Stationary front symbol

How to read it

NOAA’s Weather Prediction Center defines a stationary front as one between warm and cold air masses that is moving very slowly or not at all; its Unified Surface Analysis Manual puts the limit at less than 10 knots (12 mph) and draws it with alternating red bumps and blue spikes. NOAA’s JetStream describes the triangles on the blue parts pointing away from the cool air and the half-moons on the opposite side of the red parts, pointing away from the warm air. A cold or warm front that stops moving becomes a stationary front, JetStream says.

The WMO’s manual on weather charts calls it a quasi-stationary front and gives it alternate red and blue when a chart is drawn in colour. Iowa State University’s surface map guide describes the same alternating red and blue line.

Also searched as: alternating red and blue front, quasi-stationary front, red and blue line on a weather map, stationary front.

Look-alikes

On a Cold front symbol or a Warm front symbol all the symbols sit on one side, the way the front is moving. An Occluded front symbol mixes triangles and half circles too, but on the same side of a single purple line. On a stationary front they face opposite ways.