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

[nick sussex]

The GFS 06hrs run shows what can happen with the western based negative NAO and is a dreadful run for the European ski resorts.

 

The ECM 00hrs was similar to last night but the issue across all the outputs is that low which deepens rapidly and runs ne, this makes any change to something colder even more difficult because this helps to drag the limpet Euro high north again.

 

The issue has always been how far south and east the pattern will get and this is still up in the air, the GFS 06hrs run is just as plausible as the ECM 00hrs.

 

I'm not sure what nature is making of this weather, here the birds are singing and at this rate might start mating  as the temps are exceptional for the time of year. Last night I almost had to stick the fans on!

 

We wait to see what happens over the next few days.

[phil nw.]

There is decent agreement between the height anomalies out to day 10

 

gradually sinking the trough south east with a colder-more normal-temperaures-regime establishing across the UK.

We have seen the trend to bring the jet south towards mid-month bringing this change over the last few days.

I can't see anything more than a normal cool down though and there is no real indication of any Greenland block just a transient Atlantic ridge filtering some polar maritime into the mix in week 2.

 

Looking at the clustering around day 10 onwards

http://www.weatheronline.co.uk/cgi-bin/expertcharts?LANG=en&MENU=0000000000&CONT=euro&MODELL=gefs&MODELLTYP=2&BASE=-&VAR=cpre&HH=252&ZOOM=0&ARCHIV=0&RES=0&WMO=&PERIOD=

 

although there are varying solutions and pressure does fall over Europe we look like retaining the Atlantic mobile pattern for a while yet.

[Cloud 10]

It's an interesting one.

 

The first thing to say is that in the mid term (days 4-7) there looks to be remarkably high confidence in the ensemble suite with just a single cluster.

 

Beyond this though there is huge divergence. The strong NW sector high anomaly in the mean is skewed somewhat by the remarkably strong height anomaly of a relatively small cluster, but it's a possibility nonetheless, especially against the backdrop of a rather large spread and, resultantly, a large number of clusters beyond day 8.

 

Overall not a great suite to draw too many conclusions from in the longer term, but a rather agreed upon dip in T2m next weekend before chaos ensues.

 

SK

 

GEFS 06z ensembles are following that script as well,with a huge spread in solutions for day 8+.

 

 

 

Take you pick....

 

..........................

[Nick F]

As I mentioned the other day, in here I think, the well-agreed +ve height anomaly building over NE Canada, Labrador and eventually west Greenland appears to be the product of a wave developing in the weaker northern stream of the jet over N America

Unfortunately, the southern stream appears stronger and undercuts the ridge as it moves out into the Atlantic and toward NW Europe, so we end up with low pressure between us and the ridge. If the southern stream wasn't so strong over NA, traced back to a strong Pacific jet under a strong Alaska trough and the effects of El Nino, we would perhaps more likely see ridging mid-Atlantic and better chance for cold air to drain south.

[Iceaxecrampon]

06z run  has lost the real cold and ppn for mid November this at T+132 should move a few cobwebs up in the Cairngorm at 984mb - blizzard conditions - worth watching but not walking

 

 

 

 

 

 

 

[Polar Maritime]

The GFS shows quite a stormy period Sunday night into Monday, As a Low sweeps across Scotland. With gales or severe gales in places at times for the Northern half of the UK. Next week the GFS continues the theme with bouts of cool W/NW winds off the North Atlantic, With fronts crossing the country bringing unsettled wet/windy conditions for most especially Scotland where the upper air could turn cold enough for some wintriness over the Mountain Ranges and high passes. All looking like a typical Autumnal affair compared to recent weeks ..

Edited November 7, 2015 by Polar Maritime

[Costa Del Fal]

with all this rain we are now geting next thing will be the return of the floods in the uk. looking at the models this no let up in sight

It hasn't rained that much. Yes it's rained most days this week but not high totals overall. Plus it's been dry for some time so I'm sure the ground can cope. more rain to Coke but hardly anything too unusual.

