Weather Banter - Blocking in autumn

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Blocking in autumn

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

Blocking in autumn

Philip Eden" philipATweatherHYPHENukDOTcom 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.
snip

I'd been thinking of October 1993, Philip. It was my first autumn commuting
to Bracknell and lulled my into a false sense of security.

Jon.

Blocking in autumn

Philip Eden" philipATweatherHYPHENukDOTcom 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.

.... welcome back Philip: when I heard you on Radio 5 this morning I
thought .. "at last, the voice of sanity" - *some* of the posts over the
last week have been unbelievable.

Martin.

Blocking in autumn

"Philip Eden" philipATweatherHYPHENukDOTcom 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.

From the gliding point of view, this autumn has been very poor for mountain
wave flying in England and Wales for the simple reason that the "normal"
westerlies have been very scarce.

At the end of the thermal season, a lot of flatland pilots visit gliding
sites in to the east of major high ground such as Sutton Bank N.Yorks - (I
had planned a visit there myself) - or Long Mynd on the English/Welsh
border. But this autumn, you can count on one hand the wave days. There
have simply been very few westerly winds.

Scotland has fared slightly better with some southerly wave to the north of
the main mountains (eg Moray Coast, Cairngorm area), for example last week
when the anticyclone was over Scandinavia

Jack

Blocking in autumn

================================================== ==================
This posting expresses the personal view and opinions of the author.
Something which everyone on this planet should be able to do.
================================================== ==================

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.
--
" 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

Blocking in autumn

"Philip Eden" philipATweatherHYPHENukDOTcom wrote in message
.. .
snip
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.

Using the EWP data and MS Excel to calculate the 30 year rolling average for
September and October and assuming a dry month is one with rainfall less
than 80% of the rolling 30 year average, the last time we had a September
and an October (assuming there are no downpours before the 31st) with
rainfall similar to this year was 1985 - 18 years ago!

Victor

Blocking in autumn

"martin rowley" wrote in message
...

Philip Eden" philipATweatherHYPHENukDOTcom 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.

... welcome back Philip: when I heard you on Radio 5 this morning I
thought .. "at last, the voice of sanity" - *some* of the posts over the
last week have been unbelievable.

Martin.

Oh dear. Save as all.

Blocking in autumn

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...
BTW I was having a look at this as well and came across this page with extensive polar vortex data
and diagnostics-
http://www.pa.op.dlr.de/arctic/
see also-
http://www.atmos.washington.edu/~hakim/tropo/tropo.html

--
regards,
david

Blocking in autumn