Model Output Discussions 12z 01/09/2016

[Cheshire Freeze]

Just now, feb1991blizzard said:

It should be 1980-2010, that's industry standard surely by now, all the data for the last decade must have been verified.

It should be but I'm not sure it can be given what we see with the temperature anomaly plots with these models.

[NorthYorkMoorsSnow]

John Hammond is on Facebook live right now talking about the winter forecast on the BBC News page! 

[karlos1983]

8 minutes ago, NorthYorkMoorsSnow said:

John Hammond is on Facebook live right now talking about the winter forecast on the BBC News page! 

Pretty bullish about cold winter by all accounts. The last time they were this bullish, I'm pretty certain it was summer..... that didn't end well LOL

Edited November 1, 2016 by karlos1983

[Geordiesnow]

One thing I have noticed in today runs is the dreaded shortwave to the south of Norway, alluded to it last night we need to watch these getting modelled as it cuts off the cold air to an extent (as it has a longer track to get to these shores) and the flow turns more of a NE'ly to a Northerly. Its so frustrating seeing these features getting modelled and it seems so hard these days to get a nice clean flow of cold air.

That said, the overall outlook in terms of it will be the coldest feel of weather of the Autumn season so far is still there and that the risk of the PV dropping into Greenland is most certainly still there also.

[Abyss]

What a difference a run makes

[Ali1977]

Crazy difference on the 12z, gets rid of the cold snap quicker but lets see where it goes next. Bit of PV around Greeny on this run, which may shift East with any luck.

[knocker]

55 minutes ago, feb1991blizzard said:

It should be 1980-2010, that's industry standard surely by now, all the data for the last decade must have been verified.

Quote

SUMMARY – TEMPERATURE:
For November-December-January, lower-than-average temperatures are more probable than higher-than-average values.
Overall, the probability that the UK-mean temperature for November-December-January will fall into the coldest of our five categories is 30%
and the probability that it will fall into the warmest of our five categories is 10% (the 1981-2010 probability for each of these categories is
20%).

 

[Tom Jarvis]

Rolf the GFS is still failing. cannot get any consistency how can it swing  that big in just one run is stupid.  

[karlos1983]

This is not a great run out to 144 on GFS or UKMO on the face of it. That said, mild South Westerlies look unlikely for any great length of time.

[Seasonality]

26 minutes ago, karlos1983 said:

Pretty bullish about cold winter by all accounts. The last time they were this bullish, I'm pretty certain it was summer..... that didn't end well LOL

In their defence they predicted the extreme cold of December 2010 very well using less advanced modelling than available now. For all the bashing of the Meto that people like to indulge in they still do an excellent job and have the most trustworthy longer term forecasts in recent years imo.  Sorry mods for off topic.

[feb1991blizzard]

4 minutes ago, knocker said:

 

Is that the met office forecast? thanks in advance.

[Tamara]

On ‎29‎/‎10‎/‎2016 at 21:35, Tamara said:

At present, what is there not to like?

(As edited at the bottom of the post, there has been a problem with original images selected not appearing correctly to date on the page. You will have to take my word for it with some of the AAM plots!!)

What is not to like indeed, even if I do appear to like talking to myself.

All signals this November point to cold weather pattern establishment.

Angular Momentum tendency is set to rise again on the back of another increase in torques to come (watch the relevant plots below) and eastward moving MJO tropical convection through the Western Pacific at increasing amplitude that looks set to build further significant amplification into the pattern.  We need to factor in the lagged timelines in terms of the effects of these feedbacks

.

The Global Wind Oscillation significantly hasn't orbited in Phases 1,2,3 (the Nina attractor phases) since September and has instead completed an almost quasi stationary passage between transitional Phases 4,0,8 during October. The fact that it is orbiting back to Phase 4 currently at a slightly better amplitude than last time (and not towards Phase 1) but with relative angular momentum tendency depressed is significant in terms of the tropical and extra tropical forcing ahead which will boost angular momentum again and so surely consolidate further the disconnect to the ocean base state. Notice the considerable rise in relative AAM tendency during the second half of September that presaged the gentle upturn in fictional torques (allied to low solar activity) which alongside tropical activity in both Pacific and Atlantic has helped create the amplified pattern seen during October.

Rinse and repeat occurring again - but this time with angular momentum set at a higher level than at the start of October (ahead of forthcoming rises). The GWO plot clearly illustrates the modest but significant laddering up tendency seen since September. Set against both 40 day trends and 90 day trends

None of the above looks at all like an atmosphere that wants to go along with the ocean and officially establish La Nina, at the moment, to me.

