Model Output Discussion - heading into April

[Methuselah]

Good morning folks. 

And looks like a cooler, more unsettled spell will be with us all, come Friday; so, some standard early-June weather is in store. If the GFS 00Z is right:

    

    

    

    

    

And, despite the run-to-sun synoptic variation, the GEFS 00Z ensembles paint the same picture as before; a short, sharp dip, followed by a more gradual recovery:

     

    

Clearly one for the synoptic soothsayers to unpick!

[northwestsnow]

35 minutes ago, Alderc said:

Unfortunate Cross model agreement through T+144 of area deepening low pressure just off the north east coast of Scotland, the period from day 6-10 appears to show a much slower attempt for things to settle down and a return to more settled a sum like conditions. All areas receiving some rains by D7, but an absolute deluge further north in western Scotland with much more limited amounts further south.

Ironically looking at the charts i assumed it would be the Eastern side of Scotland that would see the most rainfall, closer proximity to the lows..

[Guest]

Continuation of the 'Dogs dinner' output from ECM - interestingly by Day8 ECM in similar agreement with GFS, relaxing high pressure in the Atlantic to the south with the Azores going home and allowing low's to start rolling over the top of the high along a reinvigorated Jet streak taking aim at the UK.....

[Djdazzle]

18 minutes ago, Alderc said:

Continuation of the 'Dogs dinner' output from ECM - interestingly by Day8 ECM in similar agreement with GFS, relaxing high pressure in the Atlantic to the south with the Azores going home and allowing low's to start rolling over the top of the high along a reinvigorated Jet streak taking aim at the UK.....

But just look at that HP at 240, poised to start edging over the U.K. durIng the second half of June. 

[Leo97t]

When it was looking like the Atlantic would stay dead I was optimistic for quick return to high pressure but I'm not too sure now. There looks like quite a lot of possible obstacles to this with Greenland blocking indicated to linger in the longer term, the Atlantic firing up and low pressure to our east. Although as we saw last year it is still possible to ditch this insidious pattern but I suspect most of June will be poor.

[Djdazzle]

4 minutes ago, Leo97t said:

When it was looking like the Atlantic would stay dead I was optimistic for quick return to high pressure but I'm not too sure now. There looks like quite a lot of possible obstacles to this with Greenland blocking indicated to linger in the longer term, the Atlantic firing up and low pressure to our east. Although as we saw last year it is still possible to ditch this insidious pattern but I suspect most of June will be poor.

Background signals still point to an improvement after mid-June. Remember they drive the models, not the other way  round. And the models will not start to pick this up yet.

[Leo97t]

1 minute ago, Djdazzle said:

Background signals still point to an improvement after mid-June. Remember they drive the models, not the other way  round. And the models will not start to pick this up yet.

Yes ik I just remember the unsettled spell was forecast to be a short interlude before a return to high pressure and it took almost 20 days - I would just be weary of forecasting too fast a return to settled conditions but I'm loving the positivity 

[Guest]

11 minutes ago, Djdazzle said:

But just look at that HP at 240, poised to start edging over the U.K. durIng the second half of June. 

Not really, its would be a really slow process if it happens at all. Would be another 3-5days from the there if low pressure again doesn't get stuck over the UK which would be a real possibility - and that's definitely not glass half full stuff. That's 20years of watching models knowing the ECM 240 chart is not great

[Frosty.]

Looking at the Extended ECM 0z operational, I don’t think that’s to bad, shallow trough continuing to fill in-situ ..a recipe for sunshine and heavy slow moving thundery showers and feeling pleasantly warm in the very strong June sun..and just look at that Azores high waiting in the wings..I’d buy that for a dollar!!!!

 

[Guest]

3 minutes ago, Djdazzle said:

Background signals still point to an improvement after mid-June. Remember they drive the models, not the other way  round. And the models will not start to pick this up yet.

But a couple of days ago the background signals were only a showing a 'blip', its now 10days (at least), the back ground signals change and evolve as do the models. As we saw again through winter the background signals didn't pan out that well so not paying too much attention to them to be honest. 

[swfc]

Well after the sunniest spring on record I guess a cooler spell of weather isn't a catastrophe is it.im not bothered about the rain amounts being high as I assume the water levels are pretty good.my biggest worry is a spanking framed hammock I've just ordered and not being able to crash out in it of an evening !!!

[mb018538]

18 minutes ago, Alderc said:

Not really, its would be a really slow process if it happens at all. Would be another 3-5days from the there if low pressure again doesn't get stuck over the UK which would be a real possibility - and that's definitely not glass half full stuff. That's 20years of watching models knowing the ECM 240 chart is not great

Yeah. I think people get fooled as it looks close....but as you say that chart is no quick return to summery conditions. Doesn’t look great this morning. Looking ever likely that after tomorrow the first half of June will be mainly cool....and going by the 00z GFS, quite wet too.

