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A “Survey” of Tornadoes and their Environments in the WFO Sterling, VA Forecast Area

A “Survey” of Tornadoes and their Environments in the WFO Sterling, VA Forecast Area. Matthew R. Kramar Senior Forecaster, WFO LWX Kyle M. Olmstead Student Volunteer, WFO LWX. Motivation.

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A “Survey” of Tornadoes and their Environments in the WFO Sterling, VA Forecast Area

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  1. A “Survey” of Tornadoes and their Environments in the WFO Sterling, VA Forecast Area Matthew R. Kramar Senior Forecaster, WFO LWX Kyle M. Olmstead Student Volunteer, WFO LWX

  2. Motivation • Provide guidance to forecasters on favorable synoptic patterns for tornadoes in the WFO LWX forecast area • Update local graphics to reflect recent geographical and temporal distribution of tornadoes by tornadic storm type

  3. Methodology • Compiled dataset of tornado events from 1992-2009 (WSR-88D era at WFO LWX) • Stratified reports by storm mode based on inspection of Level II data

  4. Methodology • Stratification of tornadoes by storm mode: • Mesocyclonic • Linear/Quasi-Linear Convective System • Sub-stratified into linear and QLCS based on QLCS definition by Coniglio et al. (2007) • Other • Disorganized, non-mesocyclonic cells, waterspout/landspout type tornado • Tropical/Tropical remnant system • No Level II data available

  5. Methodology • Stratification of tornadoes by storm mode: • Considered only mesocyclonic and linear/QLCS tornadoes • Unusual juxtaposition of shear/instability in remnant tropical environments • Potentially important role of sub-synoptic conditions in landspout/waterspout tornado development

  6. Distribution by Month (1992-2009)

  7. Distribution by Month (1992-2009)

  8. 0 1 2 3 4 5 6 7 8 9 10 11 12 13 Number of Days of Tornado Occurrence (1992-2009)

  9. Number of Days of Mesocyclonic Tornado Occurrence 0 1 2 3 4 5 6

  10. 0 1 2 3 4 5 6 Number of Days of Linear/QLCS Tornado Occurrence

  11. Methodology • Constructed synoptic composites based upon tornadic storm mode • NCEP/NCAR Reanalysis • 2.5° x 2.5° lat/lon grid • 6-hourly data • Lose mesoscale details • Seasonal impact on thermodynamic aspects? • Chose 6-hour synoptic time closest to and preceding tornado event

  12. Compositing • Variables • Geopotential Height • Zonal Wind • Meridional Wind • Vector Wind • Sea Level Pressure • Relative Humidity • Temperature • Height Levels (mb) • 250, 500, 700, 850, 925, Surface • N.B. Be careful of the color scales (no user control over this)

  13. Mesocyclonic 250mb

  14. Mesocyclonic 500mb

  15. Mesocyclonic 700mb

  16. Mesocyclonic 700mb

  17. Mesocyclonic 700mb

  18. Mesocyclonic 850mb

  19. Mesocyclonic 850mb

  20. Mesocyclonic 850mb

  21. Mesocyclonic 925mb

  22. Mesocyclonic 925mb

  23. Mesocyclonic 925mb

  24. Mesocyclonic Surface

  25. QLCS 250mb

  26. QLCS 500mb

  27. QLCS 700mb

  28. QLCS 700mb

  29. QLCS 700mb

  30. QLCS 850mb

  31. QLCS 850mb

  32. QLCS 850mb

  33. QLCS 925mb

  34. QLCS 925mb

  35. QLCS 925mb

  36. QLCS Surface

  37. COMPARISONS Mesocyclonic QLCS

  38. `

  39. ~5.74 C/km ~5.55 C/km

  40. Upper Level Features • Mesocyclonic • Relatively lower-amplitude, neutral to positively tilted shortwave trough over Upper Midwest • QLCS • Relatively higher-amplitude, negatively tilted shortwave trough over western Great Lakes region

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