Dr. Jeff Masters' WunderBlog : Extreme Jet Stream Pattern Triggers Historic European Floods | Weather Underground
The Mississippi flooded earlier this month, turning on a dime from drought to flood.
Is climate change making severe suck weather more common? I wouldn't be surprised. There is some theory that persistent high pressure blocks result from the increased height of the weathery parts of the atmosphere and slowing or movement of the jet stream. These blocks stall the passage of new fronts, so it stays dryer or wetter in one place for longer.
Quote:
Floods caused by a blocking high pressure system
The primary cause of the torrential rains over Central Europe during late May and early June was large loop in the jet stream that developed over Europe and got stuck in place. A "blocking high" set up over Northern Europe, forcing two low pressure systems, "Frederik" and "Günther", to avoid Northern Europe and instead track over Central Europe. The extreme kink in the jet stream ushered in a strong southerly flow of moisture-laden air from the Mediterranean Sea over Central Europe, which met up with colder air flowing from the north due to the stuck jet stream pattern, allowing "Frederik" and "Günther" to dump 1-in-100 year rains. The stuck jet stream pattern also caused record May heat in northern Finland and surrounding regions of Russia and Sweden, where temperatures averaged an astonishing 12°C (21°F) above average for a week at the end of May. All-time May heat records--as high as 87°F--were set at stations north of the Arctic Circle in Finland.
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