December 2017 Climate Summary

While November experienced reasonable rains over most parts of the province, rainfall during December (slide1) reverted back to poor conditions (≤10mm) over most regions.  When viewing rainfall against the historical long term means (slide 2), then below normal rainfall occurred over most of the province (red, orange and yellow shading).

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 December 2017, including corresponding historical long term means (LTA).  Rainfall for December on average was below normal, i.e. the overall mean of all these weather stations was 7mm (LTA 19mm).  Half of these weather stations each recorded a total monthly rainfall ≤4mm.  The weather station near George recorded the highest monthly rainfall (64mm), the rest however revealed much less rain for December.

As for temperatures (slide 3): December experienced normal monthly Tmax (Celsius), resulting in an overall average of 29.4 degrees, ranging from 23.2 (George, LTA 23.6) to 34.8 degrees (Citrusdal, LTA 33.6).  Monthly Tmax anomalies ranged between -1.2 (Ashton) to 1.9 degrees (Oudtshoorn).  

 

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Slide 3

Slide 3

Monthly mean early morning temperatures (Tmin) for December obtained from the various weather stations presented an overall average of 14.1 degrees, with Tmin’s at the various weather stations ranging between 11.0 (Barrydale) to 17.6 degrees (Prince Albert), both experiencing less Tmin than their LTA’s.  Monthly Tmin anomalies ranged between -1.5 to 0.6 degrees. 

Overall water level of provincial state dams decreased to 28% (last year 43%) on 8th January (slide 4), due to the lack of substantial follow-up rains during December.  Since the poor rains were experience in both winter and summer rainfall areas, the water levels of most dams over the whole province dropped accordingly.  Since George experienced somewhat better rains, the adjacent Garden Route Dam showed a slight increase. 

The poor rains in December also resulted in decreased growing conditions (slide 5), resulting in large parts of the province still being subjected to persistent extreme drought conditions. 

Predictions indicate La Nina to be at least be present during summer months returning after that to neutral conditions.  According to the SAWS forecast of 22nd December the Western Cape can expect above normal temperatures during the summer months.  There seems no indication of any improvement in rainfall conditions over the province.

Slide 4

Slide4

Slide 5

Slide5


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Agri-Oulook December 2017

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