Zimbabwe 2017/18 Seasonal update Meteorological Services Department Of Zimbabwe 20 December 2017

OCTOBER-NOVEMBER-DECEMBER (OND) 2017 Definitions Above normal: rainfall in excess of 125 % of the average Normal: Between 75% and 125 % of the average Below: rainfall below 75% of the average LONG TERM AVERAGE: averaged for period 1981 to 2010 OND OUTLOOK A 35 N 40 B 25 A 25 N 40 B 35

Long-term Seasonal onset Definitions: start of season is any day after the 1st of October that a place receives 20 mm or more in 1 or two days provided there is no dry spell of 10 or more in the next 20 days. Dry day: is a day which receives less than 0.85mm Rainday: is a day which receives 0.85mm or more rainfall Wet day: is a day with 10mm or more Mean onset (SOS) of the rainfall season (period 1981 to 2016) Standard error(SE) of SOS mean: SE ± mean onset gives the window for onset dates

Start anomaly for 2017-18 season: current SOS 2017-2018 Seasonal onset Definitions: start of season is any day after the 1st of October that a place receives 20 mm or more in 1 or two days provided there is no dry spell of 10 or more in the next 20 days. Dry day: is a day which receives less than 0.85mm Rainday: is a day which receives 0.85mm or more rainfall Wet day: is a day with 10mm or more Start anomaly for 2017-18 season: current SOS minus long-term mean onset Start of season (SOS) for current season (2017-18) according to the above definition of start of season

Raindays and wet days for 2017-2018 Definitions: start of season is any day after the 1st of October that a place receives 20 mm or more in 1 or two days provided there is no dry spell of 10 or more in the next 20 days. Dry day: is a day which receives less than 0.85mm Rainday: is a day which receives 0.85mm or more rainfall Wet day: is a day with 10mm or more Wet days anomaly for 2017-18 season: current number of wet days minus mean number of wet days to date; ref to definition above Raindays anomaly (2017-18): current number of raindays minus long-term mean number of raindays to date

Percentage of normal rainfall as from ACCUMULATED AND PERCENTAGE OF NORMAL FOR 2017-2018 RAINFALL SEASON Definitions Above normal: rainfall in excess of 125 % of the average Normal: Between 75% and 125 % of the average Below: rainfall below 75% of the average Percentage of normal rainfall as from 1 October 2017 to 13 December 2017). Accumulated Rainfall in mm as from 1 October 2017 to 13 December 2017.)

DATES WHEN WATER BALANCE GOT TO ZERO IN THE CURRENT DATES WHEN WATER BALANCE GOT TO ZERO IN THE CURRENT (2017-2018) RAINFALL SEASON

2017-2018 SEASONAL OUTLOOK UPDATE FOR JANUARY-FEBRUARY-MARCH Definitions Above normal: rainfall in excess of 125 % of the average Normal: Between 75% and 125 % of the average Below: rainfall below 75% of the average LONG TERM AVERAGE OUTLOOK