Training Guide in Surface Weather Observations - Multiple Choices

Question: What does an observer do if there are more than three weather groups, or more than three
types of precipitation are occurring?
Answer: The observer decides which three groups and/or precipitation types are more dominant
than the rest. These three groups or precipitation types are then coded in the
METAR/SPECI report in their order of dominance; the rest are not reported.
Example: Occurring: TS RA SN BR FU HZ
Thunderstorms are always reported when they occur. Moderate rain and snow (precipitation) are considered
part of the group that is coded with the thunderstorm, i.e., TSRASN or TSSNRA. This is one of the three
groups that may be reported. The choice now falls between the mist, smoke, and haze. Each is considered
a separate group. The observer needs to decide which is the least significant or which two are the most
dominant.
If the observer decides that smoke (FU) is least dominant, the present weather for this METAR report could
be: TSRASN BR HZ or TSSNRA HZ BR. The smoke is not used in the report.
Example: Occurring: TS RA SN DZ GS BR
Thunderstorms are always reported when they occur. Even if four types of precipitation are occurring, only
three can be reported. The observer must decide which of them is the least dominant.
The choice for this observation is: TSSNRAGS BR
The light drizzle was considered least dominate and was not reported.
The “Weather Phenomena Matrix” found on the following two pages gives combinations of weather
phenomena and qualifiers (intensity, proximity, and descriptor) that are to be used in METAR/SPECI
reports.
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