Model output discussion pm 13/01/2016

[swebby]

11 minutes ago, Southender said:

Am I missing something here?

The GFS OP drops to around -12 850's for London around Day 10 on the below chart. Yet this is not shown on the ensembles, unless I am looking at the wrong line?!....I thought the bright green line was the OP, or am I going colour blind?!

I am sure the location in the ensembles, especially in the low res part of the run needs to be taken with a pinch of salt.  The Devon ensembles on NW are always out of kilter with the op run (edit) in the latter stages and a few years back i rmember Steve Murr mentioning that the london ensembles that purga has posted is actually a grid ref near the isle of wight.

Edited January 20, 2016 by swebby
control run changed to op run

[Catacol]

Well - was the TS forecast unwise? Is winter really over now? Can IF get any more cryptic? Where has GP gone.... and just what on earth is happening in the strat, over in the pacific and to the modelling of the GWO for the next 2 weeks?

All models are picking up increased amplification towards the middle/end of next week, and the GFS links that with the semi-permanent high of the current winter season to build a fairly impressive Scandy block. As the trop vortex then becomes stretched (coordinated impact of trop and strat factors coming together?) we see a signal for retrogression of those heights towards Greenland. GFS op today would bring proper snowfall to the south of England on 1st Feb. ECM meanwhile turns a fairly amplified atlantic at 96h to a flat high powered westerly by 144 as the azores high strengthens and extends across mainland Europe. Yuck.

Where does the trail truly lead? Hard to say - but certainly not inevitably to a Euro high. There is a strong wave 1 assault on the strat visible at the end of next week, and confusion once again in the modelling of the MJO (GFS more coherent, ECM all over the place....). The crunch for me is that the modelling of the GWO currently has it falling fairly fast into a low orbit phase 1/2 (cant seem to post the chart? - but take it from me - it is.) This runs counter to the prediction from GP that saw a Western Pacific trough and upstream ridge as being a good signal for maintaining the GWO in a decent orbit phase 7/8. 

So - what are we to think? Ha - I suspect we genuinely dont know. I'm sure Stewart will post again with his take on the GWO forecast at some stage soon... and perhaps he over estimated the robustness of the high amplitude pattern. Or perhaps the models havent seen it yet properly and once the pacific trough/ridge scenario kicks in over the weekend we will see a sudden model shift as they pick up the signal for a sustained GWO impact.

Overall both op and mean modelling for next week has been fairly underwhelming the last few days, but on its own this does not mean the game is up for winter. There are, quite simply, too many factors pointing in slightly different directions to be at all confident of what the pattern will be by the end of next week.

 

Edited January 20, 2016 by Catacol

[fergieweather]

1 hour ago, Purga said:

In the shorter term yes but I would say that there is an increased trend to a cold solution later on with the Control bringing the cold in earlier than the Op

 

Just to add a bit more to the mix:

"The ensembles (Met O and ECM) show more support for a NW or N type in 10 days time or so, much less for any easterly or building high from the East"

Courtesy of Tom C (Met Office) posted a bit earlier on TWO.

Indeed - and likewise beyond. Through the first half of February, GloSea continues to stick to it's recent tune of an initially SW'ly flow then veering more W/NW'ly during first half of the month. The net result is a signal for colder than average conditions to develop as the month progresses. The UKMO Seasonal Consensus meeting has been taking place today in Exeter, so we hope to hear more regarding their judgement for next month later this evening.

[nick sussex]

1 hour ago, Timmytour said:

Nick....do you think the way GFS has gone might only be the start?  Any chance of it cutting off the Greenland lobe of the PV in future runs?

The 18z GFS from yesterday was here, which doesn't seem that far away from the ECM 0z....perhaps, or rather hopefully, it's picked up on a signal more quickly?

At this point its hard to say whats going to happen because although the ECM/GFS/UKMO agree on the overall pattern across the NH they're miles apart towards the ne at T144hrs.

Reading the WPC extended discussion the ECM has suffered some stinging criticism from NCEP this morning:

CHOICES ARE LARGELY A RESULT OF THOSE SOLUTIONS THAT HAVE SHOWN THE BEST RUN-TO-RUN CONTINUITY THE LAST FEW DAYS AND HAVE THE GREATEST SUPPORT FROM OTHER SOLUTIONS INCLUDING THE ENSEMBLES. OF THESE VARIOUS SOLUTIONS...THE ENSEMBLE MEANS HAVE BEEN THE STEADIEST DESPITE IRONING OUT IMPORTANT SYSTEM DETAILS...WITH THE GFS A CLOSE SECOND AND THE ECMWF THE WORST. IN FACT...THE ECMWF IS SO FAR FROM ITS OWN ENSEMBLE MEAN AND THE DETERMINISTIC CONSENSUS IN 4 DISTINCT AREAS BEGINNING SATURDAY THAT IT WAS NOT USED AT ALL IN THE BLENDING PROCESS.

Even if the ECM isn't trusted upstream theres still the issues towards the ne and this isn't just down to some differences over the USA and Canada that are causing this divergence.

