Model Output Discussion - 18z 31/10/15 onwards

[fergieweather]

First ice days of the winter showing on the ecm ens

image.jpg

Yes, there's increasing room for faith now in this change later Nov. Interesting times indeed.

[Mucka]

First ice days of the winter showing on the ecm ens

image.jpg

 

 

I just came in to post about ECM London ensembles.

Wide scatter from day 6 with plenty of milder options but what caught my eye was that any clustering is on the colder side.

 

 

Also the average dropping to around 6c from the 22nd since;

a) It is a clear trend line and not a blip.

b) Given the scatter if the colder solutions prove correct actually temps will be a good deal colder come the time.

c) This is London and since any cold attack looks likely to come from the North rather than the East temps will likely be a couple of C colder in the North.

 

Edit.

 

Great to read some encouragement from Fergie. Hope to see the MetO 15 30 day forecasts reflect this soon as that will show the MetO has some confidence in a colder spell developing later in the month.

 

Interesting times indeed.

Edited November 13, 2015 by Mucka

[Nouska]

 

I just came in to post about ECM London ensembles.

Wide scatter from day 6 with plenty of milder options but what caught my eye was that any clustering is on the colder side.

 

 

Also the average dropping to around 6c from the 22nd since;

a) It is a clear trend line and not a blip.

b) Given the scatter if the colder solutions prove correct actually temps will be a good deal colder come the time.

c) This is London and since any cold attack looks likely to come from the North rather than the East temps will likely be a couple of C colder in the North.

 

Edit.

 

Great to read some encouragement from Fergie. Hope to see the MetO 15 30 day forecasts reflect this soon as that will show the MetO has some confidence in a colder spell developing later in the month.

 

Interesting times indeed.

 

The control run takes even more of a nose dive!

 

[joggs]

Even though it's not a given re a cold shot gaining momentum,I'd have thought the mo extended range would've been tweaked a few days ago to reflect what us amateurs are now viewing.If it comes off,we'll done to BFTP for touting this a couple of weeks ago.

[Tamara]

Very interesting signals continue to be watched at this time regarding potential sign posts for the start of the winter - and which direction we might head. Tropical and extra tropical signals and the behaviour of the new seasonal polar stratospheric vortex hold a key as to how patterns will play out.

 

Embedded strong Nino holds sway with the Global Wind Oscillation in Phase 5 and set to orbit again, in quite high amplitude through 6/7/8 This supports the continuance of an active sub tropical jet stream in the reliable time period 

 

Increasing negative torque looks set to amplify the Pacific jet upstream, and then slow it later in the 10 day period with ridging potential moving also downstream to facilitate some polar maritime airflow for the UK (coldest air held further north) for a time. Much as discussed in previous post.

 

At the same time, westerly wind anomalies across the central and eastern Pacific have eased as easterly wind anomalies are increasing across the Indian Ocean. As posted in some detail last week as likely to occur, this is a response to MJO related tropical activity over the IO - which shorter term looks set to destructively interfere with the embedded ENSO state

 

This signposts some negative tendency in relative angular momentum - cue the negative torque as above. Current GEFS forecasts are taking this a stage further, and counter intuitive to the background very strong Nino state, suggest long term increased polar flow of the Jetstream (energy taken out of the classic Nino STJ flow) at the same time as the seasonal vortex organises itself to our NW.

 

While the vortex does look set to establish as one might expect, as much as NWP FI is best taken with a truck of salt, we should also be wary of longer term tropical and extra tropical model forecasts. It is the reality at T0 and not the forecast that is determinant.

 

This looks like a first attempt at a classic El Nino waning period, from a very strong base, but first time around is highly unlikely to decouple the atmospheric/ocean state. The on going Nino remains likely to return as the main contributor to anomalous convection following the spike in IO activity. On that basis, common sense tells us there exists a floor limit to any drop in AAM.

 

Therefore any switch of atmosphere/ocean forcing to a Nina-esque attractor state Phases 1/2 as currently indicated by the GEFS Global Wind Oscillation forecast (overriding the strong Nino base state) remains suspiciously counter intuitive and over progressive

 

Notwithstanding all that, these needs to be watched in the days ahead

 

GWO

 

http://www.atmos.albany.edu/student/nschiral/research/gwo/gfsgwo_1.png.

