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EnSRF Data Assimilations and Forecasts: May 24, 2011 Event

Preliminary results from EnSRF data assimilations and forecasts of the May 24, 2011 event. The Warn-on-Forecast Workshop 2 April 2014 experiment configuration, methods, and knob settings utilizing the ARPS model with 300x300x51 grid spacing and a 3 km resolution. Incorporates NAM IC/BC, Milbrandt-Yau 2-moment MP, and a 3D Ensemble Square-Root Filter with a 40-member ensemble. Experiment timeline includes surface data from ASOS and AWOS, sounding data from ARM, and WSR-88D radar data. Evaluation of updraft helicity, reflectivity, and Equitable Threat Score to assess model performance and future work suggestions.

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EnSRF Data Assimilations and Forecasts: May 24, 2011 Event

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  1. Preliminary Results from EnSRF data Assimilations and Forecasts of the 24 May 2011 Event Tim Supinie, Youngsun Jung, Ming Xue Warn-on-Forecast Workshop 2 April 2014

  2. Experiment Configuration Domain Outline Methods and Knob Settings • ARPS • 300×300×51 • 3 km grid spacing • NAM IC/BC • Milbrandt-Yau 2-moment MP • 3D Ensemble Square-Root Filter • 40-member ensemble • 6 km localization radius • 5 dBZ, 3 m s-1obs. errors • Multiplicative (1.2) and RTPS (0.9) covariance inflation Terrain Height (m)

  3. Experiment timeline and data • Surface data: ASOS (1-minute), AWOS (20-minute), OK Mesonet (5-minute) • Sounding data: ARM (3-hourly) • WSR-88D: 17 Radars, including KTLX, KFDR, and KVNX

  4. 1 km AGL Reflectivity (Analyses) Reflectivity (dBZ)

  5. 1 km AGL Reflectivity (2100 UTC Forecast) Reflectivity (dBZ)

  6. Updraft Helicity (1930-2030 UTC Forecast) 2047 UTC 2020 UTC P(UH > 50 m2 s-2) 2031 UTC

  7. Updraft Helicity (2000-2100 UTC Forecast) 2047 UTC 2020 UTC 2050 UTC P(UH > 50 m2 s-2) 2046 UTC 2031 UTC

  8. Updraft Helicity (2100-2200 UTC Forecast) 2235 UTC 2226 UTC 2050 UTC P(UH > 50 m2 s-2) 2206 UTC

  9. Equitable Threat Score (ETS) 1930 UTC FCST 2000 UTC FCST • P(Z > 40 dBZ) > 0.5 from ensemble • Z > 40 dBZ from WSR-88Ds • Full volume scans (9-14 tilts) 2100 UTC FCST

  10. Contingency Table Visualization

  11. (Preliminary) Conclusions • NEP Updraft Helicity swaths line up with observed tornadoes • Reasonably Well: Canton Lake Tornado • Okay: El Reno EF5 (UH swath deviates left) • Poorly: Goldsby Tornado (1 hour too early) • ETS drops off quickly after initialization • Model wants to move storms too quickly (closer to LCL-EL mean wind) • Unresolved supercell dynamic pressure perturbations?

  12. Future Work • 4D EnSRF (Wang et al. 2013) • 500 m simulations • Improved track forecasts? • Sounding data partitioning • Sources of vertical vorticity for the forecasts Questions?

  13. Updraft Helicity Tracks • Integrated from 0-3 km • Neighborhood Ensemble Probability • 7.5 km neighborhood Schwartz et al. (2010), Fig. 8

  14. 2100 UTC hodographs 1-10 km MSL Mean Wind (Advective) Observed Storm Motion Ensemble Mean Storm Motion

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