[SylvainTV]

2 minutes ago, swebby said:

I am sure the location in the ensembles, especially in the low res part of the run needs to be taken with a pinch of salt.  The Devon ensembles on NW are always out of kilter with the control run in the latter stages and a few years back i rmember Steve Murr mentioning that the london ensembles that purga has posted is actually a grid ref near the isle of wight.

It is not the good GFS run data that is plotted on this Wetterzentrale graph (it was probably the 00Z run). Note that the location taken for London is "Lat : 51 Long : 0" which is 50km south of London. They use the nearest point of GEFS 1.0deg data. The Isle of Wight thing was probably when GEFS data had a 2.5deg resolution.

Same thing for the GFS op resolution. It had a 2.5deg resolution in the > 192hours part of the run until the last GFS upgrade.

(On Meteociel we now use GEFS 0.5deg / GFS 0.5deg data for the graphs and interpolate between grid points, so the values are supposedly more conform for London)

[nick sussex]

Bearing in mind comments re what the UKMO think you could still have some blocking to the ne which could force the jet more nw/se in towards the UK.

At this point thankfully theres no sign of a repeat of the December horror show either in terms of rainfall or hideously mild temps.

The Euro high might make the odd re-appearance but its unlikely to hang around as it did during December.

[joggs]

12 minutes ago, fergieweather said:

Indeed - and likewise beyond. Through the first half of February, GloSea continues to stick to it's recent tune of an initially SW'ly flow then veering more W/NW'ly during first half of the month. The net result is a signal for colder than average conditions to develop as the month progresses. The UKMO Seasonal Consensus meeting has been taking place today in Exeter, so we hope to hear more regarding their judgement for next month later this evening.

Thanks Fergieweather 

[Ali1977]

So the possible easterly flow that the BBC forecast mentioned is now showing in the models, goes to show how good theirs are at picking things up / of course they didn't say definate but it's a start. Now we need to push the heights North slightly as we don't really tap into much cold UK wide looking at the charts, just southern tip of UK. Lots of changes expected next few days, and I'd like to think for the better.

[Singularity]

GLOSEA5 sounds to me as if it's trying the 'west-based NAO moving steadily east' theme.

 

Anyway, in light of that somewhat tasty GFS 06z operational, I decided to compile the GEFS outlooks for the AAM/GWO from the 15th (in red), 18th (in blue) and 20th (in green) and see how that looks:

Aha! Big changes afoot, with the much greater neg. dM/Dt in phase 8 a reflection of the expected negative MT event being picked up on, and the signs of a move toward 4/5 the beginnings of the response to that MT event that should actually take the GWO back to phase 5 and may not even visit the COD along the way, based on how large the negative AAM bias in the GEFS model has been on the approach to the previous two 6/5/6/7 orbits.

Notice also that the amount of AAM drop in the short term - literally the next few days - has been reduced a little with time. Given that falling AAM corresponds to additions of westerly momentum to our latitudes and so a boost to the polar jet (as Tamara mentioned in her excellent post last night), these slight reductions may be what's allowing the splitting jet outcome to gain a little more support in the GEFS.

There may be a similar trend going on with ECM, but not yet enough to make a notable difference. I'd say this is a classic case of 'if trends continue...!'.

 

The question over the rest of Jan has long been whether the drop in AAM will be small enough to allow enough amplification to overcome the flatter pattern encouraged by the period of more neutral/positive AO that leads us up to the SSW (and is important for the SSW to have significant impacts on the tropospheric vortex).

Evens like 1991 do show us that such a thing is entirely achievable with a bit of luck. Or maybe a lot of luck. This is Blighty, after all 

[Ali1977]

Didn't see the post from Ian earlier on, no talk of an Easterly there although he is talking about Feb. Eyes down for the 12z's.

Edited January 20, 2016 by Ali1977

[SLEETY]

sometimes the gfs pulls a rabbit out of the hat,but its rare lol,i recall once it delivered a northerly on xmas day,having picked it up at about +300 hours range and it came off and delivered snow to some parts on xmas day:),next runs awaited keenly

[Methuselah]

3 minutes ago, SLEETY said:

sometimes the gfs pulls a rabbit out of the hat,but its rare lol,i recall once it delivered a northerly on xmas day,having picked it up at about +300 hours range and it came off and delivered snow to some parts on xmas day:),next runs awaited keenly

And at others, it extrudes a Douglas Hurd!

So, what will the 12Z produce: winter wonderland or something-else entirely? Stay tuned!

[Catacol]

22 minutes ago, Singularity said:

GLOSEA5 sounds to me as if it's trying the 'west-based NAO moving steadily east' theme.

 

Anyway, in light of that somewhat tasty GFS 06z operational, I decided to compile the GEFS outlooks for the AAM/GWO from the 15th (in red), 18th (in blue) and 20th (in green) and see how that looks:

Aha! Big changes afoot, with the much greater neg. dM/Dt in phase 8 a reflection of the expected negative MT event being picked up on, and the signs of a move toward 4/5 the beginnings of the response to that MT event that should actually take the GWO back to phase 5 and may not even visit the COD along the way, based on how large the negative AAM bias in the GEFS model has been on the approach to the previous two 6/5/6/7 orbits.