 

MJO

 

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/ensplume_full.gif

 

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/CLIVAR/UKMA_phase_small.gif

 

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/CLIVAR/ECMF_phase_MANOM_51m_small.gif

 

 

Contrary to the above, it is still conceivable that modelling of MJO tropical convection is rather blind sided by the large amount of forcing 'noise' that currently exists across the tropical ocean basins, and so still need to see if future modelling picks up on activity in the Western Pacific. Any future movement, following loss of forcing signal from MJO Phase 3 towards COD, indicated thereafter to emerge from or beyond Phase 5 (cue eager bounce back in AAM following any drop) and then the prospect is alive of increasing +ve torque and important further wave feedback to combat the strengthening seasonal vortex (in tandem with the Siberian High courtesy of good early snow advance).

 

In this sense, a short term dip in AAM followed by another boost upwards would be a good prospect for winter feedbacks in providing some extra tropospheric jabbing at the vortex. Whilst short term this may be beneficial, we would not want to see any sustained loss of angular momentum to the atmosphere setting up continued winter +NAO feedbacks through longer term indicators of northern arm jet flow, rather than Nino southern stream. Such a scenario would facilitate a return to heights dominating the northern Pacific, an embedded NE Canadian/Greenland vortex, and cancelling out of the Nino rossby wave feedback thus far, negating chances of an SSW later in the winter.

 

There is at least at this time however no indicated support for any sustained collapse of the strong Nino till at least later in the winter  .A vigorous westerly assisted gyre vortex that is gaining momentum day by day is a risk/reward proposition. The stronger the vortex spins, the more spectacular the fall ultimately can be if the feedback dominoes fall the right way. The bicycle wheel spinning and stout stick analogy is always relevant every year in these discussions

 

The AO and the NAO usually remain relatively disconnected through December, until January, when the northern annual mode jives together much more tightly - because longwave pattern winter feedbacks are properly determined and established by this time

 

We are a long way from such knowledge. Long term feedback prospects cannot be determined yet..

 

As Tony (Lorenzo) said last night though, this Nino lacks precedent - so the usual watchword of not looking too far ahead with the models has particular resonance at this time

 

[johnholmes]

re this

There is at least at this time however no indicated support for any sustained collapse of the strong Nino till at least later in the winter 

The latest official update link is below

http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/index.shtml

[radiohead]

^^^ It's only the 6z so I would not worry about the downgrading of the transitional cold toppler.

 

I'm not sure what this means. The 06Z is the same computer model run on the same computers as the 12Z and 18Z etc. The only difference is that every 6 hours the program is run with the updated initial conditions.

[Captain Shortwave]

Day 6 charts

UKMO

 

GFS

 

The UKMO is certainly the most amplified, mainly due to a much more potent blast of cold air over the central parts of the USA, this in terms amplifies the pattern downstream. The GFS whilst showing greater amplification than previous runs still shows a flatter pattern with a cut off low over the same area until the cold air from Canada finally breaks through and engages this cold pool. Looking at this mornings models the UKMO seems to sit with the ECM in handling that part of the world which would give support to the later evolution from the ECM. This solution I tend to have a bit more faith in in terms of preserving the height anomaly over the Eastern seaboard as opposed to pushing it east and flattening out the pattern (AKA GFS).

Edited November 13, 2015 by Captain shortwave

[Daniel*]

Yes, there's increasing room for faith now in this change later Nov. Interesting times indeed.

Indeed, I think it is a important time/reminder to realise how uncertain & dynamic it can be.

As you posted just days ago which subsequently caused a lot of hissy fitting.

There's absolutely no current sign (stress current) of such a turnaround before January (note too today's update of the GloSea5 prognosis for D-J-M on the UKMO website and the switch towards +ve temp anomalies - albeit rather weakly - versus the October output looking into same period).

Shorter-term, the overnight EC and GloSea output has effectively zero sign now of even transient blocking spanning the next 15 to potentially 30 days inclusive. Broadscale W'rly zonality - albeit with some Pm incursions - is absolutely the form horse looking ahead and may dominate for a good part of winter too, if cross-model consensus (and equally the shared opinion of every seasonal forecaster I know) is on the money. The next key point of interest will be updates soon to EC Seasonal Model, to see how closely it mirrors - or not - the latest GloSea prognosis. The critical juncture remains later into winter and whether any colder swing then emerges (courtesy SSW).

This was posted only 4 days ago it truly does pay testament to how sudden things can evolve. Typically in the UK it seems the inverse of this happens again nothing is guaranteed but it is undeniable something is brewing.

