October 2017 Climate Summary

Rainfall during October (slide1) occurred mostly in the southern parts (green areas, i.e. around mountains in the west and also around eastern coast) of the Western Cape while the northern parts experienced poor rainfall (alternating yellow, orange and red shading).  When viewing rainfall against the historical long term means (slide 2), then below normal rainfall occurred over most of the province, with large parts (West Coast, Cape Winelands and Central Karoo) receiving normal to above-normal rainfall (green and blue shading).  Extremely below normal rainfall (0-25% of the long term mean) were identified in the northern parts of the Overberg including the adjacent southern areas of the Cape Winelands.    

Slide 1

Slide1

Slide 2

Slide2

Slide 3 presents data from specific weather stations, containing total monthly rainfall, mean monthly maximum (Tmax) and minimum temperatures (Tmin) for October 2017, including corresponding historical long term means (LTA).  Rainfall in October on average was a bit below normal since the overall mean of all these weather stations was 19mm, about 67% of the long term mean, 4mm more than September, and 10mm more than October of the previous year.  Half of these weather stations each recorded a total monthly rainfall of ≤14mm, of which 2 weather stations in the West Coast indicated no rain for October.  Conversely, the highest monthly rainfall (71mm) was recorded at George (still below average), while Rawsonville achieved second position at 57mm (above average).

 

As the province experienced warmer conditions during September, October was colder than usual (slide 3).  The normal monthly Tmax (Celsius) of the weather stations resulted in an overall 24.5 degrees average (LTA 24.7 degrees), ranging from 20.4 (George, LTA 20.5) to 28.5 degrees (Prince Albert, LTA 29).  From the latter it is easy to note that most weather stations tended towards lower monthly Tmax compared to LTA, with places like Citrusdal, Malmesbury, Murraysburg, Piketberg and Porterville showing stronger anomalies of one degree and more.  However, isolated reverse instances also occurred, meaning above normal Tmax for October, De Rust and Oudtshoorn presented extreme monthly Tmax anomalies of respectively +1.6 and +1.8 degrees.  

 

 Download Slide 3 PDF

Slide 3

Slide 3

The early morning temperatures (Tmin) for October obtained from the various weather stations presented an overall average of 8.9 degrees, rendering an anomaly of -1.3 degrees.  Tmin’s ranged between 6 (Koue Bokkeveld) to 12.4 (Klawer), both less than their LTA’s.  Actually nearly all Tmin’s were lower than the corresponding LTA, with the most extreme monthly mean (anomaly of -3.1 degrees) recorded up at Citrusdal.

The overall water level of the provincial state dams was 36% (30th October), against last year’s 60% (slide 4).  The lowest levels remained in the Karoo regions, while other dams (west and south) maintained their current water content levels.

Rains in the southern coastal and adjacent areas during the past few months have resulted in some restoration of growing conditions in these areas (slide 5).  However most of the province remains in a poor state in terms of extreme drought conditions. 

Currently ENSO has progressed towards a La Nina state implying increased probability for above normal rainfall in the summer rainfall areas.  According to the SAWS forecast of 26th October for the period Nov-Dec-Jan, above normal rainfall, against a low probability, is forecasted for the Western Cape.

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Slide 4

Slide4

Slide 5

Slide5


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Agri-Oulook April 2017

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