how is chance of precipitation calculated ?

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https://www.thoughtco.com/chance-of-rain-3444366

https://www.thoughtco.com/chance-of-rain-3444366
Chance of Rain: Making Sense of Precipitation Forecasts – ThoughtCo
Chance of rain = Confidence x Areal coverage Where confidence and areal coverage are both percentages in decimal form (that is 60% = 0.6). In the U.S. and Canada, the chance of precipitation values is always rounded to increments of 10%. The UK’s Met Office rounds theirs to 5%.

https://www.snopes.com/news/2023/08/08/precipitation-probability-explained

https://www.snopes.com/news/2023/08/08/precipitation-probability-explained
What Do ‘Chance of Rain’ Percentages Mean in Weather Forecasts?
8 août 2023[…] the likelihood of occurrence (expressed as a percent) of a measurable amount of liquid precipitation (or the water equivalent of frozen precipitation) during a specified period of time at…

https://sciencenotes.org / percent-chance-rain-mean

https://sciencenotes.org / percent-chance-rain-mean
What Does Percent Chance of Rain Mean? – Science Notes and Projects
PoP = C x A PoP = 0.75 x 0.80 PoP = 0.60 or 60% chance of precipitation. Both of these examples give the same value for the chance of precipitation but have different meanings. The first example shows that 60% of the area definitely will see some measurable rain while 40% will not.

https://www.discovery.com/science/chance-of-rain

https://www.discovery.com/science/chance-of-rain
Here’s What a Chance of Rain Really Means – Discovery
In reality, the chance of rain, or probability of precipitation (POP), is based on a mathematical formula that takes the forecaster’s confidence into account. That formula is as follows: POP = Coverage x Confidence

https://en.wikipedia.org/wiki/Probability_of_precipitation

https://en.wikipedia.org/wiki/Probability_of_precipitation
Probability of precipitation – Wikipedia
Environment Canada reports a chance of precipitation (COP) that is defined as The chance that measurable precipitation (0.2 mm of rain or 0.2 cm of snow) will fall on any random point of the forecast region during the forecast period. [6] The values are rounded to 10% increments, but are never rounded to 50%. [7] UK Met Office

https://www.weatherstationadvisor.com/what-does-the-percentage-of-rain-mean

https://www.weatherstationadvisor.com/what-does-the-percentage-of-rain-mean
What Does the Percentage of Rain Mean on a Weather App?
18 août 2022Meteorologists calculate the Probability of Precipitation (PoP) using a simple formula: PoP = C x A. Where C stands for the confidence a forecaster has that rain will occur somewhere in the forecast area, and A stands for the percentage of the area where they expect a measurable amount of rain to occur.

https://www.weather.gov/ffc/pop

https://www.weather.gov/ffc/pop
FAQ – What is the Meaning of PoP – National Weather Service
Forecasts Rivers and Lakes Climate and Past Weather Local Programs Explaining Probability of Precipitation Forecasts issued by the National Weather Service routinely include a PoP (probability of precipitation) statement, which is often expressed as the chance of rain or chance of precipitation. EXAMPLE

https://www.almanac.com/chance-rain-what-does-really-mean

https://www.almanac.com/chance-rain-what-does-really-mean
A Chance of Rain: What Does This Really Mean? | Almanac.com
4 déc. 2023So, you grab your calculator and punch in 0.6 x 0.6 x 0.6, which equals 0.216. Bingo: those are the odds that it will not rain during the entire three periods in question. It is 21.6%. Finally, you subtract this from one to get the chance that it will rain: 78.4%. Roughly speaking, there’s an 80% it will rain.

https://www.weather.gov/media/pah/WeatherEducation/pop.pdf

https://www.weather.gov/media/pah/WeatherEducation/pop.pdf
PDF PRECIPITATION PROBABILITY The likelihood of occurrence of precipitation …
….. The measurement is of liquid precipitation or the water equivalent of frozen precipitation ….. The probability is for a specified time period (i.e., today, this afternoon, tonight, Thursday) ….. The probability forecast is for any given point in the forecast area

https://windy.app/blog/how-do-we-measure-precipitation.html

https://windy.app/blog/how-do-we-measure-precipitation.html
How do we measure precipitation and what does a chance of rain, say 30% …
As a general rule in meteorology and weather forecasting, 1 mm (0.03 in) of precipitation equals one liter (0.21 gallons) of water per 1 square meter (10.7 sq foot) of area. The amount of precipitation is measured over a certain period of time, for example, per hour, day, a few days, a week or a month, or a year. lesoutrali bot