July 25, 2013, 6:27 PM — The National Oceanic and Atmospheric Administration (NOAA) Thursday switched on two new supercomputers that are expected to improve weather forecasting.
The "go live" switch over to the new systems was made today without any fanfare, just a box of donuts on hand to mark 18 months of preparation and testing. The new IBM systems are now responsible for producing forecast data that's relied on in the U.S. and around the world.
The agency had planned to go live next Tuesday, but strong storms now in the Pacific and Atlantic Oceans prompted the decision to move the date up, said Ben Kyger, director of central operations at the National Centers for Environmental Prediction.
NOAA's National Weather Service (NWS) runs the two identical, or clone systems, one in Reston, Va., and in Orlando, Fla. They can switch over in about six minutes.
The supercomputers are each 213 teraflop systems, running a Linux operating system on Intel processors. The U.S. is paying about $20 million a year to operate the leased systems.
"These are the systems that are the origin of all the weather forecast you see," said Kyger. The computing system is called the Weather and Climate Operational Supercomputing System or WCOSS.
The two previously used four-year-old IBM supercomputers, also identical, run IBM's AIX operating system and Power 6 chips, and are each capable of 74 teraflops. The upgrade will continue to improve weather forecasting over time.
It's been a complicated process to get to this point. The NWS has had to ensure that the software running on the new system is producing scientifically correct results. It had been running the old and new systems in parallel for months, and comparing the output.
This comparative testing involved examining output data to determine whether it is numerically reproducible out to five decimal places. There is also a statistical analysis of weather predictions on the new system against the actual weather conditions.
The process wasn't just an examination of numerical data. NWS scientists also studied the weather products and examined them for subtle differences. "There is a lot of human, highly experienced, subjective evaluation," said Kyger.
There are computational differences involved in switching to new chips and a new operating system. They are subtle, and appear in decimal places six through 12.
As you go further out in a forecast, the differences compound.
The changes may appear in the fifth day of an extended, five-day forecast as a difference of one degree.