Severe Weather and Storm Chasing

A behind the scenes look at what went on during a chase from June 7, 2009

AOS 121November 2, 2009

Vortex 2 photogrammetry

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

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.

Atmospheric Soundings and Skew-T Diagrams

Moist Adiabats

Dry Adiabats

Temperature

Mixing Ratio

T = TemperatureTd = Dewpoint

Lifting Condensation Level ~830mb

Level of Free Convection ~ 660mb

Level of Neutral Buoyancy ~ 280mb

Convective INhibition

Convective Available Potential Energy

LCL

Real World ExampleJune 19th Sounding from Davenport IA

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.

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???

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.

Long term Forecast (3 days)

• Look at large scale patterns

• Storm Prediction Center (SPC)

Short term Forecast (day of)

• Look smaller features– Fronts– Clouds– Balloon soundings– Base support

• Storm Prediction Center (SPC)

ComparisonLong range Short range

Morning Outlook

Tornado Hail

Our Chase

Satellite

NWS KC7:15 PM

Radar

NWS KC6:45 PM

Little Hail

Big Hail!!!!

Storm Reports

More Pictures

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

Questions

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