Hi 146,
As an ex operator in Nigeria, the ITCZ position was probably the dominant thing which descibed the local weather conditions as it moved up and down the country, slightly lagging the position of the sun's annual azimuth change with season. If the ITCZ was actually crossing the location, then as you already know, that's when the sharp rain squalls and thunderstorms would kick off usually lasting an hour or so. If the ITCZ was to the north, during the Northern Hemisphere Summer, then the rain was more persistant and could last for a couple of days, but was not as violent (all relative). When the ITCZ was to the south then then the high pressure in the Sahara kicked in and 'de Harmattan' started with bursts of thick dusty episodes, preceded by extensive fogs in some areas.
I'm sure that other areas in central Africa had other local variations, but essentially if you knew the position of the ITCZ in West Africa, you could usually made a good shot at a forcast.
What I am curious about is that the ITCZ is only indicated over the land mass of Continental Africa (maybe South America has it as well, but never operated there) Anyone have any ideas?
Regards
TOD