1. SPC Ensemble Applications: Current Status, Recent Developments, and Future Plans David Bright Storm Prediction Center Science Support Branch Norman, OK 4 th Ensemble User Workshop Tuesday, 13 May 2008 Laurel, MD Where Americas Climate and Weather Services Begin

3. Outline: SPC Ensemble Applications Current Status –Large-Scale Predictability: GEFS and NAEFS –Mesoscale Guidance: SREF Recent Developments –HWT/Spring Experiment Storm-Scale Ensemble Forecst (SSEF) –Rapid-Refresh Ensemble Forecast Ongoing and Future Plans

4. Application of the GEFS and NAEFS Day 4 through 8: Severe Weather Outlook Day 3 through 8: Fire Weather Outlook Assess the large-scale pattern and its predictability Anticipate the spectrum of possible high-impact weather Three Forecast categories: 1) Potential Too Low 2) Predictability Too Low 3) Outlook An Area

5. 168h Forecast Valid 00 UTC 22 Oct 2007 GEFS Ensemble Mean: 500 mb Height and Vorticity Application of the GEFS GEFS in NMAP2: Pattern

6. 168h Forecast Valid 00 UTC 22 Oct 2007 GEFS Ensemble Spaghetti: 500 mb Height (Single contour at 5760 m) Application of the GEFS GEFS in NMAP2: Predictability and spread

7. 168h Forecast Valid 00 UTC 22 Oct 2007 GEFS Ensemble: Mean 500 mb Height and its Departure from Normal (# of SD) Application of the GEFS GEFS in NMAP2: Departure from normal

8. 168h Forecast Valid 00 UTC 22 Oct 2007 NAEFS Ensemble: 500 mb Mean Height and its Standard Deviation Application of the NAEFS NAEFS via WEB: Predictability of the large-scale pattern

9. Mesoscale Scale 90% of products here…so most work in this area Build confidence Assess range of plausible solutions

10. Application of the SREF Ensemble The High Impact Challenge: High impact events often occur on time and space scales below the resolvable resolution of most observing, forecasting (and ensemble) systems Key Application Premise: We use knowledge of the environment, unresolved processes, and consider uncertainty, to determine the spectrum of possible hazardous weather, when and where it may occur, and how it may evolve over time

11. Applications of Mesoscale Ensemble Guidance at the SPC Develop specialized guidance for the specific application (severe weather, fire weather, winter weather) Design guidance that… –Helps blend deterministic and ensemble approaches –Provide guidance for uncertainty/probabilistic forecasts –Provide guidance that aids (deterministic) confidence –Illustrates a range of plausible scenarios –Allows for diagnostic analysis – is not just a statistical black-box –Probabilities and joint probabilities most commonly applied

12. SREF Probability of STP Ingredients: Time Trends 48 hr SREF Forecast Valid 21 UTC 7 April 2006 Prob (MLCAPE > 1000 Jkg -1 ) X Prob (6 km Shear > 40 kt) X Prob (0-1 km SRH > 100 m 2 s -2 ) X Prob (MLLCL < 1000 m) X Prob (3h conv. Pcpn > 0.01 in) Shaded Area Prob > 5% Max 40%

13. SREF Probability of STP Ingredients: Time Trends 36 hr SREF Forecast Valid 21 UTC 7 April 2006 Prob (MLCAPE > 1000 Jkg -1 ) X Prob (6 km Shear > 40 kt) X Prob (0-1 km SRH > 100 m 2 s -2 ) X Prob (MLLCL < 1000 m) X Prob (3h conv. Pcpn > 0.01 in) Shaded Area Prob > 5% Max 50%

14. SREF Probability of STP Ingredients: Time Trends 24 hr SREF Forecast Valid 21 UTC 7 April 2006 Prob (MLCAPE > 1000 Jkg -1 ) X Prob (6 km Shear > 40 kt) X Prob (0-1 km SRH > 100 m 2 s -2 ) X Prob (MLLCL < 1000 m) X Prob (3h conv. Pcpn > 0.01 in) Shaded Area Prob > 5% Max 50%

15. SREF Probability of STP Ingredients: Time Trends 12 hr SREF Forecast Valid 21 UTC 7 April 2006 Prob (MLCAPE > 1000 Jkg -1 ) X Prob (6 km Shear > 40 kt) X Prob (0-1 km SRH > 100 m 2 s -2 ) X Prob (MLLCL < 1000 m) X Prob (3h conv. Pcpn > 0.01 in) Shaded Area Prob > 5% Max 50%

