As with any hurricane season, you may have heard some phrases that you may not have understood.
The first of these is something called an eyewall replacement cycle (ERC). At some point in the life cycle of the hurricane, the eye begins to contract and grow smaller. At the same time, some of the outer rainbands begin to move inward to create a new eye wall. While this process takes place, the cyclone weakens. The new eyewall eventually organizes and the storm can then regain its original intensity, or may even become stronger. So, basically the eyewall begins to collapse while the outer rainbands move in to take its place.
Another phrase you may have hears is The Stadium Effect. This occurs within the eyewall and is often seen by hurricane hunters. This effect occurs when the eyewall widens with height as it spirals upward, creating a look similar to that of a stadium. Air moves outward as it rises due, in part, because of less friction with increasing altitude. As a result of less friction, the wind speeds increase and “fling” (centrifugal force) the parcels outward more with height.
The Brown Ocean Effect is a phrase we give to tropical systems that strengthen on land. Tropical systems usually weaken when they make landfall, but that isn’t always the case. If a hurricane moves over an area with high moisture content from evaporation, such as marshes or swamps, it might not realize that it is no longer over the ocean. Saturated soils may create conditions similar to what the cyclone experienced over the ocean. This can cause the tropical system to either hold on to its intensity or even strengthen if conditions are right.
I hope these explanations help you understand tropical systems much better. Hurricane season ends November 30th.