In Zimbabwe cyclones off the Mozambique coast are almost always bad news. Typically, our rainfall starts in November each year and runs through to March or April. The rest of the year is dry and mild to hot. In the south of the country our rains can come either from a southern system drifting across the continent from South Africa where the system constitutes the main wet season pattern. In the northern half of the country we get our main rains from the 'Inter Tropical Convergence Zone' which forms each year and moves down from the north in November.
In a typical season tropical depressions form in the Mozambique Channel or on the other side of Madagascar. These turn into cyclones if the water is warm and the right atmospheric conditions exist. One consequence of such events is that it drives the ITCZ north and often we get what locals call a 'Botswana Upper High' which gives us beautiful weather that is the nightmare of every farmer.
This year just such a system has dominated our weather in February and well into March with the result that our crops have experienced dry conditions that are threatening wide swathes of the country with hunger this winter. There is little doubt now that our tobacco crop will be smaller than last year and we will have a grain and oilseed harvest that will be well below our needs. Many towns and cities are already under water restrictions.
But a week ago a deep tropical depression developed over the lower Zambezi valley and Malawi. This sucked all the atmospheric moisture out of the region and dumped it on a large area just north of the Zimbabwe border. The outcome was floods in Malawi and the lower Zambezi basin - they had to open the sluice gates at Cahora Bassa Dam and release millions of tonnes of water into the river below the dam. The system moved slowly down the river and out to sea and in the process rapidly grew into a full blown cyclone - grade 4.
The cyclone then moved south down the Mozambique channel and drifted towards landfall at the Port of Beira - there it created havoc, a massive sea surge accompanies the system with winds up to 200 kilometres an hour. It smashed Port facilities and cut all communications with the rest of the country and its neighbour Zimbabwe. It moved over the coast at 10 kilometres an hour and dumped up to 700 mls of rain on the Eastern Highlands of Zimbabwe. The damage to infrastructure and crops will be immense and hundreds of thousands have been made homeless - even today we have no communications with Beira except by cell phone.
At the edge of the system when it disintegrated, Harare got 30 to 50 mls of rain and so did a significant area of the country - but farms to the West and South got little and remain drought stricken - so we have flood devastation and drought all in one small country. A cold front is approaching through South Africa and that might help in the south and west next week. Meanwhile today the deep depression that did so much damage to the lower Zambezi basin is back there doing even more damage.