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Curtis R. Alexander authored and/or contributed to the following articles/publications.
Progress in NOAA hourly-updated model forecasting for renewable energy guidance
NOAA has made rapid progress in the last year toward improved hourly-updated model forecasts over the lower 48 United States, significant to meet requirements for guidance for 20-150m wind and solar forecasts. This progress includes an improved version of the 3km High-Resolution Rapid Refresh (HRRR), now covering this entire CONUS domain, with b...
Institution National Oceanic and Atmospheric Administration - NOAA
Verification methods for convection-allowing models (CAMs) should consider the finescale spatial and temporal detail provided by CAMs, and including both neighborhood and object-based methods can account for displaced features that may still provide useful information. This work explores both contingency table–based verification techniques and o...
Institution National Oceanic and Atmospheric Administration - NOAA
Improvements to Lake-Effect Snow Forecasts Using a One-Way Air–Lake Model Coupling Approach
Lake-effect convective snowstorms frequently produce high-impact, hazardous winter weather conditions downwind of the North American Great Lakes. During lake-effect snow events, the lake surfaces can cool rapidly, and in some cases, notable development of ice cover occurs. Such rapid changes in the lake-surface conditions are not accounted for i...
Institution National Oceanic and Atmospheric Administration - NOAA
Representing shallow cumulus in numerical weather prediction and climate models is a significant challenge. Misrepresenting these subgrid-scale clouds can result in large errors in the downwelling shortwave radiative flux at surface, resulting in large errors in the surface temperature that results in feedbacks into the accuracy of the thermodyn...
Institution National Oceanic and Atmospheric Administration - NOAA
The High Resolution Rapid Refresh (HRRR) assimilates radar reflectivity information in order to skillfully forecast convection. This assimilation is done using an empirical relationship between reflectivity and latent heat release from hydrometeor condensation and freezing to update the temperature tendency field. The temperature tendency field ...
Institution National Oceanic and Atmospheric Administration - NOAA
The Bay Area Flood Protection Association has just recently begun funding the Physical Sciences Division and Global Systems Division (GSD) of NOAA’s Earth System Research Lab (NOAA-ESRL), as well as the NOAA Cooperative Institute for Research in the Atmosphere (CIRA), to design and build a specialized nowcast / forecast system for the 9 Californ...
Institution National Oceanic and Atmospheric Administration - NOAA
A Progress Report on the Development of the High-Resolution Rapid Refresh Ensemble
The High-Resolution Rapid Refresh Ensemble (HRRRE) is a 36-member ensemble analysis system with 9 forecast members that utilizes the Advanced Research version of the Weather Research and Forecasting (ARW-WRF) dynamic core and the physics suite from the operational Rapid Refresh/High-Resolution Rapid Refresh deterministic modeling system. A goal ...
Institutions National Center for Atmospheric Research - NCAR National Oceanic and Atmospheric Administration - NOAA
The High Resolution Rapid Refresh (HRRR) model has been the National Weather Service’s (NWS) operational rapid update model since 2014. The HRRR has undergone continual development, including updates to the Weather Research and Forecasting (WRF) Model core, the data assimilation system, and the various physics packages in order to better represe...
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
U.S. National Weather Service (NWS) forecasters assess and communicate hazardous weather risks, including the likelihood of a threat and its impacts. Convection-allowing model (CAM) ensembles offer potential to aid forecasting by depicting atmospheric outcomes, including associated uncertainties, at the refined space and time scales at which haz...
Institutions National Center for Atmospheric Research - NCAR National Oceanic and Atmospheric Administration - NOAA
Initial Development and Testing of a Convection-Allowing Model Scorecard
Evaluation of numerical weather prediction (NWP) is critical for both forecasters and researchers. Through such evaluation, forecasters can understand the strengths and weaknesses of NWP guidance, and researchers can work to improve NWP models. However, evaluating high-resolution convection-allowing models (CAMs) requires unique verification met...
Institutions National Center for Atmospheric Research - NCAR National Oceanic and Atmospheric Administration - NOAA
Stochastically Perturbed Parameterizations in a HRRR-Based Ensemble
A stochastically perturbed parameterization (SPP) approach that spatially and temporally perturbs parameters and variables in the Mellor-Yamada-Nakanishi-Niino planetary boundary layer scheme (PBL) and introduces initialization perturbations to soil moisture in the Rapid Update Cycle land surface model was developed within the High Resolution Ra...
