Doyle Rice

USA TODAY

RESTON, Va. — In a nondescript office building here, one of the world’s most powerful weather supercomputers quietly hums on a 24/7 mission to analyze billions of pieces of data that ultimately will tell you whether you need a sweater or sunscreen when you leave the house.

Forecasts, critical not only for your wardrobe choices but for ship captains, airline pilots and shipping companies, depend on sophisticated data crunching and computer models, but three years ago European models delivered a blow to the U.S. weather apparatus. The European weather models accurately predicted the path and strength of the devastating Hurricane Sandy that hit the New Jersey coastline and caused $65 billion in damage.

Now, the U.S. is on the rebound with this monumental supercomputer that collects, processes and analyzes billions of observations from weather satellites, weather balloons, airplanes, buoys and surface stations from around the world to help meteorologists make better weather forecasts.

The brand-new Cray supercomputer — designed, owned and operated by the National Oceanic and Atmospheric Administration (NOAA) — processes 3 quadrillion calculations per second. If that sounds like a lot, it is — you'd need about 12,500 high-end laptops to get close to that kind of power. Still, the supercomputer is merely the 18th fastest in the U.S. and 42nd fastest in the world, Michaud said.

NOAA's purchase of the school-bus size device stemmed partly from competition from the top European weather model — better known in some circles by its acronym ECMWF (European Center for Medium-range Weather Forecasting). It predicted Sandy's now infamous and unusual left hook in 2012 days before the top American model — the GFS (Global Forecast System).

The one-two punch pushed the U.S. to invest $44.5 million to develop better forecasts. In a case of keeping up with the Joneses, the U.S. chose Seattle-based Cray to build its new supercomputer. The company is a leading maker of supercomputers worldwide and supplied the ones used by European weather agencies. NOAA installed the Reston computer and its backup twin in Orlando, a safe distance away in case of a natural disaster, late last year.

Together, they provide a 10-fold increase in computer power over previous systems and put American forecasting systems back on par or even above European ones, said University of Washington meteorologist Cliff Mass. "It's a huge improvement over what they had," he said.

Mass was highly critical of the federal government's lagging computing capacity in recent years and called it a "national embarrassment." One consideration he has is that the new computer resources should be used for critical tasks, such as high-resolution ensemble forecasts, and not wasted on legacy (older, underperforming) models, Mass said.

The tidal wave of data NOAA sifts through each day is equal to more than twice that contained in the entire printed collection of the Library of Congress, said David Michaud, director of the office of central processing at the National Weather Service, which is part of NOAA.

In this Washington, D.C., suburb, the supercomputer takes in current weather data around the world then uses models and mathematical equations to predict the forecast in the hours, days and weeks ahead. It displays its mission proudly: large photos of lightning bolts, a hurricane, a tornado, a snowstorm and other weather phenomena cover the computer's surface.

It's not all about the machines: Meteorologists refine and interpret the computer's predictions to make timely, accurate and reliable forecasts for specific cities and regions, from day-to-day weather to ferocious hurricanes, tornadoes, floods and blizzards.

The supercomputer, hidden behind a maze of unmarked doors, would work up a damaging sweat if it weren't for an extensive cooling and ventilation system and ice-cold water flowing through its internal pipes.

A combination of cool and dry prevents condensation. Water chilled to 45 degrees circulates throughout the massive computer. NOAA keeps the room's temperature dialed to 69-72 degrees with a relative humidity of 30-50%, said IBM's Travis McPhail, project manager at IBM Global Services.

In the months ahead, the supercomputer will focus on severe weather, storm surge and river forecasting, just in time for spring's flood season and summer's hurricane season. Its speed helps it process the enormous amount of data streaming into its lines so it can provide "more timely, accurate, and reliable forecasts," NOAA head Kathryn Sullivan said.

The supercomputer showed its prowess last month, predicting an East Coast blizzard with great accuracy days before the storm, said Louis Uccellini, director of the National Weather Service.

That's only a glimpse of what's to come.

"We expect to see better forecasts for hurricanes, severe weather, floods and other extreme events this year," Uccellini said.