1. 40 th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015 Understanding SPC’s Outlooks or Everything you wanted to know about outlook probability to category conversion but were afraid to ask. Greg Carbin, Jared Guyer, Bill Bunting, Russ Schneider NOAA/NWS Storm Prediction Center

2. 40 th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015 Severe Thunderstorm Outlook Categories Bottom line… It’s about forecasting the overall coverage of severe storms… …and the intensity of those storms!

3. 40 th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015 From Probabilities to Day 2 Categories Total of all hail, wind, & torn events

4. 40 th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015 From Probabilities to Day 2 Categories Total of all hail, wind, & torn events What does Jim think will happen tomorrow?

5. 40 th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015 From Probabilities to Day 2 Categories Total of all hail, wind, & torn events 5%

6. 40 th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015 From Probabilities to Day 2 Categories Total of all hail, wind, & torn events 15%

7. 40 th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015 From Probabilities to Day 2 Categories Total of all hail, wind, & torn events 15% sig

8. 40 th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015 From Probabilities to Day 2 Categories Total of all hail, wind, & torn events 30%

9. 40 th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015 From Probabilities to Day 2 Categories Total of all hail, wind, & torn events 30% sig

10. 40 th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015 From Probabilities to Day 2 Categories Total of all hail, wind, & torn events 45%

11. 40 th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015 From Probabilities to Day 2 Categories Total of all hail, wind, & torn events 45% sig

12. 40 th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015 From Probabilities to Day 2 Categories Total of all hail, wind, & torn events 60%

13. 40 th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015 From Probabilities to Day 2 Categories Total of all hail, wind, & torn events 60% sig

14. 40 th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015 From Probabilities to Day 1 Categories Hail, wind, & torn events are considered separately. Significant severe usually results in a category upgrade.

15. Why Are These Numbers Important? Five year sample: 2010 - 2014 Day 1 Probabilistic Outlooks Day 2 & 3 Probabilistic Outlooks Because SPC Severe Weather Outlooks probabilities are reliable.

16. Forecast Exercise Case Studies for Day 2 SWO Probability Practice Greg Carbin, Jared Guyer and Patrick Marsh NWS-NCEP-Storm Prediction Center

17. Severe Weather Forecast Exercise - 00Z 500 mb heights, temps (C), isotachs (kt) - 00Z surface pressure, 2m temps/dewpoints (F), 10m wind (kt) - 00Z surface pressure, CAPE, HLCY - What states were most impacted by severe weather on this day? - Were there significant tornadoes (F2-3)? How many and where? - Were there violent tornadoes (F4-5)? How many and where? - What happened? - 00Z Supercell Composite Parameter (SCP)

18. 40 th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015 Case #1 – 500 mb

19. 40 th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015 Case #1 – MSLP/T/Td

20. 40 th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015 Case #1 – MSLP/CAPE/SRH

21. 40 th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015 Case #1 – Supercell Composite

22. 40 th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015 Case #2

23. 40 th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015 Case #2 – 500 mb

24. 40 th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015 Case #2 – MSLP/T/Td

25. 40 th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015 Case #2 – MSLP/CAPE/SRH

26. 40 th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015 Case #2 – Supercell Composite

27. 40 th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015 Case #3

28. 40 th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015 Case #3 – 500 mb

29. 40 th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015 Case #3 – MSLP/T/Td

30. 40 th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015 Case #3 – MSLP/CAPE/SRH

31. 40 th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015 Case #3 – Supercell Composite

32. 40 th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015 Case #4

33. 40 th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015 Case #4 – 500 mb

34. 40 th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015 Case #4 – MSLP/T/Td

35. 40 th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015 Case #4 – MSLP/CAPE/SRH

36. 40 th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015 Case #4 – Supercell Composite

37. 40 th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015 Here’s what happened…

38. 40 th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015 TOR = 5 F2+ = 1 F4+ = 1 DPI = 4.8 CASE #1 verification 13 July 2004: Roanoke, IL F4 and later derecho. ~400 total reports.

39. 40 th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015 TOR = 5 F2+ = 1 F4+ = 1 DPI = 4.8 CASE #1 verification 45% SIG Moderate Risk 60% Moderate Risk 13 July 2004: Roanoke, IL F4 and later derecho. ~400 total reports.

40. 40 th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015 TOR = 30 F2+ = 20 F4+ = 7 DPI = 1156 Fatalities= 89 CASE #2 verification Infamous 1985 OH/PA tornado outbreak

41. 40 th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015 TOR = 30 F2+ = 20 F4+ = 7 DPI = 1156 Fatalities= 89 CASE #2 verification Infamous 1985 OH/PA tornado outbreak 60% SIG High Risk

42. 40 th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015 TOR = 7 F2+ = 4 F4+ = 1 DPI = 38 Fatalities= 6 CASE #3 verification 3 June 1980: “Night of the Twisters!” Grand Island, NE tornado cluster.

43. 40 th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015 TOR = 7 F2+ = 4 F4+ = 1 DPI = 38 Fatalities= 6 CASE #3 verification 30% SIG Enhanced Risk 3 June 1980: “Night of the Twisters!” Grand Island, NE tornado cluster.

44. 40 th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015 TOR = 50 F2+ = 27 F4+ = 4 DPI = 633 Fatalities= 21 26 April 1991: Andover, KS and Red Rock, OK. TORNADO OUTBREAK! CASE #4 verification

45. 40 th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015 TOR = 50 F2+ = 27 F4+ = 4 DPI = 633 Fatalities= 21 CASE #4 verification 45% SIG Moderate Risk 60% SIG High Risk 26 April 1991: Andover, KS and Red Rock, OK. TORNADO OUTBREAK!

46. Severe Weather Forecast Exercise - Summary: Why is tornado forecasting so hard? - A wide range of large-scale conditions… - Generally poor forecasts of storm-scale conditions… - Any time of year… - Just about anywhere… - Tornadoes kill people and can ruin your day!

47. http://www.spc.noaa.gov Gregory.Carbin@noaa.gov