(WFRV) – It’s a TikTok that has been viewed nearly 10 million times. The TikToker claims that 30% of rain means that meteorologists are for sure saying it will rain, for just 30% of the area. How accurate is this?
Her claim is incorrect. The probability of precipitation is simply the chance of measurable precipitation (0.01″) at a given location over a specified time period.
If you are given a 30% chance of rain for tomorrow at your location, it does not mean 30% of the day it will be raining. It does not mean 30% coverage area will see rain.
What it DOES mean is that out of 10 days that match the forecast day of interest, there was measurable precipitation for 3 of those days. This is calculated through model output statistics.
For example, go into Storm Team 5 App, and click on hour by hour forecast if you are
looking for the chance of precipitation at a specific time, you will see the percentage listed.
This is giving you chance of measurable precipitation during this hour at your specific location. This is a model calculation.
Since probability of precipitation is location specific metric, Storm Team 5 uses simple words the viewer will understand a bit more when describing the likelihood of getting precipitation.
Stray / Hit or Miss / Isolated – Smart to keep an eye on the sky, but most in Northeast Wisconsin will stay dry
Scattered – we are expecting precipitation in the viewing area, but it’s not guaranteed to cover the entire viewing area.
Widespread / Likely – chances are high you will see precipitation at some point during the forecast period
On our 7 day forecast, we usually list these words under the weather icons, while the temperatures are the forecast for just Green Bay.
In short, trust your local meteorologists, and not viral TikToks.
