What you're looking at is one, dry air entraining into the system and two, an eyewall replacement cycle; there are two eye walls here; the second about 60 nm out. It has contracted about 20 nm since this photo was taken. It is important to remember during eyewall replacement cycles the tops of these storms warm and while on IR there is a change in color does not mean it isn't there; I looked at a microwave loop today and the eye continues to exist though not on visible satellite; an obscure eye doesn't dismiss the fact it remains. NHC has a chart with some skill in this area of expertise; however it remains to this day a crap shoot.