Model Output Discussion - heading into April

[Allseasons-Si]

I hope that the gfs op is an outlier at 180 with it's easterly flow because the control is a beauty with +12 uppers encroaching the south.

 

 

[Methuselah]

I wouldn't call it an 'outlier' exactly, but it's defo on the colder side of the ensembles!

    

[Frosty.]

Here’s a few nice snapshots from the GEFS 6z mean which suggests there’s plenty of settled / pleasantly warm weather coming back following the short but sharp colder shock in the next few days.

 

[Geordiesnow]

Does seem too me the further North and East you are, its likely to be drier with variable cloud and sunshine(best in sheltered Western areas) whilst the further south and west there is an increased chance of seeing thicker cloud with potential rainfall, do hope the trough has less of an influence but the models are agreeing more with the GFS runs of yesterday of the troughing coming into play after midweek. 

Any runs with the high drifting into Greenland is irrelevant too me, too far out to know for sure at this stage. 

[SLEETY]

4 hours ago, Allseasons-si said:

Well i hope the 06z gfs doesn't verify as it is disgusting with a cold NE flow prob bringing wintry showers with possible snow over high ground in the north

a stunning chart for winter but you are 3/4 months too late,move on

Wouldn’t surprise me if these chars verify ,now it’s too late for any meaningful snow,away from high ground,unless we get extremely lucky.

 

Never saw these charts throughout the whole winter,now spring arrives,it’s a different story.How typical!

[stodge]

As we await the 12Z Output, growing signs for an E'ly spell later in the month:

The 06Z GFS Mean tells the story:

Nothing too dramatic on the 850s at this time - the question is whether the air source is going to be more south than north of east.

GEM 00Z OP in a similar place:

ECM not quite there but being dragged toward the E'ly evolution. 

Nothing unusual about an E'ly in late April - we often see one as the PV finally fades - and this can transit into a colder interlude in early May. The GFS 06Z OP retrogresses in far FI with a much colder NE'ly airflow setting up.

[SMU]

If only it was Winter....

[Eugene]

A really nice GFS 12Z with extensive HP to our northwest and cold Arctic northeasterly winds. Will discourage people crowding parks like this weekend and keep people indoors reducing spread. 

[Djdazzle]

13 minutes ago, Eugene said:

A really nice GFS 12Z with extensive HP to our northwest and cold Arctic northeasterly winds. Will discourage people crowding parks like this weekend and keep people indoors reducing spread. 

All in deep FI though.

[Methuselah]

Today's GFS 12Z:

T+72: okay                 

T+168: getting iffy:      

T+240--->: dire!          

Here's hoping that run goes down the toilet!

[mb018538]

Don’t know how many times I have to keep posting the same post....but here we go again for the 12z:
 

No idea why the op run keeps going so far off course.

[Methuselah]

6 minutes ago, mb018538 said:

Don’t know how many times I have to keep posting the same post....but here we go again for the 12z:
 

No idea why the op run keeps going so far off course.

The 12Z is an outlier...

    

 

[Frosty.]

The longer term GEFS 12z mean trend is for high pressure to drift from E / NE to W / NW which opens the possibility of a chilly and less settled late April with winds from the N / NE but that’s a long ways off and there’s plenty of pleasant anticyclonic weather for most of the u k before any changes I mentioned above.

[Singularity]

Models coming together on HP locating just N or NE of the UK next weekend. Not as warm a setup as was being favoured before this weekend's runs. 

Then, we have GFS keen to 'promote' that to major high-latitude block (HLB) status, locating somewhere between NW and N of the UK for at least a few days.

I've contemplated whether the MJO, moving slowly through P1-P2, could be behind that, but the composites aren't supportive (P1 supports a Euro High and P2 a mobile N. Atlantic flow across the UK & Scandinavia). It does cross P8 beforehand, which does lend support to HLB to the NW of the UK, but that crossing only takes 3 days so I can't see a lot of forcing propagating through from that.

Seems to me, then, that GFS is seeing some manner of quick troposphere-level response (QTR) to the final warming of the polar vortex. It's a bit faster and 'sharper' with that than other guidance,including GEFS. Not seeing anything dramatic enough that I'd usually expect a QTR, though. The model has put out small batches of very HLB-dominated runs a few times in recent months, each time with no success, so I'm skeptical of what it's depicting for the final third of April. Especially the 12z... but what I contrast it would make to the opening two-thirds, if it did transpire! 

[stodge]

Singularity makes his usual interesting points - a late April E'ly is hardly unusual and neither is a cold spell in early May - both are usually related to the final warming, the weakening of the PV, amplification in the Atlantic and warmer 850s finally making it to Greenland and Iceland from either the south via a mid-Atlantic HP or from the ESE via retrogression from Scandinavia.

I've put the ECM, GEM< GFS Control and GFS OP charts together - 12Z Output for T+240.

The GFS OP looks the outlier as mb018538 has argued yet when you see the GFS OP consistently as an outlier it can mean it's seen a signal for a trend so I don't dismiss it that easily. The Control is much nearer the Mean while ECM and GEM play the spoiler LP game. It's not surprising as it happens so often whereas GFS OP has a cleaner (perhaps too clean) evolution.

