As part of the ongoing Great Lakes Fleet Experiment testing experimental TAMDAR aircraft observations, now sponsored by FAA in the 2006 Phase 2, NOAA/ESRL/GSD has continued its observation impact experiments (with and without TAMDAR) using the Rapid Update Cycle through 2006. During 2006, changes were made with the experimental RUC to improve TAMDAR quality control and to improve its data assimilation, while during the same period, AirDat (providing TAMDAR data) further refined its own processing.

NOAA/ESRL/GSD's TAMDAR RUC experiments have continued to use up-to-date assimilation/model techniques (generally corresponding to the 13km RUC, but run at 20km resolution), complete assimilation of all observation types (as used in the RUC13, including cloud analysis (GOES and METAR), full METAR assimilation with effects of boundary-layer depth, GOES precipitable water, all other aircraft, profiler (NOAA and 915-MHz boundary layer), and rawinsonde). With its hourly assimilation and full use of other observations, the RUC provides a stringent assessment for forecast value added to other pre-existing observations from TAMDAR data. The forecast experiments were strictly controlled to isolate the effects of TAMDAR data, including a resetting of common initial conditions every 48h to ensure a full control.

Forecast skill in these parallel RUC cycles with and without TAMDAR data has continued to be evaluated by verification against upper-level rawinsondes, surface observations, and precipitation. Results have, in general, shown a modest improvement in 2006 over 2005, now including a more consistent positive effect for 850-hPa relative humidity. Relative humidity results at 700-500 hPa have been less clear. A fairly strong positive impact has continued, for temperature, especially at 850 hPa, and to lesser degree for winds. The results have continued to change over time due to variations in TAMDAR vertical resolution, quality procedures for data, and geographical and diurnal variations in data density. The 2006 TAMDAR RUC experiments have helped, along with the case study investigations discussed by Szoke et al. (this conference), to improve the TAMDAR data quality and improved experimental forecasts for aviation.