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Frontal Characteristics

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).

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last updated on 12/14/10