Understanding Weather – not predicting – 11 January 2013

What happened?
The full weather stage has been brought into focus these last 3 weeks; emphasizing the clash between local individuality and the entwined complexity of a climate scene wrestling with progressive change and resistant elements of the past regime.
The final days of 2012 saw an active Tropical Convergence belt close to our northern borders coupled with an ability to tap some of this airmass and advecting into and across northern and central Namibia. This was in spite of an equally persistent upper air anticyclonic belt with a home base above the mid to lower latitude in the south Atlantic.
The appearance of an equatorial wave, the Inter Tropical Convergence Zone in its most active form, from late December through to this week, situated between 15 and 20oS, ensured a consistent moist air presence close to our northern regions. The ability to advect a broad band of this moisture was restricted by an equally persistent upper air anticyclonic core extending from our mid sub-continent westward across the Atlantic to South America, holding sway from some 16000 to 27000 feet and its core between 25 and 30oS. This high pressure presence was limited to only this quadrant of the hemisphere; across both Indian and Pacific oceans the anticyclonic patterns have changed little from the pre-Christmas stance.