NASA thinks Omega blocking event phenomenon linked to extreme weather by slowing Rossby waves

[Emily]

http://www.nasa.gov/topics/earth/features/asia-fire.html

Extreme 2010 Russian Fires and Pakistan Floods Linked Meteorologically
08.30.11

GREENBELT, Md. -- Two of the most destructive natural disasters of 2010 were closely linked by a single meteorological event, even though they occurred 1,500 miles (2,414 km) apart and were of completely different natures, a new NASA study suggests.
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Under normal summertime conditions, the jet stream pushes weather fronts through Eurasia in four or five days, but something unusual happened in July of 2010. A large-scale, stagnant weather pattern ? known as an Omega blocking event ? developed over a high-pressure ridge above western Russia. This blocking event, which divided the jet stream, had the effect of slowing the Rossby wave and prevented the normal progression of weather systems from west to east....

What caused the Omega blocking event is a mystery:

While the new study highlights the degree of interconnection that can exist between two seemingly unrelated weather events, Lau cautions that many questions remain. For example, why did such a powerful blocking high form in the first place? And did some particular process occurring on the land or in the atmosphere sustain and strengthen it?