30 year annual mean wind speed (measured in m/s) 100 metres above ground level

Wind Atlas for South Africa (and divers too)

The Wind Atlas for South Africa (WASA) project was launched in mid-March, having been funded by the Danish government (masters of wind farming), and the United Nations Development Program-Global Environment Facility (UNDP-GEF). The atlas shows wind direction, frequency, and estimated power output, and the data was collected from a grid of wind measurement stations all over the country. Its primary use will be to assist South Africans in tapping the energy of the wind to generate electricity. This is incredibly exciting, as within a few months a wind turbine offsets the carbon emissions required to construct it, and then runs virtually emission-free for up to 20 years. Also, we’re all really tired of Eskom (supplier of electricity) encouraging us to purchase less of its product (electricity), and randomly switching off the power when we’re stuck in a shopping mall parking area or trying to cook dinner. I would love to see an economist’s take on that dogshow.

WInd farm off the coast of Denmark
WInd farm off the coast of Denmark

I digress. There’s quite a bit of techinical information on the CSIR WASA site, as well as in some of the news articles describing the project, but the gist of it is that measurements have been taken over the last 2-3 years, and supplemented by a mathematical model to provide a smooth map of wind speeds across most of South Africa. Thirty years of global data was used to calibrate the model.

All well and good, you say, but how on earth is this relevant to diving? Well, you’ll notice that the Learn to Dive Today newsletter frequently contains reference to wind speed and direction, and this affects where we can dive, and when. In summer, if the southeaster has been blowing, it’s Atlantic or eastern False Bay. In winter, the northwester makes the latter two destinations undiveable, but cleans up western False Bay delightfully. So wind is pretty central in the lives of local scuba divers. Wind is also the primary generating force for waves and the massive swells that arrive at our shores from the Southern Ocean, which affects our diving too.

Wind is also fairly central to the lives of everyone else who lives in this part of the world… If you speak to any Capetonian about the weather (a favourite topic), the wind is bound to come up (in discussion, not literally)!

30 year annual mean wind speed (measured in m/s) 100 metres above ground level
30 year annual mean wind speed (measured in m/s) 100 metres above ground level

With all this in mind, it’s quite gratifying to look at a WASA map, and see that our local obsession is justified. The Cape Peninsula and Gordon’s Bay area are among the windiest in the entire area mapped. Red indicates wind speeds of 10 metres per second, the green is about 5 metres per second, and purple (there’s almost none of it) is virtually windless. The source of this map is here.

If you’re a local diver, I encourage you to pay attention to the wind. Even if the weekend’s not windy (most people’s diving time), the wind in the week before will give clues as to what the sea conditions will be. Reading the newsletters of ethical operators will give you good insight into local weather patterns, courtesy of his years of reading the wind and water. If nothing else, an awareness of the wind will lead you to feel less disappointed when a dive is cancelled because of it, and enable you to make safe diving choices about what sort of conditions you want to go diving in. Unfortunately not all dive charters will hold back on launching when conditions are poor, and you can avoid an expensive zero-viz dive or getting seasick (or lost) on the surface by watching the weather yourself and making deductions.

Published by

Clare

Lapsed mathematician, creator of order, formulator of hypotheses. Lover of the ocean, being outdoors, the bush, reading, photography, travelling (especially in Africa) and road trips.

One thought on “Wind Atlas for South Africa (and divers too)”

  1. Interesting blog this morning. So I thought you might find these interesting:

    http://www.winda/spot/3380lert.com0
    Lots of features focused on wind, but not easy to find all of them on the website (not intuitive).
    Shows history & forecasts
    Windalert recently signed a deal with Iweathar to collect data from these windstations:
    http://iweathar.co.za//stations.php
    (started by a paraglider pilot – for real time data)

    Read somewhere the Norwegians were pioneers in weather modelling. See one pretty example:
    http://www.yr.no/place/South_Africa/Western_Cape/Cape_Town/hour_by_hour.html
    The following lets you compare the results of 3 different forecast models/services – also has many other nifty features, shows history & long term forecasts:
    http://weatherspark.com/#!graphs;a=South_Africa/Cape_Town

    Nice real time weather data for Atlantic side (in Kommetjie, seems to be fairly well maintained also):
    http://www.icon.co.za/~aleroux/

    Roman Rock weather station seems to be more off-line, than online (I’m sure you know it, anyway):
    http://www.romanrockweather.co.za/weather.html

    And then also the CSIR’s wave data (Atlantic side):
    http://wavenet.csir.co.za/OnlineData/CapeTown/CapeTownwaveD.htm

    Caveat:
    Other than the Kommetjie weather station, I find the other sites more interesting than actually useful for any forecasting… But it might pass the time until we can go diving!

    Christo

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