Monthly rainfall roundup for Makhanda
Roger Rowswell – Darling Street
Last year, a comparison of rainfall was made between 2020 and 2019, the severe drought year. Having studied the resulting data closely it was evident that if the data had been compared with that of 1921 it could be seen that the two sets were very similar.
This led me to hypothesise that 2021 could be a flood year and that the interval period is not 100 years but 99 years between flood events. Time will tell.
Previous recorded flood events were in October 1823 and November 1922, an interval of 99 years. The first recorded flood in 1923 was without any rainfall data. The second was recorded both at the Grahamstown Town Hall and the Old Gaol with over 300mm in 6 days. The total annual rainfall for 1922 was 998.2mm over 84 raindays, Old Gaol record, so even without the 300mm deluge the rainfall for 1922 was about average.
In 2021, January rainfall at Darling Street was 74.8mm over 12 raindays. The long term average (LTA) for January is 65.6mm and long term median (LTMed) 66.2mm. The LTA and LTMed are based on the record starting its 36th year.
The characteristics of the rainfall so far this year has changed from drizzly rain to more intense showers. We have also had a few thunder showers which we didn’t get late last year – a positive sign.
Rainfall for the month of January 2021 as measured in four locations in Makhanda: Park Road, Darling Street, Cathcart Street and Grant Street. Figures thanks to Jim Cambray, Roger Rowswell, Gill Maylam and Robin Stobbs.
Jim Cambray – Park Road
January 2021 total: 76.6mm (January 2020 was 136.5mm)
Mean: (1986 to 31 January 2021) for January is 62.2mm
Median: 60.3mm – Range 26mm to 136.5mm (2003-2020)
Robin Stobbs – Grant Street
January 2021 total: 54.9mm (January 2020 was 96.0)
January 2021 mean: 52.85mm (1975 to 2010)
January 2021 median: 50.0mm – Range 16.5mm to 98mm (1975 to 2010)
Gill Maylam – Sunnyside
January 2021 total: 72.1mm (January 2020 was 136.4mm)
