Following up on a recent topic here: I was writing about long-range weather forecasts and how they're often worthless. There are times when the meteorologists can predict ten days out and times when they can't…but for various marketing reasons, they're always expected to formulate a ten-day projection. If you want to understand weather forecasts, you have to grasp this concept. Sometimes, they're very certain and sometimes, the various computer models are in conflict and there are too many X factors out there.
Case in point. A few days ago, the National Weather Service was predicting a 60% chance of a moderate storm in Los Angeles on 2/25 and the AccuWeather folks (a commercial firm) were predicting an 85% chance of a biggie. That was ten days in the future…and the truth was that no one at either organization felt too confident about that but, you know, they had to say something and that's what the computer models were saying. This morning, both have dropped all chance of precipitation for that date. Neither even predicts any clouds then.
The next chance of rain in Los Angeles just entered the forecast and it wasn't there yesterday. Overnight, many elements came together and now both the N.W.S. and AccuWeather are fairly certain we have a slight chance of showers starting late Saturday night and continuing into Monday morning…so it could be raining — lightly — when the stars come and go for the Academy Awards. If you decide to stake out a position outside to see them, you may be at least drizzled upon.
It's a 20% chance so it really can't be wrong. If you say 20%, you're right if it does rain and right if it doesn't. But I'll bet they're correct that there will be ominous clouds about…and it'll rain somewhere in the forecast area. Often when they say 30% or 40%, it doesn't rain where I am but I speak on the phone to some friend ten miles from me and it's pouring there. And then people who live where it doesn't rain think the forecast was wrong.
A TV weatherguy I used to know once said to me, "The hard part of doing this is that people only read the headline or only listen to the part of the weathercast where I say what the chance of rain is in all of Southern California and then they presume that chance applies to wherever they are. Sometimes, we don't know very far in advance and sometimes we do, but either way, you have to read or listen to the whole forecast to get an idea what we're saying. And of course, every so often, we completely blow it."