Testing and Refinement of a Three-Dimensional Real-Time Mesoscale Analysis (3D-RTMA) for Severe Weather, Aviation, Operational Forecasting, and Other Nowcast Applications

Collaborative work between ESRL/GDSD and NCEP/EMC has yielded significant progress toward replacing the current NCEP operational 2D Real-Time Mesoscale Analysis (RTMA) with a fully three three-dimension analysis (3D RTMA). The current 2D system produces a high resolution (~2.5 km) near-surface analyses of sensible weather elements for use for nowcasting, as well as forecast calibration and bias correction. RTMA gridded fields are heavily used within the National Weather Service (NWS), especially for the National Blend of Models (NBM). This current system is described in a number of presentations at this meeting, including a summary of work toward the next implementation (v2.8).

The goal of this 3D RTMA work is to produce a high resolution analysis of the current state of the entire three-dimensional atmosphere, with a recognition that many 2D fields are intrinsically a function of 3D space (PBL height, precipitable water, ceiling, etc.) and best diagnosed from a highly accurate three-dimensional analysis. Extending the operational RTMA to three dimensions will also allow for inherently there-dimensional fields like clouds and hydrometeors (i.e., clouds, precipitation of all forms), and eventually aerosols to be represented. A number of further application enhancements will also be possible, including provision for 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.

Recent scientific work has focused on optimizing the assumed observation errors and use of ensemble background error covariance information to obtain very close analysis fits to the observations and work to speed up the run time of the 3D RTMA system. Near term planned work includes building a cross validation capability and a running-mean type automated quality control capability.

The 3D RTMA was recently evaluated by the SPC as part of the Hazardous Weather Testbed (HWT) Spring Program. Comparison against their current “sfcOA” system indicated encouraging results for both a 3-km 3D RTMA and a version coarsened to 40-km. The tests also provided some very good feedback to the developers, as some specific issues to be addressed were identified (small-scale CAPE maximum, reflectivity “ghosting”). At the conference, we will summarize the work to date on the RTMA and describe the planned work to move it to a readiness level for transfer to operations.