Seriously, Deni, tell me what I am missing here or misunderstanding. If I'm looking at this graphic correctly, does it not show a ton of dry air in its path?
There may be other factors I'm not seeing/considering. I'm looking at this as a teachable moment as we say in ed biz.
TD 5 is in a low windshear environment and is embedded within the moist ITCZ belt. As long as there is no northerly shear to infiltrate the dry air stable air into it from the north it will have its own moist environment, that's what tropical cyclones do, transport warm moist air at the surface into the atmosphere as long as dry air in the mid levels does not disrupt the process. When that happens that's when you see that convection collapse right away until the dry air just takes over and the system dies off eventually. These small systems can be surprising and because the atmosphere does not get sampled by weather ballons the models can miss the environment around it, they can get either stronger than forecasted or much weaker than forecasted by global models.