Definition
On a Winds and Temperature Aloft Forecast (FB), a wind condition where the speed is less than 5 knots and the direction is not steady enough to forecast reliably. It is encoded as '9900' in the four-digit wind group, meaning direction 99 and speed 00.
Plain English
The wind is too weak and shifts around too much to give a useful direction or speed, so the forecast just flags it as light and variable instead of pretending to know which way it's blowing.
Context Anchor
Seen in winds aloft forecasts when the forecast wind is so weak that a specific direction is not useful.
Derivation
Light comes from an old English word meaning not heavy. In weather use, it means weak or gentle. Variable comes from Latin roots meaning changeable, which fits wind that shifts instead of coming from one steady direction.
Why Pilots Care
Tells the pilot that wind will have little effect on takeoff, landing, or cruise but direction may shift unexpectedly.
Grounding Statement
Picture a windsock barely moving and not pointing steadily in one direction.
Intuition Check
Light does not mean brightness here; it means weak wind. Variable does not mean unknown; it means the wind direction is changing or not steady enough to report as one direction.
Example Sentence 1
The 3,000-foot winds aloft showed 9900, so the briefer noted them as light and variable for the route.
Example Sentence 2
At 3000 feet the FB forecast listed light and variable winds indicating calm air with no reliable tailwind or headwind.