Severe storms need three main ingredients: wind shear, instability, and atmospheric lift.
Atmospheric lift is important to get air parcels in an unstable atmosphere to begin lifting upwards and eventually condensing into clouds. Lift is necessary to overcome a capping inversion on the most dynamic days as well.
Usually, lift is associated with an upper level storm system aloft and with surface boundaries where winds converge down low. Atmospheric lift is achieved in other ways as well.
Here’s a primer on the basics.
Some Ways to Achieve Atmospheric Lift
Low Level Convergence – This is done when winds and air masses converge along surface boundaries like drylines or fronts.
Warm Air Advection – When warmer and less dense air meets and rises above cooler and denser air, you can get enough lift for storms to form.
Orographic Lifting – This form of atmospheric lift is caused by winds meeting upward sloping terrain. Air meeting upwards sloping terrain is lifted upwards, which can create storms.
Upper Level Divergence – As winds change direction in the upper atmosphere a vacuum effect occurs. This causes air to lift upwards underneath.
Lift is Just One Ingredient, But Its Important
Chasers often overlook lift as an important ingredient to forecast.
Often, chasers sit out under a blazing sun wondering why there aren’t cumulus clouds bubbling upwards. Often, they are not coming close to approaching storm initiation despite big model numbers.
Conditional instability is the problem. An atmosphere with no way to lift air parcels through a capping inversion isn’t actually that unstable.
Thus, it is important to always remind those who chase that you need lift to create storms.
Adequate atmospheric lift often comes from surface convergence down low and some form of divergence up high on storm days.
The balance of too much or too little lift along with capping is delicate. Often, this balance makes or breaks chase days.