1. Heavy floods episodes on the 11 th and 12 th November 2008 South African case study Isaac Ngwana

2. Outline Document Reference: SMRF-PSN-NGW004-001-2012-05-09 Document Template Reference: AWC-PSN-001.1 Date of last revision: 26 August 2011 2 General rainfall patterns Main weather systems Observation network Case study Model results and verification Conclusion

3. Rainfall patterns in SA Document Reference: SMRF-PSN-NGW004-001-2012-05-09 Document Template Reference: AWC-PSN-001.1 Date of last revision: 26 August 2011 3

4. Main weather systems- responsible for flooding events TTT Tropical cyclones Cut off low Frontal system Document Reference: SMRF-PSN-NGW004-001-2012-05-09 Document Template Reference: AWC-PSN-001.1 Date of last revision: 26 August 2011 4

5. Weather observation stations in South Africa Document Reference: SMRF-PSN-NGW004-001-2012-05-09 Document Template Reference: AWC-PSN-001.1 Date of last revision: 26 August 2011 5 SURFACE OBSERVATIONS  23 climate stations  23 sea surface temperature stations  25 weather offices  35 electric _manual (aws manned)  156 automatic weather stations – unmanned  165 automatic rainfall stations  1257 rainfall (monthly; ~50 provide daily data) UPPER AIR OBSERVATIONS 9 Upper air stations ( Including the ISLANDS – Marion and Gough)

6. Weather observation stations in South Africa Document Reference: SMRF-PSN-NGW004-001-2012-05-09 Document Template Reference: AWC-PSN-001.1 Date of last revision: 26 August 2011 6 Weather observation stations in South Africa Document Reference: SMRF-PSN-NGW004-001-2012-05-09 Document Template Reference: AWC-PSN-001.1 Date of last revision: 26 August 2011 6

7. RADAR NETWORK in South Africa Document Reference: SMRF-PSN-NGW004-001-2012-05-09 Document Template Reference: AWC-PSN-001.1 Date of last revision: 26 August 2011 7

8. Case study (11 & 12 Nov 2008) - general damage Document Reference: SMRF-PSN-NGW04-001-2012-05-09 Document Template Reference: AWC-PSN-001.1 Date of last revision: 26 August 2011 8 47 people were killed Thousands evacuated Roads and bridges swept away

9. Warning System-print media Document Reference: SMRF-PSN-NGW004-001-2012-05-09 Document Template Reference: AWC-PSN-001.1 Date of last revision: 26 August 2011 9

10. Early Warning System-print media cont… Document Reference: SMRF-PSN-NGW004-001-2011-05-09 Document Template Reference: AWC-PSN-001.1 Date of last revision: 26 August 2011 10

11. 11 November 2008 Document Reference: SMRF-PSN-NGW004-001-2012-05-09 Document Template Reference: AWC-PSN-001.1 Date of last revision: 26 August 2011 11 Observations - 11 November 2008 11

12. Observed 24 hr rainfall 11 & 12 Nov 2012 Document Reference: SMRF-PSN-NGW004-001-2012-05-09 Document Template Reference: AWC-PSN-001.1 Date of last revision: 26 August 2011 12

13. 11 November 2008 Document Reference: SMRF-PSN-NGW004-001-2012-05-09 Document Template Reference: AWC-PSN-001.1 Date of last revision: 26 August 2011 13 Observations -12 November 2008 13

14. Weather systems – 11 Nov 2012 Document Reference: SMRF-PSN-NGW004-001-2011-05-09 Document Template Reference: AWC-PSN-001.1 Date of last revision: 26 August 2011 14

15. Observed weather -11 Nov 2008 Document Reference: SMRF-PSN-NGW004-001-2011-05-09 Document Template Reference: AWC-PSN-001.1 Date of last revision: 26 August 2011 15

16. Observed weather 12 Nov 2008 Document Reference: SMRF-PSN-NGW004-001-2011-05-09 Document Template Reference: AWC-PSN-001.1 Date of last revision: 26 August 2011 16

17. Observed weather -12 Nov 2008 Document Reference: SMRF-PSN-NGW004-001-2011-05-09 Document Template Reference: AWC-PSN-001.1 Date of last revision: 26 August 2011 17

18. NWP Modeling in South Africa Document Reference: SMRF-PSN-NGW004-001-2012-05-09 Document Template Reference: AWC-PSN-001.1 Date of last revision: 26 August 2011 18

19. NWP Modeling in South Africa Document Reference: SMRF-PSN-NGW004-001-2012-05-09 Document Template Reference: AWC-PSN-001.1 Date of last revision: 26 August 2011 19 ModelDomainAssimilation UM SA12LargeNo data assimilation UM SA12LargeData assimilation UM SA15SmallNo data assimilation WRF SA12LargeNo data Assimilation WRF SA15SmallNo data assimilation

20. Modeling - weather systems 12 -48 hr forecast Document Reference: SMRF-PSN-NGW004-001-2012-05-09 Document Template Reference: AWC-PSN-001.1 Date of last revision: 26 August 2011 20

21. 12 November 2008 Document Reference: SMRF-PSN-NGW004-001-2012-05-09 Document Template Reference: AWC-PSN-001.1 Date of last revision: 26 August 2011 21

22. 12 November 2008 Document Reference: SMRF-PSN-NGW004-001-2012-05-09 Document Template Reference: AWC-PSN-001.1 Date of last revision: 26 August 2011 22

23. Model -12 November 2008 Document Reference: SMRF-PSN-NGW004-001-2012-05-09 Document Template Reference: AWC-PSN-001.1 Date of last revision: 26 August 2011 23

24. Eye ball verification Document Reference: SMRF-PSN-NGW004-001-2012-05-09 Document Template Reference: AWC-PSN-001.1 Date of last revision: 26 August 2011 24

25. Warning System-SAWS website Document Reference: SMRF-PSN-NGW004-001-2011-05-09 Document Template Reference: AWC-PSN-001.1 Date of last revision: 26 August 2011 25

26. Conclusion Document Reference: SMRF-PSN-NGW004-001-2012-05-09 Document Template Reference: AWC-PSN-001.1 Date of last revision: 26 August 2011 26 11 &12 Nov 2008 flooding events were well forecast by the model Forecast warning were issued in time Necessary steps were taken by government dept. even though 47 people lost their lives Good observation data bank, but sparse Local data ingest might improve model forecast