I THINK it's for Eyewall Replacement Cycle. The eye weakens a bit before it gets stronger and bigger. (From what I gleaned from earlier Katrina threads).
Eyewall replacement cycle; in most hurricanes the eye simply collapses every 12-24 hours and another eye forms. The storm spreads out a bit, but weakens considerably while this happens. (One of our excellent hurricane experts can explain the technical details, that's just the simple explanation that I can remember.)
The reason you hear people on here worrying about "annular" hurricanes is that annular storms don't undergo eyewall replacements; they've reached a steady state where they can sustain themselves without the eye having to collapse and reform.
}:-)4
Eyewall Replacement Cycle. It's when the eye closes and opens again. Usually there is a burst of strength when the eye is opening back up coupled with a "flattening" of the wind filed. I see no indication of an ERC in this storm yet, and it may already be annular (no ERC).