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

"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 "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

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

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

Synoptic time sequence…

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

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

A COMPARISON OF RAINFALL IN 2008 AND 2010: 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 Webster et al. 2011

Monsoon Mean Rainfall Climatology Webster et al. 2011

Summary of predictions of major July rain events in Pakistan

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

Deep Convective Cores Wide Convective Cores Broad Stratiform Regions Climatology of extreme convective features shown by TRMM for 10 years of data

Broad stratiform precipitation occurred over the mountains of Pakistan Broad stratiform!  Floods! Houze et al., BAMS :09 UTC15:31UTC

Could the storm type have been anticipated?

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

Normal Isolated deep convection Broad stratiform Normal 500 mb anomaly patterns for South Asian storms observed by TRMM

500 mb pattern 28 July 2010: very abnormal Normal Isolated deep convection Broad stratiform

500 mb pattern 28 July 2010: very abnormal

500 mb pattern 28 July 2010 was very abnormal NOT NORMAL NORMAL Broad stratiform

Conclusions from Pakistan The probability of major rain periods over Pakistan was predictable ~7-10 days in advance The probability of major rain periods over Pakistan was predictable ~7-10 days in advance Not every predicted rain event produced floods 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 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 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

Leh, India, August casualties due to flood in a high altitude valley of the Indus River

1200

0200

1200

0200

1200

0200 Flash flood at Leh

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

Could remote sensing have identified this as a flood case?

Deep Convective Cores Wide Convective Cores Broad Stratiform Regions Satellite climatology shows occurrence of wide convective systems or systems with broad stratiform regions to be extremely rare

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

End This research was supported by NSF grants ATM and NASA grant NNX10AH70G