SR SSD 2000-28

Technical Attachment

Recent Changes to the Operational Meso-Eta Model System

Scientific Services Division
NWS Southern Region Headquarters

Below is the text of Technical Information Notice 00-21, issued by NWS Headquarters on September 25, 2000. It describes several changes to the Meso-Eta model system which were implemented on September 26, 2000. The changes include the following.

1. The resolution of the Meso-Eta forecast model was increased from 32 km and 45 levels, to 22 km and 50 levels. The size of the Eta model integration domain will be increased to the size of the 48 km domain that was operational from October 1995 to February 1998. This change in the Eta-22 domain will place the western boundary 900 km further west of Hawaii than In the current Eta-32. The eastern boundary, which is 150 km east of Puerto Rico and the USVI, was not affected.

2. The Eta 3-dimensional variational analysis (3DVAR) was modified to make direct use of radiances from the goes satellites and the NOAA polar-orbiting satellites.

3. A new observational non-linear quality control algorithm was incorporated into the Eta 3DVAR analysis, replacing the gross check of observations against the first guess which was previously used.

4. The vertical advection of cloud water was added to the Eta model. This will reduce the area of very light precipitation forecast by the Eta model in the eastern north Pacific.

No changes will be made to any of the standard Eta model grids or products available from the family of services (FOS), the AWIPS satellite broadcast network (SBN), or the OSO server as a result of these modifications to the Eta model system. With the increase in vertical resolution from 45 levels to 50 levels the hourly model profile data (packed in BUFR format) will now contain as many as 50 vertical levels.

Further details on these changes can be found on-line in the draft Technical Procedures Bulletin at

A presentation on these changes made to the September 6, 2000, meeting of the NWSH committee on applied forecasting techniques and implementation (CAFTI) is available on-line at Questions about these changes to the Eta model may be directed to Geoff DiMego (

This and other national technical information notices are available on the Internet at