[johnholmes]

19 minutes ago, Alderc said:

But a couple of days ago the background signals were only a showing a 'blip', its now 10days (at least), the back ground signals change and evolve as do the models. As we saw again through winter the background signals didn't pan out that well so not paying too much attention to them to be honest. 

The anomaly charts started to show the 'blip' as you call it 3-4 days ago, and suggested it might last 10-14 days. Last evening Noaa and this morening Ec-Gfs all 3 show it still for the 6-10 day period and possibly into 14. So hardly a blip. Obviously any one day may not be too much like the mean charts but overall I suspect we have somewhere between 7 and 14 days of average to be low temperatures, as to rainfall then that can only be predicted from the daily synoptic outputs. Their reliability is not great beyond 2-3 days ahead for amounts of distribution.

[mb018538]

This isn’t too great from the ECM going through June. @Tamara or anyone else’s  thoughts? Backtracking towards a more unsettled June? That Pacific push not going to materialise?

[Djdazzle]

1 hour ago, Alderc said:

But a couple of days ago the background signals were only a showing a 'blip', its now 10days (at least), the back ground signals change and evolve as do the models. As we saw again through winter the background signals didn't pan out that well so not paying too much attention to them to be honest. 

I was talking about the long term background signals, which are for mid June onwards. I'd pay a lot more attention to those than the models which, as you know, swing around wildly. Yes, they are not totally foolproof, but you'd place a lot more credence on those.

Even the extended ECM is prone to flips - we have seen that many times in Winter.

I am not saying that things won't turn out badly - but let's get some perspective first.

Edited June 1, 2020 by Djdazzle

[Leo97t]

the 06z moves the low away quickly so isn't very unsettled

[LRD]

A few days ago I suspected the upcoming cool spell was being over done. I was wrong (again)

This is a poor chart going into mid-June (although the NW might be ok):

I was hoping for some rain as it's all yellow and brown in the desert that is Bedfordshire. But I was hoping it wouldn't turn cool. A poor 10 days looks to be the form horse from Thursday onwards

[Djdazzle]

Let's look for a few positives!

The GFS 6z has the LP further north and east than on the 0z. So less of an impact on us.

EDIT: Leo beat me to it!

Edited June 1, 2020 by Djdazzle

[Tamara]

1 hour ago, mb018538 said:

This isn’t too great from the ECM going through June. @Tamara or anyone else’s  thoughts? Backtracking towards a more unsettled June? That Pacific push not going to materialise?

 

@mb018538  Thanks for posting that, it is very instructive to the direction of travel during the first half of June and fully explains current NWP

That VP anomaly forecast suggests a Western Hemisphere standing wave (convectively active) and  convective suppression across the Pacific - which is entirely consistent with the convectively coupled kelvin wave (CCKW), as assessed in the previous post(s) which is in the process of departing the Eastern Pacific and is headed to the Western Hemisphere over the course of this week.

This is the cue for angular momentum to slump back as suppression of convection (stable atmosphere and rising pressure) returns to the Pacific with associated negative tendency to the atmosphere.

The current/recent warm height anomaly to our NE is caused to retrograde through a decelerative wave feedback that aligns the downstream pattern to the developing amplified sub tropical high pressure wavelength in the Pacific. Hence the ridge/trough arrangement across the Pacific and US aligns the downstream sub tropical high well to our west in the Atlantic. In turn the fall of pressure in our domain is encouraged further.

The Global Synoptic Dynamical Model (GSDM) which comprises all the diagnostic wind-flow plots is updated daily (pm) but based on a two day consolidated data lag. Currently updated to 29th May which is clearly in advance of the pattern switch. Hence still firmly above average AAM.

The answers as to when we start finding a way out of the incoming spell are going to be found by inspecting the diagnostics day by day and then matching these as to how NWP interpret them. But as in previous posts, it must be stressed that face value ssumptions and conclusions from each NWP suite is not going to be useful or lead to accurate conclusions each time 

It should be possible later this week to post the  momentum budget plots to illustrate the torque processes that will be leading the imminent downturn in momentum associated with the chnaging wind-flow inertia within the tropics as the convective signal takes root in the WH

 

2 hours ago, Alderc said:

But a couple of days ago the background signals were only a showing a 'blip', its now 10days (at least), the back ground signals change and evolve as do the models. As we saw again through winter the background signals didn't pan out that well so not paying too much attention to them to be honest. 