The monthly average SOI officially returned to neutral/low -ve figure parity for the month of October after the peak in September - following the gradual rise that started in late Spring, and underpinning the above analysis

https://www.longpaddock.qld.gov.au/seasonalclimateoutlook/southernoscillationindex/

 

Seasonal wavelengths play a large part when it comes to both ocean/atmosphere and troposphere/stratosphere coupling. X synoptics in autumn doesn't mean X synoptics remains in winter just because background drivers stay the same

In general La Nina in winter-time is not conducive to sustaining early cold patterns for reasons I know I have repeated on many occasions.  Weak ENSO patterns (whether Nina or Nino) are certainly better than either variety of strong ENSO event - but it is low strength El Nino that adopts the ideal stratospheric pathway to vortex disruption to increase chances of cold weather this side of the North Pole heading further into winter because the higher angular momentum conditions in the atmospheric circulation, found under this regime, are primed to create repeated poleward Rossby wave flux that encourages a higher chance of keeping the vortex weak and inducing an SSW heading through the winter.

La Nina often features amplified Atlantic patterns in late autumn and early winter, but the tendency is for the upstream Pacific pattern to take control if this ENSO regime establishes into and through the winter - with anticyclones spun up over the Central Pacific which serve to push the jet northwards and create temperature gradients across Canada and the US which fuel the Jetstream downstream - especially if upper cooling down-wells from the higher layers of the stratosphere.

This year we are fortunate that the early season features subdued solar activity, trace evidence yet of the wQBO, and also we have an active Pacific pattern that features an abundance of low pressure assisted by tropical Typhoons. plus +ve torque tendencies (under rising angular momentum) which make conditions ripe for stratospheric wave breaking.

Any definitively establishing La Nina pattern, with high pressure in the Pacific (which breaks down the stratospheric pathway to vortex disturbance this side of the pole) is actually counter intuitive to cold feedbacks lasting too far into the winter. In that sense I am certainly looking beyond the colder period now on our doorstep as nothing particularly special in itself (though it definitely beats zonality, gales and rain any day!!) but it is only early November after all anyway.

I think it is also the case that weak ENSO conditions inherently feature de-coupled atmosphere/ocean states - where angular momentum tendency takes a contra position to the base ocean signal. There are plenty of examples to draw on in this respect, but most latterly during autumn and through/winter 14/15 we saw El Nino try to develop but the atmospheric circulation featured largely low angular momentum Nina like states - with the Global Wind Oscillation repeatedly orbiting Phases 1,2 and 3 during the late autumn and winter period. 

Stratospheric displacement was possible in late January in 2015, but the lack of further rossby wave development (inhibited by the Pacific pattern) frustrated this vortex weakness being exploited any further. The winter as a whole (under predominantly  -ve torques and low AAM) saw a fairly standard Nina pattern with dominant N Pacific ridge, prominent downstream Azores/Atlantic ridge and mostly flat northern arm of the jet stream riding over this. Other than the displacement vortex phase that provided about a week of moderately cold weather, the colder(er) interludes that winter were restricted to very brief and underwhelming northerly topplers.

Through October this year we have seen slightly below average SST's across central parts of the Pacific, but as described in detail above, the atmosphere has forced some westerly (Nino like) inertia to make the Pacific synoptic pattern quite different to the characteristic pattern response.  So we are seeing a converse de-coupling so far to that which was seen through 2014/15

Therefore I think we need to be very careful when saying that (weak) La Nina = cold. Because actually Nina regimes that become established and are sustained, are not generally suitable for sustaining colder patterns very far into the winter.

Fortunately any Nina should it couple up to any extent (and not withstanding the current responses which do not match it anyway) is generally assessed by consensus to be very short lived - so it may well be the case that winter stratospheric wave breaking feedbacks are not derailed - especially on the basis that both tropical and extra tropical signals suggest that the vortex will be like a cat on a hot tin roof right into the start of winter - thanks to an anti-social Pacific pattern, low solar activity, plus complicit lack of wQBO interference at this time (that usually inhibits ozone production and transport to the polar stratosphere and serves to increase cooling and strength of the vortex but remains suitably "sedated")

Edit:  Link graemlins again - the AAM plot images that appear are not all the updated images to 30 Oct I actually posted. Paul can you help again please?

