Model output discussion - 1st December onwards

[TSNWK]

Just now, *Sub*Zero* said:

Quite concerning, the rain accumulation charts for next week are showing 100mm+ in places that really cannot take any more water...

Not sure why the NAVGEM is getting in on the limelight over the last 24hrs? Hardly ever mentioned and I'm sure it's been referred to as cannon fodder in the past? It does look good for cold prospects but I certainly wouldn't be pinning any hopes on it. 

 

Because navgem is showing what most want to see.... Could be a desperate act when the cannon fodder is wheeled out.. Bit like when perb 15 for 300 plus is wheeled out.

[SMU]

20 minutes ago, *Sub*Zero* said:

Quite concerning, the rain accumulation charts for next week are showing 100mm+ in places that really cannot take any more water...

Not sure why the NAVGEM is getting in on the limelight over the last 24hrs? Hardly ever mentioned and I'm sure it's been referred to as cannon fodder in the past? It does look good for cold prospects but I certainly wouldn't be pinning any hopes on it. 

 

Surely thats obvious for the fact that its run is pretty much an extension of the UKMO 00z- the second best model..

If it was in isolation fair enough....

[nick sussex]

5 minutes ago, TSNWK said:

Because navgem is showing what most want to see.... Could be a desperate act when the cannon fodder is wheeled out.. Bit like when perb 15 for 300 plus is wheeled out.

The NAVGEM normally is cannon fodder because it picks out a solution which isn't supported by the other operational runs however its increase in amplitude over the ne USA is now being supported by the UKMO/ECM although the latter doesn't turn out as favourable. The GFS 06hrs run is also trending that way over the ne USA in the earlier timeframe, the models will now have a difficult balancing act caught between two stools, eject the UK low as a clean feature or stick with elongated shortwave energy, as you can see by the GFS 06hrs its now confused as to what to do.

I'm not saying that the chips will fall kindly but its clear that theres a lot of volatility in the outputs for the detail over the UK.

The latest NAVGEM is coming out shortly, who knows it might now drop the idea which wouldn't surprise me which would be somewhat ironic given the UKMO now backs it!

[johnholmes]

from Google

NAVGEM (Navy Global Environmental Model) is a global numerical weather prediction computer model run by NOAA. It replaced NOGAPS as the prime model in the middle of February 2013 at the FNMOC Weather model synoptic site. NOGAPS: Global weather forecast model from the "Fleet Numerical Meteorology and Oceanography Center" (USA)

Edited December 31, 2015 by Polar Maritime
tried to decease size and bold lettering - (There you go John.

[IDO]

22 minutes ago, THE CHOSEN ONE said:

So the feature that the UKMET added back in has now been removed from the 06z as well -

at T96 the atlantic starts to throw a ridge NNE but because the low over the UK is not quite sliding south ( yet ) then the ridge gets swamped & low pressure passes under our main low however

thats a significant swing to the UKMO ( also a massive infill of pressure over Norway at 120 v the 00z

so whilst the outcome is the same on the 06z - 1 / maybe 2 more swings of the pendulum like the GFS does & instead of the energy driving east under the low it will recurve up towards iceland like the NAVGEM

all eyes on the 12s

S

We are coming from different angles, you are looking at mesocale changes altering the pattern, I am looking at long wave patterns trending to a flatter Europa sector.

This run to me is a downgrade to a colder possibility due to a change in emphasis on the two wave pattern. The GFS has downgraded the strength of the block in our quadrant and upgraded the Alaskan Ridge/block compared to the 0z:

0z:   06z: 

We lose the block by D9 on the 06z but by D12 on the 0z it was still moving E/SE over Russia/Asia. That is not too bad as it will mean that  the vortex isn't coming up against the block to our east so more room to breath, and we should have less of a stormy ride within the Atlantic flow. With stable cool uppers, likely showers on the west coast, but have to watch for shortwaves developing in the jet. This is one run but a gentle pressure rise to the NW will probably dampen the Azores from pushing into the UK. Where that HLB moves is what is probably causing confusion for the US as to how much that will direct the colder uppers into the Conus. On this run at D12 compared to the 0z run,  initially less cold digging south on the latest run (conus):

06z:    0z:  

With obvious downstream repercussions. This rather than the ex-Scandi high is becoming more of the driver for our pattern after D7 IMO.

