Editing Rapid Update Cycle

{{short description|Weather forecasting system used in the U.S. until 2012}}
{{refimprove|date=May 2014}}
[[Image:Ruc212hrfcst-8-26-08.png|thumb|Graphical 12-hour forecast output from RUC2]]

The '''Rapid Update Cycle''' ('''RUC''') was an American [[Weather forecasting|atmospheric prediction]] system that consisted primarily of a [[Numerical weather prediction|numerical forecast model]] and an analysis system to initialize the model. The first operational implementation was created in 1994, with 60km resolution and a 3-hour cycle.<ref>{{Cite web |title=The Rapid Update Cycle (RUC) |url=https://ruc.noaa.gov/ruc/ruc13_docs/RUC13-preimp-24Jun05.ppt |access-date=2023-08-27 |website=The Rapid Update Cycle (RUC) ruc.noaa.gov}}</ref> 

The RUC was designed to provide accurate short-range (0- to 12-hr, later expanded to 18-hr in 2010) numerical forecast guidance for [[weather]]-sensitive users, such as those in the aviation community. Significant [[weather forecasting]] problems that occur in the 0- to 12-hr range include severe weather in all seasons (for example, [[tornado]]es, [[thunderstorm]]s, [[snow]], and [[ice storm]]s) and hazards to aviation (for example, [[clear air turbulence]], icing, and [[downburst]]s). 

The RUC ran at the highest frequency of any forecast model at the [[National Centers for Environmental Prediction]] (NCEP), assimilating recent observations to provide very high frequency updates of current conditions and short-range forecasts. This update frequency was only once an hour (the standard interval for [[Automated airport weather station|ASOS]] observation reporting), and with computational limitations and the time required to assimilate all of the data, there is approximately a one-hour delay in producing the forecasts. Because of this, it was common practice to use a one-hour forecast from the RUC as a current analysis, as the one-hour forecast would come out only a few minutes before the time it is forecasting for. There is also little possibility for error in a one-hour forecast, meaning that the RUC's one-hour forecast would not usually vary greatly from the actual state of the atmosphere at that particular point in time.

The RUC was decommissioned on May 1, 2012; it was replaced by the [[Rapid Refresh]] (RR or RAP) model, based on the [[Weather Research and Forecasting model|WRF]]. Like the RUC, the Rapid Refresh model also runs hourly out to 18 hours on a {{convert|13|km|mi|abbr=on}} grid spacing, but also covers a wider area. An experimental High Resolution Rapid Refresh (HRRR) ran by the [[Earth System Research Laboratories]] (ESRL) offers {{convert|3|km|mi|abbr=on}} resolution at 15-minute intervals.<ref>[http://rapidrefresh.noaa.gov/ Rapid Refresh information page]. NOAA. Retrieved 2010-05-15.</ref> A backup version of the RUC continued to run until that too was stopped on May 15, 2013, thus formally bringing an end to the model.

== References ==
{{reflist}}

==External links==
* [http://ruc.noaa.gov/ NCEP RUC Homepage] – Includes forecast output images and descriptions of the diagnostic variables available from the model output.

{{Atmospheric, Oceanographic and Climate Models}}

[[Category:National Weather Service numerical models]]