A Description of the v2.8 RTMA/URMA Upgrade and Progress Toward 3D RTMA

NOAA’s Real Time and UnRestricted Mesoscale Analysis systems (RTMA and URMA respectively) produce ~2.5 km near-surface analyses of sensible weather elements at hourly intervals for use in nowcasting, calibration, and bias correction - notably in NOAA’s National Blend of Models. The RTMA/URMA are implementations of a 2D variational data assimilation system.

Version 2.8 offers several enhancements, many of which have been inspired by feedback from stakeholders in addition to objective statistics. Of particular interest has been the recent advancement toward improving slow wind speed bias relative to METAR observations in RTMA/URMA. This improvement has come largely by way of introducing similarity theory-based adjustments to the wind forward operator to account for differing, non-standard heights of mesonet anemometers. This allows the RTMA/URMA to use the observations more consistently, which avoids introducing biases into the analysis owing to assumptions with non-standard station siting.

Other highlights of the v2.8 upgrade include, but are not limited to: the expansion of the significant wave height analysis to the Great Lakes and Guam domains, revised sky cover analysis with diurnal quality control, expansion of v2.7 CONUS enhancements to OCONUS domains, and quality enhancements to the non-variational URMA precipitation product.

Finally the 2D RTMA system is also undergoing significant upgrades in the transition to become a fully 3D system with sub-hourly updating capability, anticipated in the 2022 timeframe. Current progress as well as recent experience with the 3D RTMA at NOAA testbeds will be discussed in addition to the highlights of the v2.8 RTMA/URMA upgrade.