Definition
In a METAR, TS is the weather code for a thunderstorm — a localized storm produced by a cumulonimbus cloud, always accompanied by lightning and thunder, and often containing strong updrafts and downdrafts, heavy precipitation, turbulence, hail, icing, and wind shear. TS may appear alone or combined with a precipitation code, such as TSRA (thunderstorm with rain) or TSGR (thunderstorm with hail).
Plain English
TS in a weather report means a thunderstorm is happening at the airport. If a precipitation code follows, that tells you what's falling with it.
Context Anchor
Seen in METAR weather reports in the present-weather section, often before a flight or while checking conditions near an airport.
Derivation
TS is a shortened weather-report code formed from the word “thunderstorm.” In METAR coding, short letter groups are used so weather conditions can be reported quickly and consistently.
Why Pilots Care
Thunderstorms generate severe turbulence, icing, microbursts, hail, and lightning that can damage aircraft or cause loss of control.
Grounding Statement
When TS appears in a weather report, picture active storm clouds near the reporting area, not just ordinary rain.
Intuition Check
TS does not mean simply “rainy weather.” It means thunderstorm activity, which brings stronger and more sudden hazards than normal rain.
Example Sentence 1
The METAR showed TSRA, so the pilot delayed departure until the thunderstorm moved off the field.
Example Sentence 2
Checking the forecast for TS helped the crew delay departure until the line of storms passed.