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David C. Dowell authored and/or contributed to the following articles/publications.
Using the Weather Research and Forecasting Model, 80-member ensemble Kalman filter (EnKF) analyses with 3-km horizontal grid spacing were produced over the entire conterminous United States (CONUS) for 4 weeks using 1-h continuous cycling. For comparison, similarly configured EnKF analyses with 15-km horizontal grid spacing were also produced. A...
Institutions National Oceanic and Atmospheric Administration - NOAA National Center for Atmospheric Research - NCAR
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
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
Ensemble forecasts are generated with and without the assimilation of near-surface observations from a portable, mesoscale network of StickNet platforms during the Verification of the Origins of Rotation in Tornadoes Experiment–Southeast (VORTEX-SE). Four VORTEX-SE intensive observing periods are selected to evaluate the impact of StickNet obser...
Institution National Oceanic and Atmospheric Administration - NOAA
A Comparison of Near-Surface Buoyancy and Baroclinity across Three VORTEX2 Supercell Intercepts
Observations obtained during the second Verification of the Origin of Rotation in Tornadoes Experiment (VORTEX2) are analyzed for three supercell intercepts. These intercepts used a fleet of deployable “StickNet” probes, complemented by mobile radars and a mobile mesonet, to map state quantities over the expanse of target storms. Two of the d...
Institution National Oceanic and Atmospheric Administration - NOAA
What Does a Convection-Allowing Ensemble of Opportunity Buy Us in Forecasting Thunderstorms?
The High Resolution Ensemble Forecast v2.1 (HREFv2.1), an operational convection-allowing model (CAM) ensemble, is an “ensemble of opportunity” wherein forecasts from several independently designed deterministic CAMs are aggregated and postprocessed together. Multiple dimensions of diversity in the HREFv2.1 ensemble membership contribute to ense...
Institution National Oceanic and Atmospheric Administration - NOAA
Forecasting High-Impact Weather in Landfalling Tropical Cyclones Using a Warn-on-Forecast System
Landfalling tropical cyclones (TCs) are among the greatest natural threats to life and property in the United States, since they can produce multiple hazards associated with convective storms over a wide region. Of these hazards, tornadoes within TC rainbands pose a particularly difficult forecast problem owing to their rapid evolution and their...
Institution National Oceanic and Atmospheric Administration - NOAA
The 2016–2018 NOAA Hazardous Weather Testbed (HWT) Spring Forecasting Experiments (SFE) featured the Community Leveraged Unified Ensemble (CLUE), a coordinated convection-allowing model (CAM) ensemble framework designed to provide empirical guidance for development of operational CAM systems. The 2017 CLUE included 81 members that all used 3-km ...
Institutions National Oceanic and Atmospheric Administration - NOAA National Center for Atmospheric Research - NCAR
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
Advancing from Convection-Allowing NWP to Warn-on-Forecast: Evidence of Progress
The Warn-on-Forecast (WoF) program, driven by advanced data assimilation and ensemble design of numerical weather prediction (NWP) systems, seeks to advance 0–3-h NWP to aid National Weather Service warnings for thunderstorm-induced hazards. An early prototype of the WoF prediction system is the National Severe Storms Laboratory (NSSL) Experimen...
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
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
Assimilation of Pseudo-GLM Data Using the Ensemble Kalman Filter
Total lightning observations that will be available from the GOES-R Geostationary Lightning Mapper (GLM) have the potential to be useful in the initialization of convection-resolving numerical weather models, particularly in areas where other types of convective-scale observations are sparse or nonexistent. This study used the ensemble Kalman fi...
Institutions National Center for Atmospheric Research - NCAR National Oceanic and Atmospheric Administration - NOAA
Several limited-area 80-member ensemble Kalman filter (EnKF) data assimilation systems with 15-km horizontal grid spacing were run over a computational domain spanning the conterminous United States (CONUS) for a 4-week period. One EnKF employed continuous cycling, where the prior ensemble was always the 1-h forecast initialized from the previou...
