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What is LCL?

LCL stands for "lifted condensation level". This is the atmospheric level where a parcel that is lifted dry adiabatically will condense. This often marks cloud base. Low LCLs (close to ground) are more favorable for tornadogenesis.


Ben
 
Some Definitions:
Source: NWS Detroit Glossary
Lifting Condensation Level (LCL): It is the height at which a parcel of air becomes saturated when lifted dry-adiabatically.

Source: AMS GLossary
ifting condensation level—(Abbreviated LCL; also called isentropic condensation level.) The level at which a parcel of moist air lifted dry-adiabatically would become saturated.
On a thermodynamic diagram it is located at the point of intersection of the dry adiabat through the point representing the parcel's original pressure and temperature with the saturation mixing ratio line having the same value of the mixing ratio as the parcel. The pressure and temperature at the lifting condensation level are usually called the condensation pressure and condensation temperature, respectively, and the corresponding point on a thermodynamic diagram is called either the characteristic point, adiabatic saturation point, or adiabatic condensation point. See convective condensation level, conditional instability, saturation level.

Some links to look at:
SKEW-T: A LOOK AT LCL
http://www.theweatherprediction.com/habyhints/299/

THE DIFFERENCE BETWEEN THE LCL AND CCL
http://www.theweatherprediction.com/habyhints/160/

Mike
 
Low LCLs (close to ground) are more favorable for tornadogenesis.

Could someone please explain why?

I'll take a stab at this one. There have been extensive white papers written about this and could get lengthy. But, I'll try to be concise and as simple as possible.

My thoughts are that LCLs mark where a rising air parcel becomes saturated and significantly cools at a slower rate as it continues to rise (moist adiabatic is the term to describe this). Therefore, the surrounding air becomes cooler by relative comparison. This increases the instabilities at this level and the air parcel rises faster. In addition, with low LCLs, any outflow from downdrafts isn't nearly as cold and dense and less likely to interfer with or undercut a tornadic circulation and instead rises more easily. The "big picture" result is most of the air is much more "buoyant" both from inflow and downdrafts including the rear flank downdraft. This is all part of "low level buoyancy" including 0-3km CAPE which progress in understanding, identifying and forecasting is still ongoing...but definitely some solid data

A great link to more detailed information is on Jon Davies site at

http://members.cox.net/jondavies1/LLbuoypr..._background.htm for a good primer and
http://members.cox.net/jondavies1/LLbuoypr...buoy_values.htm for more detailed discussion.

I hope this helps!
 
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