three observations:
that has got to be one of the weirdest wind/pressure relationships i've seen. the storm has been steadily intensifying.. the pressure has fallen to a level more commonly associated with 145mph winds. it is barely category 3 by recon data. there is usually some lag in wind/pressure.. but not like that.
radar obs out of key west are showing a strange inner core structure. the station is far away, but the echoes indicate concentric eyewall type-structure.. with a tiny inner eyewall, a huge gap in the rain shield, then an outer eyewall.
pair these structural oddities and it has me thinking that the storm has entrained a ton of subsidence. there is more feeding from the north.. but this first patch that it started on yesterday is mostly sucked down and probably being worked out. in spite of that the pressure continues to fall. katrina will probably go through an eyewall replacement cycle and adjust to a more conventional wind/pressure relationship in the coming hours.
i'll respond to something ralph said earlier about weakening... that hurricanes past their peak tend to weaken as they near the shore. when you look at the climatology of recurving hurricanes in the gulf, their weakening phase usually begins as they pass the ridge axis. the ridge axis right now is right along the coast.. and is forecast for the coming days to remain pretty much at the coast or just south of it. of the comparisons given.. opal was an october hurricane that was caught by the trough that had been baroclinically enhancing it and sheared badly, and ivan passed the ridge axis a couple of days before landfall and had a good while to spin down. on the forecast track katrina will be passing the ridge axis as it makes landfall, so by that token it would be very close to maximum intensity.
as of right now the subsidence entrainment should continue for the next day or so, peaking again late today. after that (sunday into monday) the environment should be very close to ideal for katrina to intensify. i wouldn't be surprised if katrina approaches or reaches category 5 at some point on sunday.
going to hang tight at the ms/al border. that's what i should have been doing all along. going to stick w/ a strong 3 because it's a compromise between original ideas and what i'd forecast now.
HF 1242z27august