Dual-polarimetric and multi-Doppler analysis of a High Plains supercell

1. Dual-polarimetric and multi-Doppler analysis of a High Plains supercell Darren Clabo Nick Guy Nathan Hitchens

2. Outline • Introduction • Background • Dual-polarimetric Doppler analysis • Multi-Doppler analysis • Summary

3. Introduction

6. Soundings RIW LBF DNR

9. Surface Observations

10. Storm Information • Initiation: 2337 UTC on 4 June 2009 • First reflectivity seen aloft (8.81 km) at 2326 UTC on 4 June 2009 • Last radar scan by CSU-CHILL at 0112 UTC on 5 June 2009

11. 1km Visible Satellite Storm initiation

12. CSU-CHILL Reflectivity

14. CoCoRaHS Reports

15. SHAVE Reports

16. Background

17. Supercell Model Klemp (1987)

18. Polarimetric Radar Signatures in Supercell Thunderstorms Kumjian and Ryzhkov (2008)

19. Polarimetric Radar Signatures in Supercell Thunderstorms • ZDR arc signature • Usually found on the right southern edge of the forward flank downdraft • Shallow (1-2 km in depth) • Effect of size sorting of raindrops resulting from vertical increase in speed and veering of storm-relative winds Kumjian and Ryzhkov (2008)

20. Polarimetric Radar Signatures in Supercell Thunderstorms • Hail signature • Low ZDR value (near 0) due to chaotic orientation of tumbling hailstones Kumjian and Ryzhkov (2008)

21. Polarimetric Radar Signatures in Supercell Thunderstorms • Inflow signature • Vigorous low-level inflow into supercells may contain nonmeteorological scatterers (e.g. grass, leaves, dust) • Results in lower values of ρHV Kumjian and Ryzhkov (2008)

22. Polarimetric Radar Signatures in Supercell Thunderstorms • Updraft signature • Light debris may be ingested into updraft from inflow and a lack of hydrometeors may exist • Results in low ρHV aloft

23. Polarimetric Radar Signatures in Supercell Thunderstorms • ZDR columns • High values associated with updrafts indicative of large raindrops or water-coated hailstones • Narrow (4-8 km wide) • Increasing values associated with updraft intensification, and thus storm intensification Kumjian and Ryzhkov (2008)

24. Radar Coverage • Dual-polarized, S-band • CSU-CHILL • Single-polarized, S-band • CSU-PAWNEE • Denver NEXRAD (KFTG) • Cheyenne NEXRAD (KCYS)

25. Storm undergoing new updraft growth • Vorticity calculated using the tangential shear between two points corresponding to the maximum inbound and outbound velocities not more than 10 km apart in an area thought to contain the updraft • Updraft denoted by bounded weak echo region aloft • Red line denotes minimum vertical vorticity for a mesocyclone as described by the synthesis of Bunkers et al. (2009)

26. Dual-Polarimetric Doppler Analysis

27. 2352 UTC - Base

28. 2352 UTC – Sweep 4

29. 0013 UTC - Base

30. 0013 UTC – Sweep 4

31. 0020 UTC - Base

32. 0020 UTC – Sweep 4

33. 0046 UTC – Sweep 4

34. 0049 UTC - Base

35. 0049 UTC – Left Split

36. 0053 UTC - Base

37. 0053 UTC – Sweep 4

38. 0106 UTC - Base

39. 0106 UTC – Sweep 4

40. 0109 UTC – Base Updraft Updraft Updraft Updraft

41. 0109 UTC – Sweep 4 Updraft Updraft Updraft Updraft

42. Multi-Doppler Analysis

43. Multi-Doppler Analyses • Radar data edited in SOLOII • Removal of egregious data • Interpolated to Cartesian grid via REORDER software package • Dual- and Multi-Doppler analyses performed with CEDRIC software package • Extremely finicky!

44. Radar Ranges

45. Multi-Doppler Analyses Quad Triple Dual Dual

46. Vertical Wind Calculation Upward integration Downward integration Variable Integration

47. Continuity 090605_0109Z 090605_0106Z

48. Vertical Structure 1.50 km 3.0 km

49. Vertical Structure 4.50 km 6.5 km

50. Vertical Structure 8.0 km 10.0 km