The mean wind is the vector average of the wind across a specified layer of the atmosphere. In storm forecasting, the 0 to 6 kilometer layer-mean wind is the most commonly used version and represents the advective component of a storm's motion.
What it is measuring
A hodograph plots the tips of wind vectors from many levels on a single diagram. The mean wind is the vector average of those tips over the chosen layer. In practice, SPC and most operational tools compute it as a pressure-weighted or simple layer average, depending on the application. On the SPC hodograph, the mean wind for a given layer is marked as a distinct symbol so it can be read directly against the shear vector.
The mean wind captures the bulk motion of the layer through which a deep convective storm builds. It is not the wind at cloud base, and it is not the wind at the equilibrium level. It is the average flow that carries the whole column.
How forecasters use it
The Bunkers Internal Dynamics method for supercell motion treats storm motion as the sum of two pieces. The first is advection by the 0 to 6 kilometer mean wind. The second is propagation, a deviation vector of about 7.5 meters per second perpendicular to the deep-layer shear, to the right for cyclonic right-moving supercells and to the left for anticyclonic left-movers.
Forecasters also use layer-mean winds to estimate multicell and MCS motion, to define storm-relative flow through the inflow and midlevel layers, and to identify chase corridors. Because it is a stable, easily computed quantity, the mean wind serves as a common reference across nearly every storm motion technique.
Where the mean wind misleads
A layer with strongly veering or strongly curved shear can produce a mean wind that points in a direction few actual observed winds share. Reading the mean wind as literal steering flow through the middle of the storm ignores the fact that different parts of the storm are riding on very different flows.
The choice of layer also matters. The 0 to 6 kilometer layer is a convention, not a physical law. For shallow storms or high-based storms with elevated cloud bases, a different depth may better represent what actually steers the cell. SPC and NWS training materials remind forecasters that the mean wind is a component of storm motion, not a replacement for it.