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.

Recent Improvements To Ceiling and Visibility Forecasts In The RAP and HRRR Models


The 13-km Rapid Refresh (RAP) and 3-km convection-allowing High-Resolution Rapid Refresh (HRRR) are hourly-updating forecast models that support operational aviation weather forecasting and other short-range forecasting interests within the contiguous United States. Since 2010, the forecast accuracy of operationally restrictive ceilings and visibilities (hereafter C/V) has steadily improved in the RAP and HRRR, and is largely attributable to better representation of grid-scale cloud cover through the microphysics parameterization, and to improvements in model analysis fields via hybrid ensemble–variational assimilation of temperature and water-vapor observations. This presentation will discuss ongoing work to sustain continued C/V improvements in future versions of the RAP and HRRR. An end-to-end array of experimental model-system developments, encompassing new data-assimilation, model physics, and model postprocessing innovations, will be presented. These developments include: (1) the transition of the RAP/HRRR hydrometeor analysis from a non-variational to a hybrid ensemble–variational system, (2) application of a subgrid-scale cloud parameterization in RAP/HRRR, and (3) use of a simplified, cloud-fraction-based ceiling diagnostic during model postprocessing. Drawing from both real-time and retrospective forecasts results, the merits of these model-system developments will be evaluated, and their pathway to eventual operational implementation will be discussed.

Article / Publication Data
Available Metadata
Fiscal Year
Published On
January 01, 2017

This publication was presented at the following:

2017 - 97th AMS Annual Meeting
Amer. Meteor. Soc.
Conference presentation


Not available


Authors who have authored or contributed to this publication.

Not available