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May 2016 Climate Summary

Most areas in the Western Cape received poor rains except for the Central Karoo (slide 1). The coastal districts and Cape Winelands, which normally experience winter rainfall conditions from April onwards, experienced rains of 25mm and less (note yellow, orange and red areas) during May this year.  When comparing May 2016 rainfall against historical long term (slide 2), the discussed areas resulted in below (yellow and orange areas) to extremely below (red areas) conditions.  The Central Karoo on the other hand received comparatively better rainfall (25mm+) thereby rendering mostly above normal conditions (blue areas in slide 2).

slide 1

Slide1

slide 2

Slide2

 

Slide 3 contains data representing 36 weather stations consisting of total monthly rainfall, mean monthly maximum (Tmax) and minimum temperatures (Tmin) for May 2016 and historical long term means.  Total rainfall for May 2016 ranged dismally between 1.5mm in the West Coast to 33mm in the Central Karoo when compared to the long term (6mm to 114mm).  In addition half of the number of weather stations recorded less than 13mm of rain compared to the long term of 39mm.  The average rainfall for May this year (calculated from monthly rainfall for all 36 weather stations) is about 30% less than the long term.

 

In general the days during May this year were warmer compared to the long term due to higher Tmax values. The overall Tmax mean of the 36 weather stations for May 2016 was 23.7ºC (range 19.8ºC to 28.2ºC) averaging 1.7ºC more than the long term counterpart (22.0ºC, range 18.3ºC to 25.6ºC).  While Tmax anomalies amongst the 36 weather stations ranged between -0.2 ºC to 4.1ºC, half of these anomalies exceeded 2.0ºC.

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slide 3

Slide 3

Tmin on the other hand reported an overall average of 9ºC (very similar to the long term), while the separate weather stations ranged between 3.2ºC to 12.7ºC (slightly higher than long term).  Anomalies in this instance were less extreme (range -0.8ºC to 1.1ºC).  In terms of monthly average temperatures Murraysburg and Klawer were respectively the coldest and warmest towns in the province during May.

 

Slide 4 gives a brief view of dam levels in the province as on the 30th May which was 30% (last year 40%).  Dams that contained 20% and less water include the Brandvlei, Clanwilliam and Voëlvlei.  However, preliminary rains of June so far indicate improved levels for these dams, e.g. Clanwilliam Dam measuring 58% on the 27th June.

The dry spell of May 2016 especially in the West Coast was remarkably distinct since plant growing conditions (slide 5) were not as positive when compared to the previous month, while a similar deterioration, but less extreme, occurred in the Overberg.  Although the good rains experienced in the Central Karoo showed a decrease in area under below normal plant growing conditions, there still remains a large area experiencing poor plant regrowth conditions.  Note that the dark red areas are normally associated with veld fire scars.

 

slide 4

Slide 4

slide 5

Slide 5


Climate predictions

ENSO is currently evolving from a neutral status towards weak La Niña conditions (slide 6).

Seasonal forecasts for the period July to September concerning Western Cape (slides 7 & 8):  In general a period of normal to above normal rainfall could develop in the western side of the province; CSAG indicates high possibility for above normal rains during August for the whole province. The eastern side could expect below normal conditions for rain, except for August (CSAG).  As for temperature in general, high probability exists for below normal Tmax conditions.  Both CSAG and SAWS advises users to review updated medium and short term forecasts to identify any change.

slide 6

Slide 6

slide 7

Slide 7

slide 8

Slide 8


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Agri-Oulook March 2016

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