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Old October 20th 03, 08:57 PM posted to uk.sci.weather
Will Will is offline
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First recorded activity by Weather-Banter: Jul 2003
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Default Blocking in autumn


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Philip, it's not the blocking per se I was picking up on but the way the cold
polar vortex seems to have shifted quite a bit from it's climatological position
in October. Blocking would of course come about as a natural consequence of
this. The hemispheric circulation appears to have distorted substantially.

Eg in http://weather.unisys.com/upper_air/ua_nhem_300.html
the Canadian vortex has migrated further towards the pole and another vortex is
over northern Scandinavia/Russia.

Will.
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" Love begins when judgement ceases "
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Philip Eden wrote in message ...
Sorry to start a new thread, but I can't find the old one. I'm
surprised so many people seem to think major blocking episodes
in October are unusual. I suppose it depends what you mean
by unusual: if simply "not usual" I suppose I might be persuaded
to agree, but if you mean "rare" then I demur.

Anyone who wants to see a a good example of blocking,
rare in its longlastedness, rare in its geographical extent, and
rare in the way one sort of block followed another, take a
trip to www.wetterzentrale.de and look at the archive for
Sept/Oct/Nov 1993. During that 91-day period there were
just four days with southwesterly weather type and one with
a westerly. (Yes, the subsequent winter was zonal).

In the last 10 years we have had major blocks in October on:
4-20 Oct 1994
17 Oct - 4 Nov 1997
30 Sept - 8 Oct 1998
11-22 Oct 1999
5-21 Oct 2002, which some of us seem to have forgotten
already.

Philip Eden