A Western woman confessed that she grew up knowing that the probability of rainfall was different from what she used to think. This is a scene of rain on a street in Taipei.
A video of “rainfall probability” has recently gone viral on the Internet. A Western adult woman confessed that it took her a long Time to realize that the common knowledge of rainfall probability in weather forecasts was different from her Perception. In response, a meteorologist responded.
The video shows a woman saying to the camera that she thought the weather forecast of a 30% chance of rain in a certain area meant that there was a 30% chance of rain, but later learned that it meant there was a 100% chance of rain, but only in the 30% area.
A foreign user left a comment correcting her saying, “No, girl. That means there is a 30% chance of rain. My dad used to be a meteorologist with almost 30 years of experience.”
But another user then retorted, “I’m a working meteorologist and she (the woman in the film) is right, your dad seems to be wrong. We are predicting what percentage of people will see rainfall.”
Again, meteorologists, why would the claims be different? In response to this question, Taiwanese meteorologist Peng Qiming offered an explanation on Facebook.
Peng Qiming pointed out that there are actually two international definitions of rainfall probability: the first is “how many percent of an area will rain” (as described by the woman in the film), and the second is “how many percent of a particular location will have a chance of rain.”
He said that as weather technology and forecasting techniques continue to improve, forecasts can now be made on a “point by point” basis, so most weather bureaus and agencies around the world are now using the second definition of rainfall probability. However, there are still very special places or applications that use the first definition, but they are really rare.
According to the definition of Taiwan‘s Central Weather Bureau, precipitation probability is the predicted percentage of precipitation chance in a certain area and within a certain period of time, and the precipitation probability forecast refers to the chance of precipitation of 0.1 mm or more in 3 periods (1 period every 12 hours) in the next 36 hours in each forecast area, independent of the time and area of precipitation.
For example, if the Weather Bureau forecasts a 70% chance of precipitation in Taipei, it means that Taipei has a 70% chance of rainfall.
The US Weather Bureau’s definition of rainfall probability also uses the second one mentioned above. You can see the Bureau’s description by clicking here.
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