MesoWest Quality Control Flags Help Page

MesoWest has been designed for use by National Weather Service meteorologists and other professionals for protection of life and property. Comments/suggestions for improvement may be sent to

For downloaded or acquired MesoWest data, there is a variable called QFLAG included with each observation. This variable is used to define the quality of data from a particular station.

For all stations, the QFLAG variable for an observation is initially set to 0 (Unknown).

The first step in the quality control process involves the range checks on incoming observations for a station. If a variable in the observation is found to be outside of an acceptable range, QFLAG for that observation is changed to -1 (Suspect). If the observation time appears suspect (e.g. a "future" observation where the time reported is well ahead of the current time), but the data values pass the range checks, QFLAG for that observation is changed to 3 (Suspect Time).

The next step involves the multivariate linear regression analysis using temperature, dew point, and pressure data. Data from the previous 6 hours is used to generate absolute average difference statistics for temperature, dew point, and pressure. If the absolute average difference rises above any one of the listed thresholds (15 for temperature, 20 for dew point, 15 for pressure), QFLAG for that observation is changed to 1 (Caution).

Additionally, a separate wind check program is run which looks for stagnant wind observations over the previous 3 days. If this check reveals a suspicious pattern of repeating wind observations, QFLAG for that observation is changed to 1 (Caution).

If all checks are passed successfully, then QFLAG for that observation is changed to 2 (OK).

If the station lacks significant data used in the multivariate linear regression analysis, the QFLAG for that observation is then changed to 9 (N/A).

A summary of the values and meanings for QFLAG are shown in the table below...

QFLAG Value Description
-1 Suspect: One of the variables in an observation did not pass the "range checks".
0 Unknown: MesoWest Quality Control processes have not been applied to this observation.
1 Caution: Data in this observation did not pass one of the "statistical checks".
2 OK: Data has passed all MesoWest Quality Control processes successfully.
3 Suspect Time: The reported time of the observation appears suspect.
9 N/A: Station lacks significant data to run the multivariate linear regression analysis.