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Understanding Weather..Not predicting
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Rainfall continued its pattern of promising skies with an early cloud build-up only to be followed by a failure to produce rain of any significance.

Every week, the Economist contacts 34 weather monitoring points where invaluable primary weather information is obtained together with the weekly rainfall readings. This information is supplemented by the observation of the individuals residing at the various monitoring points. Over the past week, the observations were more or less consistent for most of the country: a good cloud build-up but very disappointing falls.
Across much of the country, the persistent pattern is that of promising skies by late morning or early afternoon followed by a few showers but most of the cloud falling flat. One saw many a good cumulus cloud flattening as it reached an inversion layer of  considerable thickness and leveled out, spreading with a prevailing wind flow at then just slowly evaporated in the drier surrounding air.
The local forecast office also commented upon this lack of upper air instability yet a lack of reliable input data on a daily basis makes it difficult to unravel current events.
El Nino that was present in the Pacific for a most of this year has made a dramatic disappearance some two weeks ago. Pacific Sea Surface Temperatures (SSTs) have even gone below average in some expanses.
The expectation for the good rainfall recorded one week ago, to continue, did not materialize. Some 60mm in the Omitara district and 37mm in Ruacana were samples of the what-might-have-been situation. Generally though, falls of only a few millimetres were more representative of the weather pattern. Tuesday, lunchtime a slight shower developed over Klein Windhoek. My friend William Thatcher called me some 20 minutes later to report a heavy shower in the Northern Industrial Area: yes,  there was a good storm active, by sight. Some 20 minutes later, another observation showed that the storm had collapsed, the cloud tops indicated this dissipation, and all this in the middle of the afternoon when maximum development should have taken centre stage!


 
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DATE: Fri 19 Dec -
Thu 08 January 2009
Volume 22 No.50