Edited November 7, 2015 by Costa Del Fal

[marksiwnc]

It hasn't rained that much. Yes it's rained most days this week but not high totals overall. Plus it's been dry for some time so I'm sure the ground can cope. more rain to Coke but hardly anything too unusual.

I would say that you live in an area not affected much by the rain of late. It has been shocking here in nw Wales for the last week. I would say easily 100 mm this week.

[nick sussex]

Looking across the outputs the UKMO at T144hrs has a much weaker low off the east coast of the USA , that would likely develop more favourably and run further south, aswell as this it looks less likely to engage those lower heights near southern Greenland.

 

The difference is quite stark between its view and that of the ECM/GFS.

[carinthian]

Several runs from ECM have shown a cut off of the westerly with warm air advection in Mid Atlantic towards Greenland. This would allow a rise in pressure to the west of the UK and allowing a route for the cold incursion down the eastern flank. Obviously very different thoughts to GFS. I would think the UKMO would not support the Europe charts at this stage but maybe one to watch for a possible speedy development. Will be talking with our snow portal service later with views on latest ECM outputs ( aka snow forecasting prospects for Eastern Alps ).

C

Well just received our latest snow portal service forecast. No snow until 19th November ! 0% then 30% chance on 19/11/16. Would seem to suggest the cold front could affect the Northern Alps by week 3. This I assume is based on Euro/ UK out -puts. Latest 06z GFS shows strengthening of Euro block at this stage, but not favoured by our expectations. Looking more likely at a drop of pressure over Norway and some weakening on the Euro high pressure dominance . Mid Atlantic pressure change could result in some rapid developments in the medium forecasts from early next week. Maybe some clues in Sunday morning runs !

C

[Costa Del Fal]

I would say that you live in an area not affected much by the rain of late. It has been shocking here in nw Wales for the last week. I would say easily 100 mm this week.

Don't want to drift off topic anymore, but as a final comment from me, sadly in NW Wales on the windward side of the mountains you will all ways receive a lot more. For the majority of us, conversely a lot

Less.

[Tamara]

Some contradicting factors forcing the atmospheric circulation pattern at this time

.
We have the entrenched Nino base state fully advertising a classic very strong sub tropical jet stream heading downstream from the Pacific. This is sandwiched between an ominpresent upper trough over the mid/NE Atlantic and stubborn downstream ridge over the nearby European mainland. The consequent long fetch, vigorous and very moist mT airsteam is too apparent not to notice.

 

http://max.nwstatic.co.uk/gfsimages/gfs.20151107/06/00/hgt300.png

 

The Pacific waters in the Nino region may have been torching, but, as is quite common in peak matured Nino events, warming occurs quite manifestly across the tropical ocean basins. The Pacific SST Nino zone continues to govern the wider picture, but current MJO tropical activity over the Indian Ocean has spiked in reaction to such relative warmth there.

 

Under a Nino atmospheric/ocean coupled state we generally find a high relative Atmospheric Angular Momentum state.  This has indeed been the case since summer. The current tropical activity over the Indian Ocean is attempting to force negative frictional torque,  and lead to a downward tendency in AAM by adding easterly winds across that part of the tropics.

 

At the same time Kelvin wave activity has been proceeding across the tropical Pacific, by which is the process of adding further westerlies to the atmosphere here.

 

The indicated drop in overall relative AAM has been indicated in forecasts recently - with the Global Wind Oscillation forecast by GEFS to head into a low amplitude and indeterminate orbit -  flirting with low tendency Phase 1. *Model bias caveat attached*

 

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

 

The greater Nino forcing restricts any sustained drop in AAM tendency, and, because the MJO activity in the Indian Ocean looks set to be a temporary feature, we should expect AAM tendency to return to its higher default state thereafter.

