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Understanding weather...not predicting 13 Jul 07 |
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Written by John Olzsewski
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Page 1 of 2
The Cape of Storms lived up to its old
seafarers' name: wet storms and high swells. Sea swell heights forced astute
skippers to sail well out to sea adding some four days to their journey time
rounding the Cape. The relatively warm state of the Agulhas current, some 2oC
warmer than normal combined with the umpteen vortices and their secondary
developments have contributed to this current scenario.
The local effect has been to instill the
coastal low activity with events of unusual intensities. Coastal low
development typically occurs in the Walvis Bay area. The initial development is
the drawing in of air from the inland plateau. This results in East Wind
intensity, the turbulence of which can lift dust and sand from the surface creating
spectacular dust storms like was reported during the week. Reports came in
describing a wall-of-dust observed on Monday across the coastal plain between
Walvis Bay and Swakopmund. The sweep of the wind-flow has similarly been
reported from, at least, some 80kms out to sea. On the odd occasion, the
extreme range of this westward sweep of dust-laden air has been reported as
reaching as far as 120kms into the ocean. Fortunately these are very isolated
occasions.The dust storm conditions have not been
noted at Gobabeb, where only blowing dust was felt. Dust/Sand storms bring
visibilities well below the 1000 metre range, which is their benchmark of
identification, while blowing dust will certainly reduce the visibility range
but not to ranges dangerous to aviation.The distance range and width of dust and
sand storms have not been well charted, largely because there are few people on
hand to provide observations, but knowledge of such a distance range would
provide useful detail regarding wind direction as well as some insight into
wind speeds. Namibia has several ranges of weather patterns which are unique to
our geographical location where both surface and upper-air wind flows and
weather are concerned.For the interior, warm-by-day to cold to
frosty by dawn conditions have prevailed.The presence of a very wide extent of
Cirrus cloud has presented the weather watcher with rich red hues at sunset and
scarlet brightness during the dawn. This broad expanse of cloud need better
explanation than there is available.
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