1. © Crown copyright Met Office Verification of forecasts of Cbs Bob Lunnon, Aviation Outcomes Manager, Met Office WAFS Science meeting, Washington, April 21st 2009

2. © Crown copyright Met Office Acknowledgement Most of this work has been done by Andrew Mirza (some help from Lauren Reid) Thanks also due for use of lightning data (Sferics), and for availability of US products

3. © Crown copyright Met Office Summary of presentation Background on lightning detection system (Sferics) used to perform verification Results of verification Conclusions/Recommendations

4. © Crown copyright Met Office Met Office Sferics system System detects the vertical component of electromagnetic radiation generated by a lightning discharge at around 13 kHz (VLF) received at a number of `sensor’ sites Strong EM emissions around 13 kHz Caused by rapid neutralisation of charge, in the lowest few hundred metres of C-G stroke Atmospheric attenuation minima close to 13 kHz The atmoSFERIC wave can propagate over thousands of kilometres along the earth / ionosphere waveguide 12 sensors in the current network connected to Exeter by communication links Received digitised waveforms sent to the Flash Location Processor (FLP) via a Data Collection System (DCS) located in a `fire-walled’ DMZ Location of a `flash’ or `fix’ determined by the Arrival Time Differences (hence ATD) Differences between at least 4 sensor out-stations are used to calculate lightning position by iterative method

5. © Crown copyright Met Office Total number of strikes recorded in July 2007

6. © Crown copyright Met Office Sferics – area of reliable data between 40 S and 80 N and between 110 W and 80 E Verification data generated in latitude bands (and crude longitude divisions) South of 20s 20 South to 20 North 20 North to 50 North North of 50 North

7. © Crown copyright Met Office Cb verification – data to be presented In the WAFS Science meeting in April in Washington we presented results for November 08 and January 09 We were asked to generate statistics for N Hemisphere summer, e.g. May 09-July09 There were data availability problems for July 09 (data for the UK SIGWX charts are not available, only 60% of US GRIB data available) We present data for May 09, June 09 and July 09 today We have plots for November 08 and January 09 if people are interested

8. © Crown copyright Met Office Southern Hemisphere extra- tropics, May 09

9. © Crown copyright Met Office Tropics, May 09

10. © Crown copyright Met Office Northern Hemisphere mid latitudes, May 09

11. © Crown copyright Met Office Northern Hemisphere, polar area, May 09

12. © Crown copyright Met Office All latitudes, May 09

13. © Crown copyright Met Office Southern Hemisphere extra- tropics, June 09

14. © Crown copyright Met Office Tropics, June 09

15. © Crown copyright Met Office Northern Hemisphere mid latitudes, June 09

16. © Crown copyright Met Office Northern Hemisphere, polar area, June 09

17. © Crown copyright Met Office All latitudes, June 09

18. © Crown copyright Met Office Southern Hemisphere extra- tropics, July 09 (no UK SIGWX)

19. © Crown copyright Met Office Tropics, July 09 (no UK SIGWX)

20. © Crown copyright Met Office Northern Hemisphere mid latitudes, July 09 (no UK SIGWX)

21. © Crown copyright Met Office Northern Hemisphere, polar area, July 09 (no UK SIGWX)

22. © Crown copyright Met Office All latitudes, July 09 (no UK SIGWX)

23. © Crown copyright Met Office Conclusions Overall “winner” appears to be US manual product (ranked first for combined latitudes for all five months under consideration) However this ranking reflects the number of grid-points in each latitude zone Number of flights per year is a function of latitude, strongly peaking in 20-50 north UK Automated product is ranked first in this zone in Nov 08, Jan 09, and May 09 US Automated product shows useful skill in the tropics There is limited data available in NH polar and SH extra-tropics Any overall results are very sensitive to exact details of verification scheme Further work was addressed in earlier presentation

24. © Crown copyright Met Office Questions & answers

25. © Crown copyright Met Office Locally observed lightning strikes in S America, case in August 06

26. © Crown copyright Met Office Data from UK sferics system for same day

27. © Crown copyright Met Office Severe US storms – 13 th March 2006

28. © Crown copyright Met Office Results ROC curves for automated and manual products, two WAFCs, November 08 and January 09

29. © Crown copyright Met Office Southern Hemisphere extra- tropics, November 08

30. © Crown copyright Met Office Tropics, November 08

31. © Crown copyright Met Office Northern Hemisphere mid- latitudes, November 08

32. © Crown copyright Met Office Northern Hemisphere, polar area, November 08

33. © Crown copyright Met Office All latitudes, November 08

34. © Crown copyright Met Office Southern Hemisphere extra- tropics, January 09

35. © Crown copyright Met Office Tropics, January 09

36. © Crown copyright Met Office Northern Hemisphere mid- latitudes, January 09

37. © Crown copyright Met Office Northern Hemisphere, polar regions, January 09

38. © Crown copyright Met Office All latitudes, January 09