Vertical wind shear is present nearly everywhere on Earth, since winds typically move faster at higher altitudes than at the surface. It can be stronger or weaker than normal, and that’s especially important during hurricane season.
Tropical storms typically start as a tropical wave, or low-pressure system associated with a cluster of thunderstorms over warm water in the tropics. Warm air over the ocean surface rises rapidly, drawing in fuel for the storm. The winds begin to rotate and can intensify into a tropical storm and then a hurricane.
Hurricanes thrive in environments where their vertical structure is as symmetrical as possible. The more symmetrical the hurricane is, the faster the storm can rotate, like a skater pulling in her arms to spin.
Too much vertical wind shear, however, can offset the top of the storm. This weakens the wind circulation, as well as the transport of heat and moisture needed to fuel the storm. The result can tear a hurricane apart.
El Niño’s and La Niña’s influence
Wind shear becomes a hot topic during El Niño years, when wind shear tends to be stronger over the Atlantic during hurricane season.
An El Niño event occurs when sea surface waters in the eastern Pacific Ocean basin become significantly warmer than average, while western Pacific Ocean basin waters become cooler than average. This happens every two to seven years or so, and it affects weather around the world.
During El Niño events, upper-level winds over the Atlantic tend to be stronger than usual, and thus stronger wind shear results. The faster air flow in the upper troposphere leads to faster wind speed with increasing height, making the upper atmosphere less favorable for tropical storm development. The eastern North Pacific, in contrast, tends to have less wind shear during El Niño.
Vertical wind shear is present nearly everywhere on Earth, since winds typically move faster at higher altitudes than at the surface. It can be stronger or weaker than normal, and that’s especially important during hurricane season.
Tropical storms typically start as a tropical wave, or low-pressure system associated with a cluster of thunderstorms over warm water in the tropics. Warm air over the ocean surface rises rapidly, drawing in fuel for the storm. The winds begin to rotate and can intensify into a tropical storm and then a hurricane.
Hurricanes thrive in environments where their vertical structure is as symmetrical as possible. The more symmetrical the hurricane is, the faster the storm can rotate, like a skater pulling in her arms to spin.
Too much vertical wind shear, however, can offset the top of the storm. This weakens the wind circulation, as well as the transport of heat and moisture needed to fuel the storm. The result can tear a hurricane apart.
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