Model output discussion - 16th Nov onwards

[fergieweather]

Do you think so? The Atlantic cold pool now is starting to look quite patchy in nature. There is quite a noticeable amount of positive anomalies surrounding our shores and throughout the Atlantic. Still some localised very cold spots but is the cold pool further disintegrating I wonder now? http://www.ospo.noaa.gov/data/sst/anomaly/2015/anomnight.11.26.2015.gif

Yes, it's easy to overstate the likely effect of the cold SST anomaly on resultant temperature of Pm/rPm air arriving here... it's likely impact looks fairly nuanced (eg versus a flow coming across cold continental origins). A much more important influence for us is how it helps fuel a stronger temperature gradient in the North Atlantic, ie greater likelihood of deeper cyclonicity. Unfortunately, impacts from 'The Blob' have been subject to Maddenology in certain papers and transposed to be precursors to deeply cold set-ups even in prevailing westerlies.

[Hocus Pocus]

Yes, it's easy to overstate the likely effect of the cold SST anomaly on resultant temperature of Pm/rPm air arriving here... it's likely impact looks fairly nuanced (eg versus a flow coming across cold continental origins). A much more important influence for us is how it helps fuel a stronger temperature gradient in the North Atlantic, ie greater likelihood of deeper cyclonicity. Unfortunately, impacts from 'The Blob' have been subject to Maddenology in certain papers and transposed to be precursors to deeply cold set-ups even in prevailing westerlies.

There is an element in truth regarding this though Ian, granted not in the sense Madden implies but if you cast you mind back to the early 80s  when the AMO was in its negative phase this resulted in NW airflows that were cooler than now, more so with the one in January 84.

[BLAST FROM THE PAST]

Yes, it's easy to overstate the likely effect of the cold SST anomaly on resultant temperature of Pm/rPm air arriving here... it's likely impact looks fairly nuanced (eg versus a flow coming across cold continental origins). A much more important influence for us is how it helps fuel a stronger temperature gradient in the North Atlantic, ie greater likelihood of deeper cyclonicity. Unfortunately, impacts from 'The Blob' have been subject to Maddenology in certain papers and transposed to be precursors to deeply cold set-ups even in prevailing westerlies.

why were nights during summer so chilly then?  And re fuelling a stronger gradient I think that's not the point, the cold pool wasn't in flow during the extremely stormy autumn of 2013...so what's that all about then?  Its either the cold pool or something else....

 

 

BFTP

Edited November 27, 2015 by BLAST FROM THE PAST

[nick sussex]

Not a great deal in tonights outputs to get people ordering in the ear muffs and woolie hats!

 

The one thing that's stood out however over the last two ECM outputs is it keeps wanting to dig low pressure further south off the eastern USA, I suppose the question at this stage is whether this is a two run wonder and whether this if it verifies will help force a lobe of high pressure further north near the UK.

 

The ECM T240hrs I would certainly take if offered given some generally underwhelming output overall.

[chionomaniac]

Yes, it's easy to overstate the likely effect of the cold SST anomaly on resultant temperature of Pm/rPm air arriving here... it's likely impact looks fairly nuanced (eg versus a flow coming across cold continental origins). A much more important influence for us is how it helps fuel a stronger temperature gradient in the North Atlantic, ie greater likelihood of deeper cyclonicity. Unfortunately, impacts from 'The Blob' have been subject to Maddenology in certain papers and transposed to be precursors to deeply cold set-ups even in prevailing westerlies.

I agree entirely on this point of importance of the blob this winter. Especially considering that the anomaly could well be coming from melt and this is likely to be negligible in winter. Anyway there is another thread for this so best to place any further postings on the topic there.

[Costa Del Fal]

And that means for the uk winter?

Well, that any winds coming from the W/NW may not be much colder than normal as some are perhaps expecting. Consequently, the amount of wintriness may not differ too much from normal either.

Edited November 27, 2015 by Costa Del Fal

[Singularity]

 

It's better than the 00z run at least, as the polar vortex achieves a lot less in the way of organisation and the Atlantic starts to look rather sluggish.

 

Right, time for that Friday night pint. I might offer ECM a sip or two... 

[Summer Sun]

West to south westerly winds starting to dominate the ECM ens becoming more settled in the south with time as well

 

 

High pressure also starting to dominate large parts of mainland Europe too

[Costa Del Fal]

Yes, it's easy to overstate the likely effect of the cold SST anomaly on resultant temperature of Pm/rPm air arriving here... it's likely impact looks fairly nuanced (eg versus a flow coming across cold continental origins). A much more important influence for us is how it helps fuel a stronger temperature gradient in the North Atlantic, ie greater likelihood of deeper cyclonicity. Unfortunately, impacts from 'The Blob' have been subject to Maddenology in certain papers and transposed to be precursors to deeply cold set-ups even in prevailing westerlies.