 

[chrisbell-nottheweatherman]

5 hours ago, knocker said:

According to the GFS (and others of course) another wet weekend is in store with a depression traversing the UK on Saturday and the fronts of another the next day so could well be another 50mm in parts that don't need it. Then next Weds it is currently modelling a depression 949mb approaching the NW of Scotland on a very strong jet. A beady will need to be kept.

Thanks for the heads-up.  That Jet Streak on the 250mB chart appears to be in the worst possible place.

[Ali1977]

To me FI has potential, the end of Jan and Feb are looking good. PV weakening all the time, heights slowly building over Arctic, jet stream around the South of the U.K. or lower......just need some WAA into Greenland now, not a lot to ask is it!!!!

[Chris K]

20 minutes ago, *Sub*Zero* said:

Quite concerning, the rain accumulation charts for next week are showing 100mm+ in places that really cannot take any more water...

Not sure why the NAVGEM is getting in on the limelight over the last 24hrs? Hardly ever mentioned and I'm sure it's been referred to as cannon fodder in the past? It does look good for cold prospects but I certainly wouldn't be pinning any hopes on it. 

 

Well the 06z GFS just showed atlantic trough domination most of the way through. I'm failing to spot the positives to be honest. Granted it will change run to run but so far the overall theme has stayed the same:

From mild and wet to cool and wet, more flooding, minimal dry weather...no matter how far south any 'shortwave' or 'undercut' seems to correct itself. We need to see the Jet losing strength but it just keeps throwing LP systems our way with force.

Still hoping the changes across the hemisphere will provide us with something cold down the line but I'll start worrying more if we are in the same situation come the second half of Jan...

[bluearmy]

Funnily enough IDO, IMO, the evolution of the 06z GFS is a positive hemispherically as the wedge of higher heights displaced west from the current build of the scrussian high is able to meet with the build of Arctic heights from the Alaskan ridge .  Result is a general Greenland height rise which will force the PFJ further south. This current evolution would be wintry nirvana if the pattern were 500 miles further south. 

[Liam J]

I think the NAVGEM looks even better than the UKMO @ 144hrs with better heights across N Europe towards Greenland? But after 144 it goes slightly pear shaped but not terrible. 

UKMO looks less solid @ 144hrs with weaker heights to the north, wouldn't like to make assumptions where it would head on the following frames, Atlantic looks to be firing up with energy heading SW to NE and possibly a deep trough to follow, then again heights may strengthen sending energy south again? I'd like to see more robust heights to the north. Probably look different on the next run anyway... The fun and games continue

 

[Weathizard]

9 minutes ago, *Sub*Zero* said:

I think the NAVGEM looks even better than the UKMO @ 144hrs with better heights across N Europe towards Greenland? But after 144 it goes slightly pear shaped but not terrible. 

UKMO looks less solid @ 144hrs with weaker heights to the north, wouldn't like to make assumptions where it would head on the following frames, Atlantic looks to be firing up with energy heading SW to NE and possibly a deep trough to follow, then again heights may strengthen sending energy south again? I'd like to see more robust heights to the north. Probably look different on the next run anyway... The fun and games continue

 

Navgem always was the best model  GFS ensembles having absolutely none of it and haven't since the beginning of this saga.. Best to start looking longer term for southern users I feel, possibly a period of winteriness is possible for the North still. Worry for the already rain sodden areas as well, concerning accu charts.

Edited December 31, 2015 by Weathizard

[IDO]

6 minutes ago, bluearmy said:

Funnily enough IDO, IMO, the evolution of the 06z GFS is a positive hemispherically as the wedge of higher heights displaced west from the current build of the scrussian high is able to meet with the build of Arctic heights from the Alaskan ridge .  Result is a general Greenland height rise which will force the PFJ further south. This current evolution would be wintry nirvana if the pattern were 500 miles further south. 

I cannot argue with you there, I am not a fan of a Euro/Russian high sitting to our east unless it has potential to retrogress, which is unlikely at the moment. The downgrade was more for this under-cutting scenario that may morph into some sort of cold UK scenario. I like the 06z run, despite the prospects that the 12z may be totally different with respect to the HLB over the Alaskan region; as it may prosper if it is sustained, when the Atlantic slows, which I suspect will be the case from around week 3.

