Definition
The change in atmospheric pressure at a given location over a defined period of time, typically the preceding three hours. It is reported as the amount and direction of pressure change (rising, falling, or steady) and is used as an indicator of approaching weather changes.
Plain English
How the air pressure at a place has been moving recently — going up, going down, or staying flat — and by how much.
Context Anchor
Seen in weather reports, weather briefings, and discussions of changing weather conditions.
Derivation
From 'barometric' (relating to the barometer, the instrument that measures air pressure) and 'tendency' (a direction of movement or change). Together: the direction in which the pressure is trending.
Why Pilots Care
A falling tendency often signals an approaching front or worsening weather that can affect flight planning and safety.
Grounding Statement
If the pressure at an airport keeps dropping through the afternoon, the barometric tendency is falling.
Intuition Check
Do not read tendency here as a guess about the future. In this context, it is a measured recent change in air pressure.
Example Sentence 1
The barometric tendency showed a steady fall of 3 millibars over the past three hours, suggesting a front was approaching.
Example Sentence 2
A steady barometric tendency on the instrument told the pilot that conditions were holding steady for the short flight.