Severe storms require a basic set of ingredients: instability, wind shear, and lift.
These ingredients are similar to what all thunderstorms need, but severe storms need ample amounts of each.
In this video, we’ll break down some of those ingredients and how they can work together to produce severe thunderstorms.
Instability is required for storm updrafts to even take shape.
To give a brief overview of instability, think of the science lesson ‘hot air rises’. This is true until it meets air that is as warm or warmer — then the air quits rising.
Simply put, instability is when cooler air exists above warm air below.
Thus, this thunderstorm ingredient is vitally important for a severe thunderstorm to take shape.
See more: What is instability?
There are two types of wind shear we worry about when it comes to severe thunderstorm ingredients.
Speed shear is winds increasing with speed with height. Speed shear is important for severe storms because it allows for updraft ventilation. When an updraft is ventilated, it tends to last longer and be more powerful.
Directional shear is the turning of winds with height. The ideal severe storm directional turning would be a south or southeast wind at the surface turning to west in the mid and upper levels of the atmosphere.
See More: What is wind shear?
Lift is what sends an unstable air parcel into the sky. Typically, you need two types of lift to create severe thunderstorms: surface and upper air.
Surface lift is achieved most commonly along surface boundaries like dry lines and cold fronts.
Upper air lift usually occurs in relation to storm systems in the mid and upper jet stream moving into a region. When both of these types of lift work in tandem, storms are a good bet on any given day.
See More: The basics of atmospheric lift