Here are some insider tips.
The POP forecast or ‘precipitation probability’ is issued to cover all or a large portion of an entire metropolitan area and is valid for any point or spot in that area, typically for a 6, 12 or 24 hour period.
Please never confuse a weather forecast with a weather observation, many do this and therefore mistakenly think that when it rains there is a 100% chance of rain. But raining now is not a prediction, it is an observation.
Otherwise, if this was the case, just before it started raining and you were dry, the chance of rain was 0%. You can see how this doesn’t work logically as a matter of common sense.
Let’s say the forecast calls for a 20 percent chance of a shower in the northern half of the Atlanta area. Eventually I shower at my house in Cobb, but the rest of Cobb County is dry and stays dry all day. If I got a shower it would be silly to say oh the chance of rain is 100% now because I’m taking a shower because the whole rest of Cobb County would be like at the same time oh the chance of rain today is 0% because I’m dry now . SMH. As Spock would say to Kirk on the Enterprise, “Most illogical captain.”
So let’s look at real world examples and apply them to a WEB site or smartphone weather APP.
Another example with actual radar footage…
The prediction was good, it’s not wrong just because you got wet means you were the unlucky 20% (unless you wanted rain for your lawn, then you were the lucky 20%). This is the real world.
Many of us learn about probability in elementary or high school. Some never do, but I hope this helps either way.
In previous blogs I pointed out (pinned tweet) that most APPS use only one model out of hundreds and it’s not even the best.
HERE IS ANOTHER PROBLEM WITH MANY WEATHER APPS:
Here are some screenshots of two popular APPS from big brands Yesterday, Thursday, September 22, between 15:45 and 17:00 …
In the first case when I look at the 5-10 day it shows a sunny day and no chance of rain:
However, at the same time the same app when i check it is hourly… instead of zero chance i get 60%! What if I only checked the first forecast tab? Oops! At the same time, the app “predicts” 0-60, depending on which tab you open.
And another popular app at the same time and place (Kennesaw)… either 79% or maybe just 15%. Depending on which tab you’re checking:
Shows the shortcomings of automation and computer coding. Checking under the hood of the same two apps shows that conflicting outputs from the algorithm can mislead you. There is no meteorologist involved in most of the apps.
For more frequent weather commentary, contact me on Twitter @MellishMeterWSB.
©2022 Cox Media Group