Since it’s been raining so frequently lately, I’ve gotten in the habit of checking my morning forecast. Everyday, the local weatherman enthusiastically displays at least 5 screens worth of graphics telling me everything from air quality to who the latest “color the weather” winner is.
Normally, I’d say the weather forecast dosen’t affect me too much. If it rains, it rains. If not, no problem. I’ve always accepted weather patterns as facts of life and, unlike the news broadcasters, I’m never really upset to find out that there is a 50% chance of rain for that day.
Sure, I like to know if there is a deadly category five hurricane heading my way, or terrible flooding, or a lightning storm, hail shower, apocalyptic comet impact, ect… but since those don’t happen often (and if they did there would be no way for me to avoid hearing about them) I never paid much attention to the weather until now.
Recently, maybe because I’m working under a professional climatologist, I have felt the need to be on top of what the atmosphere will be up to on any given day.
So like I said earlier, I’ve been watching the weather. There is one thing, however, that I just don’t get about weather prediction: Rain percentages.
Nothing gets my morning off to a more confused start than hearing that there is a 50% chance of rain today.
Upon hearing this I automatically think, “Hmmm…there is an equal chance of it not raining or raining today. It could rain or it couldn’t. It’s absolutely split down the middle.” Then I think, “No, 50% is a much larger percentage than say 10%, so there is a greater chance of rain today than if there was only a 10% chance.” But, since no two days are alike, and the forecast does not allow for a basis of comparison, I just stare at the middle-aged tweed-suited man who is now pointing to moving green blobs over New York.
Not to be befuddled so easily, I head on over to the national weather service, which gives this explanation of rain percentage calculation:
“the likelihood of occurrence (expressed as a percent) of a precipitation event at any given point in the forecast area”
Of course, now it all makes sense! That clears up everything!
So if there is a 30% chance of rain in Baton Rouge that means that there is a 30% chance of at least 0.01 inches of precipitation will fall somewhere in Baton Rouge.
30%? What does that really mean? That it could, sort of, maybe rain but probably not? What about the 50% problem? Isn’t that more like a “We don’t know if it will rain or not today” forecast.
So I decided to break it down even further:
1) I know what a percentage is. If I have 100 apples and I take away 70, 30 percent of my original one hundred apples are left.
2) Now for the hard part, that word chance. Time for the dictionary: (well actually probability is a better word:) “The likelihood that a given event will occur.”
okay.
So, I concluded that, rather than say, “It might rain today”, weathermen like to give concrete numbers like 10, 30, or 80. This way, people can rejoice or complain and give actual factual data to back up there thoughts. Plus, we’d all be dissapointed if someone went to college for years in order to tell the world what any 5 year old can say after looking at the sky for 5 seconds, “it might rain today.”
For me, I figure that anything under 30 means, “It’s not going to rain today, probably.” 0 would mean absolutely no rain.
50 still remains a mystery to me.
51 and above means, “It’s going to rain today, probably” with the chances increasing with the percentages.
anyway, i’m glad I stuck with coloring the weather. i’ll leave the prediction up to the professionals.
Well, your post was rather….enlightening? Not exactly conclusive, but who said it had to be. The point is to get your thoughts out to the curious world right? Anywho, I liked it anyhow so you can ignore this anyway.