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A low pressure area is associated with rising air while a high pressure area is associated with subsiding air. The best explanation I could come up with is either the cyclone is an exception or the above associations are not an absolute rule in the first place. However, none of the articles I read provide an explanation on this phenomenon, indicating that I am missing something trivial. Could anyone shed some light on this? I would appreciate a layman explanation.

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I will just talk about an already formed tropical cyclone. Converging winds spiral in (counterclockwise in northern hemisphere) over the warm ocean waters towards the central low pressure area of the eye.

At the eye they spiral upwards, taking the warm, moist ocean air high into the atmosphere. As it reaches cooler elevation, the air releases its latent heat, adding more energy to the storm.

So you have a tremendous volume of air converging from 360 degrees around the hundreds of miles of the storm, all converging on the eye and spiraling up with an intense updraft, creating a very low pressure near the surface in the eye/core.

High above the eye wall this upflow begins to spread out. This permits cool dry air above the eye to sink down into the central core of the eye (that is why the eye is often clear and cloud free).

So why is the hurricane core/eye low pressure when there is cool dry air subsiding down into the core/eye?

Soundings taken within the eye show a low-level layer (at surface) that is relatively moist with an inversion above, i.e., it appears that the sinking cool dry air (which warms somewhat as it is compressed in descent) never reaches the ocean surface, but only reaches within 1 - 3 km (1 - 2 mi) of the surface. See, among other sources, http://www.aoml.noaa.gov/hrd/tcfaq/A11.html.

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  • $\begingroup$ In retrospect, your answer gave me the clearest explanation. Thank you. $\endgroup$ – Jayesh Bhoot Aug 31 '18 at 4:55
  • $\begingroup$ @JayeshBhoot Glad you decided answer ok. I was on the US New England coast when Gloria hit in 1985 Sept. 27 about 1700 UC (I refused to evacuate, but left when the sea began to come up to my apartment). It was difficult to stand in the gusts 85-90 mph. The eye was amazing. It did feel slightly moist, eerily calm and sunny with blue sky after minutes before gray hurricane rage. We drove into town over treelimbs and power lines and had free beer and seafood, the restaurants having no power and giving it away. So, the explanation of an inversion in the eye at ground level felt believable. $\endgroup$ – Dalton Bentley Oct 1 '18 at 19:12

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