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Stephen S. Weygandt authored and/or contributed to the following articles/publications.
A regional ensemble Kalman filter data assimilation system based on the latest version of Gridpoint Statistical Interpolation (GSI) and an Ensemble Square Root Filter (EnSRF) package configured for the NCEP Global Forecasting System has been established for possible future application in the hourly updated Rapid Refresh (RR). The planned operati...
CONVECTIVE-SCALE WARN-ON-FORECAST SYSTEM A Vision for 2020
The National Oceanic and Atmospheric Administration's (NOAA's) National Weather Service (NWS) issues warnings for severe thunderstorms, tornadoes, and flash floods because these phenomena are a threat to life and property. These warnings are presently based upon either visual confirmation of the phenomena or the observational detection of proxy ...
The 2008 CoSPA* Forecast Demonstration *Collaboration Storm Prediction for Aviation
Air traffic congestion in the US National Airspace System (NAS) has become a serious national problem. Several studies have shown that there is a critical need for timely, reliable and high quality forecasts of precipitation and echo tops with forecast time horizons of up to 12 hours. In order to address the short-term needs of the Federal Aviat...
Rapid-refresh testing: examples of forecast performance
The currently operational Rapid Update Cycle (RUC, Benjamin et al 2004a,b) occupies the “situational awareness” niche in the National Centers for Environmental Prediction (NCEP) forecast production suite. That is, forecasters use it extensively as an aid in monitoring the latest trends in fast-breaking weather situations for the purpose of updat...
Workflow Management system for Automating Weather and Climate Simulations
Progress in Joint OSSEs. Three Joint OSSE Nature Runs and Simulation of Observations
Data assessments using simulation experiments are able to provide a quantitative evaluation of future observing systems and instruments. These experiments are known as Observing System Simulation Experiments (OSSE). The OSSE results have often been different from theoretical explanations or speculation. The OSSE proxy of the true atmosphere is c...
Dual-Doppler analysis of winds and vorticity budget terms near a tornado
Three-dimensional dual-Doppler observations with unprecedented finescale spatial and temporal resolution are used to characterize the vector wind field and vorticity generation terms in and near a weak, short-lived tornado. The beam widths of the two Doppler on Wheels (DOW) mobile radars, at the range of the tornado, are 250 m with gate lengths ...
Dual-Doppler observations with unprecedented finescale spatial and temporal resolution are used to characterize the vector wind field in and near a tornado occurring near Kiefer, Oklahoma, on 26 May 1997. Analyses of the dual-Doppler vector wind fields document in detail, for the first time, several structures associated with the tornado: a prox...
Gridpoint statistical interpolation for Rapid Refresh
The Rapid Update Cycle (RUC) is an operational mesoscale data assimilation and numerical forecasting system developed by NOAA Research Forecast Systems Laboratory (FSL) in Boulder, CO. The first version of the RUC (RUC1) became operational at the National Centers for Environmental Prediction (NCEP) in 1994. Several major upgrades have been intro...
THE RUC 3DVAR: OPERATIONAL PERFORMANCE AND RECENT IMPROVEMENTS
The RUC 3D variational analysis (and postprocessing modifications)
In this two-part study, a single-Doppler parameter retrieval technique is developed and applied to a real-data case to provide initial conditions for a short-range prediction of a supercell thunderstorm. The technique consists of the sequential application of a single-Doppler velocity retrieval (SDVR), followed by a variational velocity adjust...
In this two-part study, a single-Doppler parameter retrieval technique is developed and applied to a real-data case to provide model initial conditions for a short-range prediction of a supercell thunderstorm. The technique consists of the sequential application of a single-Doppler velocity retrieval (SDVR), followed by a variational velocity ...
NWS Technical Procedures Bulletin No. 490 RUC20 - The 20-km version of the Rapid Update Cycle
A major revision to the Rapid Update Cycle (RUC) analysis/model system was implemented into operations at the National Centers for Environmental Prediction Center (NCEP) on 17 April 2002. The new RUC version with 20-km horizontal resolution (RUC20) replaces the previous 40-km version of the RUC (RUC40).
The 20-km Rapid Update Cycle - Overview and Implications for Aviation Applications
PRELIMINARY HIGH-RESOLUTION DUAL-DOPPLER ANALYSES OF TWO TORNADIC THUNDERSTORMS
A regional ensemble Kalman filter (EnKF) system is established for potential Rapid Refresh (RAP) operational application. The system borrows data processing and observation operators from the gridpoint statistical interpolation (GSI), and precalculates observation priors using the GSI. The ensemble square root Kalman filter (EnSRF) algorithm is ...
Institutions Earth System Research Laboratory - ESRL National Oceanic and Atmospheric Administration - NOAA
A coupled ensemble square root filter–three-dimensional ensemble-variational hybrid (EnSRF–En3DVar) data assimilation (DA) system is developed for the operational Rapid Refresh (RAP) forecasting system. The En3DVar hybrid system employs the extended control variable method, and is built on the NCEP operational gridpoint statistical interpolation...
