Continued development efforts led to improvements in deterministic CAMs over a CONUS domain (e.g., NSSL-WRF, ESRL HRRR, EMC NAM Nest) including the generation of specialized output fields for explicit simulated storm attributes and hourly maximum history variables (e.g., reflectivity, updraft speed, updraft helicity, surface wind, hail size). Focused exploration of experimental CAM ensembles also expanded across the community with CAPS, SPC, NSSL, NCAR, and the USAF, among others, developing systems with varying configurations and levels of complexity. In early 2011 the SPC Storm Scale Ensemble of Opportunity became the first real-time CAM ensemble produced year-round, providing operational forecasters with guidance for severe storms, heavy precipitation, fire weather, and winter weather. Innovative post-processed statistical guidance including probabilistic storm attribute fields is now available from many experimental CAM ensembles.
Although CAM ensembles enable quantification of severe weather risks including generation of calibrated probabilistic fields, current operational practice at the SPC indicates that CAM ensembles are used to supplement (not replace) deterministic CAM output for convective storm forecasting. This is based partially on the long-standing relationship between observed radar-based storm reflectivity/dynamic structure and real-time severe weather threat assessment that has been subsequently applied to the interpretation of CAM simulated storm predictions. This approach is also analogous to the complementary use of deterministic regional/global models and larger scale ensemble systems, where a combination of detailed pattern/environment information from deterministic models and ensemble statistical output provide a broad range of information utilized by severe weather forecasters.
Implications for future CAM development and post-processing strategies to better meet the needs of operational severe weather forecasters are discussed.