For many years the National Meteorological Center (NMC) and its successor, the National Centers for Envirnomental Prediction (NCEP) labeled the characteristics of fronts on their North American analyses. The table below summarizes these characteristics, circa 1970.
Extract from WMO Code FM 46C (IAC)
The group (FtFiFc) appears near fronts on surface charts.
| Code | Ft | Fi | Fc |
| Figure | Type of Front | Intensity of Front | Character of Front |
| 0 | quasi-stationary | no specification | no specification |
| 1 | warm front | weak, decreasing (frontalysis) | frontal activity are decreasing |
| 2 | warm occlusion | weak, little or no change | frontal activity area little or no change |
| 3 | upper warm front | weak, increasing (frontalysis) | frontal activity area increasing |
| 4 | cold front | moderate decreasing | ITCZ |
| 5 | cold occlusion | moderate, little or no change | forming or existence expected |
| 6 | upper cold front | moderate, increasing | quasi-stationary |
| 7 | instability line | strong, decreasing | with waves |
| 8 | ITCZ | strong, little or no change | diffuse |
| 9 | occlusion | strong, increasing | position doubtful |
A frontal code of 457 would mean a cold front (4) with an intensity of moderate, little or no change since the last analysis (5) with waves along the front (7).