Definition
In a METAR, a descriptor is a two-letter code placed immediately before a precipitation or obscuration code to modify or further describe the weather phenomenon being reported. Descriptors include codes such as TS (thunderstorm), SH (shower), FZ (freezing), BC (patches), BL (blowing), DR (drifting), MI (shallow), and PR (partial).
Plain English
It's a short code in a weather report that adds extra detail to a weather event, telling you what kind it is or how it's behaving — for example, whether rain is showering, freezing, or coming with a thunderstorm.
Context Anchor
Pilots encounter descriptors when reading the present-weather part of a METAR, such as weather reported as showers, blowing snow, or freezing rain.
Derivation
From Latin describere, meaning 'to write down' or 'to set out in words.' A descriptor literally describes — it adds a layer of detail to whatever it's attached to. In METAR coding, it describes the character of the weather, not the weather itself.
Why Pilots Care
Descriptors change how a pilot interprets visibility, runway conditions, and potential hazards such as icing or low-level wind shear.
Intuition Check
Do not read descriptor as just any descriptive word in the report. In METAR use, a descriptor is a specific coded modifier that changes or sharpens the meaning of the reported weather.
Example Sentence 1
The METAR showed -SHRA, where SH is the descriptor indicating the rain was falling as a shower.
Example Sentence 2
Blowing snow appeared in the report as BLSN, with BL serving as the descriptor for the wind-driven snow.