Quite Ian. The gradient of contrast is certainly more of interest. Certainly some exceptionally deep lows on a few model runs of late though thankfully they have not really ventured out of FI with fairly standard autumnal fayre prevailing. 

 

In terms of SST's, it is also important to note the waters surrounding our very shores are slightly above average. Nothing significant but enough to balance out much of any cooling of air that has occurred further west in the Atlantic. Putting the two together, the resultant upper air temperature is unlikely to finish off far from normal in my view. Maybe it will strengthen again in to the winter, who knows. However if the cold pool strengthens again next summer, may the point about the importance of freshwater melt from glaciers and ice in the arctic, namely Greenland be further emphasised?

 

Anyway, not wishing to derail the topic here but perhaps important to highlight this to provide context and understanding. 

Edited November 27, 2015 by Costa Del Fal

[bluearmy]

Just note that at T336, GFSP has 1030mb and ECM Eps has 1026 mb across the south of England as a mean!!

[Scorcher]

why were nights during summer so chilly then?  And re fuelling a stronger gradient I think that's not the point, the cold pool wasn't in flow during the extremely stormy autumn of 2013...so what's that all about then?  Its either the cold pool or something else....

 

 

BFTP

 

Your point is slightly outdated in my opinion given the exceptionally warm nights we've had for most of this autumn so far. Alright it has been cloudy on many nights but cloud alone doesn't mean that we always see record warm nights which saw earlier this month.

 

Many areas also had a late first air frost and it took a pretty potent northerly for it to happen. Even the clearer nights have often been very mild so far this autumn.

Edited November 27, 2015 by Scorcher

[bradymk]

Just note that at T336, GFSP has 1030mb and ECM Eps has 1026 mb across the south of England as a mean!!

A remarkably strong high pressure signal from a set of ENS for almost two weeks away! cool, cold, average or mild though....The rise in pressure signal strong, but I bet the temperature spread is rather large with the number of possible options this far out i'm sure.

You seem keen on the GEFS parallel Nick, interesting to see how it does here and next few weeks.

Edited November 27, 2015 by bradythemole

[bluearmy]

Only keen on them cos they show a colder outlook!

on a serious note, they are an upgrade so why bother with the old model?

There may be only 20 members compared to ecm's 50 but they are running at a similar resolution to the ECM so they should be respected.

If the vortex meanders its way to Asia week 2 then that a feather in its cap

[Mildcarlisle]

And with charts like this,model watching becomes academic likes. :-)

[bradymk]

Only keen on them cos they show a colder outlook!

on a serious note, they are an upgrade so why bother with the old model?

There may be only 20 members compared to ecm's 50 but they are running at a similar resolution to the ECM so they should be respected.

If the vortex meanders its way to Asia week 2 then that a feather in its cap

true, with it being replaced Wednesday anyway, it does seem pretty pointless using the old one. Hoping it does well. I've noticed so far that it does tend to have a less diluted mean out towards 14 days compared to the old GEFS but as expected with increased res. Old one always tended to go to a flat zonal mean by time you got Into week 2 the majority of the time but seems less of the case with the new one.

Eg) old GEFS mean day 14

new GEFS mean day 14

A clearer picture from the mean with clearly more members in agreement with the potential general pattern 2 weeks away...

[blizzard81]

true, with it being replaced Wednesday anyway, it does seem pretty pointless using the old one. Hoping it does well. I've noticed so far that it does tend to have a less diluted mean out towards 14 days compared to the old GEFS but as expected with increased res. Old one always tended to go to a flat zonal mean by time you got Into week 2 the majority of the time but seems less of the case with the new one.

Eg) old GEFS mean day 14

image.png

new GEFS mean day 14

image.png

A clearer picture from the mean with clearly more members in agreement with the potential general pattern 2 weeks away...

Some great posts tonight. I think this is one of those moments when the ecm op is very late to the party. The gfs is just like a dog with a bone with height rises in the UK vicinity in the 9 - 10 day range. I expect the ecm op to come on board tomorrow.

[Ravelin]

Some great posts tonight. I think this is one of those moments when the ecm op is very late to the party. The gfs is just like a dog with a bone with height rises in the UK vicinity in the 9 - 10 day range. I expect the ecm op to come on board tomorrow.

Well if they don't start converging soon one of them is going to have to do an almighty flip at short range. My interpretation is that the 5 day mark is currently where they start to diverge.