Something like the CFS week 3 and 4 anomalies: 

[Ali1977]

2 minutes ago, IDO said:

I cannot argue with you there, I am not a fan of a Euro/Russian high sitting to our east unless it has potential to retrogress, which is unlikely at the moment. The downgrade was more for this under-cutting scenario that may morph into some sort of cold UK scenario. I like the 06z run, despite the prospects that the 12z may be totally different with respect to the HLB over the Alaskan region; as it may prosper if it is sustained, when the Atlantic slows, which I suspect will be the case from around week 3.

Something like the CFS week 3 and 4 anomalies: 

Those CFS would bring a cold prolonged wintery spell wouldn't they?

[SMU]

Updated NAVGEM 06z 120

no change

the updated 06z JMA 84 v the 12z 96 yesterday ( slight time gap )

has now taken away the wave & replaced it with a ridge

also the 06z ENS suite is the very 1st GFS suite of this whole 'projection' to find 1 ( maybe 2) runs with the -10c line into england by T144

people can carry on ignoring the changes if they want....

look at the GFS consistency V the NAVGEM over the last 24 hours

s

Edited December 31, 2015 by THE CHOSEN ONE

[Glacier Point]

Hugely interesting 2-4 week period upcoming.

The MJO cruising through the Pacific has triggered a pattern change to a notable -AO and more neutral NAO, although in reality the NAO is more positive still due to a residual trough signal in the North-east Atlantic. Fundamentally the game has changed as angular momentum has been moved upwards and the consolidation of the MJO in the next week is going to take it to the heady heights of +3SD. For an angular momentum junkie like me, these are rarified times and emphasises the lofty company we're keeping - only 1997/8 and 1982/3 witnessed such high levels of global westerly wind balance. GEFS product below is off the scale !

This poses a really good opportunity to get stuck into the likely upcoming broad scale hemispheric patterns.

The surge in westerly winds over the tropics is forecast to peak around the 6th January. That makes sense with MJO where it is now and likely to be in the next week, allied to sub-seasonal low frequency forcing related to El Nino. It will take around 21 days for these anomalous westerly winds to be fluxed poleward. Note the previous trend for fluxing of positive (westerly) and negative (easterly) wind anomalies over time. That sets up a date around the 27th January where we would normally expect the NAO to fully respond to this forcing and flip properly negative.

The EC EPS is rather more keen than the GEFS /GFS in dislodging a part of the blocking high over the Kara Sea (favouring more of an Alaskan ridge). This subtle development opens the door for pressure to fall in the Western Pacific as the high drifts south and east. This also appears to coincide with a Kelvin Wave (yes, I'm using that term correctly) passing through the region. Net result should be for a further addition of westerly winds and spike in tendency in relative angular momentum around the 9th / 10th January. This should induce further hemispheric amplification as the Asian jet is extended and retracted. Allowing 10 days from this point, suggest a northerly type evolution (but still emphasis on cyclonic) is likely between 15th and 20th January. Outside chance of heights rising to our NE from this, but would favour the northerly route.

Thereafter It gets really interesting. With an element of tropical forcing returning to the Indian Ocean (and possibly returning to the Western Pacific thereafter), the global angular momentum budget will have reached a high water mark and the only place for tendency in relative angular momentum to go is down, but still within a high overall angular momentum base state. That coincides with the expected lagged impact of the momentum fluxes from the tropical wave in the next week.

The GWO framework is extremely useful here as it gives an indication of probabilities of each relative phase when taking account of high angular momentum. Given high angular momentum above +2SD, the only relevant phases here are phases 5, 6 and 7.

The initial surge in angular momentum will drive the GWO into high amplitude strongly favouring phases 5 and 6 during the next 2 weeks. Composites favour a Greenland high but that should be adjusted a little to reflect existing and near time conditions, with the emphasis on phase 6 suggesting a continuation of the cyclonic pattern across NW Europe, including Scandinavia. Not overly cold, particularly with the residual+NAO imprint to the pattern, but between 15th and 20th, expect a cooling down.

