Severe thunderstorms and heavy rainfall caused flash flooding in parts of Gauteng province in South Africa on November 9th, 2016. Areas most affected were Johannesburg and Ekurhuleni. The flooding resulted in at least 4 deaths and property damage, including delayed or diverted flights at OR Tambo International Airport. Major roads were flooded with submerged vehicles. The South African Weather Service warned of further heavy rains and flooding over the following days in several provinces.

1. SEVERE THUNDERSTORMS RESULTING IN FLASH FLOODING
WREAK HAVOC IN GAUTENG
Severe thunderstorms resulting inheavy downpours and flash flooding, hit
parts of Gauteng on the afternoonof the 9th
November 2016. Areas that
were most affectedwere the City of Johannesburg and Ekurhuleni
MetropolitanMunicipalities. This comes twodays after isolatedsevere
thunderstorms resultedinflashflooding in the Silver Lakes areain Pretoriaas
well as inareas inBuccleuch, Edenvale and Bedfordview.
Damage to property was reported, which included OR Tambo International
Airport where there were also some flights which were either diverted or
delayed. Major roads were affectedandthere were cars submerged or swept
away on the R24, N3 and N12 highways, (see figure 1 below). At this stage at
least 4 fatalities have been reported.
The South African Weather Service hereby expresses its condolences and
sympathy to those who have lost their lives and property during this
extremely severe weather event.
SUMMARY AND DISCUSSION
A watch for severe thunderstorms was issued at 14:15 for the southern parts
of Gauteng.
This watch was escalated to a warning for severe thunderstorms with heavy
downpours and small hail at 16:33 for the following areas:

2.  Midvaal, moving towards Lesedi and southern Ekurhuleni.
 17:23: City of Johannesburg and Ekurhuleni.
The first signal that indicated that the alert was justified, was the development
of a band of thunderstorms observed via satellite and radar imagery, moving
into the area during the late afternoon from about 14:00 local time onwards.
These severethunderstorms produced heavy rain within a short space of time,
which subsequently lead to flash flooding.
UPCOMING EXPECTED WEATHER
Further rainfall is expected today and tomorrow over the North Eastern Free
State, KwaZulu-Natal, Gauteng, Mpumalanga, eastern North West and
Limpopo, until the weekend. There still remains a very high risk of heavy rain
which will result in flooding in more places during this period.
Heavy rains are expected tomorrow, 11 November 2016 over:
 North-eastern Fee State,
 Western parts of KwaZulu-Natal,
 Gauteng,
 Mpumalanga,
 Eastern parts of North West
 and southern Limpopo
WHAT DOES A SEVERE THUNDERSTORM WARNING MEAN?
A severe thunderstorm warning is issued when a thunderstorms contains one
or more of the following severe weather criteria:
 Hail of greater than 19mm diameter or large amounts of small hail
 A tornado
 Wind gusts 50 kts (93 km/h) or more
 Heavy downpours leading to localised urban or flash flooding
PRECAUTIONS TO TAKE DURING FLOODING
 If walking outdoors, avoid crossing rivers and swollen streams where
water is above your ankles.

3.  Just 15cm of fast-moving flood water can knock a person off their feet,
and a depth of 60cm feet is enough to float a car.
 Never try to walk, swim or drive through fast-moving flood water. Stop,
turn around and go another way.
 Listen to the special warnings on radio and/or television
 Abandon your home immediately if evacuation is recommended, before
access is cut off by flood water.
 Never drive into water covering the road. You would not know how
deep it is or if the road has been washed away.
 If the vehicle stalls, leave it immediately and seek higher ground
 Be especially cautious at night when it’s harder to recognize flood
dangers.
The South African Weather Service will continue to monitor any further
developments relating to this weather system and will issue subsequent
updates as required. Furthermore, the public is urged to regularly follow
weather forecasts on television and radio. Updated information can also be
found at www.weathersa.co.za as well as via the SA Weather Service Twitter
account @SAWeatherServic