How weather forecasting computers work

March 22nd, 2013 at 9:14 am by under Weather

Weather forecasting methods have come a long way in the last 50 or 60 years.

In the past, meteorologists were required to spend hours putting together hand-drawn maps of weather conditions in order to accurately portray the current “weather picture” and be able to forecast the weather going into the future.

Nowadays, super computers can do a lot of the data compiling for us. And not only do these super computers help give meteorologists an accurate picture of what is happening with the weather NOW, but they also are a great help with forecasting the weather for the FUTURE.

If you’ve ever been curious about how these machines help meteorologists forecast the weather, check out the (relatively simple) explanation below from Scott Mackarow’s weather blog:

Thursday, March 7, 2013

Why is it so hard to give an accurate forecast?  The answer is really quite complex, so I’ll try to tackle one part of the broader scope of weather forecasting that I’m familiar with: numerical weather forecast modeling.

What is a numerical weather forecast model?

Meteorology is essentially the study of the physics of the atmosphere.  Using basic scientific concepts such as Newton’s Law of Motion and the Laws of Thermodynamics, the physics behind how the atmosphere works can be represented through a series of equations.  If you sprinkle in some fluid dynamics and mathematical methods such as time stepping, you can derive a set of equations that can tell you how the current state of the atmosphere will change into the future.

Read more on Scott Mackarow’s weather blog.

So what is the problem you ask?  Good question!  Let’s break down several factors of numerical weather forecast modeling that can lead to an inaccurate forecast.

I. Input data and assimilation
Your weather forecast is only as good as the data you put into it and how you actually get this information into the model.  As with many things in life, the phrase “you are what you eat” is as true as ever in weather modeling.  One of the statements I made above is that our equations “can tell you how the current state of the atmosphere will change in the future.”  The key word here is “current state”.  In order for our weather model equations to tell us anything useful about the future, we need to first have a good understanding of what the weather is doing right now.  To accomplish this, we need to gather as many atmospheric observations as possible.  In the U.S., we have one of the largest networks of observations available on the planet that can be used as input data to the forecast model.  This network includes (but is not limited to) measurements at the surface, from satellites, weather balloons , radar, aircraft, and even GPS measurements (used for moisture).  Many of these measurements are available globally as well.

Read the rest of the explanation on Scott Mackarow’s weather blog.

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