Definition
A wind that blows parallel to curved isobars at altitudes high enough to be free of surface friction, resulting from the balance between the pressure gradient force, the Coriolis force, and the centrifugal force created by the curved flow path.
Plain English
Wind that flows along curved lines of equal pressure, well above the ground where friction no longer slows it down. Three forces -- the push from high to low pressure, the deflecting effect of Earth's rotation, and the outward pull of curving motion -- balance each other so the wind follows the curve.
Context Anchor
Seen in aviation weather and winds aloft discussions, especially when describing wind flow around curved pressure patterns near highs and lows.
Derivation
Gradient' comes from the Latin 'gradus,' meaning 'a step.' In weather, a pressure gradient is the rate at which pressure changes from one place to another -- the 'steps' between pressure values. The gradient wind is the wind that results from that pressure gradient acting on curved flow.
Why Pilots Care
Understanding gradient winds helps pilots anticipate wind directions and speeds at altitude for accurate navigation and fuel calculations.
Grounding Statement
Picture a weather chart with curved lines circling a low-pressure area. Above the friction layer, the wind doesn't cut across those lines -- it follows them around the curve.
Intuition Check
Gradient does not mean a runway slope here. In this term, it refers to a change in air pressure over distance that helps drive the wind.
Example Sentence 1
At cruise altitude the aircraft was riding the gradient wind, which curved smoothly around the low-pressure system shown on the chart.
Example Sentence 2
Pilots adjust headings based on the gradient wind reported in the area forecast.