Type Tracking

Is the cold front on your doorstep a growing, storm-laden monster with 50-knot winds or is it a nonevent, a mere wind-shift in clear skies? Although little advertised, there is a way to decode a front's intensity and trend. It's hidden in the chapter on surface analysis charts in the FAA's Aviation Weather Services, or AC-00-45E. To see the code in action, visit the Web site (www.awc-kc.noaa.gov/awc/aviation_weather_center.html) and click on the "surface analysis chart" link. The code uses three numbers in sequence, and it's printed near the plotted front's surface position. Here's how to break the code:

The first number indicates the type of front:

1 Quasi-stationary at surface
2 Quasi-stationary above surface
3 Warm front at surface
4 Warm front above surface
5 Cold front at surface
6 Cold front above surface
7 Occlusion
8 Instability (squall) line
9 Intertropical front
10 Convergence line

 

The second number indicates the intensity of the front:

1 No specification
2 Weak, decreasing
3 Weak, little or no change
4 Weak, increasing
5 Moderate, decreasing
6 Moderate, little or no change
7 Moderate, increasing
8 Strong, decreasing
9 Strong, little or no change
10 Strong, increasing

 

The third number indicates what the National Weather Service calls the character of the front:

1 No specification
2 Frontal area activity, decreasing
3 Frontal area activity, little change
4 Frontal area activity, increasing
5 Intertropical
6 Forming or existence expected
7 Quasi-stationary
8 With waves
9 Diffuse
10 Position doubtful

 

AOPA Wx Watch - Winter Wise - More fronts, moving faster

BY THOMAS A. HORNE (From AOPA Pilot, December 2001.)