As always you have such good info, thanks much.

Regarding just one thing, "Katrina wasn't exactly dealing with a moist airmass either just after it crossed florida, and it spun up anyway" -- she really struggled with that dry air, and didn't really spin up until out of it, in spite of other favorable conditions.

Remember several folks here were sure Katrina would "blow up" as soon as she got off the western FL coast. Instead she really struggled, tenaciously hanging onto each pressure drop, for several days, but not able to get beyond Cat 2, in spite of the lower pressure, due mainly to dry air, and not until she got over the loop current was she able to strengthen enough to fight off the dry air and develop into a major hurricane. There is no loop current in the SW GOM, even with many other favorable conditions. The forecast path is very similar to Emily's for the portion over the Yucatan, and that took a lot out of Emily, which I believe hit as a solid Cat 3, but barely made it back up to Cat 3 at landfall in Mex. If this system goes faster after leaving the Yucatan, less time to spin up; if it goes slower, cooler water could well up and cap strengthening.

BTW a lot of convection blowup in the last couple hours for TD20. Since windspeed has increased back to 25kts and remained steady at buoy 42056, while the wind dir has not changed much (system is nearly stationary?), if they find winds at 35 kts at the center, could we be seeing Stan shortly with the recon?

Looking at the visual sat images, the shear pattern is a little weird (some areas of the storm have shear to the N, and some to the S). Can someone provide some general info about upper level winds, outflow, and shear above tropical storms/hurricanes.
well, i don't call the pressure falling from 985mb down to 950-ish with dry air intruding 'struggling', but yeah, it didn't really go off the deep end until the subsidence stream let up. as for upwelling slowing strengthening... uh, it would have to stall for days. and days. warm water column in the southern gulf is still pretty deep. opal barely moved for two days down there about ten years ago and wasn't any poorer for it. -HF