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Interpreting Data

How do I interpret the symbols used on the Synoptic charts?

There are three main symbols used on the synoptic charts. The first is the pressure labels. High pressure centres are marked with an red ?H? and the corresponding pressure at the centre of the high. Low pressure centres are marked with a blue ?L? and the corresponding pressure at the centre of the low.

The second group of symbols is the troughs and fronts. These are drawn in yellow. Cold fronts are marked as solid yellow lines with triangles pointing in the direction the front is moving. Warm fronts are marked as solid yellow lines with semi-circles pointing in the direction the front is moving. Troughs are marked as dashed yellow lines.

The final group of symbols is the arrows. These relate to wind direction and temperature. The arrows point towards the direction that the wind is blowing to.

Blue arrows indicate a cold airmass, likely resulting in temperatures 5 or more degrees below average.

Green arrows indicate a mild airmass, likely resulting in temperatures close to or slightly below average.

Brown arrows indicate a warm airmass, likely resulting in temperatures close to or slightly above average. Red arrows indicate a hot airmass, likely resulting in temperatures 5 or more degrees above average. Note that the length of the arrow does not correspond to wind strength - all arrows are the same length.

Occasionally, tropical cyclones may also appear on the weather charts. These appear as an orange cyclone symbol.

Jetstreams are also drawn on the analysis chart. These are marked by shaded blue areas with a white arrow indicating their direction of movement.

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