We talk about troughs and ridges occasionally when we do the weather. Typically, troughs are synonymous with cool environments, and ridges are synonymous with warmer environments. But, one of the most important aspects of forecasting troughs is how they are shaped. Their orientation can dictate whether a storm will strengthen, weaken, or unchanged.
There are three types of tilts, a positive, negative and neutral tilt.
Just like on a graph, a line with a positive slope is one that is oriented from the lower left of the point of origin to the upper right. Therefore, a positively tilted trough is one that is oriented from the southwest to the northeast. A neutral trough is oriented from north to south, and a negatively tilted trough is pointing from the northwest to the south east.
A negatively tilted trough is one which is the most recognized and has the most importance. The way this is positioned will allow a storm to grow and strengthen. Colder air will have the ability to lay on top of the warmer, more humid air that the storm is feeding from at the surface. With cold air aloft and warmer air closer to the ground, instability is created, allowing for convection and a strengthening of a storm system. Click here to see what a negatively tilted trough looks like.
The opposite is true for a positively tiled trough. Since colder air is not directly on top of the warmer air, there will be very little if any instability. Click here to see what a positively tilted though looks like. However, a positively tiled trough can swing around and become negative with enough momentum from winds in the upper levels.
There are many other factors that go into the genesis as well as dissolution of storms, but just the simple shape of a trough can pan out the future of a large scaled event.
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