December is almost upon us, and so has anyone seen any sensible predictions for the winter? . I've seen mention in the press of "a very cold winter", but nothing based on data, or on something that sounds scientific (e.g. North Sea temperatures, El Nino, North Atlantic Oscillation, and all those other things I dimly remember).

Trevor

On 29/11/2018 13:03, Trevor Harley wrote:
December is almost upon us, and so has anyone seen any sensible
predictions for the winter? . I've seen mention in the press of "a
very cold winter", but nothing based on data, or on something that
sounds scientific (e.g. North Sea temperatures, El Nino, North
Atlantic Oscillation, and all those other things I dimly remember).


My own forecast, based on SST anomalies in the Atlantic alone, is that
it should be a more mobile winter than usual with lower than usual
pressure between Iceland and Norway. Pressure near the Azores should be
above average. This suggests a mild and windy winter.

As has happened before, other factors, such as SSW in particular, could
boot this out of the window quite easily. We'll see.

--
Graham P Davis, Bracknell, Berks. Web-site: http://www.scarlet-jade.com/
With great power comes great electricity bill.
OS: Linux [openSUSE Tumbleweed]

On Thursday, 29 November 2018 13:03:21 UTC, Trevor Harley wrote:
December is almost upon us, and so has anyone seen any sensible predictions for the winter? . I've seen mention in the press of "a very cold winter", but nothing based on data, or on something that sounds scientific (e.g. North Sea temperatures, El Nino, North Atlantic Oscillation, and all those other things I dimly remember).

It's a tricky one, as there are opposing teleconnections at work. The QBO is in westerly descending phase - which encourages a stronger stratospheric polar vortex, which in turn encourages mobility on the troposphere and makes SSW events less likely. Opposing this is the imminent El Nino which IIRC encourages blocking in the first half of winter. Also in opposition at the moment is the MJO which is encouraging blocking at the moment.

FWIW: I think we will see limited blocking and slow progression in the first half of winter, with a more mobile scenarion in the second half.

--
Freddie
Ystrad
Rhondda
148m AMSL
http://www.hosiene.co.uk/weather/
https://twitter.com/YstradRhonddaWx for hourly reports (very few tweets getting through currently)
Stats for the month so far: https://www.hosiene.co.uk/weather/st...201811NOV.xlsx

Freddie wrote:

On Thursday, 29 November 2018 13:03:21 UTC, Trevor Harley wrote:
December is almost upon us, and so has anyone seen any sensible
predictions for the winter? . I've seen mention in the press of "a
very cold winter", but nothing based on data, or on something that
sounds scientific (e.g. North Sea temperatures, El Nino, North
Atlantic Oscillation, and all those other things I dimly remember).

It's a tricky one, as there are opposing teleconnections at work.
The QBO is in westerly descending phase - which encourages a stronger
stratospheric polar vortex, which in turn encourages mobility on the
troposphere and makes SSW events less likely. Opposing this is the
imminent El Nino which IIRC encourages blocking in the first half of
winter. Also in opposition at the moment is the MJO which is
encouraging blocking at the moment.

FWIW: I think we will see limited blocking and slow progression in
the first half of winter, with a more mobile scenarion in the second
half.

My stock reponse when asked about prospects for the coming winter is

"There will be weather"

Not particularly helpful but it should be 100% accurate :-)

--
Norman Lynagh
Tideswell, Derbyshire
303m a.s.l.
https://peakdistrictweather.org
twitter: @TideswellWeathr

In message ,
Trevor Harley writes
December is almost upon us, and so has anyone seen any sensible
predictions for the winter? . I've seen mention in the press of "a very
cold winter", but nothing based on data, or on something that sounds
scientific (e.g. North Sea temperatures, El Nino, North Atlantic
Oscillation, and all those other things I dimly remember).

Trevor

There's some interesting analysis by Gavin Pearson he

https://www.gavsweathervids.com/wint...r-forecast.php
--
John Hall
"Hegel was right when he said that we learn from history
that man can never learn anything from history."
George Bernard Shaw (1856-1950)

On Thursday, November 29, 2018 at 9:18:36 AM UTC-5, Freddie wrote:

It's a tricky one, as there are opposing teleconnections at work. The QBO is in westerly descending phase - which encourages a stronger stratospheric polar vortex, which in turn encourages mobility on the troposphere and makes SSW events less likely. Opposing this is the imminent El Nino which IIRC encourages blocking in the first half of winter. Also in opposition at the moment is the MJO which is encouraging blocking at the moment.

