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Forecasting



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I understand how you can tell if there is going to be a storm or not by using satellites and Almanacs, but how do you forecast what the temperature will be?

Ashley W.

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A good question indeed and let's straighten you out as well. We use various weather instruments to help us predict the weather, satellites included. An Almanac is an average of past years' weather and while that does give us climatological information it doesn't necessarily help us forecast the weather at all or the temperatures for a day. If we're having an arctic outbreak for the week then the climate data from the past is fairly useless.

We forecast the weather using various tools from weather balloons to doppler radars to other things like upper air charts. Forecasting temperatures is tricky, it's based on a lot of different factors in a day. How much sun we have to how much rain just fell, all of those go into it. To help us along we have the use of numerical weather prediction models or NWP's. These are big super computers that take the atmosphere and make a model of it going into the future. There are several of these models, not all of them do well in Utah and it's up to the forecaster to be skilled enough to use the model accurately.

These models help us predict anything from temperature to spin in the atmosphere way above our heads! They are actually really cool. If you click the link on the right you can see what a model looks like, they have all sorts of nifty colors. But besides the colors, they give us valuable information. The models are based on EQUATIONS of the atmosphere and how it behaves.

Besides the graphical models which you saw in the link (the graphical weather map) there is also text output. The second link will take you there. This is what the model is telling us it thinks the temperature will be. Now, all of these are used as GUIDANCE and are not exactly what will happen. It is up to us to use our meteorological backgrounds to fine tune these forecasts and also take into account local effects. Local effects being fresh snow on the ground and a clear night ahead or something like canyon winds or lake breezes. Models also help us to predict effects like rain and snow which will then influence the forecast temperatures.

Using persistence (what it was today for example) also helps us get a feel of what will happen tomorrow if the air mass is roughly the same. The models help us to predict the weather and we also use current observations too like what the weather is like up the road in say, Washington state or even in Idaho. We track cold fronts and see what kind of temperature and other changes they bring.

Hopefully this will help you understand a little better on how we do are jobs, there's a lot to it for sure.

Answered by KSL Meteorologist Dina Freedman.

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