSLP (contoured, hPa) at 1200 UTC 9 March 2005

39. 0000 UTC 9 March 2005 Heavy snowfall resulted from a combination of an Arctic frontal passage and secondary coastal cyclogenesis Snowfall (shaded, in.) accumulation map displayed over terrain for the 8–9 March 2005 event produced from NCDC GHCN Daily Summaries 1000–850-hPa thickness (shaded, dam) and MSLP (contoured, hPa) at 0000 UTC 9 March 2005

40. BB’ 0000 UTC 9 March 2005 B B’ Snowfall (shaded, in.) accumulation map displayed over terrain for the 8–9 March 2005 event produced from NCDC GHCN Daily Summaries Heavy snowfall resulted from a combination of an Arctic frontal passage and secondary coastal cyclogenesis 1000–850-hPa thickness (shaded, dam) and MSLP (contoured, hPa) at 0000 UTC 9 March 2005

41. 1000–850-hPa thickness (shaded, dam) and MSLP (contoured, hPa) at 0000 UTC 9 March 2005 (above) Cross section along 42.5°N of θ (shaded, K) and temperature (contoured, °C) at 0000 UTC 9 March 2005 (right) e B B’ 0000 UTC 9 March 2005 BB’

42. 950-hPa 850-hPa 1000–850-hPa thickness (shaded, dam) and MSLP (contoured, hPa) at 0000 UTC 9 March 2005 (above) Cross section along 42.5°N of θ (shaded, K) and temperature (contoured, °C) at 0000 UTC 9 March 2005 (right) e Level selection based on Fuhrmann and Konrad (2013) 500-hPa–600-hPa DGZ B B’ 0000 UTC 9 March 2005

43. 72-h Backward Trajectories (950 hPa) 72-h backward trajectories for 950 hPa (blue) ending at 0000 UTC 9 March 2005 with representative trajectories bolded (above) and corresponding time series (right) for the representative trajectories

44. 72-h Backward Trajectories (850 hPa) 72-h backward trajectories for 950 hPa (blue) and 850 hPa (green) ending at 0000 UTC 9 March 2005 with representative trajectories bolded (above) and corresponding time series (right) for the representative trajectories

45. 72-h Backward Trajectories (DGZ) 72-h backward trajectories for 950 hPa (blue), 850 hPa (green), and DGZ (red) ending at 0000 UTC 9 March 2005 with representative trajectories bolded (above) and corresponding time series (right) for the representative trajectories

46. IVT magnitude (shaded, kg m − 1 s − 1 ), MSLP (contoured, hPa), AR axis (black line), and 72-h backward trajectories for the DGZ (red) at 0600 UTC 8 March 2005 Atmospheric River: 0600 UTC 8 March 2005 AR objectively identified for entire duration of the event DGZ trajectories travel in close proximity to AR axis beginning at 0600 UTC 8 March 2005

47. IVT magnitude (shaded, kg m − 1 s − 1 ), MSLP (contoured, hPa), AR axis (black line), and 72-h backward trajectories for the DGZ (red) at 1200 UTC 8 March 2005 Atmospheric River: 1200 UTC 8 March 2005 AR objectively identified for entire duration of the event DGZ trajectories travel in close proximity to AR axis beginning at 0600 UTC 8 March 2005

48. IVT magnitude (shaded, kg m − 1 s − 1 ), MSLP (contoured, hPa), AR axis (black line), and 72-h backward trajectories for the DGZ (red) at 1800 UTC 8 March 2005 Atmospheric River: 1800 UTC 8 March 2005 AR objectively identified for entire duration of the event DGZ trajectories travel in close proximity to AR axis beginning at 0600 UTC 8 March 2005

49. IVT magnitude (shaded, kg m − 1 s − 1 ), MSLP (contoured, hPa), AR axis (black line), and 72-h backward trajectories for the DGZ (red) at 0000 UTC 9 March 2005 Atmospheric River: 0000 UTC 9 March 2005 AR objectively identified for entire duration of the event DGZ trajectories travel in close proximity to AR axis beginning at 0600 UTC 8 March 2005

50. Atmospheric River: 0000 UTC 9 March 2005 IVT magnitude (shaded, kg m − 1 s − 1 ), MSLP (contoured, hPa), AR axis (black line), and 72-h backward trajectories for the DGZ (red) and AR axis (pink) at 0000 UTC 9 March 2005 DGZ trajectories and AR trajectories originate in the subtropics

51. Source of cold air was an Arctic frontal passage The objective AR identification algorithm and the trajectory analysis suggest that an AR was an important ingredient for the event An AR was objectively identified for the duration of the event DGZ trajectory parcels travel in close proximity to the AR axis AR trajectories and DGZ trajectories originate in the subtropics 8–9 March 2005 Event Summary

52. Conclusions Source of cold air differed for each event 28–30 October 2011: cold pool is suggested to have formed in-situ from diabatic cooling 8–9 March 2005: advection of cold air following an Arctic frontal passage ARs have differing roles in each event Not an ingredient for the 28–30 October 2011 event Important ingredient for the 8–9 March 2005 event Special thanks to Alicia Bentley and Benjamin Moore

53. Atmospheric River Objective Identification Methodology adopted from Lavers and Villarini (2015) Finds maximum IVT at each latitude that exceeds a climatological threshold Determines if 13 continuous latitudinal points crossing 40 ° N exceed the IVT threshold Longitudinal differences between points can be no greater than 4 °

54. Atmospheric River Objective Identification Methodology adopted from Lavers and Villarini (2015) Finds maximum IVT at each latitude that exceeds a climatological threshold Determines if 13 continuous latitudinal points crossing 40 ° N exceed the IVT threshold Longitudinal differences between points can be no greater than 4 °

55. Atmospheric River Objective Identification Methodology adopted from Lavers and Villarini (2015) Finds maximum IVT at each latitude that exceeds a climatological threshold Determines if 13 continuous latitudinal points crossing 40 ° N exceed the IVT threshold Longitudinal differences between points can be no greater than 4 °

56. Atmospheric River Objective Identification Methodology adopted from Lavers and Villarini (2015) Finds maximum IVT at each latitude that exceeds a climatological threshold Determines if 13 continuous latitudinal points crossing 40 ° N exceed the IVT threshold Longitudinal differences between points can be no greater than 4 °

57. 12 h Snow Warning Criteria Source: NWS Forecast Office Philadelphia/Mt Holly