1. Administration through the Hollings Scholarship Program
“Environments of Non-Significant Cool Season Severe Weather Events in the Southeastern United States”
William A. Komaromi
University at Albany
Storm Prediction Center
David Imy & Jared Guyer
This research was supported by an appointment to the National Oceanic & Atmospheric
Administration through the Hollings Scholarship Program
9/21/2018

2. Outline Project Purpose Background Methodology Results Next Steps
Conclusion
Acknowledgements

3. Project Purpose
To help Storm Prediction Center forecasters better differentiate the subtle differences between significant tornado and non-significant tornado environments during the Southeastern United States cool season.

4. Background
2005 Kar’retta Venable of Jackson State University at Jackson, Mississippi
2006 Amanda Kis of University of Wisconsin at Madison
F2 or stronger tornadoes
Environmental parameters

5. What I have done:
Examined environments of non-significant tornado events.
Made comparison to significant tornado environments.

6. Cases were identified that occurred:
Methodology
Cases were identified that occurred:
During a 12z to 12z timeframe
In the cool season months from October 1st to the end of February
Geographically within a Southeast U.S. domain…

7. As pictorially defined here:

8. Anticipated Outcome Subtle differences
Significant tornado days will have…
Higher wind speeds
More directional shear
Warmer and moister low-levels
Colder temperatures aloft
… than non-significant tornado days.

9. What cases did I look for?
Days with 2+ tornadoes or 15+ severe hail and/or wind, but with no tornadoes of F2 or stronger intensity.

10. Some days were very small events
Tornado Tracks
+ Damaging Winds
Severe Hail

11. Others were widespread outbreaks
Tornado Tracks
+ Damaging Winds
Severe Hail

12. Event days were broken up into five categories:
Significant Tornado Days (F2+): 150 cases
Non-significant tornado days: 145 cases
Weak Tornado Days (F0, F1): 103 cases
Severe Hail / Wind Only Days: 42 cases
All tropical events were removed

13. Data Collection Archived: Nearest: Favored Warm Sector Surface Plots
Radiosonde Data
Nearest:
Spatially
With Time
Favored Warm Sector

14. Data Organized in Excel

15. Many Graphs Were Created

16. Thousands of Gempak Maps

17. Box and Whiskers Format
90th percentile
Middle
50%
10th percentile

18. Results
Temps, dewpoints, thickness, and theta-e all very similar at all levels for all 4 cases!

19. Results: Significant tornado and non-significant tornado events:
Surface Temps 65–75°F
Surface Dewpoints 60–70°F
mb Thickness 5600–5700m
925mb Theta-e K
700mb Temps 1-7°C

20. Wind Speed – Best Differentiator

21. Wind Speed – Best Indicator
Wind speeds of:
40+ kts at 850mb
45+ kts at 700mb
60+ kts at 500mb
Represent middle 50% of significant tornado events, but near the outer 90th percentile in non-significant tornado events.

22. Wind Direction
Poor differentiator
All veered with height

23. Wind Direction Unexpected finding:
Significant tornado events had less veering than the others from 700mb to 500mb.

24. Next Steps
Comparison can be made for instability, helicity and other convective parameters.
Thereafter, a final paper will be published.

25. Conclusions
The greatest differentiator between significant and non-significant tornado events was stronger winds at 850, 700 and 500 mb.
Overall differences in all other parameters are very subtle.

26. Acknowledgements
Galway, J. G., and A. Pearson, 1981: Winter tornado outbreaks. Mon. Wea. Rev., 109,
Guyer, Jared L., Imy, David A., Kis, Amanda, and Venable, Kar’retta, 2006: Cool Season Significant (F2-F5) Tornadoes in the Gulf Coast States.
Johns, R. H., and C. A. Doswell III, 1992: Severe local storms forecasting. Wea. And Forecasting, 7,
National Climatic Data Center,
Plymouth State University Meteorology Program,
North American Regional Reanalysis Homepage,
Vescio, M. D., and R. L. Thompson, 1993: Some meteorological conditions associated with isolated F3-F5 tornadoes in the cool season. Preprints, 19th Conf. On Severe Local Storms, Minneapolis, MN, 2-4.