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The notation of a weather chart and a synoptic observation: the present-weather glyph families and the counting rule behind them, cloud genera from the WMO's own Cloud Atlas, upper-air and pressure conventions, warning scales and the coded report forms. The group's organising fact is that the whole present-weather table is learnable through one rule — the shape says what is falling and the count says how hard — and that broadcast graphics and synoptic charts draw wind in opposite directions.
A tiny line drawing of how pressure has moved over three hours.
Filled dots whose number and grouping give rain's intensity and continuity.
Six-pointed asterisks whose number gives the snowfall's intensity.
Commas standing for drops too small to be rain.
A capital R with a hooked tail and an arrowhead.
Three stacked horizontal lines marking visibility below a kilometre.
An angular infinity-like mark for suspended dry particles.
A solid triangle beneath a precipitation mark.
A triangle with a dot, marking ice pellets from a storm.
A domed shape on a flat base, marking heaped fair-weather cloud.
A heaped cloud drawn with a spreading anvil top.
A flat horizontal layer, the lowest and dullest cloud.
Fine curved streaks marking high ice cloud.
A patterned mid-level layer of rounded cloudlets.
A circle shaded in eighths to show how much sky is cloudy.
A zigzag or marked line along an axis of high pressure.
A worded warning tied to a defined Beaufort force.
Defined words from good to fog for how far can be seen.
An arrow showing wind direction on a public forecast map.
A broad banded arrow showing a fast upper-level current.
A line marking air streams meeting and rising.
A graded colour scale from yellow to red for expected impact.
Numbered intensity scales that differ between ocean basins.
A colour ramp showing how strongly rain reflects radar.
Five-figure groups encoding a whole observation for transmission.
A coded aviation weather report in fixed abbreviated fields.