Model Output Discussions 12z 01/09/2016

[fergieweather]

EC Monthly has large above average 500hPa GPH & MSLP anomalies to NW of UK into early Nov (the +ve GPH signal then remains to end of run), with low pressure over Scandinavia 1st week of the month. GloSea5 is in agreement with this for 1st week of Nov. Into 2nd week onward, GloSea maintains a weaker +ve MSLP signal over and to NW of the UK. Bias between anticyclonic v cyclonic signature is indistinct by then. So in summary: a leaning towards N/NW'ly mean flow early Nov. Neither model suggests anything other than modest progression, with likelihood of any vigorous westerly regime continuing to look much lower than normal.

[Ravelin]

@doctor32

The ECM 0Z has the high too so backs up the UKmet

Edited October 25, 2016 by Ravelin

[Matthew.]

ECM 0z has cold air flooding from the NW for the 1st November, -4 uppers and a quick look at the vortex:

[winterof79]

18 minutes ago, Matthew Wilson said:

ECM 0z has cold air flooding from the NW for the 1st November, -4 uppers and a quick look at the vortex:

What a splendid chart for early November.Vortex's Sat Nav has lost the plot and gone walkabout.

[knocker]

The ecm is not dissimilar to the GFS albeit a slightly different interpretation at the end with HP again ridging in but to be expected with this pattern. Cold air dropping down to the eastern Med. with snow in the Alps.

[johnholmes]

17 hours ago, bluearmy said:

Hi John - the upper low is on the 00z ecm op run so it's bound to be on a chart showing the average of the run days 6/10 ??

remember that this Chart is a representation of the ecm /gfs op runs only. Nothing to do with the ensembles 

well aware of all that ba, been using them for 8 years, but thanks; it is the depth that caused my comment

not sure where or how the above has appeared, could not find it last evening!

Also this morning the EC anomaly has no sign of the cut off low I referred to. Not unusual for either EC or GFS to be so inconsistent even with these mean charts but NOAA rarely shows this kind of day to day change.

Edited October 25, 2016 by johnholmes

[johnholmes]

The quote below from the post by Fergie, to me, sums up how the anomaly charts are slowly coming to their pattern. That is that a flow from north of west into the UK day 6-10 and extending out on the NOAA 8-14. I never pretend to predict further. The main question as the quote suggests is will the ridging effect have more effect than the troughing at 500mb, and thus at the surface and how far east will the main plunge of any cold air go.

'..Bias between anticyclonic v cyclonic signature is indistinct by then,...'

[knocker]

1 minute ago, johnholmes said:

The quote below from the post by Fergie, to me, sums up how the anomaly charts are slowly coming to their pattern. That is that a flow from north of west into the UK day 6-10 and extending out on the NOAA 8-14. I never pretend to predict further. The main question as the quote suggests is will the ridging effect have more effect than the troughing at 500mb, and thus at the surface and how far east will the main plunge of any cold air go.

'..Bias between anticyclonic v cyclonic signature is indistinct by then,...'

That is indeed the question.

[bluearmy]

18 minutes ago, johnholmes said:

well aware of all that ba, been using them for 8 years, but thanks; it is the depth that caused my comment

not sure where or how the above has appeared, could not find it last evening!

Also this morning the EC anomaly has no sign of the cut off low I referred to. Not unusual for either EC or GFS to be so inconsistent even with these mean charts but NOAA rarely shows this kind of day to day change.

And that's why I caution against these charts unless they are used by someone who understands anomalous runs like yourself. Note the NOAA charts are ensemble means based so won't be skewed by a dodgy op run. 

[johnholmes]

17 minutes ago, bluearmy said:

And that's why I caution against these charts unless they are used by someone who understands anomalous runs like yourself. Note the NOAA charts are ensemble means based so won't be skewed by a dodgy op run. 

Totally agree ba, a couple of those showed up last evening I think, taken carefully they are fine for a general idea of the upper flow 6-14 days ahead just now and then I might stretch my ideas to about 20 days or so!

[fergieweather]

The EC monthly run looks unconvincing when set against 00z EC ENS. Herein lies the cautionary note regarding lagged models for extended range. They can quickly fall behind the curve...!

[bluearmy]

6 minutes ago, fergieweather said:

The EC monthly run looks unconvincing when set against 00z EC ENS. Herein lies the cautionary note regarding lagged models for extended range. They can quickly fall behind the curve...!

Bear in mind individual eps suites can be skewed on occasion Ian but I did think the 46 looked rather more like last tuesdays with more Euro high anomolys present than Fridays which was back on the Euro low anomaly songsheet 

without decent clustering, I'm not convinced the 46 post day 25 is particularly informative anyway and we rely on you for any detail in that direction. 

