| Flag | Definition |
|---|---|
| 1 | Not used |
| 2 | Not used |
| 3 | Not used |
| 4 | Not used |
| 5 | Not used |
| 6 | Not used |
| 7 | Uncertainty consistent with NWS practices and the
instrument or observation used to obtain the data |
| 8 | Greater uncertainty than 7 because values were
interpolated or estimated |
| 9 | Greater uncertainty than 8 or unknown |
| 0 | Not definable |