1. Severe Weather and Storm Chasing
A behind the scenes look at what went on during a chase from June 7, 2009
AOS 121
November 2, 2009
Vortex 2 photogrammetry

2. Thunderstorm Process
Air that is warmer than its surroundings is positively buoyant and will rise.
As air rises, it does expansion work, and cools.
Dry Adiabatic Lapse rate ≈10oC/km
Moist Adiabatic Lapse rate ≈6.5oC/km

3. Thunderstorm Process Cont’d
Using a Skew-T diagram, we can see the effect of lifting a parcel of air from the surface.
If the surface parcel is warmer, it is likely to rise and form a thunderstorm.

4. Atmospheric Soundings and Skew-T Diagrams

5. Temperature
Dry Adiabats
Moist Adiabats
Mixing Ratio
Td = Dewpoint
T = Temperature

6. Level of Neutral Buoyancy ~ 280mb
Level of Free Convection ~ 660mb
Lifting Condensation Level ~830mb

7. Convective Available Potential Energy
Convective INhibition
LCL

8. Real World Example
June 19th Sounding from Davenport IA

9. Summary
A Saturated parcel will cool at a slower rate than a Dry air parcel.
Convective Available Potential Energy measures the amount of potential energy in the atmosphere.
By understanding Skew-T diagrams, we can predict when severe weather may occur.

10. Storm Chasing Objective
Identify weather patterns that will produce rotating thunderstorms.
Find a storm that will produce a tornado, and be a safe distance away, yet close enough to see it…
Sound easy???

11. NO WAY!!!
A long-lived tornado is on the ground for 10 minutes, and its path length is only a few miles.
Most tornadoes are on the ground less than 1 minute.
If you are on the wrong side of the storm, all you will see is hail crushing your windshield.
Needle in a Haystack.

12. Long term Forecast (3 days)
Look at large scale patterns
Storm Prediction Center (SPC)

13. Short term Forecast (day of)
Look smaller features
Fronts
Clouds
Balloon soundings
Base support
Storm Prediction Center (SPC)

14. Comparison
Long range Short range

15. Morning Outlook
Tornado Hail

16. Our Chase

17. Satellite
NWS KC
7:15 PM

18. Radar
NWS KC
6:45 PM

19. Little Hail

20. Big Hail!!!!

21. Storm Reports

22. More Pictures

23. Storm Prediction Center
Acknowledgements
NWS Kansas City Office
Storm Prediction Center
Storm Chasing Class ‘09

24. Questions
???