Forecasting utilizes techniques

I’ve heard many times, that the job of weather person is the only profession where you can be wrong half the time and still get paid. All joking aside however, forecasting the weather is a very challenging and complex process, especially in mountainous areas where elevation changes can mean many kinds of weather in a relatively small area. In the winter, a difference of 1 or 2 degrees can mean the difference between snow, ice or just plain old rain. On a hot, humid day in the Midwest, a brief break in the clouds can lead to just the warm-up necessary to trigger severe thunderstorms where none might have occurred otherwise.

Forecasting the weather is an art as well as a science. All the computer technology in the world cannot make up for knowledge of the nuances of local climates. In this way, a longtime resident can sometimes have the “upper hand” on an outsider trying to make a forecast. Here are some of the techniques meteorologists use to come up with their most visible product, the forecast.

Persistence: Persistence forecasting is a technique that assumes the next day’s weather will be similar to today’s. In a region such as this, which often sees long stretches of hot and dry weather during the summer, persistence forecasting can be a good first guess at what the next 24 hours will be like.

Pattern recognition: This is a technique that is used by forecasters with many years of experience. Though no two weather scenarios are ever exactly alike, experienced forecasters will recognize patterns in the position of high and low pressure, or signatures in the satellite and/or radar loops that lead to a particular weather outcome. Some weather patterns are even given names, like the cool season “Pineapple Express.” It is easy to spot this tropical fetch on a satellite image. One look at that setup and a meteorologist can pretty much guarantee mild and wet conditions across our area.

Climatology: This technique is most useful when folks are asking for longer range forecasts beyond seven days. A long-range forecast usually trends toward climatology. In other words, the forecast would be similar to whatever the average conditions for that time of year are expected to be. I could give a forecast for Aug. 11 and say that highs will be in the mid-80s and lows will be in the mid-50s. The chance for precipitation would be 10 percent or less. I could be reasonably confident in that forecast because the average high for that day is 87 degrees and the average low is 55. August is also normally a very dry month, which means that rain chances on any given day are quite low.

Computer models: This is really the bread and butter of the modern weather forecaster. Twice a day, 365 days a year, weather balloons are launched at over 900 sites worldwide (93 stations in the U.S.). The instruments take various measurements from the surface of the earth to the upper levels of the atmosphere. This data is then fed to numerous computer programs that use complex scientific calculations to estimate the “state of the atmosphere” at any given point at various time frames in the future. There are several different computer models that cover various parts of the globe. Sometimes the models agree, sometimes they contradict one another. It is the meteorologists job to look at the computer model output and decide which one makes the most sense.

In the end, despite all the techniques in our forecast arsenal, weather prediction is still an inexact science and we’re going to get it wrong sometimes. Hopefully though, we learn from our mistakes. And as technology improves, so will the accuracy of the local weather forecast.