Vertical wind shear is the most dominant when it comes to examining tropical cyclones. It is the change in wind speed and direction at high elevations in the atmosphere. When a strong vertical wind shear is present, the top of the tropical cyclone can start to shift. Once this happens, the storm can be uneven and cause the storm to unwind as dry air comes through and warm moist air flows into the storm. So, when a strong wind shear happens, the jet stream is over the Atlantic and creates a rapid increased wind speed at higher elevations of the atmosphere. So, when dry air comes through with cold sea surfaces, it can progressively decrease the tropical cyclones development, and also, will reduce the number of tropical cyclones to form for that particular season if this continues to occur. Although, in the Pacific when the jet stream is not covering the eastern Pacific, it actually creates more tropical cyclones to develop over the eastern Pacific Basin.
Horizontal wind shear, although, is the speed or direction of wind over the surface of the ocean. When there’s a strong horizontal wind shear, the storm can be can pushed away or broken up. So when there’s a strong horizontal wind shear in the Atlantic for example, it’s indicating that a cold front is approaching. So, the strong winds coming from the south that are ahead of the front are followed by strong west to northwest winds, which are occurring at the front’s visitation.
This image shows that when the storm is more resistant to wind shear, which means there’s a weak wind shear, the storm winds decrease less rapidly, which ends up making the storm bigger. Now when the storm is less resistant to wind shear, meaning there’s a strong wind shear, the storm winds decrease more rapidly, which ends up making the storm weaker.
When wind shear is in the low to moderate range, it can cause a hurricane to intensify. So as winds come from the same direction as the tropical cyclone circulates, it can cause the tropical cyclone to swirl faster and intensify. It can be hard sometimes to detect wind shear because it’s constantly changing just like our atmosphere always changes, so sometimes its hard to tell if wind shear is actually causing the storm to weaken. Low to moderate wind shears tend to shove hurricanes into warmer waters, which is where hurricanes are perfect to intensify. That’s why low to moderate wind shears tend to cause hurricanes to intensify because it wants it to go towards that warmer air and water. Now if the winds are going in opposite directions, you have low to moderate winds coming from the middle and bottom of the development and upper level winds coming from the top of the development, but they’re both coming from opposite directions, which then causes the storm to weaken.
This video shows that when lower to moderate level winds come in from the left and you have upper level winds coming from the opposite direction, you can see the decrease in the development of the storm, which then decreases the winds.
To make it make sense, when there’s a strong horizontal and vertical wind shear, and both having opposite wind directions, the storm will decrease and therefore, the winds will increase. Now if there is a weak horizontal and vertical wind shear, and both have similar similar wind directions, the storm will intensify and the winds will pick up rapidly and the storm will become massive. Now when talking about low to moderate in horizontal wind shear, that occur below and middle of the storm, and you have opposite wind directions in the upper levels of the atmosphere that are still horizontal wind shears, that’ll decrease the storms development. So, when the sea temperatures are warm and there’s low wind shear, that’ll increase the intensity of the storm. Climate change is also to affect the wind shear. The more greenhouse gases we put in the air will weaken the wind shear over the east coast, which in fact will make the intensity of the next upcoming hurricanes more stronger. These affects are suppose to happen rapidly and fast but it is to affect in the 2040’s if we keep putting a large amount greenhouse gases into our atmosphere. We really only have 20 years to try to fix this issue but to do that, we need to reduce greenhouse gases and also, be more prepared for the next upcoming severe weather that is to come our way.
So far we have talked about how tropical storms will increase, decrease, or stay the same and we see that they will typically increase as climate change continues to warm. We also talked about how the storm surge will be affected with a warming climate and how that impacts people. It’s clear that storm surges will get higher as climate continues to warm because sea level is rising due to warmer temperatures and this will impact people badly because they will be at higher risk of devastating damage and flooding. Low wind shear is expected from a warming climate which, will create more intensified hurricanes with warmer sea surface temperatures and that’s very bad because hurricanes will be more stronger than they are today, which, will cause more devastating damage. In my next blog we will talk about how coastal populations will increase risks of stronger hurricanes and how more people being on the coast will cause a warmer climate and the impacts it will have for future cyclones.
“Behind the 2015 Atlantic Hurricane Season: Wind Shear & Tropical Cyclones.” NOAA’s Atlantic Oceanographic and Meteorological Laboratory, August 9th, 2015. https://www.aoml.noaa.gov/news/behind-the-2015-atlantic-hurricane-season-wind-shear-tropical-cyclones/
Deroberts, Nicole. “Climate Change is Destroying a Barrier That Protects the U.S. East Coast from Hurricanes.” Columbia Climate School Climate, Earth, and Society, Earth Institute. May 24th, 2019. https://news.climate.columbia.edu/2019/05/24/wind-shear-hurricanes-east-coast/
The Weather Channel. (August 9, 2013). Hurricaneology: Wind Shear. The Weather Channel [Video] https://www.youtube.com/watch?v=tCyErJRRjPw
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