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Deluges |
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The most well known deluge is the 'great flood' when Noah built his ark and it supposedly rained solidly for 40 days and 40 nights. It has been calculated that if the total rainfall over the Earth were averaged out, each place would get something like 800 millimetres of rain a year (around 34 inches). Rainfall varies enormously, of course. One of the wettest places in the world is Cherrapungi in northeast India where, in 1861, the annual rainfall reached 26,000 millimetres (over 1000 inches). It regularly gets over 10,000mm (430 inches) every year. ...on the 26 November 1970 on the Caribbean Island of Guadeloupe 38.1mm... fell in just one minute.
The most intense rainfall ever recorded was on the 26 November 1970 on the Caribbean Island of Guadeloupe where 38.1mm or 1.5 inches fell in just one minute. Whereas over a complete 24 hours, Reunion, in the Indian Ocean, recorded 1,850mm (73 inches) in March 1954, and at Mount Wai-ale-ale in Hawaii they have up to 350 rainy days each year.
These heavy rains fall for two reasons. Firstly, the southern Asian southwest monsoon and secondly super-cells within cumulonimbus clouds, which can be associated with hurricanes, tornadoes or severe thunderstorms. ...in a super-cell there is only one up and downdraught...
These large thunder clouds are formed as warm, moist air rises quickly forming updraughts of air and compensating downdraughts. In a super-cell there is only one up and downdraught, which allows the cloud to grow much larger than normal giving much heavier rain. The rainfall can be as much as 200mm in an hour, or eight inches. Such deluges give rise to flash floods and mudslides.
It is the super-cells within the tropical cyclones, such as hurricanes or typhoons that produce very heavy downpours as these storms start to move inland. In the southwest monsoon, on the other hand, the rain can be nearly as heavy and last for a long period of time. ...at the base of the Himalayas, Cherrapungi is one of the wettest places on Earth. In the northern Summer, high pressure over the Indian Ocean and low pressure over continental Asia pulls in very moist air from the Arabian Sea and the Bay of Bengal. This provides both life sustaining rains and life threatening deluges and floods. This is why, at the base of the Himalayas, Cherrapungi is one of the wettest places on Earth. It's beaten only by its near neighbour Mawsynram, which has an annual rainfall average of 11,430mm (450 inches). Most of this falls between June and November!
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