NOAA supercomputers to forecast better weather?

The National Oceanic and Atmospheric Administration announced this week that it has finally completed a nine-year, $180 million project aimed at installing new supercomputers to aid in more accurately predicting weather. The primary IBM supercomputer is now called Stratus. Its backup is dubbed Cirrus.

The new supercomputers, based on IBM Power 575 Systems, are capable of making 69.7 trillion calculations per second. According to NOAA, the faster the calculation speeds, the greater the chances that meteorologists can rapidly update severe weather forecasts as dangerous weather affects local communities. Billions of bytes are entered into the supercomputers each day to help predict the weather more accurately.

Just how important NOAA's new supercomputers are to our understanding and prediction of weather is easily understated.

Right now, Stratus contains about 20 weather models that predict worldwide weather accurately for about five days. A few decades ago, weather models could forecast weather accurately up to only about two days.

Those 20 weather models rarely change. They analyze conditions such as temperature, humidity, and precipitation to give organizations ranging from the National Weather Service to local meteorologists data on which they can base forecasts.

According to Ben Kyger, director of central operations for the National Center of Environmental Prediction, a division of NOAA, "We analyze weather conditions on grids we lay over maps of the world. In order for meteorologists to accurately predict a hurricane's path, for example, NOAA needs to pinpoint weather conditions in 1-kilometer grids of distance." Right now, those spans "are not even close to that."

How does it work?
In order to improve forecasting, a lot of work needs to be done. Right now, scientists from around the world are analyzing Stratus' weather models to find ways to improve them. When they think that they've come up with an improvement, NOAA analyzes the new models.

If it likes what it sees, NOAA takes it open source. It installs the new model on the Cirrus supercomputer to run in parallel with the approved model on Stratus. Scientists, weather experts, and even you and I can view the new model and inspect it for errors. Errors found are removed or tweaked. If no errors can be found, and the new data enhances weather forecasting, it will be put into operation and replace the existing model that it improved upon.

In previous generations of weather forecasting, "most meteorologists looked at a single model and based an entire forecast off that," Kyger explained. "Today, with the help of Stratus and Cirrus, those same meteorologists can look at all 20 models, set them in motion, and see how long they all predict the same weather." This new technique is called Ensembling.

When the models are the same, the forecast is a practical guarantee. But when they start diverging (usually at around five days, according to Kyger), weather becomes more difficult to predict. There is far less certainty. Rain or snow forecasts are even more difficult, which is why sites like Accuweather.com or Weather.com feature percentage changes of precipitation. NOAA believes that thanks to the power and capacity of the new supercomputers, those forecasts will become more accurate over time.

Perhaps the most interesting tidbit about NOAA's new supercomputers is how they can change how we derive weather information from the Web. Kyger said weather forecasting and accuracy is an "evolutionary" process, so it might be difficult for Web surfers to see changes in how Web sites predict weather. But as Kyger pointed out, those changes will definitely be put into effect. And even if we don't notice them, the weather forecasts of sites such as Accuweather and WeatherBug are set to become more accurate.

Unfortunately, though, when it comes to weather predictions, real accuracy is a long way off. So be sure to take all those forecasts with a healthy helping of salt.