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21 October 2010

Update: Tornado - Florisbad/Soutpan area in the Free State on the 13 October 2010.

The Florisbad fossil site consists of a sequence of Quaternary deposits associated with a thermal spring, situated 45 km NNW of Bloemfontein in central South Africa (28°46’S, 26°04’E).

Tornado struck the Floribad Quaternary Research Station

By Dr James Brink

On Wednesday afternoon at approximately 16:15 a tornado struck the Florisbad Quaternary Research Station. - I was working in the fossil lab with two electricians, who were doing upgrading and maintenance. A storm was building up and the noise of the wind increased markedly. When I started to open the sliding door of the lab to check the source of the noise, I could see lots of dust and branches/objects flying past. I realised that it was an unusual kind of storm and closed the lab door. This was followed by a loud crash, when a tree was uprooted and narrowly missed the lab, but crushing the vehicle of the electricians in the process. The noise lasted for only a short while and when I went outside to investigate, there was still rain, and occasional hail. When the rain stopped, we could follow a clear path of destruction, which started to the left of our entrance gate, where a c. 15 m section of a brick and steel fence was blown over, trees were uprooted and branches were twisted off and bent. The path of destruction was confined and it followed an erratic route continuing in an easterly direction over the historic bathhouse, the old ablution building, passing to the south of the fossil lab and into the neighboring fields. There is evidence of a smaller secondary path of destruction, possibly a smaller tornado that followed a more northerly route through our lapa/braai area, missing the huts that we use for accommodation, uprooting a large tree and damaging smaller ones, before apparently joining the path of the one that caused most of the the damage. - I am not familiar with tornadoes, but abruptness of the event, the erratic and confined routes of destruction and the evidence for very strong upward currents, with sheets of corrugated iron caught in the high branches of trees and overhead wires, being transported over several km, suggest to me that we had at least two tornadoes passing through Florisbad on Wednesday, 13 October 2010.

We are pleased that the fossil lab was untouched, but the damage to the historic bath house and other structures is severe and these will need urgent attention.

Images of the damage caused by the storm:

Severe damage to the historic bath house

Severe damage caused by a fallen tree to this light delivery vehicle 

 Significant image of tree damage.  Important is the damage to the middle tree which clearly reflect the strength of the storm.

Brick and steel fence blown over.

Dr. James S. Brink
Florisbad Quaternary Research
National Museum

SAWDIS - After reading Dr Brink's report and other eye witness reports and also viewing several other  images of storm damage in the area it is clear that the damage sustained by this storm reflect that a tornado did struck the Florisbad area on the 13 October 2010. Possible strength: F0 - F1 on the The Fujita Scale.  Please note: A key point to remember is this: the size of a tornado is not necessarily an indication of its intensity. The Fujita Scale is based on damage, not the appearance of the funnel. Storm spotters, storm chasers and other weather observers often try to estimate the intensity of a tornado when they are in the field, basing their judgement on the rotational speed and amount of debris being generated as well as the width. However, the official estimate is made afterT the tornado has passed. he Fujita Scale is very subjective, and varies according to how experienced the surveyor is.  However, the less experienced the surveyor is, the more likely he/she is to be awed by the damage, and the more likely they are to give it a high rating.

The SAWDIS would like to express it thanks and appreciation to the following people who supplied the SAWDIS with valuable information of this event: 

1. Dr James Brink
2. Die Volksblad
3. Gordon Richardson
4. Julius Pistorius (For his real-time observation on the day of the storm and informing the SAWDIS)
5.  Pieter Myburg
6.  Sven Ouzman
7.  Zoe Henderson
8.  Nico Oelofse
9.  Stormchasing SA
10.  JP Human