Notice also that the amount of AAM drop in the short term - literally the next few days - has been reduced a little with time. Given that falling AAM corresponds to additions of westerly momentum to our latitudes and so a boost to the polar jet (as Tamara mentioned in her excellent post last night), these slight reductions may be what's allowing the splitting jet outcome to gain a little more support in the GEFS.

There may be a similar trend going on with ECM, but not yet enough to make a notable difference. I'd say this is a classic case of 'if trends continue...!'.

 

The question over the rest of Jan has long been whether the drop in AAM will be small enough to allow enough amplification to overcome the flatter pattern encouraged by the period of more neutral/positive AO that leads us up to the SSW (and is important for the SSW to have significant impacts on the tropospheric vortex).

Evens like 1991 do show us that such a thing is entirely achievable with a bit of luck. Or maybe a lot of luck. This is Blighty, after all 

Thanks S - said so much better than I could put it. I clearly chose the wrong degree when taking History... at times like this I would love to have an MSc in Meteorology!

I suspect the weekend is going to be a key period of model watching as we see if the forecast surge of amplitude in the pacific can kick our own heights profile into something more likeable, just as hopefully a swift kick to the goolies is delivered to the Strat vortex...

[bluearmy]

Not the best day for NOAA to pull the gfsp for 4 runs!

anyway, the easterly solution is predicated on trough disruption against the blocks (East Atlantic and sceuro) which push low heights into Europe and advect the cold this way whilst supporti ng the block to our East. The euro just not interested in this solution.

 

[karlos1983]

if the 12z show what the 06z GFS produced, or something close I will be a happy Karlos

http://www.meteociel.fr/modeles/gfse_cartes.php?&ech=192&mode=0&carte=1

After securing my tickets for Barca V Arsenal at the Camp Nou today, that would top my day off!!

Overall just seeing if the trend exists or not

[Nouska]

10 minutes ago, bluearmy said:

Not the best day for NOAA to pull the gfsp for 4 runs!

anyway, the easterly solution is predicated on trough disruption against the blocks (East Atlantic and sceuro) which push low heights into Europe and advect the cold this way whilst supporti ng the block to our East. The euro just not interested in this solution.

 

Maybe not but at +300 hours, the greatest uncertainty is to our north east.

[Ali1977]

5 minutes ago, Nouska said:

Maybe not but at +300 hours, the greatest uncertainty is to our north east.

I'm hoping the METO meeting today's changes thoughts towards a poss Easterly - a W/NW flow although can be cold , rarely produces snow for us Southeners.

The set up at the minute doesn't look like a prolonged continental flow is poss going off the 06z as the high is only around Denmark and not Northen Scandy, this makes it tough for any undercut.

[nick sussex]

So far the GFS 12hrs run is less favourable, more energy spilling east near Iceland and weaker pressure rises near Svalbard.

If the GFS gets to an easterly here from its T102hrs set up then it will need to overcome more hurdles.

[Singularity]

Hmmn.

GFS 12z as of +105 compared to 06z for same time:

Considering the jet stream charts as well (not shown), I figure it's not quite as good to the NE (Atlantic trough not quite as far west) nor over the U.S. (jet stronger and flatter), but the shortwave to our west has dug south a fair bit better. Risk of that just leading to a cut-off to the SW though.

 

Edit: just looked on Meteociel and the stronger upstream jet makes a hash of things in the Atlantic. Still getting nicely amplified over the western U.S. though and it's a close call with the higher heights over Svalbard as of +126.

It may turn out better than the 00z but not as good as the 06z...?

Edited January 20, 2016 by Singularity

[Timmytour]

11 minutes ago, nick sussex said:

So far the GFS 12hrs run is less favourable, more energy spilling east near Iceland and weaker pressure rises near Svalbard.

If the GFS gets to an easterly here from its T102hrs set up then it will need to overcome more hurdles.

Yep can't see it happening on this run.... not seeing the heights get north over scandinavia like they did on the 6z

[warrenb]

GEM not buying it this time either. Meto is snoozefest.

[Timmytour]

So GFS 12z v 6z for what is now T168

   v 

It's the differences in the runs that please me......not specific ones but, after the relative consistency it had begun to show last night, the inconsistency now shown says that nothing is set in stone and everything's still to play for

 

[Eskimo]

GFS churns out one of the worst runs in 4-5 weeks. GEM even up to +108h shows an agreement with the new GFS run. As Timmy mentioned however, the wild swings even up to the 6 day mark still hold a crumb of comfort. 

Edited January 20, 2016 by PerfectStorm

[Alexis]

 

120 hours is the crunch period - basically a race north east between the low and the high. Low wins in the 12z unfortunately.

Most decent Scandi highs are the result of the Azores High going walkabout like this.

Edited January 20, 2016 by Alexis
.

[Eskimo]

The consistent feature is the Russian high. It's still there, but unfortunately was too far east on the 12z to make any impact on our weather. The high does drift slowly westwards into deep fi. 

(For some reason I can't copy and paste meteociel images)