A relatively small set of changes for the RUC was implemented on Thursday, May 6, 1999, for the 1200 UTC run. Most of these changes involve post-processing. Another change regarding the speed of RUC processing has already been made and is discussed further below.
BACKGROUND: The RUC surface temperature and surface dewpoint fields are diagnosed from the RUC native grids using lapse rate information to a topography grid that is closer to actual METAR elevations. This has been done with the RUC1 and RUC2 systems.
With the fixes, biases of analyzed surface temperature and dewpoint compared to actual METAR observations are reduced from 2 deg C to 0 in the western United States, and standard deviation differences of temperature are reduced from about 2 deg C to a little over 1 deg C over the United States as a whole. These improvements also benefit the Lifted Index calculations.
As of about 28 April 1999, NCEP allocated 10 processors on the Cray for all runs for the RUC as part of improving the use of the Cray for the overall NCEP model suite.
The effects of this change are that RUC forecast grids at 0300, 0600, 0900, 1500, 1800, and 2100 UTC are available about 25-30 min earlier than previously. Analyses at all times are available about 5-8 min earlier, as are the 3-h forecasts at non-3-hourly times.
NCEP/NCO has decided to keep this fast processing of the RUC on the Cray3 until the IBM SP-2 transition takes place in the July-August 1999 period.
As always, please send questions or comments to the RUC forum at http://maps.fsl.noaa.gov/forum/eval, or email or call me directly.