The reasoning for the breakdown has already been fully explained and assessed in at least two my own posts already (as well as others who have contribued in this respect) and is panning out according to suggestions. Possibly slightly faster than might have been anticipated.  So the "background signals" have not changed - it is simply that NWP is fully advertising the cooresponding change over a 10 day period - but which is completely consistent with the diagnnostic as explained above (and assisted by @mb018538 posting the VP 200 tropical convection forecast anomaly up to mid month)

 This does not show how the tropical>extra tropical forcing may be evolving during this time to impact the rest of the month. We have to pragmatically look around each corner as it presents itself rather than start second guessing the next one and even a third one before dealing with first things first.

I think that in general there is too much agitating happening in this thread - and despite reasons provided previously not to agitate   It is still two/three days before the weather pattern really breaks down (as expected) but already there are too many posts extrapolating way out in time the pattern change based on pessimistic hunches and because current NWP doesn't show any return of ridging. It won't within the time-period under dicussion. 

Until the upstream catalyst to hold the amplified wave in the Pacific is removed and set the downstream wavelength accordingly, then it is highly unlikely that the Atlantic/Azores sub tropical ridge is going to have too much eastward ridging influence. It will simply ebb and flow to our west with troughs riding around its northern and eastern flanks. Precisely what NWP is generally advertising at present for the coming ten days (with a couple of days this week until that pattern properly starts establishing). 

How things evolve leading up to mid month will revolve around how far momentum drops back in the intervening time and how much attempt the atmosphere therefore attempts to couple with the ongoing negative tendency (cooling) within the ENSO zone. It is also a case of monitoring the e/QBO descent  - which has been something of an enigma to date with some countervailing and contradictory aspects to its profile layers. Negative tendency with the troposphere and the stratosphere as contrived by a strengthening e/QBO signal is presisely what we don't want to see in order to avoid a cool unsettled spell becoming something sustained towards a default pattern.

These summaries have suggested neither of these are yet apparent, beyond the fluctuation of the tropical>extra tropical cycle of which is about to enter its negative tendency phase (i.e Western Hemsiphere and Indian Ocean wavelength). if this was to become a default standing wave, in tandem with signs of negative tendency between the stratosphere and troposphere implying stronger and longer lasting Atlantic blocking mechanisms migrating to higher latitudes (aka 2007 as worst case scenario) then that would be the time to properly agitate. However it is far too early to do this - not least because proxy data for the atmsophere (e.g AAM, SOI, QBO) are much less advanced and neutral overall than the start of summer 2007 when all where strongly heading into a La Nina & unstable stratosphere/troposhere regime.

The coming few weeks are going to start to answer a lot of these questions. No reason at this time to write off months at a time (or whole seasons) But we cannot fit our weather preferences to the diagnostic and have to present what we find whether it is agreeable to taste, or what we might not prefer

. Answers will present themselves one corner at a time, but with the required time allowed to supply those answers..

 

 

Edited June 1, 2020 by Tamara

[Djdazzle]

As usual @Tamara, an informative post.

[LRD]

22 minutes ago, LRD said:

A few days ago I suspected the upcoming cool spell was being over done. I was wrong (again)

This is a poor chart going into mid-June (although the NW might be ok):

I was hoping for some rain as it's all yellow and brown in the desert that is Bedfordshire. But I was hoping it wouldn't turn cool. A poor 10 days looks to be the form horse from Thursday onwards

GFS is representative of the above 

[Djdazzle]

2 minutes ago, LRD said:

GFS is representative of the above 

I suppose in that time frame, it's not really a surprise. I'm pretty much accepting of a 10 day spell of cooler weather, although rainfall amounts will be variable.

[LRD]

1 minute ago, Djdazzle said:

I suppose in that time frame, it's not really a surprise. I'm pretty much accepting of a 10 day spell of cooler weather, although rainfall amounts will be variable.

I think for Day 10, that's a pretty impressive match

I agree - the idea of a significant cool down is something we need to get used to. Just hope we get some rain. Then thunderstorms, warmth and sun can dominate from later June to early Sept!

[Djdazzle]

1 minute ago, LRD said:

I think for Day 10, that's a pretty impressive match

I agree - the idea of a significant cool down is something we need to get used to. Just hope we get some rain. Then thunderstorms, warmth and sun can dominate from later June to early Sept!

Let's hope so - I'll miss the sun and warmth!

[Yarmy]

Despite the Northerly flow and below average temps advertised on the output, there still doesn't appear to be a great deal of precipitation in the outlook, especially in the East. May was the driest on record in the UK. The situation around here is getting desperate:

Drought fears grow as dry spell continues - Farmers Weekly

WWW.FWI.CO.UK

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Government representatives and farm leaders are to discuss drought measures as a lack of rain further damages harvest prospects across the country. Low