Understanding Weather Not Predicting It
Understanding Weather Not Predicting It
06 September 2010
published by www.economist.com.na
Namibia — What happened?
Weather as we have known it, chapter and verse, surprise or expectation, has wandered and it is becoming seen as (obviously) a cousin, but with distinct variation keeping the similarities just that much removed from the previously expected range.
This is not just a local displacement, the shift is truly world-wide. The variance would seem to range from place to place, area to area, but departure from the previous ranges is definite.
During this last week, the expected procession of cold fronts and anticyclonic ridges lined up and progressed across the southern ocean. The rhythm was there true, but the pulse varied.
A cut-off vortex developed to the west of the Cape: no landmass to block it. Such developments can sit for a matter of hours, then generate movement and provide weather. At this stage, the pattern has wandered, switched and changed and its weakening developments now lie south of the continent. It has left a zone of confused swell in its wake, stormy but not initiating marine warnings. But in its aftermath 2 secondary vortices with trailing (linking) frontal troughs so that its area of activity broadened. This rare, unlikely, range of activity enabled the succeeding anticyclone forming a ridge southeastwards to the latitude of Bouvet Island. Gough Island enjoyed some hours of easterly wind as a result!
The resultant circulation did everything to perpetrate cut-off-type activity.
We are not alone in experiencing such developments. Around the expanse of the southern oceans, similar activity has been described on the surface synoptic charts for days, running into weeks even.
We are entering a rainfall year dominated by La Nina (still developing). The prospects focus on the north-south-north surface and adjacent (upwards) air circulation with an optimism regarding rainfall. Whether of not these patterns affecting synoptic patterns across these recent days will persist or recur across the developing season remains to be seen and the effect where expected synoptic patterns are concerned is also open to query.
But, as with all weather, this is just what the whole story is about: regular observation and resultant assessment furthering knowledge across the full range. The link to the changing climate should become more apparent, so, hopefully, enabling better insight regarding not only the whole stage, but also the local scene and its unfolding prospects.
Whats coming?
The quite static airmass present across much of southern Africa, north of the cold-front range south of the Orange valley, shows little movement. The resultant haze persists, so thick that nighttime skies reveal only planets and the brightest of galaxies (stars to our sight). Wind-flows vary from light easterly in the north, to almost calm across mid-Namibia, but exposed to some westerly infiltration in the south. But still haze-bound: no prospect of rain. The haziness limiting visibilities is always a wintertime risk, it has been exacerbated by veld-fires in both Zambia and Zimbabwe. The generally westward orientation of the lower airflows has established this input and there seems to be little influence to sweep it out.
Synoptic outlooks show little overall displacement until well into the new week.
