Scientists at the U.S. National Science Foundation National Center for Atmospheric Research (NSF NCAR) have begun running real-time 3-kilometer (1.9-mile) experimental weather forecasts for the entire globe. This achievement, a milestone for meteorology, can lead to significant advances in worldwide weather prediction.

The real-time forecasts are more fine-scale than other real-time global weather models and so detailed that they can capture individual thunderstorms around the world. Although still in the experimental phase, the research points the way toward better protecting society from extreme weather events.

“We’re demonstrating that it is possible to run a 3-kilometer global forecast in real time, which is a major step in advancing weather prediction capabilities,” said NSF NCAR scientist Craig Schwartz, who is leading the research. “This project really highlights the potential to provide more valuable information about severe weather to those in harm’s way around the world.”

To create the forecasts, Schwartz and his colleagues are using an advanced computer model, the NSF NCAR-based Model for Prediction Across Scales (MPAS). They’re running it on the Derecho supercomputer at the NSF NCAR-Wyoming Supercomputing Center in Cheyenne.

The research team produces a single forecast each day, which goes out 60 hours. The scientists will continue to run the forecasts until the end of this month. Their next step will be to  evaluate the accuracy of the 3-kilometer forecasts to see how they performed relative to other forecasts. 

As they test different approaches, the scientists are also using MPAS to run a real-time 8-member ensemble of 3-kilometer forecasts over much of North America. Those forecasts go out 5.5 days, or 132 hours.

Simulating points in the atmosphere

Weather models use a grid system to represent the atmosphere, applying the laws of physics to simulate temperature, humidity, and other properties at selected points. The closer the points are spaced together, the greater the potential for accurate forecasts — although other factors come into play as well, such as how the model assimilates data from observations to produce the initial representation of the atmosphere that serves as the basis for a forecast.

The NSF NCAR forecasts are so fine-scale that they consist of about 65.5 million horizontal 3-kilometer grid cells over Earth’s entire surface. At each cell, forecasts are made at 55 vertical layers ascending into the atmosphere.

The latest generation of weather models is extraordinarily effective for weather prediction, and forecasts have become increasingly accurate in recent decades. But Schwartz said that global 3-kilometer models offer the potential for improving forecast accuracy even more, especially in remote regions of the world, which is important both for oceanic flights and communities at risk of extreme rainfall and flooding.

“These types of detailed global forecasts can be critically important to multiple users,” Schwartz said. “We are at the threshold of making significant strides in prediction.”

The 3-kilometer forecasts may be viewed every day through the end of this month on a publicly available NSF NCAR webpage.

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