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The April 28, 2011 Severe Weather and Flash Flood Event

The April 28, 2011 Severe Weather and Flash Flood Event. Mike Evans / NWS Binghamton, NY. Outline. Large-scale pattern / meso -analysis Radar data High resolution model output Summary. 500 mb heights and vorticity. Surface plot – 09z.

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The April 28, 2011 Severe Weather and Flash Flood Event

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  1. The April 28, 2011 Severe Weather and Flash Flood Event Mike Evans / NWS Binghamton, NY

  2. Outline • Large-scale pattern / meso-analysis • Radar data • High resolution model output • Summary

  3. 500 mb heights and vorticity

  4. Surface plot – 09z

  5. Equivalent potential temperature, omega and wind speed cross section – 12z

  6. SPC surface and 700 mbfrontogenesis – 09z

  7. SREF CAPE and 850 hPa wind

  8. SPC analysis 0-1 km shear and significant tornado parameter

  9. SPC Guidance

  10. Reflectivity and storm relative motion 0522 – 0540 UTC

  11. Reflectivity and storm relative motion 0654 – 0830 UTC

  12. Reflectivity and storm relative motion 0945 UTC

  13. Normalized rotation – Erin tornado (QLCS)

  14. Normalized rotation – Danby tornado(QLCS – broken S)

  15. Normalized rotation – Pharsalia tornado (mini-supercell)

  16. Normalized rotation – McDonough tornado (mini-supercell; range folding)

  17. Normalized rotation – Columbus tornado (mini-supercell; RFD spin-up)

  18. Normalized rotation – Herrick tornado(QLCS)

  19. Severe reports

  20. BGM CWA tornado climatology

  21. High resolution model 1 km AGL reflectivity – valid 09z

  22. High resolution model 1 km AGL reflectivity – valid 12z

  23. HRRR 1 km AGL reflectivity valid 08z

  24. Summary • Tornadoes and flash floods affected central New York and northeast Pennsylvania during the early morning on the 28th. • This was only the 2nd time since the late 1990s that a tornado was reported in our area between midnight and 9 am. • Tornadoes occurred with a variety of convective storm structures and a variety of rotational evolution patterns.

  25. Summary continued • 00z hi resolution model runs forecast a variety of structures; mostly broken lines of convection, composed of small line segments and some individual cells. • The 00z HRRR model was too weak with the line (especially over NY), but subsequent runs trended toward a better forecast. • All of the 00z models were too far west (too slow) with the convection from 06z through 12z.

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