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“Environments of Non-Significant Cool Season Severe Weather Events in the Southeastern United States”

“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

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“Environments of Non-Significant Cool Season Severe Weather Events in the Southeastern United States”

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  1. “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

  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 • 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: • 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 • 1000-500mb Thickness 5600–5700m • 925mb Theta-e 320-340K • 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, 1072-1080. 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, 588-612. National Climatic Data Center, http://www.ncdc.noaa.gov/oa/ncdc.html Plymouth State University Meteorology Program, http://vortex.plymouth.edu01 North American Regional Reanalysis Homepage, http://www.emc.ncep.noaa.gov/mmb/rreanl/ 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. William.Komaromi@noaa.gov

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