Very helpful that recon was able to fly Marco. It is pretty clear that Marco probably became a depression while still largely over land, and began rapidly intensifying as soon as it had completely pulled out over water. Teeny-tiny windfield, and very easy to miss the max winds by just remote sensing tools, and area buoy and ship reports.

Marco remains in a fairly favorable environment. Given its small size and likely continuation of at least a fairly favorable environment until landfall, continued intensification looks entirely possible. I might guess Marco has a decent chance of pulling an overnight surprise, a la Lorenzo and Humberto (2007).

On the other hand, as a very small tropical cyclone, Marco remains at the whim of any twist or turn of the upper-level winds, and as of this edit, there appears to be some increasing southwesterly shear interrupting things a bit more.