Institution National Oceanic and Atmospheric Administration - NOAA
Stratiform Cloud-Hydrometeor Assimilation for HRRR and RAP Model Short-Range Weather Prediction
Accurate cloud and precipitation forecasts are a fundamental component of short-range data assimilation/model prediction systems such as the NOAA 3-km High-Resolution Rapid Refresh (HRRR) or the 13-km Rapid Refresh (RAP). To reduce cloud and precipitation spinup problems, a nonvariational assimilation technique for stratiform clouds was develope...
Institution National Oceanic and Atmospheric Administration - NOAA
A regional ensemble Kalman filter (EnKF) data assimilation (DA) and forecast system was recently established based on the Gridpoint Statistical Interpolation (GSI) analysis system. The EnKF DA system was tested with continuous three-hourly updated cycles followed by 18-h deterministic forecasts from every three-hourly ensemble mean analysis. Ini...
Institution National Oceanic and Atmospheric Administration - NOAA
The Rapid Refresh (RAP) is an hourly updated regional meteorological data assimilation/short-range model forecast system running operationally at NOAA/National Centers for Environmental Prediction (NCEP) using the community Gridpoint Statistical Interpolation analysis system (GSI). This paper documents the application of the GSI three-dimensiona...
Institutions Earth System Research Laboratory - ESRL National Oceanic and Atmospheric Administration - NOAA
This study describes the initial application of radiance bias correction and channel selection in the hourly updated Rapid Refresh model. For this initial application, data from the Atmospheric Infrared Sounder (AIRS) are used; this dataset gives atmospheric temperature and water vapor information at higher vertical resolution and accuracy than ...
Institution National Oceanic and Atmospheric Administration - NOAA
Satellite Radiance Data Assimilation within the Hourly Updated Rapid Refresh
Assimilation of satellite radiance data in limited-area, rapidly updating weather model/assimilation systems poses unique challenges compared to those for global model systems. Principal among these is the severe data restriction posed by the short data cutoff time. Also, the limited extent of the model domain reduces the spatial extent of satel...
Institution National Oceanic and Atmospheric Administration - NOAA
A North American Hourly Assimilation and Model Forecast Cycle: The Rapid Refresh
The Rapid Refresh (RAP), an hourly-updated assimilation and model forecast system, replaced the Rapid Update Cycle (RUC) as an operational regional analysis and forecast system among the suite of models at the NOAA National Centers for Environmental Prediction (NCEP) in 2012. The need for an effective hourly-updated assimilation and modeling sys...
Institution National Oceanic and Atmospheric Administration - NOAA
The 13-km Rapid Refresh (RAP) and 3-km convective-allowing High-Resolution Rapid Refresh (HRRR) are hourly updating weather forecast models that use a specially configured version of the Advanced Research WRF (ARW) model and assimilate many novel and most conventional observation types on an hourly basis using Gridpoint Statistical Interpolation...
Institution National Oceanic and Atmospheric Administration - NOAA
The 13-km Rapid Refresh (RAP) and 3-km convective-allowing High-Resolution Rapid Refresh (HRRR) are hourly updating weather forecast models that use a specially configured version of the Advanced Research WRF (ARW) model and assimilate many novel and most conventional observation types on an hourly basis using Gridpoint Statistical Interpolation...
Institution National Oceanic and Atmospheric Administration - NOAA
An operational upgrade of the RAP and HRRR model systems at NCEP is planned for August 2016. This coordinated upgrade (RAP version 3 and HRRR version 2, RAPv3/HRRRv2) includes many enhancements to the data assimilation, model, and post-processing formulations that result in significant improvements to nearly all forecast aspects, including uppe...
Institution National Oceanic and Atmospheric Administration - NOAA
Update of the Status of Numerical Weather Prediction
1:30 p.m. – 3:00 p.m. Update of the Status of Numerical Weather Prediction Numerical Weather Prediction (i.e., weather models), apart from climatology, are the basis for all weather forecasts beyond about 2 hours into the future. Aviation weather hazards are forecasted either through further processing (e.g., inflight icing and turbulence) o...
Institution National Oceanic and Atmospheric Administration - NOAA
A technique for model initialization using three-dimensional radar reflectivity data has been developed and applied within the NOAA 13-km Rapid Refresh (RAP) and 3-km High-Resolution Rapid Refresh (HRRR) regional forecast systems. This technique enabled the first assimilation of radar reflectivity data for operational NOAA forecast models, criti...
Institution National Oceanic and Atmospheric Administration - NOAA
The High-Resolution Rapid Refresh (HRRR) is a convection-allowing implementation of the Weather Research and Forecasting model (WRF-ARW) with hourly data assimilation that covers the conterminous United States and Alaska and runs in real time at the NOAA National Centers for Environmental Prediction. Implemented operationally at NOAA/NCEP in 201...
Institution National Oceanic and Atmospheric Administration - NOAA
The High-Resolution Rapid Refresh (HRRR) is a convection-allowing implementation of the Advanced Weather Research and Forecast model (WRF-ARW) that covers the conterminous United States and Alaska and runs hourly (for CONUS; every three hours for Alaska) in real time at the National Centers for Environmental Prediction. The high-resolution forec...
Institution National Oceanic and Atmospheric Administration - NOAA