The climate over NCD is determined by the influence of two surface pressure systems. From May to October trade winds originating from a subtropical high-pressure system located to the south of NCD blow consistently from the southeast. Wind strengths of up to 25-30 knots are common late in the season although lower velocities occur at the start of the season. During this period the city experiences a marked dry season and water demand is significantly high.
From December to March the city is influenced by the movement of the Inter Tropical Convergence zone, first southward and the northward. This zone is where air streams pass over the NCD and moist
north-westerly winds occur bringing regular daily rainfall. In both April and November, transitional periods between the two seasons influence the two pressure surface systems and so the NCD experiences humid and still conditions.
The city’s average annual rainfall is
approximately 1197 mm approximately with a distinct wet period from December to April. Rainfall is often unpredictable and often very heavy at this time. Temperatures are high throughout the year. Seasonal variation is small and is exceeded by daily variation with the
night-time minimum contrasting with the daytime maximum. |
