6:33 PM ET, August 7, 2023
How a sunny morning helped fuel today's dangerous storms
From CNN meteorologist Mary Gilbert
The threat of severe weather Monday across the eastern United States is huge — but for many, the day started with clear or mostly sunny skies. If it's bright and sunny in the morning, how can there be severe thunderstorms later?
Thunderstorms need three things to be vibrant: moisture, lift, and instability. Heating from sunlight fuels two of these factors.
On days when there is not a cloud in the sky, the sun heats the ground quickly and efficiently, giving the air at the surface a great deal of instability and thus forcing it to rise. Rising air of this type will rise rapidly until it reaches the saturation point — the point at which the air cools enough to form rain — after which a storm is born.
These are lift, which is anything that forces the air up, and instability, which is a measure of how much air is able to move upward when it is pushed by lift during work.
There was significant instability in locations such as Washington, D.C., after early morning clouds largely dissipated and allowed much sunlight to reach the surface, leaving the atmosphere ripe for dangerous storms.
Once a storm forms, under the right conditions it can strengthen and become severe. Severe thunderstorms are then capable of unleashing damaging wind gusts, hail, and even tornadoes.
Given enough instability, height, and moisture, thunderstorms can quickly turn a morning that looks great outside into a dangerous daytime endeavor.
