You've probably heard us say these words during one of our weathercasts a thousand times: There's a chance this afternoon for "Isolated" or "Scattered" thunderstorms. And while they may sound to the ear like their interchangeable, they do in fact have a different definition in the world of Meteorology. And in large part this breakdown is guided by terminology from the National Weather Service.
It's really pretty simple.
Isolated Thunderstorms means: 10% to 20% in areal coverage. Here's a hypothetical example. Say Mecklenburg County makes up 100% of the areal coverage. Isolated Storms would mean that only 10% to 20% of the county would see thunderstorms. This means that 80% to 90% of the ground would stay dry.
Scattered Thunderstorms means: 30% to 50% in areal coverage. So, scattered means there are more thunderstorms across the area than in an isolated thunderstorm scenario. And that still means there's a 50% to 70% chance that most places would not see measurable rainfall.
In forecast scenarios where we call for a better than 60% chance for showers and thunderstorms, we'll use terms like "numerous" and "widespread" or "likely."
So there you have it, if you've ever wondered about the phraseology we use in forecasting for showers and thunderstorms.
One other thing to keep in mind, these terms do not have anything to do with the strength or possible severity of the thunderstorms that do form.
Is there more than one kind of rain? We'll leave that for another discussion.