1. A Review of the March 28, 2007 Tornado Event Teresa Keck NWS North Platte, Nebraska Courtesy of Mike Hollingshead

2. Introduction  March 28, 2007 in review  Forecasts leading up to event  Vorticity Generation Parameter (VGP) emphasis in the warning process  VGP application for future events

3. In Review

4. Progression of Day 1 Outlook

5. Day 1 Tornado Outlook

6. Highlights  Dryline retrograded west by early afternoon shifting focus westward.  The VGP forecast and analysis graphics helped refocus the forecast team to the potential for tornadoes in a storm environment where radar signatures were not clear cut.  Storms moved from 34 to 52 knots while moving through the eastern panhandle and slowed to around 26 knots as storms intensified prior to tornado development.  The 0.5 degree elevation slice was over 10 KFT off the ground.  Twelve tornadoes occurred in a 2 hour and 8 minute period. The largest tornado was rated an EF 2 that tracked 17 miles across Perkins county.

7. NAM 500MB Height & Wind Speed

9. Surface Analysis 29/0000Z

10. Visible Image

11. NAM12 CAPE and CIN 29/0000Z

12. LAPS CAPE and CIN 28/2300Z

13. LAPS CAPE and CIN 29/0000Z

14. LAPS CAPE and CIN 29/0100Z

15. LAPS Compared to RUC Wind Profile

16. Vorticity Generation Parameter - Resource  Rasmussen and Blanchard 1998 study  Box and whisker plot of VGP showing the 10 th to 90 th percentile  Estimates the rate of tilting and stretching of horizontal vorticity by a thunderstorm updraft  Levels 0 – 3 km on average with values of 0.2 or greater suggesting an increasing possibility of tornadic storms.  Model data and LAPS analysis

17. NAM12 VGP 29/0000Z

18. RUC VGP 28/2100Z - 29/0000Z

19. Composite Radar 29/0000Z

20. Radar Reflectivity 29/0001Z

21. LAPS 0-3km VGP 28/2300Z

22. Composite 28/2300Z

23. LAPS 0-3km VGP 29/0000Z

24. Composite 29/0000Z

25. LAPS 0-3km VGP 29/0100Z

26. Composite 29/0100Z

27. LAPS 0-3km VGP 29/0200Z

28. Composite 29/0200Z

29. LAPS 0-3km VGP 29/0300Z

30. Composite 290300Z

31. Future use of VGP  Review other events to look for similarities and influence of gradients  Correlations in VGP for ranges created when CAPE and wind shear environments vary (low CAPE to high shear verses high CAPE to low wind shear)  Storm types

32. Questions…