When Hurricane Ian ripped through Florida and the Carolinas, almost every report from a weather forecast described the affect that wind shear had on the impending storm. So it begs the question, what exactly IS wind shear, anyway, and what does it have to do with hurricanes?
What is Wind Shear?
Wind shear is a change in wind speed or direction, typically as you go up into the atmosphere. This is known as vertical wind shear. Strong upper level winds destroy the storms structure by displacing the warm temperatures above the eye and limiting the vertical accent of air parcels, which means that wind shear can make or break a tropical storm or hurricane.
How does Wind Shear affect Hurricanes?
Wind shear is brought up often during tropical forecasting because it can make or break a storm. It’s one of the most critical factors when talking about the formation or destruction of a cyclone. Wind shear simply put is this – a change in wind speed or direction, typically as you go up into the atmosphere.
How does Wind Shear affect Hurricane Formation?
Wind shear hurts tropical cyclones by removing the heat and moisture they need from the area near their center. Shear will also distort the shape of a hurricane by shearing it (blowing the top away from the lower portion), so that the vortex is tilted.
What about Horizontal Wind Shear?
Horizontal wind shear is the change in direction or speed of winds over the surface of the ocean. When a storm encounters strong horizontal wind shear, the storm can be whisked away or shredded by strong uni-directional winds.
An example of strong horizontal wind shear may be along the Atlantic coast of the United States with the approach of a strong cold front or blast of colder air. In this case, strong southerly winds ahead of the front are followed by strong west to northwest winds in the front’s wake.
Wind Shear can Weaken, but also Strengthen a Storm
In some rare cases, wind shear in low to moderate amounts can cause a tropical cyclone to strengthen. Wind shear can push a tropical cyclone into warmer waters, which are more favorable for development.
Just like a sport-tuned exhaust system can give the motor on an automobile more horsepower, wind shear can also vent the tropical cyclone just enough to allow it to strengthen. Increasing winds blowing from the same direction as the circulation around a tropical cyclone can cause the storm to spin faster and strengthen.
Areas of Wind Shear can be Difficult to Spot
Forecasting areas and intensity of wind shear can be more challenging than forecasting the strength and movement of a tropical cyclone itself. This is because wind shear, like the rest of the atmosphere, is constantly changing, may not be easily detected and rarely remains completely stationary.
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