Kenyan Long and Short Rains: Effects of Movement of the ITCZ

[acbrixton]

Just seen this interesting account on the BBC New World Weather site of the differing lengths of the bi-annual rainy seasons in Kenya as the ITCZ moves south and north...why would the 2 movements produce rainy seasons of notably different lengths?

"World News

Torrential rains in Kenya displace thousands by Laura Gilchrist

Kenya’s seasonal rains have brought flooding to parts of the northern and coastal areas of the country, forcing thousands of people to flee their homes.

The ‘short rains’ occur around this time of year as the Inter-Tropical Convergence Zone (ITCZ) migrates southwards. Kenya sees another period of rains between April and June known as ‘long rains’ when the ITCZ moves northwards again. The ITCZ is the dividing line between the southeast and northeast trade winds, and oscillates with the sun from season to season. It is usually characterised by heavy rains and thunderstorms, and hence gives Kenya the two rainy seasons as it passes through.

The flooding brought by the torrential rains has reportedly killed ten people. Four drowned on Tuesday night near Isiolo, around 125 miles (200 kilometres) northeast of the capital Nairobi, and six drowned at the weekend near the Indian Ocean port of Mombasa.

Around 3,000 have reportedly been displaced from various parts of the country, fleeing their homes as floods destroyed roads and bridges and inundated schools.

The ‘short rains’ normally run between mid-October and mid-December, with Nairobi’s average monthly rainfall reaching a peak of 114 millimetres (4.5 inches) in November. The annual average for the capital is around 900 mm (35 in), but as little as 500 mm (20 in) or as much as 1,500 mm (59 in) of rain could be recorded in a year."

Can anyone shed light on this please?

Regards

ACB