I suspect, judging from satellite imagery, that Bonnie's enhancement this morning is partially due to interactions with the frontal/midlatitude environment to it's north. The center is on the NW side of the mass of convection, a rather typical tropical/hybrid structure. If I recall correctly, we saw this with Danny a few years back, maybe even Earl not too far back. She's undergoing strengthening right now it seems, but I wouldn't say explosively. Near-hurricane strength is still a good bet.
You may be wondering how a tropical system can develop within a midlatitude environment, and I'll try to explain it a little. I'm not saying it's the predominant force behind Bonnie's growth, but it's probably playing some role.
Essentially, on a very basic level, there are two types of instabilities - barotropic and baroclinic. Baroclinic is what we actually see in the atmosphere, whereas barotropic is more idealized. However, tropical systems are nearly barotropic, while midlatitude systems are baroclinic in nature. That's the distinction I'd like to make here; the rest is just gory details. In any case, these instabilities drive the formation and growth of these systems.
The tropical case is more simplistic than the midlatitude case under this scenario (though many other factors I won't go into influence only tropical development); in this framework, the midlatitude case can be simplified to the tropical case by making a couple of assumptions. The energies behind the two instabilities are different, however.
Essentially, with interactions with the midlatitude environment, you get an additional set of energy - not an additive thing, just a slight bit more energy available for instability - for the tropical cyclone. The processes are still approximately tropical in nature - and the system is still tropical, particularly considering the warm waters of the Gulf and the core of the system - but I'd be willing to bet a high-resolution (cyclone phase) analysis of the core of Bonnie would suggest that the storm does not a very deep warm-core (tropical) structure.
I'd like to reiterate that this is a very simplified view of things, but may provide a little insight into the current enhancement and appearence of the system.
11am advisory & discussion are out - not much new, though they note the possibility of Bonnie reaching hurricane status in the 12-18hr period before weakening near landfall. Don't see any reason to disagree with that or the track. 11am Charley info still to come.
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