Wave-1 events that typically lead to vortex displacements don't tend to favour cold outbreaks over Eurasia, unlike splits that support widespread cold weather in Europe. Although it's not always that simple, jan '87 in an example. https://t.co/56DdvZq73O pic.twitter.com/jjpnyTGij0

— giacomo masato (@giacomomasato) December 2, 2018

"Wave-1 events that typically lead to vortex displacements don't tend to favour cold outbreaks over Eurasia, unlike splits that support widespread cold weather in Europe. Although it's not always that simple, jan '87 in an example."

Surely that depends on where the PV is displaced to - anything has to be better for the UK than having the PV over Canada/Greenland.

If the PV is displaced over Siberia, then that should lead to severe cold over Russia and eastern Europe - we then just need the cold block to encroach ever westwards.

"Wave-1 events that typically lead to vortex displacements don't tend to favour cold outbreaks over Eurasia, unlike splits that support widespread cold weather in Europe. Although it's not always that simple, jan '87 in an example."

Surely that depends on where the PV is displaced to - anything has to be better for the UK than having the PV over Canada/Greenland.

If the PV is displaced over Siberia, then that should lead to severe cold over Russia and eastern Europe - we then just need the cold block to encroach ever westwards.

 

I imagine that the problem might be that Siberia has a huge extent east to west, so that if the vortex is centred over the eastern half it could be too far east to have much impact on the UK's weather.

 

I imagine that the problem might be that Siberia has a huge extent east to west, so that if the vortex is centred over the eastern half it could be too far east to have much impact on the UK's weather.

Someone has posted the following on another weather site - I leave it to others to comment on whether it passes muster, but it makes sense to me:

"My impression from reading around is that the deal with displacement events is that they nearly always (due to the more dominant role of the Asian mountains meaning the warming and anomalous anticyclone develop over the N. American side) push the vortex toward some part of Eurasia from Canada/Greenland, which entails either a passage or take up of residence closer to the eastern North Atlantic. During this time, eastern N. Atlantic cyclogenesis can be enhanced, bringing the UK near or above average temps overall with bouts of wind and rain... however, the situation can change drastically if the displacement is large enough send the polar vortex right across to Siberia. Then the increased potential cyclogenesis region is over the continent where it struggles to achieve much, and more of a ridge-friendly environment establishes across the eastern N. Atlantic. This is not a sequence that involves propagation of anomalies downward like we see with the split-SSW events; it's simply the absence of the usual stratospheric temperature gradient that aids ridging in the eastern N. Atlantic.

I've also seen musings that a displacement far enough away from the pole could achieve similar results with the vortex in line with countries as far west as Scandinavia, but if I recall correctly, we chased such potential last Dec only to be disappointed. So it seems to me that it's how far east it goes that matters as to whether we experience the less common of the outcomes."

I've just been looking back through my local data for the past ten years and it is very interesting to see a distinct block of five coldish winters followed by five consecutive mildish ones. In fact the only winter, going by most parameters that was milder than any of the last 5 was 2011-2012 and that was mainly due to some  exceptionally high February temperatures. Even that winter still had more frosts than the last five and a -9C !  And that would probably have been overall colder than last winter were it not for the late February extreme of last winter.

I don't have the data but I suspect the previous five years to 2010 were mild so will this year be the start of a new block? We will see.

 

So what models would they use to come out with those summary outlooks for winter 18/19? where do they get the info from?

They talk about windstorms ...not rain storms? I found this paragraph interesting:

"While there will be plenty of windstorms throughout the winter, we do not expect the Beast from the East to return. That's not to say there won't be cold and snow, but accumulating snowfall will be limited to the more typical areas," he added.

Well now you can see... 

This outside chance of snow on Thursday was only ever going to be a brief hors d'oeuvres, so I don't mind if it doesn't come off (in fact, a day or two of cold with a sprinkling of snow just feels like a tease)

I'm hoping for more prolonged good and cold conditions as we get a lot closer to Xmas. 

