My travels this recent long weekend took me in an easterly direction, namely Bushman’s River, across from Kenton-on-Sea — a completely different environment to the Garden Route and my beloved Langkloof, which I often visit.
Many believe that the further east one goes (subtropical thunderstorm region) the higher the average rainfall is, but I have constantly been reminded by farmers in the region that this is not the case, especially in the Alexandria area.
Travelling that route sparked the debate when viewing the condition of the vegetation in the area.
Besides the well-irrigated grassland grazing, the rest of the surroundings generally looks like a highveld winter scenario, though the region is coming out of summer rainfall season.
Any weather enthusiast will know that we have a bit of a “rain shadow” to the east of the Bay, but how far does it extend, and where does it start?
Looking at the figures, it starts close to the eastern outskirts of the Bay, as many residents of Bluewater Bay can attest.
Our airport maintains an average of about 600mm, but just 20km away to the east, as the crow flies, at the Coega IDZ, the average drops to just over 400mm.
This is roughly in line with the averages of the Addo and Kariega areas, which are further inland.
That is insane if one considers that this is a mere 20km away, but it reiterates the influence of topography on weather systems and ultimately climate.
How far does this “rain shadow” extend?
With no official data available before Port Alfred (more than 200km away), where the rainfall recovers to 600mm per annum, one can only guess whether this is a gradual increase or not.
It is not until we reach East London that we see a marked increase in average rainfall exceeding 800mm per annum.
By the time one reaches Port St Johns (200km from East London), we see the rainfall increase to a figure exceeding 1,000mm per annum.
It is a pity there is so little data available over the eastern half of our province, and especially the former Transkei, where some of the most violent storms in the region occur, often sprouting destructive tornadoes and damaging microbursts.
The more quality data we have and ingest into forecast models, the more accurate they will be, thus enhancing early warning systems which are vitally essential for many of these vulnerable communities.
Lately, meteorological commentators have criticised the lack of availability of radar data and upper-air data as the main cause of the reduced effectiveness of forecasting and nowcasting severe storms, as was highlighted in a recent cloudburst event in the Roodepoort area in Johannesburg.
Though these commentators have targeted radar data availability, it is the surface data that is used for more than just forecasting.
Agriculture, commerce, construction, insurance, research and every aspect of our lives is influenced by the weather, thus having the data to make educated decisions is vital for the wellbeing of all.
It is for this reason, and more especially the recent cyber-hack on our weather service, that many, especially farmers, are acquiring their own weather stations to record shifts in weather patterns.
Gone are the days where weather stations cost an arm and a leg, with modern electronics making them more affordable to a wider section of the public.
Many weather enthusiast hobbyists can even purchase one just for fun.
Many upload their data to online platforms to be shared with other enthusiasts, but most keep their data for personal use only.
It would be great if everyone shared their data, as the weather belongs to nobody and what happens in my or your area can affect each other’s areas. Thus, sharing benefits everybody.
During an extreme event, what makes for better conversation than comparing readings of different areas, whether obtained from a weather platform or social media.
The interest on my social media platform during the drought, when posting rainfall figures of the Langkloof (our main catchment for the Kouga, Churchill and Impofu dams), was astounding.
Weather is and will always be a great conversation starter.
This week in history:
1981 — floods reported in the greater Mossel Bay area
Dam levels
70.76% down from 71.24% the previous week. Impofu was slightly down at 53.98%.
Weather safety tips:
While extremely rare, it is possible to be struck by lightning while showering due to lightning travelling through plumbing. The risk is very low, as buildings act as a Faraday cage, protecting occupants from direct strikes.
The Herald
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