As satellite pictures have greatly increased the amount of information provided meteorologists, the pictures have also led to some changes in theories concerning various phenomena. One such phenomenon so affected is the Intertropical Convergence Zone, or as it is frequently referred to now, the zone of Intertropical Confluence (ITC).

The ITCZ, or ITC, is an area where the winds of the Northern and Southern hemispheres converge. The Regional Tropical Analysis Center denotes this zone as "A nearly continuous fluent line (usually confluent) representing the principal asymptote of the Equatorial Trough." In general, it is an area where horizontal convergence of airflow is occurring.

Figure 9-3-4 shows a typical cloud band associated with the ITCZ. It is within this cloud band that disturbances frequently occur. The cloud band, at times, is narrow (2 to 3 degrees latitude) and continuous for thousands of miles. At other times, it is discontinuous and is characterized by a number of large cloud areas 5 to 10 degrees in latitude across. On occasion, vertical cloud patterns are observed within the ITCZ cloud band.

Generally, disturbances along the ITCZ move from east to west and can move poleward and develop into tropical storms. These disturbances are referred to as "equatorial waves" and are most frequent in the doldrum portions of the equatorial trough. Here, low-level cyclonic wind shear is present over large areas. This, together with friction, produces the forced convergence necessary for the development of the individual cloud systems that form the ITCZ cloud band. Figure 9-3-5 shows the cloud pattern typical of an active doldrum trough in the Western Pacific. It has been determined that the presence of surges of airflow from one hemisphere to the other is one of the controlling factors of ITCZ clouds. As air moves across the equator, anti-cyclogenesis takes place. This results in a reduction or clearing of clouds along one portion of the ITCZ cloud band and an intensification of the cloud band in advance of the burst of cross-equatorial flow.