It’s a phrase meteorologists use all the time.
“The ingredients are coming together for an active night of severe weather.”
We aren’t talking about flour, sugar and chocolate chips. We mean that the atmosphere is becoming favorable for thunderstorms to develop – some of which could be strong to severe.
What You Need To Know
- Thunderstorms need moisture, instability and lift to develop
- Oceans are a good source of moisture
- Instability describes upward and downward movement of air
- Fronts, topography and upper-level movement help provide lift
There are three key ingredients to thunderstorm formation: moisture, instability and lift.
Moisture
Oceans are the primary sources of moisture transfer in our atmosphere.
The warm waters of the Gulf of Mexico and the warm currents off the East Coast add a lot of moisture to the atmosphere because evaporation is greater in warm ocean waters than in cold ocean waters.
Moisture can also come from plants, which is common across the nation’s mid-section where cornfields add a lot of moisture to the atmosphere through a process called evapotranspiration.
Instability
Air is constantly rising and sinking. Air is unstable when it continues to rise in what are called warm updrafts. This happens near the Earth’s surface. In a standard environment, air rises and cools.
When this happens, water vapor condenses, forming clouds. If the updrafts continue, this unstable air mass continues the cloud formation, creating towering cumulonimbus clouds, which we know as thunderstorms.
Lift
This is the final ingredient in our thunderstorm recipe. Lift describes the upward motion into the atmosphere. This upward nudge happens because of air density.
There are several different ways to start this upward motion.
Uneven heating of surfaces during the day can create different air densities. This difference in densities is a common source for lift.
Lift can also occur thanks to surface features such as cold fronts, dry lines or outflow boundaries from previous storms.
The topography also encourages lift. Air rising over mountains can create thunderstorms.
