A METAR includes the group VRB04KT. What does this describe?

METAR wind groups follow a fixed template: three digits of direction, two or three digits of speed, an optional G and gust value, then the unit KT. VRB replaces the direction digits when the wind is too variable for a single direction to be meaningful, which typically happens at low speeds. So VRB04KT parses as variable direction, 4 knots. For a remote pilot the reading matters more than the arithmetic: light and variable means the wind can arrive from any quadrant without warning, which is exactly the condition that produces unexpected drift during a precision hover or an unplanned tailwind on landing.

VRB indicates the wind direction is variable, and 04KT gives the speed as 4 knots. The group therefore describes a light wind with no consistent direction, which is the standard way METAR reports a wind too shifty to assign a heading.

A METAR is a coded surface observation with groups in a fixed order: station, time, wind, visibility, weather, sky condition, temperature and dewpoint, altimeter. Recognizing which group you are looking at comes from its position and its unit suffix.

VRB sits where the three direction digits would be, so it can only be a direction. The number before KT is always the speed — the unit tells you what the digits mean.

Light and variable is not the same as calm. VRB04KT still moves a small aircraft, and because the direction is unpredictable it deserves more caution than a steady 4 knots.

• •Reading VRB as a variable speed rather than a variable direction
• •Mistaking the wind group's digits for visibility or vertical visibility
• •Treating light and variable as equivalent to calm