 

As IO tropical forcing declines, the full effects of the underlying and dominating Nino circulation resumes and laddering back up of the GWO to the previous summer/autumn 5/6/7 re-cycling orbit, which characterises ocean/atmosphere Nino-esque coupling, should follow

 

Although potential from Nino poleward propagation of wave activity remains for the much longer term, without further progress of tropical activity east to imprint and engage the powder keg SST anomalies of the Pacific, we are not going to see the type of significant positive torque action which would inflict tropospheric Rossby wave activity blows to the fast developing seasonal polar vortex - and mean much earlier interest for those seeking real cold synoptics

 

There has been some early cautious optimism there might be an early salvo of this type. Such tropospheric blows seem highly likely to be required as the vortex is developing strongly in tandem with the prevailing +QBO. This, inhibiting the type of Brewer Dobson ozone poleward transport and production in the polar stratosphere which weakens/offsets the developing strength of the vortex.

 

To try and put all these developments into simple synoptic English:

 

The indicated drop in AAM in the short term is implicated in most synoptic modelling. It infers some temporary modest amplification in the Pacific jet stream, with a consequent hint of a flattening shift soutwards in the Atlantic sector ahead of this, at the same time as something of a retraction westwards occurs of the downstream Euro ridge. The result is that pressure falls more uniformly over the UK and the angle of attack of depressions becomes more west-east focussed.

 

Also implied upstream, in this modest amplification process, is a temporary reduction of the Pacific jetstream - and this may allow sufficient transitional amplification of any upstream ridge to provide airstreams from a more mP vector as the wave pattern transports eastwards across the hemisphere ahead of the next renewed Pacific jet streak.

 

 

Clearly, temperatures in this regime are likely to return to something closer to normal, from the abnormal heights we have been seeing, with some transient wintry potential perhaps furtherest north and over hills.

 

Its nice to seek out attractive synoptic perturbations of better things, such as have been appearing in the GEFS suites - but its hard to realistically see much suggestion of any HLB occurring in these circumstances.

Realistically, the external stratospheric forcing background as it stands is not going to assist any significant amplification attempts, and in the absence of any real wave activity currently suggested, it looks a big ask to provide the opportunity of any early meaningful cold. As many who read these pages hope for.

 

As already hinted above in terms of the evolution of the large scale synoptic pattern, it is most likely that once the IO tropical forcings have waned, a resumption of a stronger STJ from upstream seems likely. The GWO orbit, as suggested above, would provide indications as to when this is likely to occur. It also suggests continuation of the Nino feedbacks for poleward Rossby wave activity over the Pacific that are thought to assist prospects for stratospheric warmings later in the winter. *Caveat +QBO fulled vortex*

 

The approach to winter, it has to be said in summary, looks relatively inauspicious. I suspect it might be best to manage ones expectations early accordingly, and let proceedings develop in order to identify later possibilities. One key area to watch is any developing central Pacific signature, or Modoki. This, if it evolves as it might well do, has positive implications for Nino feedbacks to improve Atlantic/European synoptics and switch the +NAO state later in the winter

.

All this is some way off though and its obviously too early to do much other than speculate. Which is also way beyond the purpose and topicality of this thread obviously

.

For the rest of this month and into early December the main watch is how the vortex consolidates itself proper. Which, by current evidence as chiono suggests and illustrates in the stratosphere thread, it looks set to do with some purpose.

 

Plenty of course can happen, and there will of course be developments of interest along the way. But, fwiw, in my opinion at least, and taking into account the information to hand right now, it will likely get tougher to achieve cold synpotics before it gets easier perhaps later

[Frosty.]

The Gfs 12z op run shows quite a change from the current exceptionally mild conditions to colder weather for a time later next week with an incursion of 528 dam thicknesses, more especially across scotland where it becomes cold enough for showers to turn wintry, particularly on high ground and then we alternate between milder, wet and windy and colder, brighter and showery. It's a generally very unsettled run with gales / severe gales and bouts of rain, heavy at times, the strongest winds & largest rainfall totals probably across northwest scotland but there are at least signs now of some short lived colder incursions during the next few weeks, especially further north. 

