Hurricane Erin, while no longer a Category 5 storm, is a huge storm. Part of why it's become so large is a process known as the eyewall replacement cycle.
An infamous example of an eyewall replacement cycle happened before Hurricane Katrina made landfall.
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What is the eyewall replacement cycle?
The eyewall replacement cycle (ERC) is the hurricane's way of trying to sustain itself. Category 5 storms, while incredibly intense, cannot keep that kind of energy going for very long.
It's like the figure skater analogy. If a figure skater has their arms wrapped tightly, they spin faster. In most cases, however, you'll see them bring their arms out as a way to keep spinning. BUT, they spin much more slowly.
What are the stages to the "ERC?"
You start out with a neatly defined eye to the hurricane. That's essentially your first step. A lot of times, you'll either have energy outside the small eye robbing it of energy. Or, the eye is simply too small to keep staying that organized.
The ERC then begins with the eye shutting off. We saw this happen Monday morning. Meanwhile, the wind field grows outside the center of the storm.
As energy is dispersed outward from the center of the storm, the storm becomes larger.
The wind field to the storm continues to grow as each ERC happens. By the time Erin is off our coast, the tropical storm force wind gusts may stretch 700 miles from west to east.
However, we don't expect those sorts of gusts this far inland.
What does this mean for our coast?
Large storms - and their subsequent large wind fields - can bring significant impacts to coastal communities. These impacts range from storm surge to rip currents to coastal flooding and wind.
Rip current risks will be moderate-to-high from the Florida coast all the way up to New England throughout the week.
Storm surges of two-to-four feet are expected along the Outer Banks, hence the storm surge watch that's been issued.
There is also a tropical storm watch in effect until further notice from the Outer Banks to the Virginia and Maryland coastlines.
Have questions about the weather and how it works?
Send me an email with the subject line 'Ask the Meteorologist:' to cmichaels@jshu.net.