[--MAIN HOME--] [--ALL HABYHINTS--] [--FACEBOOK PAGE--] HABYTIME MINI LECTURE 47: 0 to 3 KM CAPE AND TORNADOES METEOROLOGIST JEFF HABY CAPE is the Energy per mass that is available for a buoyantly rising parcel of air. CAPE is a measure of instability. Higher instability contributes to an environment in with thunderstorms and severe thunderstorms can occur. When it comes to the relationship between CAPE and a tornadic environment, an important index value to study is the 0-3 km CAPE. This is found by calculating the CAPE between the surface and 3 km while ignoring the CAPE at a higher elevation than 700 mb. The reason the 0-3 km region of the sounding is important to study is because this is generally where updraft initiation for thunderstorms occurs and where the best speed and directional shear is located. The diagram below shows an example of weak 0-3 km CAPE and an example of strong 0-3 km CAPE. In the weak 0-3 km CAPE example, CAPE does not begin until well above the surface. In the strong 0-3 km CAPE example, CAPE exists in a deep layer between the surface and 3 km. In the strong 0-3 km example, the LFC (Level of Free Convection) is closer to the surface as compared to the weak 0-3 km example. When 0-3 km CAPE is strong and the LFC is close to the ground, this allows the parcel to rise at the wet adiabatic lapse rate starting closer to the surface and thus this leads to higher CAPE overall within the entire troposphere. When 0-3 km CAPE is relatively strong, there will be better overlap between horizontal vorticity (generated by speed and directional wind shear) and updraft initiation. This allows a mesocyclonic circulation to have a closer interaction with the boundary layer and Earth’s surface. This can increase the likelihood that a tornado could develop.