From the 20th we should see a shift in the emphasis of the GWO more towards phase 7 (and not phase 8 as this would require much more significant removal of westerlies which is unlikely given the high benchmark we are operating at). Phase 7 composite for January suggests a west based -NAO, although I've included the composite for February as this will be towards month's end. Stress again, don't be too literal with the interpretation with these composites and the probability of the AO and NAO being more negative at this time should be factored into the composite. This suggests a definite trend to colder conditions towards month's end with the likely key parts for us in NW Europe being a more defined  European trough and anomalous ridges centred across the North-east Atlantic.  The trough signal across the SE and E USA does imply blocking more towards Greenland.

mjo forecast.bmp

Edited December 31, 2015 by Glacier Point

[blizzard81]

2 hours ago, bluearmy said:

Looking at NAEFS  and I'm struggling a tad to work out the charts in week 2. It seems to want a positively tilted East Atlantic trough above a s euro high anomoly. the GEFS and GEM ens are not showing this anomoly. Seeing as NAEFS is produced as a combo of the two model outputs, I'm confused. 

Incidentally, there is now a disagreement between GEFS and ECM ens re the AO/NAO. GEFS keeps the AO very negative throughout the two weeks whereas ECM slowly returns it to around neutral. the NAO remains slightly negative to the end of week 2 on GEFS but returning to slightly positive values on the eps. 

Yes, various gfs members showing the return of the dreaded euro high this morning. If that trend continues over the next couple of days then I really will fear for us coldies and the prospects for the rest of this winter.

[Ali1977]

6 minutes ago, blizzard81 said:

Yes, various gfs members showing the return of the dreaded euro high this morning. If that trend continues over the next couple of days then I really will fear for us coldies and the prospects for the rest of this winter.

Temporary warming maybe, things will change late Jan. This time next week FI may look a whole lot better..GPs post above covers this.

[knocker]

The ext ecm this morning appears to have gone off the idea of height rises to the west so it's still at odds with the GEFS and the uncertainty of the evolution should be noted. It has the trough down the eastern seaboard, ridge Alaska but the Russian HP is virtually gone. This would portend an unsettled westerly regime but as already noted the evolution is in a state of flux.

[Day 10]

33 minutes ago, THE CHOSEN ONE said:

Updated NAVGEM 06z 120

no change

the updated 06z JMA 84 v the 12z 96 yesterday ( slight time gap )

has now taken away the wave & replaced it with a ridge

also the 06z ENS suite is the very 1st GFS suite of this whole 'projection' to find 1 ( maybe 2) runs with the -10c line into england by T144

people can carry on ignoring the changes if they want....

look at the GFS consistency V the NAVGEM over the last 24 hours

s

latest Navgem and UKMO to compare, not a million miles apart

[Liam J]

6z NAVGEM still looking good but small changes compared to the 00z as the low over N France is further north meaning the colder air is away further to the NE, small changes in detail make a big difference. 

00z  06z 

ECM looks better @ 144hrs with colder air further into the UK and sub zero 850's covering France and N Spain, also ECM OP not without interest with snow potential.. Just looked at the control run and later on some serious snow depths for the north with 36 inches in Scotland! And the snow line further south at times than the OP chart below. 

 

[booferking]

All i have to say is anything can happen from now on in im taking this from day by day from now on in,  really is crazy to predict the outcome of anything now can,t remember the last time i seen so much uncertainty.

[Glacier Point]

Actually Knock, the EPS and GEFS means are not that dissimilar at t360 over the Asian sector. The evolution slightly different with the EC dropping more of the ridge south-east during week 2 whereas GEFS retains stronger heights in the Arctic portion. The models differ substantively in the degree of amplification across the Eastern Pacific and North Atlantic.

[knocker]

6 minutes ago, Glacier Point said:

Actually Knock, the EPS and GEFS means are not that dissimilar at t360 over the Asian sector. The evolution slightly different with the EC dropping more of the ridge south-east during week 2 whereas GEFS retains stronger heights in the Arctic portion. The models differ substantively in the degree of amplification across the Eastern Pacific and North Atlantic.

Yes wouldn't argue with that GP. I must admit I was concentrating more on the NA which is not wise.

[Methuselah]

13 minutes ago, booferking said:

All i have to say is anything can happen from now on in im taking this from day by day from now on in,  really is crazy to predict the outcome of anything now can,t remember the last time i seen so much uncertainty.

I know what you mean, booferking - do all the reverential references to the NAVGEM model mean that all the other models (last week's 'big three') are suggesting another 2-3 weeks' mild, wet, rubbish?

[Day 10]

14 minutes ago, Ed Stone said:

I know what you mean, booferking - do all the reverential references to the NAVGEM model mean that all the other models (last week's 'big three') are suggesting another 2-3 weeks' mild, wet, rubbish?

No