Keith234 -- the pressure drop and convective organization are somewhat interrelated. The mechanism for the organization of bands within a cyclone remains somewhat unknown & up for debate -- new theories come around every so often, each of which improves on the previous one -- but they can help provide at least part of the heating in the atmosphere necessary to result in a pressure drop at the surface; with symmetric convection, you can see a more symmetric pressure field/pressure drop/wind field. That's usually only with very weak storms near formation, however; inner core processes drive it beyond there.