FRONTS - "DON'T EVEN THINK ABOUT SAYING 'LOW'!"
Rules for Finding Fronts
  1. Look for a strong temperature gradient (difference). The front will be at the warm side of the sharpest gradient.
  2. Likewise, look for a strong dew point gradient. The front will be on the warm side of the gradient.
  3. The front will be found in a pressure trough.
  4. Look at the three hour pressure changes, known a tendencies. With the passage of the front the pressure will decrease then increase, giving a trace which looks like a check mark, or check tendency.
  5. Look for a sharp change in the wind direction. A cyclonic shear in the wind usually indicates frontal passage.
  6. Check weather and cloud patterns that are usually associated with different kinds of fronts.

FRONTS

Fronts: A narrow transistion zone, or boundary, between disparate synoptic scale air masses whose primary discontinuity is density. Fronts are commonly associated with a moisture gradient, a pressure trough, a wind shift and/or various sensible weather phenomena. A front is a convergent boundary. It is synoptic scale along the length of the front, but mesoscale across the front itself.

A quick look at a surface cyclone

There are four types of fronts: cold, warm, occluded and stationary. Each front marks the transition zone between air masses.

COLD FRONTS

- Cold fronts are marked by blue lines with triangles pointing toward the warm air, indicating the direction of motion.

- slope (m) = 1/50 to 1/150

- Cold fronts usually generate strong lifting and hence ahead of the front there are usually areas of moderate to strong convection.

Precipitation is usually in the form of showers and thunderstorms.

WARM FRONTS

- Warm fronts are marked by red lines with half circles penetrating the cold air and indicating the direction of motion.

- m = 1/100 to 1/300

- Warm fronts generally force air to rise over the frontal boundary and continuos precipitation is likely. However if the air on the warm side of the front is unstable, thunderstorms and showers are possible.

STATIONARY FRONTS

- Stationary fronts are mrked by alternating blue lines with a triangle and red lines with a half-circle, using the same convention as before. There is no movement.

OCCLUDED FRONTS

- Occluded fronts occur when the cold front "overtakes" the warm front, pushing the warm air above the surface.

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