Edited November 7, 2015 by Frosty.

[ANYWEATHER]

Evening all..! I cant really get too excited about  tonights output, if you want colder conditions that is..... up to T+168. Still very mild for a time in the south picticuarly  but this toning down as we go through the week. I would imagine the talking point will be the straggling weather front across the Uk during Tuesday into Thursday across central parts of the Uk  and North Wales for example could well see a lot of rain marking the boundary between cold and mild. The north of Britain will see the most disturbed weather, the other half seeing the quietist of the weather and perhaps may even pull out Jack Frost and fog, as fleeting pressure rises from the south,,,,,Probably near to the climatological  weather for the Uk in the coming week...    

[Man With Beard]

ECM tonight has pretty much ditched even a return to average temperatures, let alone a cold spell. 3/4 days of exceptional mild (19C today in the east, perhaps the word "warm" is still appropriate?), a 1/2 day cool down to average and then back to the super-mild next week. Euro high gaining a little strength once again, after looking vulnerable for a while. After several cool/average temp months, above average is back with a vengeance.

[Newberryone]

ECM tonight has pretty much ditched even a return to average temperatures, let alone a cold spell. 3/4 days of exceptional mild (19C today in the east, perhaps the word "warm" is still appropriate?), a 1/2 day cool down to average and then back to the super-mild next week. Euro high gaining a little strength once again, after looking vulnerable for a while. After several cool/average temp months, above average is back with a vengeance.

One can sense an air of despondency and with every good reason considering the latest Ecm. Basically unsettled up to Thursday and far less so afterwards as height rises from the south look set to feature yet again. Very little either tonight to suggest this locked in pattern is about to change anytime soon. 

[legritter]

Well looking at current charts not much in the way of anything cold or even cool on the horizon ,BUT the upper atmosphere and other variables are busy probably cooking up our coming winter ,so hang on gang we just dont know whats in store just yet .

[Singularity]

I've not been taking much stock in those properly cold GFS runs of the past few days and with reasons that Tamara has summed up expertly this afternoon. GFS has begun to move somewhat stutteringly toward the possibility of a briefly more mixed spell followed by the Euro High making a comeback (just look at the 06z and 18z runs), and while it may be being a bit quick on those runs, I can see where that comes from given the state of the teleconnections.

 

ECM's 12z det. also looks less inclined to bring much in the way of PM air into play beyond day 10, particularly compared to it's 00z det., though the usual caveats apply of course.

 

I feel that we may see a lot of dynamite stocked up under the polar vortex this winter (so to speak!), but with no guarantee that the match will be lit soon enough to do us much good.

[knocker]

Taking an overview of this morning's gfs the one thing that stands out is the reemergence of the European high. Even towards the beginning of the run when unsettled weather and systems  moving in from the Atlantic are the main player it begins to exert more influence but towards the end it really loses the plot (apparently) with a deep trough to the west and Scandinavian ridging resulting in significant WAA. I'm making no suggestion that this will come to fruition, and as yet stirrings in the woodshed there are not, as by the end of the run there is a return to normality.

Charts weatherbell and http://www.tropicaltidbits.com/

Edited November 8, 2015 by knocker

[Frosty.]

Anyone up for another exceptionally mild anticyclonic spell later in november?....the Gfs 00z shows another build of high pressure from the south which soon becomes centred across the near continent to the southeast with a long southerly draw and temperatures widely into the low to mid teens celsius close to 60 f and locally in the south as high 16/17 c  62 f. This is turning into an amazingly mild / warm autumn, surely one of the warmest? 

Edited November 8, 2015 by Frosty.

