The one thing
that we have learned is that the jet stream is able to hugely divert weather
conditions anywhere but certainly over North America . We have been experiencing an extreme of the
jet stream. Most winters it largely
stays put. Most of the time it varies
very little over a known channel. The
problems occur when it decides to go a little crazy like this winter.
The net
global heat may vary little from year to year, but it is no fun to find that
Arctic conditions have moved south while the Arctic
warms up.
This winter
got hard and difficult from the beginning and has sustained it throughout. I have no doubt that dying flocks of birds
represent the fatal exhaustion of large numbers of birds trying to maintain
their position in suddenly declining conditions. The cold has simply lasted too long.
By now we
should have had a break in the weather allowing recovery.
How a freak diversion of the jet stream is
paralysing the globe with freezing conditions
By NIALL FIRTH
Last updated at 12:53 PM on 22nd December 2010
It's snowing in Australia
and California yet 'warm' in Greenland
The
freezing conditions that have blasted Britain
are being blamed on a series of weather patterns that are bringing Arctic
temperatures to much of western Europe, California
and even Australia
One of
the main factors is a change in the position of the jet stream - the
fast-moving current of air that moves from west to east, high in the
atmosphere.
Changes in
the jet stream's path can cause massive changes in weather conditions across
the globe and may be why Australians are now shivering their way through summer
and the current freezing conditions in California
In a
normal British winter - when conditions are mild and soggy - the jet stream
lies over northern Europe , at an altitude of
between 35,000 to 50,000 feet.
Daily
mean temperature anomalies around the world between 1st December and 20th
December compared with the 30 year long term average between 1961 and 1990
During
these grey winters, Britain 's
prevailing winds come from the west and south west, and bring with them warm
and moist air from the sub-tropical Atlantic .
This
year a high-pressure weather system over the Atlantic is blocking the jet
stream’s normal path and forcing it to the north and south of Europe .
The
areas of high pressure act like stones in a stream - blocking the normal flow
of milder air from the west and instead forcing colder air from the north down
across the UK
In California more than 12 inches of rain has fallen in
parts of the Santa Monica Mountains in the south and 13 feet of snow has
accumulated at Mammoth
Mountain
And
Australians expecting to bask in early summer sun this Christmas are instead
shivering as icy gusts sweeping up from the Southern Ocean have blanketed parts
of east coast states New South Wales and Victoria with up to four inches of
snow.
When the
jet-stream is blocked by high pressure it dips southwards and lets freezing air
flood in from the Arctic regions.
Other
weather patterns are also causing havoc across the may also be affecting the
weather, such as the current in the tropical Pacific Ocean, called La Nina,
which is disturbing the jetstream over the north Pacific and North America.
A
combination of our usual wet Atlantic weather systems striking these freezing
cold fronts results in huge amounts of snowfall – and brings Britain
A Met
Office spokesman: ‘The problem is we are not getting the warmer Atlantic air
that normally keeps our winters mild.’
‘We can
see that it is unseasonably warm over Canada
and Greenland , this is where warm air has been
diverted.’
He said
that any change in the pressure over the Atlantic would need to last for
several days before we would notice any change in the weather in Europe .
Freezing-cold
winters and milder winters tend to cluster in groups, as the jet stream changes
its path.
Experts
are still unsure why this is but suspect it may be related to the EL Nino
weather system as well as changes in sea temperatures and solar activity.
A system of high pressure has forced the jet
stream further south, allowing biting cold winds in from the north
Read more: http://www.dailymail.co.uk/sciencetech/article-1340436/Why-cold-warm-Greenland-Diverted-jet-stream-letting-icy-blast-Arctic.html#ixzz19N4IKD7e
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