Pakistan Flood Pakistan Flood 2010:2010:

P. J. WebsterP. J. WebsterR. A. Houze, Jr.R. A. Houze, Jr.P. J. WebsterP. J. WebsterR. A. Houze, Jr.R. A. Houze, Jr.

International Weather & Climate Events of 2010, AMS Annual Meeting, Seattle, 25 January 2011International Weather & Climate Events of 2010, AMS Annual Meeting, Seattle, 25 January 2011

Could it have been predicted? Could it have been predicted?

withwith

V. Toma, H. Kim, K. Rasmussen, U. V. Toma, H. Kim, K. Rasmussen, U. Romatschke, S. Medina, S. Brodzik, D. Romatschke, S. Medina, S. Brodzik, D. Niyogi, and A. Kumar, Niyogi, and A. Kumar,

"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-moonAugust 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-moonAugust 2010

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

Upcoming papers:

• Webster et al. (2011, GRL)• Houze et al. (2011, BAMS)

Monsoon Mean Rainfall Climatology

Webster et al. 2011

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

ECMWF Ensemble Forecast analyzed by Webster et al. (2011)

• 51 Ensemble members• 50/80 km resolution• Compared to CMORPH

precipitation product

Webster et al. 2011

4-Day ensemble mean forecast

Webster et al. 2011

Summary of predictions of major July rain events in Pakistan

Does the type of storm matter?

• TRMM climatology shows different kind of rainstorms in eastern vs western Himalayan region

Deep Convective

Cores

Wide Convective

Cores

BroadStratiform

Regions

Climatology of extreme convective features shown by TRMM for 10 years of data

Normal

Normal 500 mb anomaly patterns for South Asian rainstorms

Nor

mal

Normal 500 mb anomaly patterns for South Asian rainstorms

Normal

500 mb pattern 28 July 2010: very abnormal

Nor

mal

Normal

Time sequence…

700 mb wind (~3 km)700 mb wind (~3 km)

LL LL LLLL

HH

Water vapor anomaly500 mb windWater vapor anomaly500 mb wind

Rain

Broad stratiform precipitation occurred over the mountains of Pakistan

Broad stratiform!

Floods!

Houze et al., BAMS 2011

ConclusionsWhat was predictable about the Pakistan floods?

•2010 was not an abnormally rainy year in Pakistan•The probability of major rain periods over Pakistan was predicable ~7-10 days in events

Could floods have been anticipated?

•Not every predicted major rain event produced floods•The July 28 storms occurred over deforested mountains•And they 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

What can be done in the future?

Webster et al., BAMS November 2010

Proof of concept in Bangladesh

•Could be applied to other basins•Need downscaling for type of storm and topography

EndEndThis research was supported byThis research was supported by

NSF grants ATM-0820586 and ATM-0965610 and NASA grant NNX10AH70GNSF grants ATM-0820586 and ATM-0965610 and NASA grant NNX10AH70G