Commentary – Floods in UK Caused by Extreme Rains in Indonesia?

by Sabrina I. Pacifici on February 12, 2014

Bloomberg: “The U.S. is freezing and the U.K. is flooded. Clearly, Indonesia is at fault. That, in any case, is my layman’s interpretation of a report this week from the U.K.’s meteorological agency, the Met Office. It makes fascinating, if nerdy, reading that can be boiled down to a few basic conclusions:

* The extended, extreme weather on both sides of the Atlantic is connected in a kind of butterfly effect that began in the Pacific and ended in Europe.

* Persistent rains over Indonesia and a pressure system in the Pacific bent the Asian-Pacific jet stream north, which forced cold polar air south and dumped snow and sub-zero temperatures on the U.S. As the polar air spreads south and east to the Atlantic, it has bumped into warmer tropical air, creating a “temperature gradient” that generates storms.

* At the same time, a band of fast winds that blow high in the atmosphere over the equator happened to flip direction, from east-west to west-east, something it does about every 14 months in a process called “quasi-biennial oscillation.” This has had the effect of super-charging the Atlantic Jet Stream, which starts over North America and acts as a conveyor belt to carry storms across to Ireland and the U.K. Because this jet stream has been 30 percent stronger than usual this winter, and had some big storms to carry, it has dumped a lot of very powerful rain storms at its destination.

Or, in the words of the Met Office report: “These extreme weather events on both sides of the Atlantic were embedded in a persistent pattern of perturbations to the upper tropospheric jet stream.”

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