Skip to main content
U.S. flag

An official website of the United States government

Dot Gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.


The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

The 20-km Version of The RUC


A new version of the Rapid Update Cycle (RUC) with 20-km resolution and significant changes in model and assimilation techniques is being implemented at NOAA’s National Centers for Environmental Prediction (NCEP) in summer 2001. The RUC, a high-frequency mesoscale analysis and forecast model system, has become a widely used source for short-range weather forecasting guidance in the United States, especially for aviation, severe- storm, and public-forecasting applications. This paper describes the primary components of the 20-km RUC and how it differs from the 40-km RUC (Benjamin et al. 1999) that has run at NCEP since April 1998. The overall goals for the 20-km RUC implementation have been the following: • Take advantage of increased computer power at NCEP by using increased spatial resolution • Improve RUC performance for quantative precipitation forecasting, especially in the warm season • Improve RUC initial conditions, which are especially important given its niche for short-range forecasts. These goals are realized in the 20-km RUC by incorporating improved modeling and data assimilation techniques, assimilating new observation data, and eliminating bugs. The primary model changes in the 20-km RUC model concern its treatment of convection, explicit clouds using mixed-phase microphysics, and land-surface processes. The key assimilation changes are the introduction of a three-dimensional variational (3dVAR) analysis in the RUC native hybrid isentropic-sigma vertical coordinate and assimilation of GOES cloud-top data to modify RUC hydrometeor fields. In the following sections, we give more detail on resolution, assimilation, and model changes, and then present some recent results.

Article / Publication Data
Available Metadata
Fiscal Year
Published On
January 01, 2001

This publication was presented at the following:

14th Conf. on Numerical Weather Prediction
Conference presentation


Not available


Authors who have authored or contributed to this publication.