Institutions National Center for Atmospheric Research - NCAR National Oceanic and Atmospheric Administration - NOAA
Biases in the Prediction of Convective Storm Characteristics with a Convection Allowing Ensemble
The severity, duration, and spatial extent of thunderstorm impacts are related to convective storm mode. This study assesses the skill of the High-Resolution Rapid Refresh Ensemble (HRRR-E) and its deterministic counterpart (HRRRv4) at predicting convective mode and storm macrophysical properties using 35 convective events observed during the 20...
Institution National Center for Atmospheric Research - NCAR
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
High-resolution Doppler radar velocities and in situ surface observations collected in a tornadic supercell on 5 June 2009 during the second Verification of the Origins of Rotation in Tornadoes Experiment (VORTEX2) are assimilated into a simulated convective storm using an ensemble Kalman filter (EnKF). A series of EnKF experiments using a 1-km ...
Institution National Center for Atmospheric Research - NCAR
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 forcing and origins of an internal rear-flank downdraft (RFD) momentum surge observed by the second Verification of the Origin of Rotation in Tornadoes Experiment (VORTEX2) within a supercell occurring near Dumas, Texas, on 18 May 2010 is assessed through ensemble Kalman filter (EnKF) storm-scale analyses. EnKF analyses are produced every 2 ...
Institution National Oceanic and Atmospheric Administration - NOAA
Results from simulations are compared with dual-Doppler and total lightning observations of the 29–30 May 2004 high-precipitation supercell storm from the Thunderstorm Electrification and Lightning Experiment (TELEX). The simulations use two-moment microphysics with six hydrometeor categories and parameterizations for electrification and lightni...
Institution National Oceanic and Atmospheric Administration - NOAA
To assist the National Science Foundation in meeting the needs of the community of scientists by providing them with the instrumentation and platforms necessary to conduct their research successfully, a meeting was held in late November 2012 with the purpose of defining the problems of the next generation that will require radar technologies and...
Institutions National Center for Atmospheric Research - NCAR 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
As part of NOAA’s Warn-on-Forecast (WoF) initiative, a multiscale ensemble-based assimilation and prediction system is developed using the WRF-ARW model and DART assimilation software. To evaluate the capabilities of the system, retrospective short-range probabilistic storm-scale (convection allowing) ensemble analyses and forecasts are produced...
Institution National Oceanic and Atmospheric Administration - NOAA
The Mesoscale Predictability Experiment (MPEX)
The Mesoscale Predictability Experiment (MPEX) was conducted from 15 May to 15 June 2013 in the central United States. MPEX was motivated by the basic question of whether experimental, subsynoptic observations can extend convective-scale predictability and otherwise enhance skill in short-term regional numerical weather prediction. Observatio...
Institutions Earth System Research Laboratory - ESRL National Center for Atmospheric Research - NCAR 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
Nine sets of 36-h, 10-member, convection-allowing ensemble (CAE) forecasts with 3-km horizontal grid spacing were produced over the conterminous United States for a 4-week period. These CAEs had identical configurations except for their initial conditions (ICs), which were constructed to isolate CAE forecast sensitivity to resolution of IC pertu...
Institutions National Center for Atmospheric Research - NCAR National Oceanic and Atmospheric Administration - NOAA
Warn-on-Forecast System: From Vision to Reality
Abstract In 2009, advancements in NWP and computing power inspired a vision to advance hazardous weather warnings from a warn-on-detection to a warn-on-forecast paradigm. This vision would require not only the prediction of individual thunderstorms and their attributes but the likelihood of their occurrence in time and space. During the last de...
Institution National Oceanic and Atmospheric Administration - NOAA
Assessing RRFS versus HRRR in Predicting Widespread Convective Systems over the Eastern CONUS
This study provides a comparison of the operational HRRR version 4 and its eventual successor, the experimental Rapid Refresh Forecast System (RRFS) model (summer 2022 version), at predicting the evolution of convective storm characteristics during widespread convective events that occurred primarily over the eastern United States during summer ...
Institution National Center for Atmospheric Research - NCAR