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26 August 2011

Difference in rainfall figures for Mossel Bay

This question drew my attention.

I stay on a +- 900 sq meter yard, with two weather stations and two normal
manual rain gauges, within about 20 m of each other, out in the open
without any environmental restrictions.

The readings on these can differ quite a lot, even in this small area. It
is not unusual to measure something like 18/20/22/25 mm between the four

This shows why published rain records sometimes don't seem realistic. I
watch rain radar images regularly in the rainy season in our area, and it
is sometimes amazing how small the center of a thunder storm can be,
delivering a lot of rain on a very narrow path, passing even through a
small town like Secunda with areas of heavy rain and areas of almost no

The same is also true for temperature differences in, say, a 10 x 10 km
area. In Secunda the temperature can vary by as much as 3 or 4 degrees in
my experience, depending on exact location!


Cor Rademeyer

SAWDIS: Cor, thank you very much for your email. Great to read about your observations. I must admit that there is sometimes a 1 - 2 mm discrepancy in the figures measured in Heiderand, Mossel Bay. However definitely not 40mm but then it is not known how and where the SAWS measure rainfall in Mossel Bay. I agree fully with "patchy" rain in areas.  It would be interesting to install a few automated weather stations in and around Mossel Bay to get a better understanding of  the rain patterns in the area.  Unfortunately the lack of funds prohibit the purchase of weather stations.