NOAA 2002-067
Contact: Patricia Viets
NOAA News Releases 2002
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Predicting the nation's weather just got a boost because of a new weather computer model that has just become operational, according to the Commerce Department's National Oceanic and Atmospheric Administration (NOAA). The model improves the accuracy and timeliness of short-range weather forecasts, particularly for the aviation community and for the general public.

The Rapid Update Cycle (RUC20) model was developed at NOAA's Forecast Systems Laboratory (FSL) in Boulder, Colo., and funded by NOAA and the Federal Aviation Administration (FAA) Aviation Weather Research Program. Called the RUC20 because of its 20-km resolution, it improves forecasts widely used for aviation, severe-weather forecasting, and general weather forecasting.

"The Storm Prediction Center uses the RUC model extensively in its severe weather forecast operations," said Joe Schaefer, director of NOAA's Storm Prediction Center in Norman, Okla. "Operational computer model advances like this made possible by the advanced capabilities of the new National Weather Service supercomputer promise to advance our skill in forecasting tornadoes and other forms of hazardous weather to protect the American public."

The model was implemented on April 17 at the National Centers for Environmental Prediction (NCEP) in Camp Springs, Md., part of NOAA's National Weather Service (NWS). Using the latest observations from commercial aircraft, wind profilers, satellites, radars, weather balloons, and surface stations, the RUC20 produces new analyses and short-range forecasts on an hourly basis, with forecasts out to 12 hours every three hours, the highest-frequency updating of any forecast model at NCEP.

"The RUC20 takes another step forward toward representing the complexity of real weather and provides considerable improvement for short-range forecast users," said Stan Benjamin, manager of the RUC project at FSL.

The model covers the continental United States and is run on a 20 km grid. The RUC20 is an improved version of an earlier model. Featuring increased horizontal resolution (from 40 km to 20 km) and more vertical levels (from 40 to 50), the RUC20 improves the overall accuracy of weather data being fed into aviation-weather and other weather applications. The major improvements of the RUC20 over its predecessor are better cloud and precipitation forecasts, and better wind and temperature forecasts near the surface. The RUC20 also provides improved forecasts of icing and turbulence conditions hazardous for aviation.

"Improved numerical forecast models are extremely important to the prediction of potentially hazardous weather conditions for aviation operations," said Greg Burke, chief of the FAA's Office of Air Traffic Systems Development. "The increased resolution of the RUC20 model will help identify weather phenomena that were previously not well defined."

The smaller grid spacing used by the RUC20 provides better resolution of variations in land elevation, land-water boundaries, and other land-surface features. This detail leads to improved forecasts of regional and local precipitation and surface wind phenomena. The RUC20 incorprates satellite cloud data to improve its cloud, icing and precipitation forecasts. It also handles convective and non-convective clouds more effectively.

For aviation operations, the RUC20 enhancements will result in better forecasts in the vicinity of warm and cold fronts, where bad weather tends to concentrate, including areas of potentially hazardous turbulence and icing, and more accurate forecasts of surface winds, temperature, and precipitation. RUC forecasts of jet-level winds and temperature, critical for U.S. flight routing and air traffic management, are also improved.

"Improvement in Aviation Weather Center products due to RUC20 improvements over the current RUC2 will enhance the en-route warning, forecast, and advisory program serving the National Airspace System," said Jim Henderson from NOAA's Aviation Weather Center in Kansas City. "In an evaluation of the experimental fields at the AWS, the forecast of both convective and non-convective cloud tops showed a major improvement as did the forecast of visibility fields. "

Computer modeling is central to all NWS weather, flood, and climate forecasts. Throughout the day, data are collected by a vast array of observing systems such as the network of weather balloons, Doppler weather radars, sensors on commercial aircraft, automated surface observing systems, and advanced satellites. The data are processed through powerful computer models run at NCEP's Maryland facility. The computers generate predictions for forecasters, allowing them to anticipate weather conditions from one hour to weeks and seasons in advance. Of all the models running at NCEP, the RUC20 is designed for the most immediate guidance – within the next 12 hours.

Among the many users of the model are NOAA's Aviation Weather Center in Kansas City, Mo., NOAA's Storm Prediction Center in Norman, Okla., National Weather Service forecast offices, commercial airlines, and any users that need immediate information on the state of the weather in the next few hours.

The Commerce Department's National Oceanic and Atmospheric Administration (NOAA) is dedicated to enhancing security and national safety through the prediction and research of weather and climate-related events and providing environmental stewardship of our nation's coastal and marine resources. To learn more about NOAA, please visit

NOAA/FSL collaborated with NCEP and the National Center for Atmospheric Research (NCAR) on development of the RUC20.

For more information on the RUC20, visit the web site at