Jet stream responsible for weather chaos

Wednesday 08th Sep 2010 by theWeather Club

Meteorologists believe that the devastating Russian heat wave and Pakistan floods are being caused by one unusual weather pattern - a static jet stream in the Northern Hemisphere. The jet stream is a fast-moving high-altitude air current circling the earth from west to east. But in the past month, a 'blocking event' has brought the jet stream to a halt, keeping weather patterns stationary over certain countries "Over Pakistan, the weather pattern is just staying with the monsoon, and the monsoon is bringing drenching rains," meteorologist Josh Fisher told reporters.
"But this jet stream is also bringing dry air from eastern Africa right up into Russia and this continuous heat wave is allowing the wildfires to build."

The effects of the stalled jet stream have been catastrophic. In early July the USA and Canada saw a heat wave that caused numerous deaths and power cuts. In Russia an unrelenting heat wave has triggered over 500 wildfires, leaving Moscow cloaked in heavy smog, and doubling the cities daily mortality rate. And the world is watching as the monsoon rains continue to drive a humanitarian disaster in Pakistan.

Mr Fisher said 'Rossby' waves - spinning wind currents that combine to shape the jet stream - are responsible for the present situation. These waves have been stronger this year, and are working against the jet stream which has brought it to a halt. This blocking pattern while difficult to predict generally lasts between eight to 11 days. Mr Fisher continued. "The one that brought the hot temperatures to the US lasted over a week, while the current one affecting Pakistan and Russia has been persisting for already around eight days and could last for a few more."