The Real-Time Mesoscale Analysis (RTMA) of the National Centers for Environmental Prediction (NCEP) includes 5 km resolution hourly analyses of temperature, wind, and moisture. Surface observations used in the RTMA must presently: (1) fall within 12 minutes of the top of the hour and (2) be received at NCEP by 25 minutes past the hour. Hence, both the valid time at which observations are available and the latencies in the transmission of the observations can potentially influence the quality of the RTMA analyses. The timing and latency of mesonet observations available around the nation are examined using the MesoWest (http://www.met.utah.edu/mesowest) archive.

Sensitivity of ADAS surface analyses to the valid time and latency of mesonet observations is examined using the ARPS Data Assimilation System (ADAS) on the same grid used by the RTMA in the western U.S for a sample of roughly 170 analyses. Similar preliminary data denial experiments with the RTMA for the nation as a whole are also presented in order to assess directly the sensitivity of the RTMA to the mesonet observations available to the analyses.