Three characteristics that determine how severe a warm season thunderstorm will be are low level speed and directional wind shear, the upper level wind, and instability (amount of positive buoyancy). Strong surface wind adds fuel to a storm just as an influx of oxygen adds fuel to a fire. Strong surface winds transport moisture and momentum into a developing storm. Terms such as moisture convergence and surface inflow describe this process. Directional shear causes low level wind rotations which can cause tornadic conditions to be more favorable. The upper level wind has many effects on a thunderstorm, which include: a sheared anvil, and upper level divergence (mass is removed from the top of the storm which intensifies the upward pressure gradient within a storm). Upper level winds (between 500 and 300 mb level) of greater than 100 knots is considered significant. The amount of buoyancy determines the updraft strength. The warmer the air within the storm is (compared to the surrounding environmental air), the faster the air will rise within the storm. CAPE values of greater than 1,500 J/kg and LI values less than -5 indicates a very buoyant troposphere. All these factors and others combine together to determine the severity of a thunderstorm.

A trigger mechanism is any process that initiates precipitation or storm development. It is in reference to a process that causes a precipitation or storm event and without this process precipitation or storms would not have occurred. Common trigger mechanism examples are lifting mechanisms, increase of low level moisture, daytime heating, instability and wind shear. The most common type of trigger mechanism that will be referenced are lifting mechanisms such as fronts and other low level convergence boundaries. Severe weather situations will often have several triggers. The trigger that initially sets the storms into motion will often be referenced as the trigger for the severe storm event.