R. A. Houze, Jr., U. Romatschke K. L. Rasmussen

1. R. A. Houze, Jr., U. RomatschkeK. L. Rasmussen Mesoscale Aspects of Storms Producing Floods over Arid Mountains University of Washington AGU Fall Meeting, Remote Sensing of Natural Hazards, San Francisco, 9 Dec 2011

2. "Almost 20 million people need shelter, food and emergency care. That is more than the entire population hit by the Indian Ocean tsunami, the Kashmir earthquake, Cyclone Nargis, and the earthquake in Haiti—combined.” Secretary-General Ban Ki-moon August 2010

3. 2000 lives lost, extensive livestock, household, infrastructure & agricultural ($20B)

4. Recent papers: • Webster et al. (2011, GRL) • Houze et al. (2011, BAMS)

5. Synoptic time sequence…

6. 700 mb wind (~3 km) H L L L L Water vapor anomaly 500 mb wind Rain

7. ECMWF Ensemble Forecast analyzed by Webster et al. (2011) • 51 Ensemble members • 50/80 km resolution • Compared to CMORPH precipitation product

8. A COMPARISON OF RAINFALL IN 2008 AND 2010: Webster et al. 2011 • 2010 produced devastating floods but was not an outlier meteorologically • The hydrological uniqueness came because of the number of prior extreme events over the mountainous north, run-off due to drought in 2009, deforestation, and the TYPE OF STORM

9. Monsoon Mean Rainfall Climatology Webster et al. 2011

10. Summary of predictions of major July rain events in Pakistan Webster et al. 2011

11. The type of storm matters… • TRMM climatology shows different kind of rainstorms in eastern vs western Himalayan region

13. Climatology of extreme convective features shown by TRMM for 10 years of data Deep Convective Cores Wide Convective Cores BroadStratiformRegions

14.  Floods! Broad stratiform precipitation occurred over the mountains of Pakistan 15:31UTC 17:09 UTC Broad stratiform! Houze et al., BAMS 2011

15. Could the storm type have been anticipated?

16. Normal 500 mb anomaly patterns for South Asian storms observed by TRMM Normal Isolated deep convection

17. Normal 500 mb anomaly patterns for South Asian storms observed by TRMM Normal Normal Isolated deep convection Broadstratiform

18. 500 mb pattern 28 July 2010: very abnormal Normal Normal Isolated deep convection Broadstratiform

19. 500 mb pattern 28 July 2010: very abnormal

20. 500 mb pattern 28 July 2010 was very abnormal Broadstratiform NOT NORMAL Broadstratiform NORMAL

21. Conclusions from Pakistan • The probability of major rain periods over Pakistan was predictable ~7-10 days in advance • Not every predicted rain event produced floods • The type of storm mattered—the flooding storms had mesoscale stratiform characteristics normally seen only in storms far to the east • The possibility of such cloud systems occurring in the west could be seen in the forecast wind pattern and from a knowledge of the satellite climatology

22. Leh, India, August 2010 • 300 casualties due to flood in a high altitude valley of the Indus River

24. 1200

25. 0200

26. 1200

27. 0200

28. 1200

29. Flash flood at Leh 0200

30. Afternoon convective scales grew upscale to form a mesoscale system that moved off the plateau and fed on low-level moisture Rasmussen and Houze 2011

31. Could remote sensing have identified this as a flood case?

32. Satellite climatology shows occurrence of wide convective systems or systems with broad stratiform regions to be extremely rare Deep Convective Cores Wide Convective Cores BroadStratiformRegions

33. Conclusions from Leh • The flood producing storms were squall lines of mesoscale proportions • The squall lines fed on moisture from low levels when they moved off the Tibetan Plateau • Such storm are rare over the Tibetan Plateau • Again, a satellite climatology of storm type for the region would help to anticipate such an event.

34. End This research was supported by NSF grants ATM-0820586 and NASA grant NNX10AH70G