For the gradient wind to follow cyclonically curved isobars the pressure gradient force must be slightly stronger than Coriolis to provide the centripetal force.
Because of the frictional drag of the earth's surface, wind speeds at ground level are much lower than those in the unobstructed flow several hundred feet higher (gradient wind).
In the absence of actual upper-level data, the probability distribution of gradient wind speed and direction can be estimated from the Weibull model derived from the surface anemometer records.
If conditions are such that these three effects are in balance, it is referred to as gradient wind, and as the geostrophic wind if there is no isobar curvature.
This pressure is not particularly low compared to many other outbreak setups but the pressure gradient was strong which induced strong gradient winds and significant advection in the warm sector.
Dynamics and circulation: forces which drive the atmosphere, geostrophic and gradient winds, thermally driven circulations, the general circulation, air masses and fronts, vertical structure of weather systems and storms, weather radar.
In wind tunnel simulations, the wind speed corresponding approximately to the gradient wind is the free-stream speed above the simulated atmospheric boundary layer, which is usually recorded as the experimental reference speed.
As the magnitude of the Coriolis is directly dependent on wind speed it follows that the wind speed around a low is less than would be expected from the pressure gradient force and the gradient wind is sub-geostrophic.
Not all solutions of the gradient wind speed yield physically plausible results: the right-hand side as a whole needs be positive because of the definition of speed; and the quantity under square root needs to be non-negative.
For the three forces to be in equilibrium the Coriolis must exceed the pressure gradient force and consequently the gradient wind speed must be greater than would be expected from the pressure gradient force and is thus super-geostrophic.
The height above ground where surface friction has a negligible effect on wind speed is called the "gradient height" and the wind speed above this height is assumed to be a constant called the "gradient wind speed".