Model Output Discussion 01/09/17

[Sky Full]

GFS predicting the coldest upper air so far this Autumn to spread across the UK on Sunday bringing the possibility of wintry precipitation almost anywhere in the west....

   

   

   

   

Not bad at all for November and SO much better than last year and the year before at this time of year so even if it doesn't quite materialise like this there is much to be optimistic about.  Dare we hope for even better charts in December?  It's been a long time coming....

[karlos1983]

9 minutes ago, Summer Sun said:

At t168 this morning UKMO and GFS are fairly close with high pressure to the south and low pressure to the north-west

Do my eyes deceive me, or is there also a Mid lat High edging north ....

[northwestsnow]

UKMO model really struggling to get colder air in actually, perhaps beeb going off this model?

Early hours sunday is 144 and the 850's are hardly conducive to snow for pretty much everyone away from high ground in NW Scotland

 

[Summer Sun]

The ECM ens continues to show a downward trend for temps later in the week

Northern Scotland

[Geordiesnow]

3 minutes ago, northwestsnow said:

UKMO model really struggling to get colder air in actually, perhaps beeb going off this model?

Early hours sunday is 144 and the 850's are hardly conducive to snow for pretty much everyone away from high ground in NW Scotland

 

Yep the UKMO seems to followed the GFS of last night in respect of the details for us so instead of a nice convective NW'ly coming In, we got cloud and rain instead. Details are still not certain so I'm not getting my hopes up that the ECM is right sadly. 

[Frosty.]

42 minutes ago, johnholmes said:

This morning ECMWF-GFS both show a meridional flow into the UK, Ridging/+ve heights in the Atlantic up to Greenland with very marked troughing over the UK and then down into Europe. The NOAA version last night did not show this so a sitting on the fence time until all 3 are very similar for a couple of days. 

John is spot on as always, if I could have changed what I said in my earlier post it would be that taking the 00z runs at face value, all roads appear to lead towards cold with a growing chance of snow which is what I'm hoping for, as I'm sure are many on netweather..fingers crossed!

[northwestsnow]

Well last one from me i have to head out but already GFS6Z looks colder by 72

[knocker]

Although better agreement than last night there are still major differences between the GEFS and EPS anomalies. Upstream these concern the Siberian vortex and the Aleutian ridge (or not) although the lobe in NE North America is okay. Downstream although the percentage play is for ridging in mid Atlantic, the intensity and orientation of this, in conjunction with the trough further east, is yet to be finalized (for one the EPS is far more amplified) and thus high confidence in the detail remains a tad elusive,

[Jonan92]

In this run the shortwave takes longer to clear, the block starts rising later and will be weaker.

00z

06z

[frosty ground]

5 minutes ago, Jonan92 said:

In this run the shortwave takes longer to clear, the block starts rising later and will be weaker.

00z

06z

Not sure the Mid Atlantic Block looks stronger, also increased heights to our north. 

Edited November 20, 2017 by frosty ground

[karlos1983]

Just now, frosty ground said:

Not sure the Mid Atlantic Block looks stronger, also increased heights to our north. 

Some nice WAA heading to Greenland to boot!

 

[weirpig]

Way in fi now   no point in looking any further.  Northerly looks odds on at the moment  how low the uppers will be and were is still up in the air.   Also a pattern is emerging for renewed heights into greenland after that.    decent charts at the moment.

[Dennis]

is it possible....exiting times ahead

[karlos1983]

Forgetting the detail at this point, this screams potential to me. PV is on Holiday, and finally heights to our south diminishing! I've seen enough.

As Dennis says, exciting times.  

Edited November 20, 2017 by karlos1983

[snowblizzard]

14 minutes ago, karlos1983 said:

Forgetting the detail at this point, this screams potential to me. PV is on Holiday, and finally heights to our south diminishing! I've seen enough.

As Dennis says, exciting times.  

 Is the High 1040 to our West likely to retrogress towards Iceland/Greenland?

[swfc]

5 minutes ago, snowblizzard said:

 Is the High 1040 to our West likely to retrogress towards Iceland/Greenland?

Looking at the nhp no it will topple

All in fi tho

[bluearmy]

Looking at the eps extended mean it looks very promising with low euro heights persisting. However, the clusters reveal a variation in how this is happening so best to give the evolution some time so that the 6/8 day firms up. 