Gut feeling is that the ECM is the one that will start to readjust (I'm hoping I'm not just basing that on the GFS being the more 'interesting' path). Probably means it'll actually be the GFS that moves.

[Singularity]

 

Much more of a Siberian polar vortex lobe on the GFS 18z det. run which brings it close to ECM's 12z det. in that region.

 

The problem with having a Euro High at the same time is also well demonstrated.

 

The run goes on to do a nice job of illustrating the potential benefits of a Siberian vortex lobe if the Euro High can retrogress into the Atlantic, but also just how difficult it may be to get that to happen!

 

 

Worth noting that the Atlantic jet really loses its intensity for a time on this run, again similar to where the ECM 12z det. was going as of +240 hours. A snapshot when it's at its weakest and waving about like a wind sock:

 

 

The corresponding SLP/500 mb Height chart shows high pressure dominating all the way from the central U.S. to Norway with hardly an interruption. Notice too the rising heights in the Greenland area which GFS seems to enjoy teasing us with from time to time. A decent high right over the N .Pole too which reflects the displaced nature of the vortex.

 

I suspect the usual longer range modelling issues are at play here; they have a habit of moving the polar vortex about too cleanly, when in reality there tends to be fragments left behind - all too often in the vicinity of Greenland. On the other hand, if the stratospheric vortex really is displaced as far from Greenland as GFS keeps showing at the moment, the odds of 'cleaning up' over Greenland will rise significantly. Yet I've also seen GFS overdo the movement of the strat. vortex on some occasions in the past so this has to be a case of waiting and seeing, as most of the displacement remains beyond 10 days range, which tends to be as far ahead as I place much stock in the charts at 30 hpa for example.

 

For entertainment value, here's the +384 of the 18z, which also shows that wave activity still ticking along nicely:

 

Edited November 28, 2015 by Singularity

[knocker]

This morning's gfs run is a classic example of a very mobile NW/SW flow featuring the interplay between the Pm and Tm airmasses via systems travelling ENE to the north and the HP to the SW/SE. Illustrated by 850mb temps of -5C on the 4th and +11C on the 4th!!. Three charts picked at random as an illustration

Charts courtesy weatherbell

Edited November 28, 2015 by knocker

[Captain Shortwave]

GFS, ECM and GEM at day 7

 

GFS

 

ECM

 

GEM

 

All of them try to get a decent ridge up into Europe with a good deal of the UK becoming influenced by it. The GFS and GEM become mostly dry for several days especially so in the south whilst the ECM holds a more mobile solution but even then shows further ridging of the Azores high to be possible. No point talking about the temperatures as the set up is a fine line between very mild and fairly chilly depending on the direction and strength of the winds.

[Newberryone]

Ecm 00z and other suites/models painting another rather dismal outlook in the reliable time frame with regards to cold prospects with a continuation of euro heights, not to mention an AH.  Still, Eire looks like copping the worst of any wet and windy weather over the forecast period.

Edited November 28, 2015 by Newberryone

[knocker]

Some interesting cyclogenesis with the ecm. A drop of 46mb in twenty four hours down to 928mb as a depression tracks NE from the eastern seaboard and phases in with another depression located SE Greenland.

http://www.tropicaltidbits.com/

Edited November 28, 2015 by knocker

[northwestsnow]

Ecm 00z and other suites/models painting another rather dismal outlook in the reliable time frame with regards to cold prospects with a continuation of euro heights, not to mention an AH.  Still, Eire looks like copping the worst of any wet and windy weather over the forecast period.

Yes ECM is pretty horrid for coldies again this morning with a +NAO dominating right out to day 10 and probably beyond.

GFS looks better in FI with the high retrogressing towards Greenland

[Ravelin]

Despite my prediction last night, this mornings GFS run looks like the odd one out at 120hrs. At that point the ECM, UKMO and GEM all try to push a transitory ridge of high pressure into the south of Scandinavia.

At the same time the GFS however has a good sized area of low pressure sat over the North of Scandinavia.

Although checking through yesterday's runs the GFS has never had heights near Scandinavia at that point so it's consistent.

Moving on a bit and the GFS loses its recent obsession with trying to cover the whole of Europe and the Atlantic with high pressure in FI on this run. Will it make a comeback on the 6Z?

Edited November 28, 2015 by Ravelin

[bluearmy]

just looking at the anomoly charts i saved last weekend and in respect of the 10 day charts - a pretty good job but the strength of the euro heights   and the w atlantic troughing underestimated

 

further ahead now the 16 day gefsp is now comparable to the ecm 10 day.  guess what - greenland low anomoly not picked up and neither is the euro high anomoly!!   twas ever thus.