Let's face it, when it comes to making plans in the future, a lot of them depend on the weather conditions. As meteorologists, we get asked to give forecasts or predictions for dates well into the future. Things such as, "I have a wedding in May, will it storm that day?" or "When will the first big snow storm of the season hit?" How about this, "How many tornadoes will there be this weekend?"
Without a doubt, it can be frustrating to get an answer of "I don't know", or "check back again tomorrow". Meteorologists are supposed to know these things, right? So why are they seemingly hiding this information? Why won't they just come out and say what the weather will be like?
Well, the honest truth is, we may not know at times. That does not, however, mean we are worthless or uneducated nor does it mean we won't know at some point in the near future.
Be it TV meteorologists or meteorologists that work for the National Weather Service, nobody is trying to hide or hold back information from those seeking it. So why don't we know "for sure" what the weather is going to be like six months from now or when that first major snow storm of the season will get here? Keep in mind we are predicting the future on a giant rock that is hurling through space at hundreds of miles and hour all while spinning on an axis. You have to allow for a little bit of wiggle room!
Think about this: You have a young child. Do you know (for sure) what that child is going to be when it grows up? A lawyer, a doctor, the next president of the United States? No; not for sure. Do you have expectations and/or hopes? Of course. As time goes on and you watch your child grow, you are able to get an understanding of what path they may take in life. Perhaps you start to see a pattern or a trend. At this point, your confidence would increase on where that child is headed and you'll feel more inclined to brag or boast.
That same analogy can be used for weather forecasting. We look at forecast models and those models -- which are computer simulations based off of complex mathematics -- give us an idea of what may happen in the atmosphere. The problem is, those models 1) only go out so far, 2) are only reliable to a certain extent, 3) they can change dramatically from run-to-run (each new version).
Research proves that forecasts are getting better by the year. Our skill and accuracy on a three-day forecast has improved greatly from where it was just a decade ago. Part of this can be attributed to better technology; faster computers and better sources of data. However, going beyond just five days, the forecast (on average) suffers. The variable swings become larger, the mathematics behind the process become more complex.
However, there are meteorologists--like our own Chief Meteorologist Gary Lezak--that have been studying the atmosphere and believe there is a new, overall pattern that develops each year. Once the pattern is discovered, forecasts can be derived and reliable outlooks can be issued. And while it's possible to pinpoint a small window of when a storm may happen, it is still very difficult to determine the magnitude (such as how much snow will fall) down to exact details. For example, we could say there is a chance for thunderstorms between May 10th and 14th and highs will be in the upper 70s to lower 80s. We will NOT be able to give you exact wind speeds, or cloud cover, or exact temperature at a given time.
Another way to think of weather forecasting is looking at a river. Let's say we put a plastic boat the size of a loaf of bread into a starting point of a river. From there, we would need to forecast where down the river that boat will be in two days, in four days, and in five days. Not only that, but we'd need to know which direction the boat is facing and if the boat took on any water.
This might be easy to do for the two-day forecast. You could measure the speed of the water and make calculations. But what about other objects in the river? What about minor falls or rises in the river's elevation? All of those variable can throw off your forecast of this boat, especially when it comes to that forecaster farther into the future.
The atmosphere truly is no different. Basically, we have rivers of air (and moisture) moving along above our heads. The storm systems act as our boat and they travel along these rivers. Sometimes they stick to a projected path. Other times one small variable or one minor "block in the road" throws the whole thing off.
As a meteorologist, our job is to study the daily forecast models and give a forecast, which is a prediction of the future, based on the data we see at that time. Forecasts can and do change based on new information. And there are times when confidence is too low or the predictability is too low to say what will happen. Thus, the only answer we may have at the time is: we don't know. However, with new information or discovering a pattern, we may be able to crack the code of the atmosphere and provide a forecast.
So when you're wondering why the weather person won't just tell you when it's going to snow or what the weather will be like at exactly 5:30pm in three months, just know it's not because they are hiding something or trying to lead you on. There simply is not enough good information to make an accurate and trustworthy forecast at that time. Now, could someone still make a general, broad forecast? Yes, but it has a higher chance of being wrong, especially if it occurs during severe weather season. Or you may not get the answer you are hoping for. And then we're back to yelling at the meteorologist because they are wrong all the time... Be sure to see my discussion on that topic; read it here.
I'd be happy to answer questions you may have, and I'll keep the "I don't know" answers to a minimum, I promise. Feel free to email me jd.rudd[at]kshb.com, or you can talk to me on Twitter (@jdrudd) and Facebook.