Route and aerodrome climatology relevant to Nigerian/West African operations
This domain tests seasonal and diurnal weather patterns affecting Nigerian and West African routes, aerodromes and alternates.
Seasonal pattern
Nigeria has a wet season roughly April–October in the south and a shorter, later wet season in the north; the dry season is dominated by the Harmattan, a dry dusty north-easterly flow from the Sahara. The ITD migrates north in summer, bringing monsoon moisture. Southern coastal areas can have a short dry break in August, the “little dry season”; the north has a single rainy peak. Coastal fog and low stratus occur with humid onshore flow and night cooling; dust haze reduces visibility in the north during Harmattan.
Operational effects
Convective storms, squall lines and heavy rain affect take-off, landing and alternates; wet runways reduce braking action. Harmattan dust can reduce visibility to a few kilometres and obscure terrain; it also lowers humidity. Sea-breeze fronts near Lagos can change wind direction and bring low cloud. Temperature is high year-round; density altitude is significant at hot inland aerodromes.
Worked example
A January morning flight from Lagos to Kano: Lagos may have humid haze or coastal stratus with visibility 3–6 km; Kano is likely under dry Harmattan dust with visibility 2–5 km and a north-easterly wind. In July the same route is in the wet season: expect CB or squall-line activity, heavy showers and a moist south-westerly monsoon flow, with Kano greener and more convective. Plan alternates and fuel accordingly.
Traps
Do not assume all of Nigeria has the same rainy season. Harmattan is not fog. Coastal fog can be advection or radiation. Afternoon convection is not confined to the coast. Seasonal averages do not replace METARs and TAFs.