Frontogenesis Identification

Frontogenesis is the development of a front where none has
previously existed or the intensification of an already existing 
front.  Generally, if the contrast between two air masses becomes 
greater, frontogenesis has occurred. 

To identify frontogenesis, compare the current surface chart or 
1000-500 mb thickness chart to previous charts.  This comparison 
is relative, a visual comparison of the analysis.  See if the 
thickness lines are closer together or farther apart.
       	
Thickness isopleth gradients.  
Thickness isopleth gradient tightening indicates frontogenesis. 
If thickness isopleths are closer spaced on the current 1000-500 
mb thickness chart than they were on the previous chart, 
frontogenesis has occurred (Figure 4-12).  Of course that’s 
because gradient tightening implies an increase in temperature 
advection, therefore more temperature contrast between the air 
masses.

Isotherm gradients.  
The same idea works on a surface chart’s isothermal analysis.  
If the isotherms on the current surface chart are more closely 
spaced than previously, the isotherm gradient is tighter and 
frontogenesis is occurring.	

Isobar Gradients.  
Other considerations to be made are isobar gradient tightening 
and/or an increase in cyclonic curvature.  These are signs that 
frontogenesis is occurring.  Make a relative comparison of 
current chart and previous charts to determine frontogenesis. 

Frontal Inversions.  
Skew-T’s are another good tool.  The presence of a frontal 
(temperature) inversion on a Skew-T will indicate frontal 
strength.  An inversion is when the temperature curve gets 
warmer with height.  This is opposite what is normal for the 
atmosphere; temperatures ordinarily decrease with height The 
frontal inversion is a vertical depiction of a transition zone 
between the air masses and the frontal surface aloft.  If a 
frontal inversion increases (becomes warmer with height) on 
the current Skew-T compared to the last Skew-T, it means that 
there is now greater temperature contrast between the two air 
masses, and this is frontogenesis.