Stability Assessment » Lifted Index (LI) Definition
Definition: Lifted Index
The lifted index (LI) is calculated as the difference between the observed temperature at 500 hPa and the temperature of an air parcel lifted to 500 hPa from near the surface. The more unstable the environment, the more negative the LI.
LI values have been empirically linked to convective events as follows:
LI Value | Severe Weather Potential |
-2 | Weak |
-3 to -5 | Moderate |
-6 or less | Strong |
These threshold values are valid for the eastern 2/3 of the United States. The values must be modified upward (i.e., less negative) for higher elevations such as in western Canada and the U.S. As with CAPE, you should never rely solely on LI to evaluate the convective potential.