International Cloud Atlas
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Additional symbols

(Section 3.1.6)

As shown in chart below, additional symbols have been established to indicate the nature of showery precipitation, the trend over time and location. These can be combined with one or sometimes two basic symbols.

Table 20. Nature of showery precipitation, trend over time and location

Symbol

Nature and/or Trend

Shower, slight

Shower, moderate or heavy

Has increased (or formed) during the preceding hour

Has decreased during the preceding hour

During the [past hour, but not at the time of observation

Not at the station, but within sight (estimated within 5 km)

Not at the station, but within sight (estimated beyond 5 km)

For example:

  • Symbol  denotes fog that has become thinner during the preceding hour;
  • Symbol  indicates rain showers during the preceding hour but not at the time of observation.
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The text enclosed in grey-shaded boxes, like this example, comprises Annex I to the Technical Regulations (WMO-No. 49) and has the legal status of standard practices and procedures.

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