When you see on the screen that there is a 10 or 50 percent chance of rain, it doesn't really mean that.
The probability for calculating precipitation actually describes what the chances of rain are at any given time over a certain area, it says Nova.rs
Namely, 10 percent or 50 percent does not mean that there are so many chances of rain, but 10 percent of a certain territory will get rain. In other words, when someone says there's such and such a chance of rain tomorrow - when there's a 50 percent chance of precipitation, that doesn't mean there's a one in two percent chance you'll get wet.
The mainstream understanding of the weather is due to the public believing that when meteorologists say there is an 80 percent chance of rain, they have an 80 percent chance of rain. So when it doesn't happen, viewers blame the meteorologists.
What many do not know, and the important missing factor in understanding the probability of precipitation, is the area.
According to the National Weather Service (NWS) in Houston, the Probability of Precipitation (PoP) actually describes the chance of rain at any given time over a certain area, writes gizmodo.com.
The mathematical formula says – Probability of Precipitation (PoP)= CxA, where C is the belief that precipitation will occur somewhere in the forecast area, and A is the portion of the area that will receive measurable amounts of precipitation, if it occurs at all.
Here's an explanation - using various models and data, a meteorologist will consider the chances of rain occurring somewhere in the forecast area and determine how much of that area has a chance of rain. For the National Weather Service (NWS), this can mean a large area. For example, if meteorologists are 100 percent sure that it will rain in the lower third of the area and 100 percent sure that it will not rain in the upper third, then the chance of rain in the entire area will be 30 percent.
This rarely happens, but in most cases, the forecaster combines degree of probability and area coverage. If the forecaster is only 50 percent sure that precipitation will occur and expects it, and it does not occur, and rain is expected in 80 percent of the area, the probability of precipitation is 40 percent.
The weather forecasters are not lying to you when they say every day that there is a 50 percent chance of rain and it doesn't fall - this means that it may not rain in your area, but in another area, which is not in your visual range, it rains every day.
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