EMC SUPPORT FOR AVIATION FORECASTING EFFORTS USING THE ETA MODEL Geoff Manikin NOAA/NCEP/EMC/ Camp Springs, MD and SAIC/GSC Beltsville, MD Geoff DiMego and Tom Black NOAA/NCEP/EMC Camp Springs, MD This presentation was made at the Ninth Conference on Aviation, Range, and Aerospace Meteorology in Orlando, FL on 9/13/00. It demonstrates current output from NCEP's Eta model relevant to aviation forecasting efforts and discusses some upcoming changes to the model. Fig. 1 shows the Eta output of interest to aviation forecasters in both gridded and bufr format. Fig. 2 shows a sample Eta visibility forecast with the accompanying observations for verification. The Eta uses the Stoelinga-Warner algorithm; units are km. The areas of reduced visibility are generally forecast well, but the model tends too predict values that are too low. Fig. 3 shows an Eta forecast of 10-meter wind speeds (left) and a forecast of wind gust potential (right). Units are knots. The wind gust algorithm determines the depth of the boundary layer, finds the maximum wind in the layer, and mixes a height-weighted fraction of that speed to the surface. It is being tested for future addition to the model. Fig. 4 shows the observed surface winds (left) and wind gusts (right) for comparison with Fig. 3. This forecast seems to do fairly well just east of the Rockies and over the intermountain west. It is noticeably poor over interior southern California. Fig. 5 shows a series of Eta hourly forecasts of turbulent kinetic energy (TKE) and the accompanying forecasts of 250 mb isotachs. The 24-hr forecast shows the development of a TKE feature. At 25 hours, the feature is being advected to the northeast. At 26 hours, the main feature has moved well to the northeast and weakened. At 27 hours (not shown), the feature is completely gone. An explanation of ETA TKE is found here. Fig. 6 shows the detail that is lost in looking at a high resolution model forecast on a low resolution grid. It compares the 2-meter temperature forecasts from the SAME MODEL RUN on a 22-km output grid (#221) and a 90-km output grid (#104). Fig. 7 shows the division of the Eta grid 221 files into 'tiles.' Users who wish to utilize the high resolution grid 221 output but are unable to deal with the huge files can download just the region(s) they need. Fig. 8 was a picture of the web page which displays Eta forecast meteograms. The page can be found here. Fig. 9 shows a sample of an Eta forecast of meteograms for surface variables. These plots, derived from hourly BUFR data, are more effective than gridded data for time precision for events such as frontal passages, precipitation onset/end, and precipitation type changes. Fig. 10 shows a sample of an upper-air Eta forecast from the meteogram web site. Winds, cloud water, cloud ice, and the 0 and -15 degree C isotherms are displayed. Fig. 11 shows the future plans for the Eta Data Assimilation System (EDAS). Fig. 12 shows the improvements to the analysis that some changes to the 3DVAR initialization are having. The top plot compares observed and operational Eta analyzed soundings for Nashville, TN. The bottom shows the same for the new version of the Eta, and a much better fit to the data is seen. Fig. 13 shows the future plans for the Eta model. Note that the 22-km Eta has been implemented on 9/26/00. Details can be found in the TPB. Also, the extension of the model to 84-hours will be delayed, probably until early 2001. Fig. 14 shows the domain for the 22-km Eta. The domain, which had been slightly reduced when the 32-km Eta was implemented on the IBM supercomputer, is enlarged. Fig. 15 compares the Eta model terrain over the western U.S. in the versions of the model run with horizontal resolution of 32 km and 22km. Fig. 16 shows differences in forecasts of a cyclone near Alaska in the 22 and 32 km versions of the Eta. The differences are likely due to increased resolution and the use of radiances. Forecasters indicated that the 22-km Eta's forecasts of a deeper storm was better than the prediction by the 32-km model. Fig. 17 shows an orographic precipitation case over southern California in the winter of 1998 and the huge impact resolution has in a model's ability to predict extreme amounts. The 10-km Eta provided tremendously useful guidance forecasters for this event.