[Ali1977]

6 minutes ago, bluearmy said:

Bear in mind individual eps suites can be skewed on occasion Ian but I did think the 46 looked rather more like last tuesdays with more Euro high anomolys present than Fridays which was back on the Euro low anomaly songsheet 

without decent clustering, I'm not convinced the 46 post day 25 is particularly informative anyway and we rely on you for any detail in that direction. 

Are the 00Z EC ENS showing something different?

[feb1991blizzard]

240 mean  still looks half decent though looks like it might fade afterwards which is understandable.

 

[Ali1977]

1 minute ago, feb1991blizzard said:

240 mean  still looks half decent though looks like it might fade afterwards which is understandable.

 

That doesn't look like it will fade to me , the NH profile looks very blocked and open to some WAA from that high sitting in the Atlantic.  Still a complicated setup for the models to work out I think, especially showing the differences between the different models and their ensembles.  We are no where near winter yet but it still makes for good viewing.

[Gael_Force]

1 hour ago, johnholmes said:

The quote below from the post by Fergie, to me, sums up how the anomaly charts are slowly coming to their pattern. That is that a flow from north of west into the UK day 6-10 and extending out on the NOAA 8-14. I never pretend to predict further. The main question as the quote suggests is will the ridging effect have more effect than the troughing at 500mb, and thus at the surface and how far east will the main plunge of any cold air go.

'..Bias between anticyclonic v cyclonic signature is indistinct by then,...'

Fergies latest post below indicates 24 hours makes a big difference too. We are seeing some big changes in the 12 hours between model runs but is this so unlikely, bearing in mind the models are trying to sort out a highly unusual state of affairs in the Arctic?

[feb1991blizzard]

1 minute ago, Ali1977 said:

That doesn't look like it will fade to me , the NH profile looks very blocked and open to some WAA from that high sitting in the Atlantic.  Still a complicated setup for the models to work out I think, especially showing the differences between the different models and their ensembles.  We are no where near winter yet but it still makes for good viewing.

What I mean by fade is the high would get smaller and further south because it gets muted by climatology as the further you go, at least some ensembles will always show the more default pattern, all depends on the clustering.but given earlier posts, which suggest ECM 0z doesn't back up EC monthly, it doesn't sound as promising.

[fergieweather]

4 minutes ago, Gael_Force said:

Fergies latest post below indicates 24 hours makes a big difference too. We are seeing some big changes in the 12 hours between model runs but is this so unlikely, bearing in mind the models are trying to sort out a highly unusual state of affairs in the Arctic?

UKMO indicate that the ongoing model turmoil for Atlantic developments/major trough disruption into medium range can be traced back to key analysis differences emerging in western-central Pacific. In other words, we're seeing the back-end of modelling issues harking from other side of the globe. I doubt this will resolve any time soon...!

[phil nw.]

We can see gradually the pattern reverting to a more Atlantic regime now that the Scandinavian blocking has faded.

This was always the possibility once waa  pouring into the pv from tropical storms was removed.Nothing overly mobile yet overall and although we do see the jet picking up across the north there is still a lot of mid-latitude blocking around and this will likely see many areas getting colder nights with some frosts and fog around.

We still have some +ve heights across the Arctic indication of a weaker vortex but this doesn't rule out some Icelandic lows moving across the north as we can see on current outputs. 

[Eskimo]

There's more swing on these charts than Louis Armstrong could ever muster.

00z                                                               06z

 

[weirpig]

Interesting  Gfs 6z   run there.  quite a lot of ridging in the Atlantic  followed by outbreaks of north westerly/ Northerlies   and ending in fi  with quite a potent northerly  originating from a low coming from the north.  it would certainly feel raw for early November .  If it were to verify  that is.

 

 

 

Edited October 25, 2016 by weirpig

[Paul_1978]

Meanwhile, latest AO and NAO forecasts suggest they will remain firmly negative into the first week of November, with suggestions that these will remain negative beyond. Which can only be a good thing if it's cold you're after.

[johnholmes]

24 minutes ago, Paul_1978 said:

Meanwhile, latest AO and NAO forecasts suggest they will remain firmly negative into the first week of November, with suggestions that these will remain negative beyond. Which can only be a good thing if it's cold you're after.

As with any model output, forecasts of A) and NAO need treating with a lot of caution beyond about 7 days.

[Frosty.]

The GEFS 6z mean is a lot more bullish about a cold shot than the 00z was. These charts are encouraging for those of us who would like to see a polar / arctic maritime incursion during early november with height rises to the w /nw and a scandi trough..makes a nice change from the constant awful charts this time last year which continued through most of the winter! 

Edited October 25, 2016 by Frosty.

[Frosty.]

Plenty of cold GEFS 6z perturbations, and there were others

Edited October 25, 2016 by Frosty.