Institutions National Center for Atmospheric Research - NCAR National Oceanic and Atmospheric Administration - NOAA
One primary goal of annual Spring Forecasting Experiments (SFEs), which are coorganized by NOAA’s National Severe Storms Laboratory and Storm Prediction Center and conducted in the National Oceanic and Atmospheric Administration’s (NOAA) Hazardous Weather Testbed, is documenting performance characteristics of experimental, convection-allowing mo...
Institution National Oceanic and Atmospheric Administration - NOAA
Data assimilation (DA) methods for convective-scale numerical weather prediction at operational centres are surveyed. The operational methods include variational methods (3D-Var and 4D-Var), ensemble methods (LETKF) and hybrids between variational and ensemble methods (3DEnVar and 4DEnVar). At several operational centres, other assimilation algo...
Institution National Oceanic and Atmospheric Administration - NOAA
Object-Based Verification of a Prototype Warn-on-Forecast System
An object-based verification methodology for the NSSL Experimental Warn-on-Forecast System for ensembles (NEWS-e) has been developed and applied to 32 cases between December 2015 and June 2017. NEWS-e forecast objects of composite reflectivity and 30-min updraft helicity swaths are matched to corresponding reflectivity and rotation track objects...
Institution National Oceanic and Atmospheric Administration - NOAA
In this study, the utility of dimensioned, neighborhood-based, and object-based forecast verification metrics for cloud verification is assessed using output from the experimental High Resolution Rapid Refresh (HRRRx) model over a 1-day period containing different modes of convection. This is accomplished by comparing observed and simulated Geos...
In this study, object-based verification using the method for object-based diagnostic evaluation (MODE) is used to assess the accuracy of cloud-cover forecasts from the experimental High-Resolution Rapid Refresh (HRRRx) model during the warm and cool seasons. This is accomplished by comparing cloud objects identified by MODE in observed and simu...
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
The Weather Research and Forecasting Model: Overview, System Efforts, and Future Directions
Since its initial release in 2000, the Weather Research and Forecasting (WRF) Model has become one of the world’s most widely-used numerical weather prediction models. Designed to serve both research and operational needs, it has grown to offer a spectrum of options and capabilities for a wide range of applications. In addition, it underlies a n...
Institutions National Center for Atmospheric Research - NCAR 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
Progress Toward Improved Solar Forecasts in Hourly Updated RAP and HRRR Forecasts
The High-Resolution Rapid Refresh (HRRR) 3km hourly updated model is now being run operationally at NOAA's National Centers for Environmental Prediction (NCEP). A focus on improved cloud/solar forecasts has been central to development of HRRRv2 and HRRRv3 experimental versions, along with the parent 13km Rapid Refresh (RAP). Experimental, advanc...
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
Relatively little is known about how topography affects convective storms. The first step toward understanding these effects is to investigate how topography affects storm environments. Unfortunately, the effects of topography on convective environments is not easily observed directly. Instead, we resort to using output from the High-Resolution ...
Institution National Oceanic and Atmospheric Administration - NOAA
2020 HFIP R&D Activities Summary: Recent Results and Operational Implementation
This technical report describes the activities and results of the Hurricane Forecast Improvement Program (HFIP) that occurred in 2020. The major development focus remained in building the next generation hurricane model, the Hurricane Analysis and Forecast System (HAFS) within the Unified Forecast System (UFS), primarily for track and intensity ...
Institutions Earth System Research Laboratory - ESRL National Oceanic and Atmospheric Administration - NOAA
Overlapping Windows in a Global Hourly Data Assimilation System
The US operational global data assimilation system provides updated analysis and forecast fields every six hours, which is not frequent enough to handle the rapid error growth associated with hurricanes or other storms. This motivates development of an hourly-updating global data assimilation system, but observational data latency can be a barri...
Institutions Earth System Research Laboratory - ESRL 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
This study evaluates simulated radiance forecasts from a series of controlled experiments consisting of FV3-LAM forecasts with different configurations of model physics and vertical resolution. The forecasts were produced during the 2020 Hazardous Weather Testbed Spring Forecasting Experiments on the same forecast cases. The evaluation includes ...
Institution National Oceanic and Atmospheric Administration - NOAA