Understanding Eyewall Replacement Cycles in Hurricanes
It is common for strong and powerful storms to undergo eyewall replacements, which allow for a brief period of weakening, like we saw with Milton going from a Category 5 to a Category 4 early Tuesday.
What is an Eyewall?
An eyewall is a ring of tall thunderstorms that produce heavy rains and usually the strongest winds. As hurricanes strengthen, the eyewall becomes tighter and more intense until it reaches maximum strength in its environment.
Eyewall Replacement Cycles
A new eyewall may then begin to form on the outside of the previous inner eyewall, which cuts off the energy for the intense inner eyewall. This causes it to collapse and weaken. As a result, the storm’s strength and intensity decrease, which is often referred to as an eyewall replacement cycle.
The Cycle’s Impact on the Storm’s Strength
As the outer eyewall regains organization, the storm will often re-increase in intensity. This process can take several hours (around 12 to 18) to complete. The forecast models have extreme difficulty with predicting an eyewall replacement cycle.
Expansion of the Wind Field
Although an eyewall replacement cycle can reduce the category of a hurricane, we can also experience the expansion of the wind field. This means the hurricane force winds and tropical storm force winds begin to reach out over a larger area. In the case of Milton, we are expected to see an expansion of the wind field as it weakens and approaches Florida.
Important Takeaways
- An eyewall replacement cycle does not necessarily mean the storm will not be a threat.
- The storm’s category may decrease, but it will still be a major and dangerous storm at landfall.
- The expansion of the wind field can lead to a larger area affected by hurricane force and tropical storm force winds.
FAQs
Q: What is an eyewall?
A: An eyewall is a ring of tall thunderstorms that produce heavy rains and usually the strongest winds.
Q: How does an eyewall replacement cycle work?
A: A new eyewall forms on the outside of the previous inner eyewall, cutting off the energy for the intense inner eyewall and causing it to collapse and weaken.
Q: What happens after an eyewall replacement cycle?
A: The storm may re-increase in intensity as the outer eyewall regains organization, which can take several hours to complete.
Q: Does an eyewall replacement cycle make the storm less of a threat?
A: No, it does not necessarily mean the storm will not be a threat. The storm’s category may decrease, but it will still be a major and dangerous storm at landfall.