Edited November 13, 2015 by Daniel*

[carinthian]

Well, the ECMWFs next viewing will reveal something interesting for next weekend regarding snow potential for the North.

 C

[Cheshire Freeze]

GEM is insane at just 150hrs

 

 

Perhaps more importantly it backs the UKMO over the GFS RE what happens over the states with a deeper cold plunge over there.

 

GFS is grim into FI- not something I'd want to see repeated on the 18z!

Edited November 13, 2015 by CreweCold

[Chris K]

Indeed, I think it is a important time/reminder to realise how uncertain & dynamic it can be.

As you posted just days ago which subsequently caused a lot of hissy fitting.

This was posted only 4 days ago it truly does pay testament to how sudden things can evolve. Typically in the UK it seems the inverse of this happens again nothing is guaranteed but it us undeniable something is brewing.

So what if this turns out to be a brief PM incursion once it hits a reliable timeframe and we return to a more westerly regime? Ian did not mention anything about cold shots not happenning at all, just the general winter period signals at the time of his posting.

We could see a couple of spells of snow yet still end up with positive monthly anomalies right?

Edited November 13, 2015 by Chris K

[Polar Maritime]

Yes Chris and the Models continue to show that broad pattern from West to North.

Edited November 13, 2015 by Polar Maritime

[Allseasons-Si]

GEM is insane at just 150hrs

 

 

Perhaps more importantly it backs the UKMO over the GFS RE what happens over the states with a deeper cold plunge over there.

 

GFS is grim into FI- not something I'd want to see repeated on the 18z!

And with possible reloads in it's latter frames

[Methuselah]

GEM is insane...

 

 

Quite possibly!

[Cheshire Freeze]

If ECM goes with UKMO and GEM then I think we have to weight towards that situation- however the GFS is horrid and no matter how many models go against it, I will always remain very cautious until the moment it backs down!

Edited November 13, 2015 by CreweCold

[london and south east kent]

Hi all are we seeing a back track with the gfs .Will the ecm go the same way will the cold snap cold spell happin we will see

Edited November 13, 2015 by abbie123456

[Mucka]

If ECM goes with UKMO and GEM then I think we have to weight towards that situation- however the GFS is horrid and no matter how many models go against it, I will always remain very cautious until the moment it backs down!

 

Let's hope ECM sticks to its guns and we get a nice JMA this evening, that wills ettle the nerves a little (until the next run  )

 

As we all know it is quite diffiicult to get air cold enough over the UK to support snow falling to low levels and there are sure to be ups and downs along the way this time as well.

Looking at GFS ensembles for N England, they do seem to be getting progressivlely colder (by small amrgins) each run so they are at least very slowly trending the right way even though the Op is not keen.

Hopefully we will see the mean 850 temp drop below the magic -5 over the next few days.

The change to a cooler/colder flow is tantalisingly just outside any reliable timeframe so it will be case of siit back and enjoy the ride (or not) over the next few days.

 

Over to ECM/JMA.

[Cloud 10]

 

 

Over to ECM/JMA.

 

 

Be nice if the 12z NAVGEM was a blueprint for them.

 

[Summer Sun]

At t144 ECM follows UKMO

 

[Cloud 10]

ECM 144 hrs.

 

 

What happened next?..

[Mucka]

Well hello Greenland...

 

Edited November 13, 2015 by Mucka

[Summer Sun]

High pressure building over Greenland low pressure to our east leaving us in a north to north westerly flow

 

 

-8 850's slowly filtering down into Scotland

 

 

Any precipitation would be turning increasingly wintry in the north

 

[Panayiotis]

Im back for the winter and what interesting synoptics we have for late November! Time frame that needs to be watched is 120hrs, GFS fails to get enough WAA towards Greenland and allows a lobe of the PV to break through the block over E USA and flatten it:

GEM and ECM have a much more amplified pattern where enough WAA is allowing the block to strengthen, and therefore blocks any low pressure systems. In doing this it forces more WAA towards Greenland as these lows become -vely tilted and therefore strengthening the block:

Subsequently we get charts like these developing, 2 days after:

Edited November 13, 2015 by Panayiotis

[bluearmy]

Cue mr murr - the day 7 ecm op upgrades the possibility of the pattern cutting below the greeny ridge which would essentially cut it off and sustain a colder pattern