16. Severe Event of April 7, 2006 SREF severe weather fields increased forecaster confidence resulting in a “High Risk” outlook First ever Day 2 outlook High Risk issued by SPC More than 800 total severe reports –3 killer tornadoes and 10 deaths

17. http://www.spc.noaa.gov/exper/sref/ SPC SREF Webpage for Mesoscale High-Impact Applications http://w1.spc.woc.noaa.gov/exper/sref/frames.php?run=case_2007060703 Case study support added for WFOs

18. http://www.spc.noaa.gov/exper/sref/ SPC SREF Webpage for Mesoscale Applications is Popular

19. SPC SREF Webpage for Mesoscale Applications: Plumes

20. Click on forecast hour for dSREF/dt depiction (Courtesy of Steve Listema and Steven Zubrick, WFO Sterling) SPC SREF Webpage for Mesoscale Applications: dSREF/dt

22. Decomposition of severe: –Probability of > 1 tornado Improved calibrated thunderstorm Rapid Refresh Ensemble System (RREF) –Based on time-lagged RUC –Guidance for convective initiation (and initial operational storm scale ensembles will likely require scaled time lagging Recent SREF Developments and Plans

23. RREF: Calibrated Hourly Thunderstorm Probability

25. Storm Scale

26. Future Applications: Explicit High Impact Ensembles NOAA Hazardous Weather Testbed (HWT) HWT Spring Experiment  Focused on experimental high-res WRF forecasts since 2004 (dx ~2-4 km) Convection allowing ensemble forecasts (2007-2009) to address uncertainty  10 WRF members  4 km grid length over 3/4 CONUS  Major contributions from: SPC, NSSL, OU/CAPS, EMC, NCAR Evaluate the ability of convection allowing ensembles to predict:  Convective mode (i.e., type of severe wx)  Magnitude of severe type (e.g., peak wind)  Aviation impacts (e.g., convective lines/tops)  QPF/Excessive precipitation  Year 1 Objective (2007): Assess the role of physics vs. initial condition uncertainty at high resolution 2003 Spring Experiment

28. 2 km AGL 5 km AGL Convective Mode: Supercell Detection Besides simulated reflectivity, need a quantitative tool for supercell detection and strength in deterministic and ensemble forecasts

29. Probability Updraft Helicity > 50 m 2 /s 2 Supercell Detection F026: Valid 02 UTC 22 Apr 2008 UH > 50 + 25 mi

30. Probability Updraft Helicity > 50 m 2 /s 2 Radar BREF 0142 UTC 22 Apr 2008

31. Probability Updraft Helicity > 50 m 2 /s 2 View of the left split looking south from Norman, OK (0145 UTC 22 Apr 2008) (Numerous large hail reports up to 2.25”) Jack Hales

32. Convective Mode: Linear Detection Determine contiguous areas exceeding 35 dbZ Estimate mean length-to-width ratio of the contiguous area; search for ratios > 5:1 Flag grid point if the length exceeds: –50 miles –100 miles –200 miles

33. Probability Linear Mode Exceeding 200 miles Squall Line Detection F024: Valid 00 UTC 18 Apr 2008 Linear mode + 25 miles

34. Probability Linear Mode Exceeding 200 miles Squall Line Detection F026: Valid 02 UTC 18 Apr 2008 Linear mode + 25 miles

35. Squall Line Detection Probability Linear Mode Exceeding 200 miles F028: Valid 04 UTC 18 Apr 2008 Linear mode + 25 miles

36. Base Reflectivity 0140 UTC 18 April 2008 Radar Reflectivity Valid 02 UTC 15 May 2007

37. Linear Convective Mode: Impacts

39. Direct Severe Guidance from SSEF Probability of Severe Thunderstorms based on “synthetic reports”

40. Direct Severe Guidance from SSEF Probability of Severe Thunderstorms based on “synthetic reports”

41. Direct Severe Guidance from SSEF Probability of Severe Thunderstorms based on “synthetic reports”

42. Direct Severe Guidance from SSEF Probability of Severe Thunderstorms based on “synthetic reports”

43. Summary: Ensemble Applications in High Impact Forecasting Ensemble approach to forecasting has many similarities to the deterministic approach – Ingredients based inputs – Diagnostic and parameter evaluation Ensembles contribute appropriate levels of confidence to the forecast process –Ability to view diagnostics and impacts in probability space Calibration of ensemble output can remove systematic biases and improve the spread Ensemble techniques scale to the problem of interest (weeks, days, or hours)