[IDO]

GFS and ECM now modifying their height bias in the last few runs and their phantom  outputs a few days ago are gone. Up to D10 we have the N/S split with the better drier conditions in the south as the jet sinks the Euro heights:

 

D10:   

 

As far as upper temps go the mean stays above the seasonal average for most of the next 16 days:  

 

So above average surface conditions but not quite as mild as the first third of November. The D15 GEFS clusters suggests that a continuation of the current theme is most likely (80%):

 

 

CFS weeklies for w3 & w4 suggest a N/S divide as well:   

 

Looking at the strat vortex placement it looks like we could (assuming coupling) benefit from more influence from HP in our region as it has room to stretch, so I wouldnt rule out transient ridging close to the UK. With the vortex firing up, and a NH zonal flow likely to build up steam, any favouring placement of the jet to at least avoid the worse of the wind and the rain, is a plus. This and the El Nino, look the drivers for the medium term, and if that is the case, our best chance of cold will be the second half of Winter.

Edited November 8, 2015 by IDO

[knocker]

The GEFS 6-10 anomaly this morning in very mach in favour of zonality and a N/S split over the UK. The 11-15 introduces a deeper trough to the west that could portend more cyclonic activity for all thus unsettled with temps around average.

 

[bluearmy]

The extended modelling out two two weeks on gefs and ECM are not building a strong p/v this side of the NH. (And haven't wanted to either). at two weeks and the spread makes the mean less relevant. between Alaska and ne Siberia seems favourite whilst we have some decent clustering. the point here is that whilst it seems that the vortex will begin to strengthen, is it feasible that it will do so far enough away from the Atlantic sector to allow any number of solutions other than a roaring Atlantic jet. The assumption that a strong vortex involves deep purples around Greenland is not a given.

[johnholmes]

The anomaly charts still show a generally westerly 500mb flow out to day 14/15 and perhaps beyond. The 'kink' that ECMWF-GFS showed in the flow yesterday has gone this morning. NOAA has so far not suggested that option. The only possible glimpse of this is the smallish +ve heights shown NE Canada-western Greenland.

Nothing substantial enough to really excite any cold watcher.

links below

http://mp1.met.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

http://www.cpc.noaa.gov/products/predictions/610day/500mb.php

for slightly further ahead the MJO (GFS version)

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/mjo.shtml

actual and predict show nothing more than 1-3.

link to probable 500mb pattern for November for those below

http://www.americanwx.com/raleighwx/MJO/MJO.html

[Singularity]

The extended modelling out two two weeks on gefs and ECM are not building a strong p/v this side of the NH. (And haven't wanted to either). at two weeks and the spread makes the mean less relevant. between Alaska and ne Siberia seems favourite whilst we have some decent clustering. the point here is that whilst it seems that the vortex will begin to strengthen, is it feasible that it will do so far enough away from the Atlantic sector to allow any number of solutions other than a roaring Atlantic jet. The assumption that a strong vortex involves deep purples around Greenland is not a given.

 

If I recall correctly, one of the best, and most extraordinary, examples of this happened in early Feb 1991; the vortex was strong but displaced away from the Atlantic/Europe sector, allowing a Eurasian ridge to gain enough latitude to bring some exceptionally cold air around its southern flank. I wonder if in that case, the severity was in part down to the cold having been bottled up for so long up until that point by the strong vortex? We wouldn't have quite the same resource to work with from such a setup late this month but you never know I suppose! The GFS 00z det. seems to be heading in that sort of direction as of +384 - but that's so far ahead that it's wishful thinking at its finest.

 

In the meantime, the 'second coming' of the inflated Euro High seems to be gaining ground for Sunday 15th onward, though not without interruptions as the pattern tries to remain flatter following that brief anomalous Walker Cell/MJO behaviour in the Indian Ocean.

 

I find it remarkable how disheveled the vortex still looks at the end of the GFS 00z det. run - but it's definitely starting to pull together by that time, starting around the 21st. That powerful strat. vortex can't be held at bay much longer, surely.