Evaluation of a Prototype Version of the 3D-Real-Time Mesoscale Analysis (3D-RTMA) for Situational Awareness and Nowcast Applications

The Real-Time and UnRestricted Mesoscale Analysis (RTMA/URMA) are NCEP operational analysis systems that provide detailed analyses of surface and sensible weather elements. These analyses are heavily used by National Weather Service (NWS) forecasters in a variety of ways (situational awareness, bias correction for the National Blend of Models, verification). The current RTMA/URMA is based on a 2DVar application of a specialized form of the Gridpoint Statistical Interpolation (GSI) system and aspects of it are described in other presentations at this WAF/NWP conference.

In this presentation, ongoing collaborative work between NCEP/EMC and ESRL/GDSD) to evolve the current 2D RTMA/URMA to a fully three three-dimension analysis (3D RTMA) with sub-hourly updates will be described. In this new 3D RTMA, 2D fields that are intrinsically a function of 3D space (PBL height, precipitable water, ceiling, etc.) are diagnosed from the 3-D RTMA fields, yielding full physical consistency through use of a very accurate high-resolution model background. Extending the operational RTMA/URMA to three dimensions will also allow for the creation of nowcasting products, including full-column representation of standard meteorological fields such as temperature, water vapor, and wind, as well as hydrometeors (i.e., clouds, precipitation of all forms), and eventually aerosols. The 3D RTMA will also include land-surface diagnostics (e.g., soil moisture, snow state from multi-level land-surface fields), and convective (e.g., hail size, supercell rotation tracks) fields, developed in collaboration with the National Water Center (NWC) and National Severe Storms Laboratory (NSSL), respectively. The 3D RTMA will potentially improve analysis fields for the NOAA National Blend of Models (NBM) project and add a 3-dimensional perspective including cloud-hydrometeor fields. It could also allow merging in of the NCEP/SPC Hourly Mesoscale Analysis and also provide an initial set of fields for a unified NOAA nowcast system.

GSD and EMC have created a shared code repository, from which a 3D RTMA version is being built that will be run in parallel to the operational 2D RTMA, allowing comparison and evaluation of the 3D RTMA. GSD is also running two prototype versions of an hourly 3D RTMA, allowing for testing of variations in the horizontal correlation length scale used in the analysis. As refinements from both EMC and GSD to the 3D RTMA are made, the associated code updates will be moved over to the shared code repository. In this presentation, scientific results from the latest test version will be shown, along feedback received from test evaluations by various user groups. We will also include a description of ongoing testing and evaluation work toward an operational implementation (tentatively planned for 2021).