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.)