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- Title
An Hourly Assimilation–Forecast Cycle: The RUC.
- Authors
Benjamin, Stanley G.; Dévényi, Dezsö; Weygandt, Stephen S.; Brundage, Kevin J.; Brown, John M.; Grell, Georg A.; Kim, Dongsoo; Schwartz, Barry E.; Smirnova, Tatiana G.; Smith, Tracy Lorraine; Manikin, Geoffrey S.
- Abstract
The Rapid Update Cycle (RUC), an operational regional analysis–forecast system among the suite of models at the National Centers for Environmental Prediction (NCEP), is distinctive in two primary aspects: its hourly assimilation cycle and its use of a hybrid isentropic–sigma vertical coordinate. The use of a quasi-isentropic coordinate for the analysis increment allows the influence of observations to be adaptively shaped by the potential temperature structure around the observation, while the hourly update cycle allows for a very current analysis and short-range forecast. Herein, the RUC analysis framework in the hybrid coordinate is described, and some considerations for high-frequency cycling are discussed. A 20-km 50-level hourly version of the RUC was implemented into operations at NCEP in April 2002. This followed an initial implementation with 60-km horizontal grid spacing and a 3-h cycle in 1994 and a major upgrade including 40-km horizontal grid spacing in 1998. Verification of forecasts from the latest 20-km version is presented using rawinsonde and surface observations. These verification statistics show that the hourly RUC assimilation cycle improves short-range forecasts (compared to longer-range forecasts valid at the same time) even down to the 1-h projection.
- Subjects
WEATHER forecasting; WEATHER; TEMPERATURE; GEOPHYSICAL prediction; NATIONAL Centers for Environmental Prediction (U.S.); METEOROLOGY
- Publication
Monthly Weather Review, 2004, Vol 132, Issue 2, p495
- ISSN
0027-0644
- Publication type
Article
- DOI
10.1175/1520-0493(2004)132<0495:AHACTR>2.0.CO;2