Parcel Selections

Convective Available Potential Energy (CAPE) - the integrated "positive area" in J/kg (from the LFC to EL) for the lifted parcel. Thunderstorm updraft strength is related to CAPE, though water loading and entrainment of environmental air tend to reduce actual updraft velocities in the middle and upper troposphere compared to those predicted by parcel theory (max updraft velocity = ((2 * CAPE)**1/2)). Low to mid level updraft velocities in supercells often exceed parcel theory estimates due to the pressure effects with the rotating updraft.

Convective Inhibition (CINH) - the integrated "negative area" in J/kg (from the original parcel level to the LFC) for the lifted parcel. The negative area represents the amount of energy needed for a parcel to reach its LFC.

Lifting Condensation Level (LCL) - the level at which a lifted parcel becomes saturated. The LCL height corresponds to cloud base height for forced ascent.

Lifted Index (LI) - the difference between the lifted parcel temperature (at 500 mb) and the 500 mb temperature in the sounding. Negative values denote parcels that are warmer than the background 500 mb temperatures, and are thus buoyant or "unstable".

Level of Free Convection (LFC) - the last level where a parcel becomes buoyant, or "warmer" than the environmental temperature at the same level. The LFC represents the bottom of the layer containing CAPE.

Equilibrium Level (EL) - the level where the lifted parcel again equals the environmental temperature, working upward from the LFC. The EL represents the top of the layer containing CAPE.

Maximum Parcel Level (MPL) - the maximum level which a parcel will attain through "parcel theory". Above the EL, the parcel is "cooler" than the environment, but continues to climb due to momentum it gained below the EL. Eventually, that momentum is lost and the parcel's ascent ends. That point is the MPL.