Anvil vs. wind
As the anvil is forming, it is under the influence of upper level winds. Typically as you go higher in the troposphere, winds increase. Under stable conditions with a high pressure, winds in the upper part of the troposphere can be very weak, below 10 km/h. However, under more unstable conditions when a jetstream may be present aloft, wind speeds can exceed 200-250 km/h. The strength of upper level winds strongly influences the form of the anvil. We take a look how.