(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.
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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.
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In short, trust your local meteorologists, and not viral TikToks.