The reason not all forecasts sound the same


For most people, one of the biggest surprises about the weather is that not all forecasts come from the same source. A common comment on social media when we post our forecast is “the National Weather Service is predicting something different”, or “that’s not what The Weather Channel is saying”.

Here at FOX6 Weather we choose to do our own forecasting. It’s the more difficult track to take but it makes sense. If I am going to go on the air with a forecast, it might as well be mine. Plus I spent a lot of years in school learning how to do this, so why not use the knowledge? The upside: when the forecast is correct, I can rightfully take credit. The downside: when the forecast is a bust, I can rightfully get the blame.

Of course perception is everything, and since most people think all forecasts are the same, one wild forecast reflects badly on all the forecasters. It does happen often, especially when a large storm system is approaching our area with rain and snow. One forecast source (could be a newspaper, radio station, TV station) may call for a foot of snow while the remainder of the forecasts call for flurries or under 2″ of snow. The forecast with the one foot forecast is the one that people remember. (I talk about this in my previous blog “The Psychology of Snow Forecasting“.)

I don’t know for certain, but I assume the weather departments at the other TV stations prepare their own forecasts just like we do. This begs the question: why are the forecasts often very different? This speaks to the heart of atmospheric science.

The atmosphere is dynamic, always in flux. Much of forecasting is objective: just the facts, please! These are the hard numbers, e.g. the computer model output from the various numerical prediction models. Then there is the subjective part of weather forecasting. Every meteorologist may have their own opinion on how a weather system will evolve. This is based on their personal experience with past situations. Get 10 meteorologists in a room looking at the exact same data and you will end up with 10 slightly different forecasts.

Art and science combine in forecasting. The non-meteorologist often tells us we’re “just guessing”, especially when forecasts are updated as the storm approaches. But that is simply the nature of the atmosphere. It’s evolving. Our forecasts need to reflect that.

Unlike many other pursuits, where A + B = C in a simple and predictable relationship, in weather forecasting A + B = a whole bunch of possibilities.