NOAA 97-R213


Contact:  Randee Exler             FOR IMMEDIATE RELEASE
          Marilu Trainor           5/1/97

EXPERIMENTAL MODEL FORECASTS CONDITIONS
EVERY 10 KILOMETERS

The National Weather Service has begun testing a new experimental computer model that will assist forecasters to predict weather conditions across the western United States with more detail than ever before. The model, known as the Eta-10, allows forecasters in 24 modernized National Weather Service offices in Arizona, California, Idaho, Montana, Nevada, Oregon, Utah and Washington to monitor the development of weather systems down to a 10 kilometer grid.

"The experimental Eta-10 model represents an evolution in weather forecasting," said Ronald D. McPherson, director of the NWS' National Centers for Environmental Prediction (NCEP). "By looking at weather systems in such a small area, forecasters can get more details of the weather conditions impacting the local community."

Computer modeling is the foundation of all NWS weather and flood forecasts. Several times a day data is collected by a vast array of observing systems such as the network of weather balloons, Doppler weather radars, automated surface observing systems, and advanced satellites. The data is used in computer programs at NCEP's Environmental Modeling Center (EMC) in Camp Spring, Md. The models solve a series of complex equations that simulate the present and future states of the atmosphere. The computer simulation presents the atmosphere in a three-dimensional grid, each point on the grid representing a location where a calculation is made.

Called grid resolution, the distance between data points determines the model's ability to resolve' or to see the details of weather features in a focused way. The closer the grid points, the more detailed and accurate the weather forecast.

The NWS Western Region was selected for test because it encompasses a wide variety of climatic areas within the eight state region. The western United States includes many terrain features, especially mountain ranges, which affect weather conditions. Testing the models at desert, coastal and high altitude sites will also help forecasters analyze high resolution grid models. The NWS Western Region is headquartered in Salt Lake City.

"Forecast office evaluations have shown that the Eta-10 model produces improved precipitation forecasts in the mountains," said NWS Western Region Scientific Services Division Chief Andy Edman. "A typical storm in the West can generate varying precipitation amounts ranging from a few sprinkles in protected valley areas to several inches of rain in high mountain basins. The Eta-10 forecast model often captures this important variation of precipitation, which can lead to improved flood forecasts."

The experimental Eta-10 model is a refined version of NCEP's current Eta model. The model forms the basis of twice daily forecasts of weather elements such as precipitation, temperature, wind, dew point and cloud coverage. The first operational implementation of the Eta model began in 1993 as an 80 kilometer grid. Currently, the NWS runs both a 29 and 48 kilometer grid resolution of the Eta model operationally. Forecasters put the new, experimental 10 kilometer model to a test during the 1996 Summer Olympics to generate weather forecasts for specific sporting events.

Currently, the experimental Eta-10 experimental model runs on the National Oceanic and Atmospheric Administration's Cray C-90 supercomputer in Suitland, Md. Once a day, the experimental model analyzes the high-resolution data and prepare forecasts for 33 hours into the future.

Because of the large amount of computer space needed to run the experimental model, the agency cannot use the Eta-10 on a regular, operational basis until it acquires the next generation supercomputer with more memory, disk space and computing power. The NWS plans to acquire a new supercomputer in late 1998. Until the new computer is available, NCEP will run the experimental model for three months to complete a thorough evaluation of the model. After the three-month test period, the model occasionally will be used to help forecast critical weather events wherever and whenever they occur such as severe thunderstorms in the Midwest during the spring and summer and winter storms in the Pacific Northwest and Great Lakes regions.

When the new model becomes fully operational, the NWS intends to run the model four times a day, providing forecasts out to 48 hours for all of North America including Alaska, Hawaii and Puerto Rico.

The Environmental Modeling Center (EMC) is one of nine National Centers for Environmental Prediction. Located in Camp Springs, Md., EMC improves weather, marine and climate predictions for the United States by developing and improving computer models of the atmosphere and oceans. For more information on the EMC and numerical modeling, visit the Center's web site at: http://nic.fb4.noaa.gov:8000