Understanding Weather – not predicting – 20 December 2012

What happened?
”Weather” is renowned for its ability to achieve the unusual and do so with scant advice to the onlooker. A week ago a quite familiar synopsis was present with a moist band to the north and an active, cut-off vortex above our southern skies. These patterns usually depart quickly, clearing away in a matter of hours.
But there was much surprise to follow.
The northern pattern drifted westward, limiting precipitation quite considerably across the northeast: few showers were noted and the activity to the west was also limited. Diversity of airflow patterns across the area and with altitude emerged as the pattern unfolded. The slack wind-flows one finds in proximity to the zone of convergence which characterises the equatorial rainfall belt do bring about a level of stagnation. Both the Cuvelai and Kavango catchments only had downpours typical for this time of year.