1. An Examination of the March 1-2, 2009 East Coast Gravity Wave Using High- Resolution Operational Data Sets Alan M. Cope NOAA/National Weather Service Mount Holly, NJ

2. Outline Introduction Introduction Background on Gravity Waves Background on Gravity Waves Meteorological Setting Meteorological Setting One-minute ASOS Data One-minute ASOS Data WSR-88D Radar Data WSR-88D Radar Data Signals from NAM-WRF Signals from NAM-WRF Conclusions Conclusions

3. Introduction

4. Timing of Gravity Wave Trough -Overnight March 1-2, 2009 - With moderate snowstorm - Moved northeast 30-35 kt -Pressure falls up to ~ 8 hPa - Surface Wind Gusts 40-50 kt -Downed trees and power lines - Loss of electric power overnight

5. Pressure Falls (hPa) with Gravity Wave Passage

6. Wind Gusts (kt) with Gravity Wave Passage

7. Background on Gravity Waves

8. Idealized Cross-Section of a Gravity Wave (from Schneider, 1990)

9. Typical Synoptic Environment and Sounding for Gravity Waves (from Koch and O’Handley, 1997)

10. Meteorological Setting

11. HPC Surface Pressure and Frontal Analysis 0300 UTC, March 2

12. 250 hPa Analysis from the RUC 80-km 0000 UTC, March 2

13. Sounding from Wallops Is., VA - 0000 UTC March 2

14. Sounding from Upton, NY - 0600 UTC March 2

15. Satellite WV Image at 0315 UTC, March 2

16. Composite Radar Reflectivity at 0600 UTC

17. One-Minute ASOS Data

18. 1-Minute ASOS Surface Pressure and P-Change at Wakefield, VA

19. 1-Minute ASOS Surface Pressure and P-Change at Patuxent River, MD

20. 1-Minute ASOS Surface Pressure and P-Change at Atlantic City Int’l Airport

21. 1-Minute ASOS Surface Pressure and P-Change at Boston, Logan Int’l Airport

22. Expanded View of 1-Minute ASOS Data

24. WSR-88D Radar Data

25. KDOX 0.5 deg Base Velocity - 0512 UTC

26. KDOX 0.5 deg Base Velocity - 0616 UTC

27. KDOX Base Velocity Cross Section – 0542 UTC

28. KDOX Base Velocity Cross Section – 0600 UTC

29. KDOX CAPPI Reflectivity at ~5000 ft – 0606 UTC

30. KDOX Reflectivity Cross Section at 0606 UTC

31. Signals from the NAM-WRF

32. NAM 21-hr Forecast, valid 0900 UTC March 2

33. NAM 09-hr Forecast, valid 0900 UTC March 2

34. Conclusions Large-amplitude gravity wave caused severe weather Large-amplitude gravity wave caused severe weather Conditions similar to other gravity wave case studies Conditions similar to other gravity wave case studies One-minute ASOS data very useful to identify wave (should be available real-time) One-minute ASOS data very useful to identify wave (should be available real-time) Doppler radar showed unusual wind pattern with hurricane force winds just above the surface Doppler radar showed unusual wind pattern with hurricane force winds just above the surface Operational 12-km NAM-WRF indicated possible gravity wave event well ahead of time. Operational 12-km NAM-WRF indicated possible gravity wave event well ahead of time.

35. The End Thanks for your attention! Questions???