The GFS Mean still suggests an E'ly of some sort in the medium term and beyond so I think that's still the form horse and it's going to be a question of timing. Again, northern blocking late April-early May is nothing unusual. It can drop favourably for the UK and early May is often the best time to visit the NW Highlands and Hebrides which can benefit from the E or SE'ly set up.

[Cheshire Freeze]

GFS FI is quite brutal for a time if you're looking for warmth.

That is a stunning N Atlantic high shown 

Edited April 12, 2020 by CreweCold

[MATTWOLVES 3]

ECM mean keeps us largely under the influence of High Pressure throughout the next 10 day's, bar the odd incursion from a little low to the SW.. I would Imagine it will feel rather warm at times in any sunnier moments, especially with shelter.. But cooler towards the Coasts... The overall 850s from the mean suggest around 0c..this trend in temps shows like holding out to the months end going on the 14 day mean... But it still looks relatively dry for a large chunk... Enjoy your evenings and don't have nightmares...

[Man With Beard]

The ECM has certainly moved towards the GFS for the coming weekend with a slightly less strong ridge to our east, and consequently it has dropped the very high temperatures though still above average with a SE draw - still likely to be in excess of 20C in the southern half at times. 

The UKMO still looks very warm for next Saturday / Sunday though - much better size and positioning of the ridge - would still see low-mid 20s as a possibility :

[johnholmes]

Looking at the 500 mb charts for an idea on what our weather may be in the 6-10 day time frame.

Monday 13 April

Ec-gfs and both have closed upper ridge with ec further n than gfs idea, and still, on gfs anyway, the idea of a closed upper low circulation s of this ridge

Noaa quite a change from the one above; the main trough is not that much different, in position or shape, but it is the large contour ridge couple with +ve heights in the uk area that really show up; still some sign on the 8-14.

So the 3 are fairly similar especially with regard to the presence of ridging in the uk area and probably n of the uk, ? e or w, probably e on balance.

So a quiet spell but probably a better few days sun and temperature the further you are from the east coast!

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

Climate Prediction Center - 6-10 Day 500mb Outlook

WWW.CPC.NCEP.NOAA.GOV

 

[Methuselah]

Today's GFS 06Z suggests this week might be a tad 'less dire' than some of yesterday's runs did...Maybe it's got fed-up of being a cold outlier!

    

[Methuselah]

At T+240, and things still not looking three bad. Okay, so nothing like the heat the ECM was predicting, only a few days' back, but not those raging, frigid NE'erlies either.

    

[Man With Beard]

ECM clusters this morning broadly support the migration of heights to the north-west, but also suggest the op run is being rather fast in doing this. At T168 and T192, you can see the op cluster is the most progressive in removing heights from the UK - less progressive clusters, which look more like this morning's UKMO, hold a slight majority.

  

By T240, even though heights are clearly NW at this point, it isn't clear how the interaction with a trough to the south will play out - scope for an easterly to pick up (probably not a northerly due to the absence of a strong Scandi trough), but also scope for a trough to be retained to the SW or to not be present at all - both latter examples could allow warmer air to continue to filter off the continent. Probably a 50/50 call on a cool/warm balance by this stage, and possibly local affects with east coast areas more likely to be chilly with some sort of northerly influence (this may set in at some point between D6 and D10). NW Scotland may do well in this set-up.

By D15, it looks like the NW ridge remains favoured - though with anomalies being slight over Europe, no real way of predicting how this will affect the UK at this stage.

[Methuselah]

25 minutes ago, Man With Beard said:

ECM clusters this morning broadly support the migration of heights to the north-west, but also suggest the op run is being rather fast in doing this. At T168 and T192, you can see the op cluster is the most progressive in removing heights from the UK - less progressive clusters, which look more like this morning's UKMO, hold a slight majority.

  

By T240, even though heights are clearly NW at this point, it isn't clear how the interaction with a trough to the south will play out - scope for an easterly to pick up (probably not a northerly due to the absence of a strong Scandi trough), but also scope for a trough to be retained to the SW or to not be present at all - both latter examples could allow warmer air to continue to filter off the continent. Probably a 50/50 call on a cool/warm balance by this stage, and possibly local affects with east coast areas more likely to be chilly with some sort of northerly influence (this may set in at some point between D6 and D10). NW Scotland may do well in this set-up.

By D15, it looks like the NW ridge remains favoured - though with anomalies being slight over Europe, no real way of predicting how this will affect the UK at this stage.

And with the GFS in broad agreement, HP ending-up somewhere to our north, I eagerly await the outcome of May-time's accelerating continental warming...

    

[knocker]

34 minutes ago, Man With Beard said:

ECM clusters this morning broadly support the migration of heights to the north-west, but also suggest the op run is being rather fast in doing this. At T168 and T192, you can see the op cluster is the most progressive in removing heights from the UK - less progressive clusters, which look more like this morning's UKMO, hold a slight majority.

  

 

B

Allowing for the limitations of the map projections  I would have said the det run is pretty close to main cluster at 168 and the jury is still out at 192

[mb018538]

Looks like we’ve got some Northern blocking incoming (who’d have thought it eh), so will have to see where the pieces fall as to what we get. It may be the north and west is best, and we could get a strong cool easterly in the south, with a greater chance of some ppn. Ensembles have really backed down from the very warm suggestions of a couple of days back (mean down to 5 from 8), though still a fair number showing some warmth in a weeks time before it turns cooler.