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Written by John Olzsewski
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Page 1 of 3
A thin cloud cover over much of central
Namibia is a clear signal that the water in the Pacific Ocean, very far away
from our shores, is getting colder. The South Pacific weather picture has been
showing a definite shift into the La Nina range for the past four months.
This weather pattern is evidenced by a drop
in the Sea Surface Temperature (SST) across the eastern equatorial Pacific Ocean.
The SST there is now some 4oC below normal.
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<*><*>During a typical El Nino the water
temperature in the Pacific can be anything up to 5oC above normal.
This warmer water usually arrives on the Peruvian coastline around Christmas
hence the name El Nino. When the water becomes cooler and the temperature drops
below normal, scientists use the name La Nina to describe the opposite of El
Nino.<* />Since March this year, weather patterns in
our part of the world, the eastern parts of the South Atlantic, ranging from the
Agulhas current (close to the shoreline) to the pressure patterns regularly
appearing across the mid and eastern Atlantic, have delivered a constant
picture of conditions influenced by La Nina.<* />Yet, paradoxically, the US government's
meteorology agency, NOAA, is not yet convinced that a true La Nina is in place.
A point that emphasizes and supports this uncertainty is the limited extent of
cooler surface water. In the true La Nina state, cooler surface water should
cover much larger areas in the centre of the Pacific.<* />The inference is that the Trade Wind
outflow is obviously stronger but not yet strong enough to thrust its
consistently cooler air that far across the Pacific. This situation provides
more questions than there are ready answers.<* />We also have the actively looming
disturbance of Global Warming which sees a change in climate at a faster pace
than normal. These considerations support the present uncertainty on the
immediate future of the La Nina system's growth.<* />
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