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May 2017 Climate Summary

The ongoing drought in the Western Cape continued into May this year, with May actually receiving less rain than April (slide 1).  Most parts of the province received less than 10mm rain.  When taking the historical long term statistics into account (slide 2), then most of the province received ≤50% of normal rains for May (orange and red shading), the north eastern side on the other hand the Central Karoo indicated somewhat less extreme conditions (depicted by the yellow shading).  The western side of the province, being predominantly a winter rainfall area, was severely affected by poor rains (0 to 25% of the historical long term means).    

Slide 1

Slide1

Slide 2

Slide2

Slide 3 consists of data taken from 38 weather stations, depicting total monthly rainfall, mean monthly maximum (Tmax) and minimum temperatures (Tmin) for May 2017, including corresponding historical long term means.  The overall mean rainfall for May 2017 (calculated as the average of mentioned weather stations) was 5.5mm compared to the long-term mean rainfall for May (37mm), resulting in 15% of the long term.  Half of the weather stations recorded total monthly rainfall of ≤ 4mm, of which 8 weather stations indicated ≤1mm to no rain.  Conversely the highest monthly rainfall of 24mm (long-term 44mm) was recorded at George.

 

The monthly mean Tmax at the various weather stations ranged between 21.4 ºC (Murraysburg) to 29.3 ºC (Klawer), compared to the long term averages ranging from 18.4 ºC (Koue Bokkeveld) to 25.9 ºC (Klawer).  The latter clearly indicates higher Tmax’s for 2017, averaging at nearly 2.5 ºC higher compared to the corresponding long term average.  All but one of the weather stations resulted in positive Tmax anomalies (≥ +0.5 ºC), of which anomalies of above 4 ºC were recorded at least four localities.

Monthly mean Tmin at the listed weather stations ranged between 4.3 ºC (Murraysburg, long term 2.9 ºC) to 12.7 ºC (Klawer, long term 11.9 ºC) with an overall average of 9.1 ºC (long term 9.2 ºC).  

 

 Download Slide 3 PDF

Slide 3

Slide 3

The state of provincial dam levels (slide 4) on the 29th of May dropped to an overall average of 18% (last year 30%), indicating a further downward trend for most dams in the province.  The water level of the dams in the Karoo regions ranged between 0 to less than 10%, while that of Theewaterskloof Dam, the largest dam in the province, decreased to 13% (last year 30%).

The persistent below normal rainfall accompanied by high temperatures resulted in the further deterioration of plant growth conditions in the province (slide 5).

ENSO remains neutral, the possibility of the appearance of El Niño later this year is less evident but still achievable.  According to SAWS, statement released on the 25th of May, above normal rainfall and above-normal temperatures are forecasted for the Western Cape for the period June to September.   Due to high uncertainty in forecasts, users are advised to regularly review updated medium and short term forecasts to identify any intermediate change.

Slide 4

Slide4

Slide 5

Slide5


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Agri-Oulook April 2017

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