That is right i4hanish,

As I posted above and just to add to what Ken said

The LI is

There are so many things at play, for example the Lifted Index (Li's) What is a lifted Index, it is the temperature difference between the environment Te(p) and an air parcel lifted adiabatically Tp(p) at a given pressure height in the troposphere (lowest layer where most weather occurs) of the atmosphere, usually 500 hPa (mb). The temperature is measured in Celsius. WHAT???? pretty full on.

So lets make that easy to understand. What is a lifted Index?

The Lifted Index is a measure of the atmosphere's stability (or instability) and is used to determine the thunderstorm potential. Parcels of warmer air may start to rise if they are warmer than surrounding air, and this is called Convection. This Parcel of air will continue to rise from the ground and when it reaches a height of Approx. 5500M (the 500MB on charts) the temperature of that Parcel is subtracted from the temperature of the atmosphere at 500MB. When that figure shows a higher negative value it means it will continue to rise.

So why is that important to look for? Thunderstorms are fueled by strong rising air, thus the Lifted Index is a good measurement of the atmosphere's potential to produce severe thunderstorms. BUT, If the Lifted Index is favorable for severe storms but other conditions are not met, then no storms may form at all.