[knocker]

The METO have issued a heavy rain warning for Weds in the north west of England

Edited November 20, 2017 by knocker

[Nick F]

As John mentioned earlier, the models firming up on a meridional pattern developing downstream over the Atlantic and northern Europe by the end of the week, as a deep trough digs down over eastern N America, a ridge pushes north to Greenland while a deep trough digs south over Europe.

Longer term, the 00z EPS extended to day 15 and the EPS clusters suggest -ve height anomaly / troughing over mainland Europe while +ve heights remain to the W and NW - which always a good sign. However, we've seen a lot of chopping and changing over recent days from the ensemble guidance, so I would personally want to see more runs to firm up on this signal for potential for pressure rises to the N and NE above the Euro trough leading to a flow E of N eventually.

Although the models are agreeing on the broadscale 500mb pattern, there are some difference from the morning's operational / high res runs with regards to the surface. Both 00z UKMO and GFS high res runs had a low in the west and a low to the NE Thursday night / early Friday, GFS has low to the W of Scotland while UKMO a low to SW of Ireland. Both delay the onset of cold artic flow expected to sweep south this weekend, by this secondary low that develops along the cold front, while the ECMWF high res hasn't got this low to the west and brings in colder air quicker to end the week.

 

However 06z GFS seems to remove this deep low near the west the 00z had early Friday!

00z and 06z GFS for 00z Friday -  spot the difference easily west of Scotland!

00z 06z

This differences so early on at the surface, with regards to secondary low development, seem to be why the BBC may be a little uncertain with regards to the potential for cold air sweeping south to end the week and through the weekend and its extent and coldness.

UKMO has this secondary low (note I don't like using the word 'shortwave') running across southern areas Saturday - delaying the cold - GFS and ECMWF don't have it though.

GFS and ECMWF bring another secondary low SE from Greenland / Iceland area early next week, differences in track this far out, which could reload a N or NWly flow from the arctic by Tuesday. Thereafter potential for pressure rises to the north which may allow a more NEly flow to develop - big uncertainties as early as this weekend with regards to arctic blast, so although interesting and nice to see the potential next week, it maybe worth not looking too far ahead for now!

Edited November 20, 2017 by Nick F

[karlos1983]

Just for fun... P20 anyone? 

Pretty decent agreement in the highlighted area for colder uppers to arrive.

Edited November 20, 2017 by karlos1983

[Methuselah]

I'm thinking the HP out in the Atlantic might eventually hold the key to our future sanity:

Will it ridge north all the way to Greenland, and provide us all with some much-needed early season snowfall with winds directly from the Arctic? Will it link-up with any height-rises that might form in the Scandinavia region and, once again, provide us all with some much-needed early season snowfall? 

Or...will it simply sink into France-Spain or the Azores, and provide us with endless weeks' mild, damp dross?

In all honesty, I haven't a clue...

Edited November 20, 2017 by Ed Stone

[weirpig]

Chilly set of ensembles  on the 6z run  below is the graph for middle England, It shows chilly Temps coming up  also not without interest for a touch of the white stuff  even this far South.   the mean really dosent get above zero

Edited November 20, 2017 by weirpig

[Singularity]

13 minutes ago, knocker said:

The METO have issued a heavy rain warning for Weds in the north west of England

Yes this does look pretty unpleasant for the NW with the rain band becoming quasi-stationary along a line pretty much as visible in the chart you've shown, leading to daily totals (as the Met Office outline) of 25-50 mm widely and higher (perhaps much higher with 100 mm mentioned in the CF's assessment) than that on west-facing slopes of high ground.

With that event on the way, I'm hoping UKMO is wrong to make so much of the Fri-Sat low and track it so far north; that too may be a large quasi-stationary front type event capable of producing similar daily totals. GFS 06z has across the SE but not for too long, and ECM 00z only grazed the SE corner, so there's hope.

 

Very interesting signs longer-term have developed over the past 48 hours. Need to see them maintained for a few days before properly raising the bar of expectations.

[karlos1983]

Very encouraging set of 15 Day ensembles.

Cant upload image since the server went down for some reason 

Edited November 20, 2017 by karlos1983

[northwestsnow]

3 minutes ago, karlos1983 said:

Very encouraging set of 15 Day ensembles.

Cant upload image since the server went down for some reason 

I was expecting something seasonal mid to long term as per Bluearmy post about ext eps, also the beeb monthly talking about colder and drier weather as we go into December- while we have low pressure sinking into Europe it aint going to mild.

Edited November 20, 2017 by northwestsnow