FWIW: I think we will see limited blocking and slow progression in the first half of winter, with a more mobile scenario in the second half.

========

Yes, it is a tough on, and those are some of the challenges with which we have been wrestling. Add to that the nature of this El Nino - Modoki or at least a hybrid rather than a classic east-based event, which suggests high-latitude blocking has a higher probability late winter (around February). Current QBO and GLAAM are pertinent and, as you say, should discourage SSW episodes but do not preclude such late winter blocking.

MJO is going to be progressing to areas which are more amenable to mobility through December. Of course, it's an intra-seasonal guide rather than seasonal but I'd expect a degree of zonality / +NAO to continue into January, and Atlantic SSTs suggests overall +NAO. Low solar likely becomes more of a factor in the next 1 o 3 winters.


Stephen
Indianapolis IN.

On Thursday, 29 November 2018 19:52:52 UTC, Stephen Davenport wrote:
On Thursday, November 29, 2018 at 9:18:36 AM UTC-5, Freddie wrote:

It's a tricky one, as there are opposing teleconnections at work. The QBO is in westerly descending phase - which encourages a stronger stratospheric polar vortex, which in turn encourages mobility on the troposphere and makes SSW events less likely. Opposing this is the imminent El Nino which IIRC encourages blocking in the first half of winter. Also in opposition at the moment is the MJO which is encouraging blocking at the moment.

FWIW: I think we will see limited blocking and slow progression in the first half of winter, with a more mobile scenario in the second half.

========

Yes, it is a tough on, and those are some of the challenges with which we have been wrestling. Add to that the nature of this El Nino - Modoki or at least a hybrid rather than a classic east-based event, which suggests high-latitude blocking has a higher probability late winter (around February). Current QBO and GLAAM are pertinent and, as you say, should discourage SSW episodes but do not preclude such late winter blocking.

MJO is going to be progressing to areas which are more amenable to mobility through December. Of course, it's an intra-seasonal guide rather than seasonal but I'd expect a degree of zonality / +NAO to continue into January, and Atlantic SSTs suggests overall +NAO. Low solar likely becomes more of a factor in the next 1 o 3 winters.

I'm beginning to agree with you. The MJO has become weaker, so will have less of an influence. Also, looking at extended range output, the hemispheric wave number appears to be increasing with time - so maybe we'll have zonality right across northern Europe and in to west Asia come Christmas :-)
Model diagnostics for NAO still appear to be favouring neutral or slightly -VE into December, though, which is a bit odd. But maybe the zonality is going to be displaced south of normal, which can have the same effect on NAO figures IIRC.

--
Freddie
Ystrad
Rhondda
148m AMSL
http://www.hosiene.co.uk/weather/
https://twitter.com/YstradRhonddaWx for hourly reports (very few tweets getting through currently)
Stats for the month so far: https://www.hosiene.co.uk/weather/st...201811NOV.xlsx

On Friday, November 30, 2018 at 8:10:52 AM UTC-5, Freddie wrote:

I'm beginning to agree with you. The MJO has become weaker, so will have less of an influence. Also, looking at extended range output, the hemispheric wave number appears to be increasing with time - so maybe we'll have zonality right across northern Europe and in to west Asia come Christmas :-)
Model diagnostics for NAO still appear to be favouring neutral or slightly -VE into December, though, which is a bit odd. But maybe the zonality is going to be displaced south of normal, which can have the same effect on NAO figures IIRC.


========

Yes, that's how I see it into early December. Then the jet lifts north with +NAO developing and allows what we expect will be predominant milder (and often wet) flows for the rest of the month. MJO is actually projected to strengthen again through December from Phase 1 to 3 (Indian Ocean) which should mean LP track across NW Europe then farther north later in the month... although latest CFSv2 weakens it more quickly by mid-December than previously, and more quickly than ECMWF.


Stephen
Indianapolis IN.