DM~ As someone had already posted, the area of "breadcrumbs" you described, is the ITCZ ( some refer to it as the ITZ ); either way, is the zone which generally exists several degrees on either side of the equator. It is this zone or area that disturbances and tropical waves move westward ( N. Hemisphere ). Often times significant waves move off the African coast, only to eventually dissapear in this general area. On other occassion, what may appear as cloud free, might suddenly appear areas of convection. In some years this zone lies closer to the equator, and in others, lieing closer to 10N. Though not a distinctive measure of any organized or iminent development, the very fact that we may now, or perhaps in the future have an increase in convective activity in this zone, does portend to a greater degree of surface convergence ( winds approaching form the equator - from the south, and surface winds entering the picture from some other direction. Given fairly low pressures, along with some decent convergence, and walaaa! You have blobs of cumulonimbus popping. A good continuous blow up of these storms suggests rising air, combined with some mid level or low level vorticity from a tropical wave, and suddenly you have the firing mechanism to potentially initiate an increased cycle of inflow and the possible start of some cyclonic rotation.

At this point, the upper air may act as a cap, resisting this rising column of air, or if conditions are right, act as a vaccuum helping to expel the rising warm air as it cools, which in turn helps to pull this rising air even quicker.

There certainly does seem to be some sort of pulsating process that occurs where this ITCZ activity will seem to wane, and perhaps surge for a week or two.