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Understanding Weather – not predicting – 12 April 2013

What happened?
With the double-barrelled impact of global warming and the induced change of climate, much of our conventional knowledge of climate, has been displaced by new patterns. Although the newer range of patterns are similar to historical patterns, they reveal nuances with quite far reaching effects. Exactly what the global and regional dynamics of these variant patterns are, is not yet well-understood by meteorologists.
In other words, synoptics and patterns which have been known to produce identified weather systems can no longer be relied upon to do the same in today’s circumstances. To make it more interesting, what we might build into our knowledge today may not hold good some few years down the line as both the warming and the change factors progress from the current situation.
The analogy with mythical Pandora’s box may not be as far-fetched as we might wish to believe.
A good example is the readiness of anticyclonic cores to proceed along the 40oS track but with varying ability to establish rain-bearing patterns inland and thence across much of Namibia. For much of this new millenium, this ability has held good; but this year this synopsis has seen the upper air core, which feeds the surface cell, dominate the upper air above Namibia: a decided departure from past experience. It must be truly said that one can not be sure whether or not this is a brief irruption or if this is to be part of a future trend.
The close interlinking of our weather patterns with those elsewhere across the southern hemisphere is a realm which is acknowledged but lacks detail regarding the how’s and why’s of this linkage. The influence of the Pacific Ocean and its events have long been acknowledged, but what is still lacking is detail as to where and to what extent our local weather is affected. From detail on record, consistency is limited regarding the entire country (let alone adjacent districts) during one specific event, while intensity or lack of it has also varied from one event to the other. Subtle shifts of synoptic patterns are there awaiting revelation.
Some moist air penetrated before the weekend, yielding quickly as a cold frontal trough crossed the south during Tuesday and a few light showers fell mostly across the South. The dry air pattern was back above the country.
What’s coming?
With a major trough and its cold front moving south of the Cape, being driven by an anticyclone well to the south, our dry air patterns remain into next week, by which time low-level moisture extends into our skies; but this is absorbed by the dry upper air, though. There is a chance of light showers from central Namibia southeastward but very limited falls only are expected. The desired rains of widespread intensity are unlikely from the current synopses. Worst case offers scant relief during this calendar year.

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