NASA's seasonal forecast model has served up another extraordinary temperature outlook for February. Last month it showed remarkable cold for the eastern US; this month the cold anomaly is in northern Europe, and even more pronounced. It's entertaining, at least! pic.twitter.com/PAmUZKNgiu

— WorldClimateService (@WorldClimateSvc) December 10, 2018

This outside chance of snow on Thursday was only ever going to be a brief hors d'oeuvres, so I don't mind if it doesn't come off (in fact, a day or two of cold with a sprinkling of snow just feels like a tease)

I'm hoping for more prolonged good and cold conditions as we get a lot closer to Xmas. 

There has been the very faintest of hints in extreme FI that this could come off Martin, still the low percent call but it can't be unequivocally ruled out just yet.

 

There has been the very faintest of hints in extreme FI that this could come off Martin, still the low percent call but it can't be unequivocally ruled out just yet.

Fingers crossed, Ian!

December met office Ensemble-mean maps continues to suggest northern blocking over winter

Am surprised that the met office 3 month outlook didn't receive a very enthusiastic  response.

We have got used to a procession of NAO + winters.

The Meto  outlook is not saying that we are in for a severe winter but it opts for an overall NAO -.

It suggests the highest chances of impacts from cold weather will be later in the winter presumably February.

Looking at the indicators that suggest NAO - we have

1.Moderate ENSO increasing the likelihood of NAO -in late winter.

2.Polar vortex weaker than normal in late winter

3.Stratospheric events increasing  chance of colder conditions later on.

4.Solar minimum which increases likelihood of a weak stratospheric circulation and cold weather weather alter in winter

Indicators that suggest NAO+ we have

1.QBO in westerly phase ,ncreasing likelihood of NAO +Ve

2.Pattern of SST anomalies increases the chance of NAO + conditions in early winter.

Overall it seems a to me there are enough NAO - signals to deliver at least  a couple of cold spells of cold and snow.

If the SSW propagate downward, we could see something after 10/15th of january, thus they are not all very impactful on sensible weather but if the troposphere and stratosphere will be primed for proficient "communication", or "coupled" this season, we could see this happening and a cold 2nd half of January could be on the charts, and even through out February...

If the SSW propagate downward, we could see something after 10/15th of january, thus they are not all very impactful on sensible weather but if the troposphere and stratosphere will be primed for proficient "communication", or "coupled" this season, we could see this happening and a cold 2nd half of January could be on the charts, and even through out February...

Source?

https://www.metoffice.gov.uk/binaries/content/assets/mohippo/pdf/public-sector/forecast-temp-jfm-v1.pdf

Am surprised that this encouraging METO forecast for Jan-March has not recieved more attention.

As expected it looks like my winter forecast has gone bust! At least it stayed on track for most of December.

Bang goes the theory - or maybe the deep cold will eventually arrive, just not as soon - time will tell.

Anyway Happy New Year to everyone on here - here’s to another year of reading some great and interesting posts.

https://www.metoffice.gov.uk/binaries/content/assets/mohippo/pdf/public-sector/forecast-temp-jfm-v1.pdf

Am surprised that this encouraging METO forecast for Jan-March has not recieved more attention.

Yes, it is quite a strong signal for cold, but more particularly Feb-March. January the probabilities look quite balanced actually.

 

Source?

Source of what? the SSW or the monitoring charts or analyses?

SSW  occouring

http://ds.data.jma.go.jp/tcc/tcc/products/clisys/STRAT/ 

Monitoring 

http://www.cpc.ncep.noaa.gov/products/stratosphere/strat-trop/gif_files/time_pres_TEMP_MEAN_ALL_NH_2018.png

Analyses

 this winter teleconnection and sometimes when the QBO is switching phase for a westerly one (positive) a possible SSW occours and the Polar Vortex weakens and divide propagating to the troposphere with consquences such has a PV split. At this moment it could well be a major SSW event taht could lead to a rising prussure between the North Greenland or Scandy in 15-20 days time.

The gph 10mb profile could not look any better for the UK once it propagates down. The 30 mb profile looks better with every run. Middle of last Feb 10 days prior to beast I said I would not be surprised to see synoptics showing -15c -16c 850 temps showing up and 12 days later they did. 

This time around  the strat profile looks even better and longer lasting. Patience is the key here. There still does not appear to be much evidence in the h500 charts of any ssw downwelling and it may be another 7 to 10 days before we see a consistent trop response to the ssw with a very -AO and abundant high latitude blocking.