Understanding Weather – not predicting – 15 March 2013

What happened?
There is a considerable need for greater detail in daily weather charts. Computer models are faced with blank areas on both surface and upper air charts. These lacunae are filled in from satellite images which are based on specific programmed assumptions. The results often, are not accurate.
This last week gave a good example.
For most of this season, the weather was dominated by an out-of-place middle layer anticyclonic core extending across the South Atlantic, bringing in cold dry air from the south. Any lower moisture input could make precious little convective effect on this upper presence. Future outlooks presented a more promising situation regarding air flow and moister input but this did not materialise and rainfall across the country remained far below normal.
So what went astray?
Across the southern hemisphere, charts show surface anticyclonic cells ranging from some 35oS to the 45oS latitudes regularly, but not for the South Atlantic. The overall explanation appears complex. It varies from the rest of the hemispheric pattern, it is equally variant from the northern hemisphere, too.