Seasonal Weather Forecast Talk Show on Capricorn FM and North West FM Categories of Weather Forecast Nowcast (0-6 hours) DETERMINISTIC Short-term (1-7 days) DETERMINISTIC Medium-term (up to 30 days) DETERMINISTIC/PROBABILISTIC Seasonal (3 months) PROBABILISTIC How skillful was last month s Seasonal Forecast? This is an important part of forecasting. Firstly, what was last month s seasonal forecast? Probabilities for below-normal rainfall conditions over Limpopo Province (LP) and the northeastern and southwestern parts of North West Province (NWP) are forecast during the period from July to September. The forecasting system indicates greater probabilities for below-normal rainfall conditions over NWP during August to October, whilst in early spring it indicates raised probabilities for above-normal rainfall conditions over the northeastern parts of LP (Figure 1). Figure 1: Probabilistic above-normal (left panel) and below-normal (right panel) rainfall forecast for three overlapping seasons valid for the period of July to September 2013 1
The likelihood is forecast of mid-winter maximum temperatures (day temperatures) becoming above normal for both LP and NWP. The tendency of warmer maximum temperatures is gradually expanded from the west of NWP during early spring whilst LP will continue to experience below-normal maximum temperatures during early spring (Figure 2). The minimum temperature (night temperature) forecast system is indicating warmer conditions than normal for most of LP and NWP, with the exception of the southwestern parts of NWP for which cooler conditions are expected during July to September (Figure 2). Figure 2: Probabilistic maximum (left panel) and minimum (right panel) temperature forecasts for the three overlapping seasons valid for the period of July to September 2013 How much rainfall was received in the month of June? Figure 3: Total rainfall for June 2013 2
Figure 3 is an accumulation of 10-day rainfall surfaces created by a combination of ARC-ISCW and South African Weather Service automatic weather station data with satellite rainfall estimates from NOAA CPC (National Oceanic and Atmospheric Administration Climate Prediction Center) available through FEWSNET (Famine Early Warning Systems Network). During the month of June 2013, LP and NWP received 0-5mm of rainfall. What is the seasonal outlook for the coming season (August to October 2013)? Figure 4: Probabilistic above-normal (left panel) and below-normal (right panel) rainfall forecast for three overlapping seasons valid for the period of July to September 2013 Figure 4 indicate the probabilities for above-normal rainfall conditions over the eastern parts of LP and below-normal conditions in NWP during the period from August to October. The forecasting system indicates greater probabilities for below-normal rainfall conditions over 3
NWP during September to November and October to December periods, whilst in early spring it indicates raised probabilities for above-normal rainfall conditions over the northeastern parts of LP for the same period (Figure 4). Examples of actual values for both NWP and LP are given in Tables 1 and 2 respectively. Table 1: Climatic rainfall and temperature for Potchefstroom station, North West Province Potchefstroom JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC Max Tem 26.60 27.12 25.60 22.80 21.15 18.61 18.36 22.31 25.33 26.67 26.86 26.86 Min Temp 15.79 15.11 13.45 9.90 6.20 3.27 2.01 5.41 8.81 12.26 13.69 14.99 Rainfall 142.24 72.25 87.91 47.92 14.53 13.42 0.81 7.68 14.23 50.30 79.91 105.37 JFM FMA MAM AMJ MJJ JJA JAS ASO SON OND NDJ DJF Max Tem 26.44 25.17 23.18 20.85 19.37 19.76 22.00 24.77 26.29 26.80 26.77 26.86 Min Temp 14.78 12.82 9.85 6.46 3.83 3.56 5.41 8.83 11.59 13.65 14.82 15.30 Rainfall 100.80 69.36 50.12 25.29 9.59 7.30 7.57 24.07 48.15 78.53 109.17 106.62 Table 2: Climatic rainfall and temperature for Lephalale station, Limpopo Province Lephalale JAN FEB MAR APR MAY JUN JUL AUG SEPT OCT NOV DEC MaxTemp 31.98 32.58 31.26 28.48 26.70 24.45 23.95 26.68 30.43 31.79 31.40 31.78 Min Temp 20.60 20.04 18.60 14.07 9.12 6.07 5.04 8.70 13.69 17.84 18.86 19.86 Rainfall 144.50 214.96 37.12 35.90 7.56 13.22 7.01 9.96 14.90 64.05 71.89 63.23 JFM FMA MAM AMJ MJJ JJA JAS ASO SON OND NDJ DJF MaxTemp 31.94 30.77 28.81 26.54 25.03 25.03 27.02 29.63 31.21 31.66 31.72 32.11 Min Temp 19.75 17.57 13.93 9.75 6.74 6.60 9.14 13.41 16.80 18.85 19.77 20.17 Rainfall 132.19 95.99 26.86 18.89 9.26 10.06 10.62 29.64 50.28 66.39 93.21 140.90 4
The maximum temperatures (day temperatures) are forecasted to become above normal for both LP and NWP during August to October. The tendency of warmer maximum temperatures is gradually expanded from the west of NWP during early spring (Figure 5). The minimum temperature (night temperature) forecast system is indicating warmer conditions than normal for most of LP and NWP, with the exception of the southwestern parts of NWP for which cooler conditions are expected during August to October (Figure 5). Above-normal minimum temperatures are expected to continue during the September to November and October to December periods. These conditions are expected to worsen the current drought conditions experienced in NWP. Figure 5: Probabilistic maximum (left panel) and minimum (right panel) temperature forecasts for the three overlapping seasons valid for the period of August to October 2013 5
Why is this explanation and Seasonal Weather Forecasts of critical importance? Climate largely determines the success or failure of food production. More than 70% of food and nutrition insecure people are rural and therefore directly or indirectly dependent on agriculture for their livelihood. Seasonal weather forecasts as a planning tool can largely change food and nutrition insecurity to food and nutrition security. Growth originating in agriculture is almost three times more effective in reducing poverty than growth in any other sector of the economy. This was reiterated during a 2013 International Food Security Futures Conference. You are the farmers; you have the responsibility not only of food production but of food security, poverty reduction and economic growth in South Africa. The rural population is expected to peak between 2020 and 2050 which could mean intensified and exponential rural poverty and food and nutrition insecurity. Only you, our food producing farmers, can prevent a future catastrophe! Farmers would be wise to base their agricultural production planning on scientifically-based seasonal weather forecasts. Disclaimer The ARC-ISCW and its collaborators have obtained data from sources believed to be reliable and have made every reasonable effort to ensure accuracy of the data. The ARC-ISCW and its collaborators cannot assume responsibility for errors and omissions in the data nor in the documentation accompanying them. The ARC-ISCW and its collaborators will not be held responsible for any consequence from the use or misuse of the data by any organisation or individual. For further information please contact the following: Obed Phahlane 012 310 2520 PhahlaneO@arc.agric.za Mahlatse Phuthi 012 319 6668 MahlatseP@daff.gov.za Kentse Setshedi 012 319 2967 KentseS@daff.gov.za Adri Laas 012 310 2518 ISCWinfo@arc.agric.za 6