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Natural Conv. Boundaries
METEOROLOGIST JEFF HABY
Two ways of categorizing convergence boundaries are natural and man-made convergence boundaries. This writing will focus on natural
convergence boundaries. Natural convergence boundaries help create convergence when the wind is from a particular direction.
One of the most common convergence boundaries are ones created by elevation changes. When the land elevation changes, wind flow is
forced to interact with this boundary. Higher above the surface the wind is less influenced by friction, but when it moves into a
higher elevation land region the wind will be forced to interact with the land. This will cause the air to slow down. This slowing
causes convergence to occur. This convergence occurs most significantly on the windward facing slope of the elevated region. The windward
side in any particular weather situation is going to depend on the wind direction. This location can be a burst point for convection to
occur due to the extra lifting provided by the windward slope. The slope does not have to be a mountain. Gently rising elevation
changes over large areas and big hills can also aid in burst point convergence.
Other natural boundaries are more subtle but can also act as the focal point for first convection. One example is a water and
land boundary. Wind flows faster over water thus when it interacts with land it will slow down and convergence. This is especially
true over large lakes and ocean-land boundaries. Another example is plains and forest boundaries. The plains region tends to be
flatter with less trees and this causes the wind to be stronger. When this air flows into a forest region it can lead to convergence. A
final example is a natural boundary produced by river valleys. The land sloping on each side of the valley and vegetation changes away
from the river over distance can lead to convergence taking place. When no storms have formed yet but are about to, a convergence
boundary is a popular place for first convection due to the extra lift provided.