While Katia does exhibit some of the fundamentals for an annular hurricane, she is not quite there yet. Here is a good definition of Annular hurricanes from Wikipedia:
Note that one of the formation requirements IS an eyewall replacement cycle. Another is a lack of banding features - and Katia still has a feeder band to the northeast. SSTs are at 28C which is within the acceptable range, but its on the high side. Although highly uncommon I've seen ERCs in Cat I and Cat II storms. Why they happen in some weaker hurricanes but not others is still one of the mysteries of hurricanes.
Regarding the size of the eye, its actually a misconception that a large eye size normally means a stronger hurricane. In August, 2000, Hurricane Alberto varied from a Tropical Storm to a Cat III Hurricane over a period of almost 3 weeks and was considered to be annular at various times during its evolution - including Cat I in the north Atlantic - with a 60 mile wide eye. In 1978, Hurricane Fico in the eastern and central Pacific moved to the west just to the north of 15N for 9 straight days with a 60 mile wide eye and intensities that varied from Cat I to Cat IV, but Fico was not annular. Fico still had a 60 mile wide eye when it passed southeast of the Big Isle on August 20th as a Cat II. However, you are probably correct that an annular hurricane always has a large eye.
Maybe Katia will get to the annular state in a day or so. Certainly a topic of good discussion as long as we can keep it focused on Katia. ED
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