Edited November 1, 2016 by Tamara

[Ali1977]

This run looks quite good to me, yes we lose the cold NE wind but now comes in a cold NW one - which seems more in line with what some models are saying and with little PV these NW winds are subject to break letting WAA upto the pole.

[karlos1983]

10 minutes ago, Seasonality said:

In their defence they predicted the extreme cold of December 2010 very well using less advanced modelling than available now. For all the bashing of the Meto that people like to indulge in they still do an excellent job and have the most trustworthy longer term forecasts in recent years imo.  Sorry mods for off topic.

It was tongue in cheek, I respect the MetO. But It is still bullish so early on, they must have a very strong belief that it will play out as predicted.

Edited November 1, 2016 by karlos1983

[knocker]

1 minute ago, feb1991blizzard said:

Is that the met office forecast? thanks in advance.

It's the just published winter forecast. I assumed that's what you were talking about but I admit I didn't check.

[snowy weather]

5 hours ago, feb1991blizzard said:

No, i just remember vaguely, I'm sure it was late 2010 and the article was in the telegraph around mid January 2011 talking about the stratosphere, there might be a link to it in the MOD thread around 2011 but good luck if you can find it!

Ok thanks

[Barry12]

NH profile looks better on this run which is more important down the line...

Edited November 1, 2016 by Barry95

[feb1991blizzard]

3 minutes ago, knocker said:

It's the just published winter forecast. I assumed that's what you were talking about but I admit I didn't check.

No, I was talking about the NWP long range models (raw data), that they always seem to over do the temperature on anomaly forecasts regardless of the H500 pattern contradicting the temp output and that some of the maps are entirely red which is practically impossible and Crewecold made a good point that it depends what climatology they are set against.

[knocker]

2 minutes ago, feb1991blizzard said:

No, I was talking about the NWP long range models (raw data), that they always seem to over do the temperature on anomaly forecasts regardless of the H500 pattern contradicting the temp output and that some of the maps are entirely red which is practically impossible and Crewecold made a good point that it depends what climatology they are set against.

Right forget I posted in that case.but without checking I would be amazed if they didn't use the latest climate period. Any other just would not make sense

[The PIT]

Well the FI feature for next Monday is biting the dust that may have brought some Snow quite far south. Now it's a fairly weak feature but should bring Snow to Scottish Hills though maybe the far north England. So a brief rather cold possibly cold spell some showers for exposed areas dry elsewhere and frosts for the next few days.  I guess nobody will be looking at deep FI as it shows a return to mild weather.

[knocker]

8 minutes ago, feb1991blizzard said:

No, I was talking about the NWP long range models (raw data), that they always seem to over do the temperature on anomaly forecasts regardless of the H500 pattern contradicting the temp output and that some of the maps are entirely red which is practically impossible and Crewecold made a good point that it depends what climatology they are set against.

As a matter of interest the EPS 46-day uses:

Climatology based on weighted hindcast constructed from total of 20-years [1996-2015] and 11-members and 3 cycles for a total of 660 members. This model based climatology is called the ECMWF M-Climate.

[northwestsnow]

Fascinating ukmo this evening

http://old.wetterzentrale.de/pics/Rukm1201.htm

http://old.wetterzentrale.de/pics/Rukm1441.html

Scandy high anyone

Edited November 1, 2016 by northwestsnow

[Ravelin]

6 minutes ago, The PIT said:

I guess nobody will be looking at deep FI as it shows a return to mild weather.

I'd hardly say a 'return to mild', more like a return to fairly average, especially for November. Also depend on how far into FI you go as there's always this...

Likely to be short lived I'll admit.

I'd say the best reason not to look to far into FI is just how different the GFS runs are even before it gets into shallow FI, never-mind deep FI

Edited November 1, 2016 by Ravelin

[feb1991blizzard]

1 minute ago, knocker said:

As a matter of interest the EPS 46-day uses:

Climatology based on weighted hindcast constructed from total of 20-years [1996-2015] and 11-members and 3 cycles for a total of 660 members. This model based climatology is called the ECMWF M-Climate.

Thanks, I would assume that the ECM seasonal model uses similar, I did say that the ECM and GLOSEA5 along with the JMA are really the ones to take notice of.

[The PIT]

2 minutes ago, Ravelin said:

I'd hardly say a 'return to mild', more like a return to fairly average, especially for November. Also depend on how far into FI you go as there's always this...

Likely to be short lived I'll admit.

I'd say the best reason not to look to far into FI is just how different the GFS runs are even before it gets into shallow FI, never-mind deep FI

Well