‘Doppler’ Dave Speelman: Why The Different Weather Forecasts?

By Doppler Dave Speelman, ABC 7 Chief Meteorologist.

I got a question from a dedicated viewer to KVIA the other day that I though was very interesting. The questions is this: “Why do forecasts differ from one meteorologist to another?” This particular viewer was referring more specifically to all of the local television weather forecasts. This was not the first time I heard this and talking to my other meteorologist friends in the media, this question surfaces from time to time.

Putting together a weather forecast can be fairly quick (about one hour) or a bit more time consuming (several hours or more). It all depends on how much time you spend analyzing weather data, your experience forecasting in the particular town or city and your knowledge of what you are looking at.

For instance, The National Weather Service puts out two daily forecasts for the entire area. These forecasts give the high and low, precipitation probabilities, wind speeds and explain what kind of weather is expected over the next several days. All meteorologists can look at this data and use it completely, partially or not at all. That is why I say putting together a forecast can be fairly quick – we can just basically cut and paste.

Another way to forecast is to actually analyze many of the weather computer models (nearly a dozen) that we receive on a daily basis. These models get updated throughout the day – some more often than others. These various models can take time to look at and analyze. At times, one model may predict a cold air mass coming while another one predicts it will stay warm. One model may predict snow, another rain. These weather computer models can also change from one model run to another. For instance, one day a particular model can show a cold front coming in tomorrow night. This same model the following morning may show the cold front pulling up short of our area and not even being a factor in our temperatures. So, it all depends on what model a meteorologist looks at and how much credibility he gives to the particular model.

Knowledge of the region and education is important as well. Having a grasp on how storms move through this area and how the mountains and elevation play a part in our weather is critical. Experience (time spent living in this area) forecasting in a particular part of the country is also a big plus.

So, much of a forecast depends on how much time is spent preparing and analyzing and what the particular meteorologist thinks will evolve in the atmosphere. Weather is not an exact science and we all miss the forecast from time to time, but at least you have an idea of how we go about it. It’s your call as to who is more accurate, although I like to think we are.