Over the past 6 hours, the eye has completely collapsed and is attempting to regenerate. Microwave shows what appears to be a gigantic 60nm eye trying to form around the old 15-20nm eye that is barely hanging on. This is the 9:40utc microwave pass.
However, what I noticed that really grabbed my attention was the change in IR structure over the past 9 hours. Compare the two following pictures:
Note the complete shedding of outer convection and the wrapping of the outer bands over each other. This is classic preparation for an annular storm. From Wikipedia:
"Observations show that an eyewall replacement cycle can lead to the development of an annular hurricane. ... Annular hurricanes have been simulated that have gone through the life cycle of an eyewall replacement. The simulations show that the major rainbands will grow such that the arms will overlap, and then it spiral into itself to form a concentric eyewall. The inner eyewall dissipates, leaving a hurricane with a singular large eye with no rainbands."
That appears to be exactly what is happening with Igor. Igor is not yet annular, but it looks to be in the development process. The biggest hampering aspect is the southern rain band is not fully formed, meaning that the new outer eye is not 100%, allowing the old inner core to continue to be driven moisture from the south. Whether Igor completes the ERC and becomes annular or is able to regenerate the old eye and stay non-annular is yet to be seen.
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