Storm top dynamics
Anvil growth is an estimate of storm top divergence after the storm has reached its equilibrium level. It is an excellent way to estimate the strength of an updraft as
the anvil initially begins to spread. We define it here as the areal change per time of anvil cloud contained within a particular cloud top temperature contour. See below.
The schematic above shows that anvil growth can be a combination of horizontal and vertical growth of the overshooting top. It all depends on how close to the overshoot you pick your temperature contour.
- If you define your temperature contour near the edge of the anvil, anvil growth will more approximate pure divergence
- If you define your temperature contour near the center of the storm top, anvil growth will be a combination of divergence and vertical velocity