Model output discussion - 20th Feb onwards

[Daniel*]

1 hour ago, Costa Del Fal said:

Sorry if I misunderstood. Not been feeling to well recently so been reading quite fast to try and catch up on things. 

I suppose what if anything turns out as good as originally modelled with our weather. Lol. Agree to an extent perhaps  the best of the temps look a little less widespread now but nothing unusual to see. Mid teens should be quite achieveable in the sun though and certainly it should feel very pleasant. I'd be stunned if it's a cloud fest, particularly as the high looks to set up shop very close to us or even on top of the U.K. Maybe cloudier at first though as the warm uppers override cold sea temps. 

One day in December in my back yard it reached 16C with limited sun remarkably overcast an extradonairy month for all the wrong reasons, I doubt this will be surpassed anytime soon. 

[March]

If the BBC say 11-12C for around 5+ days away I say that's a good sign as they always underrepresent mild at that range. Or at least they did all last spring/summer. 

[Milhouse]

Whilst cloud cover and potential frost and fog are still possibilities it does look like the main talking point will be the start of a generally drier and settled period, one that weve not seen for a very long time. At times such as this though, I will always remember the high pressure spell of early March 2012 which failed to deliver the warmth that was promised with hp centred too much over the UK. The end of the month made up for it though.

 

 

[IDO]

Yes its great to see 8 days plus of UK HP dominated weather with at least a few days of a very mild upper flow thrown in for good measure:

D4 and a bit:   D13: 

This current "cold spell"  down south has just been cold rain and another 10 days of that was not a tempting prospect.

After that, a negative AO and probably colder, but no clear signal as to where the blocks and cold will position themselves for our island just yet, though a continuation of a UK HP cannot be ruled out with the Azores being such a player this winter. Fingers crossed.

[chris55]

Id bet there will be plenty of breaks in any cloud that is under the high come the weekend. The general orientation doesn't scream cloudy high to me for the majority, especially as we head into next week. Plus with a stronger sun emerging it'll soon get to work burning off any residual cloud. Id say mostly clear skys with potential for a little fog to come down overnight.

[Thundery wintry showers]

I think it depends on what model run you're looking at.  Most previous runs had the high pressure barely covering the south, and a moist tropical maritime flow on its northern flank, but the GFS 12Z has the high on top of the British Isles, which would most likely lead to somewhat sunnier conditions.

GFS 12Z:

http://nwstatic.co.uk/viewimage.pbx?type=gfs;date=20160306;time=12;ext=168;file=h500slp;sess=5e33d52352dfc1d6f04cebbcc5d18330;

ECMWF 00Z:

 

Edited March 6, 2016 by Thundery wintry showers

[Singularity]

That sure is some wind/rain event that GFS makes of the midweek system;

3 hour snapshots:   

Accumulations prior to event:   After event:  

70 mm in little more than 30 hours for some parts. I wouldn't consider that extreme if it was restricted to high ground, but that's not the case here... indeed totals where the air runs into such terrain would probably be 10-20 mm higher.

 - but before anyone goes out to buy a boat, ARPEGE develops the low as it departs the UK to the SE, which means we escape with totals about a tenth of what GFS produces. 

So where's the middle ground? NMM perhaps?

  

30-40 mm widely with 50 mm locally and up to 60 mm over high ground. Sounds reasonable enough IF the low develops as it reaches the UK rather than as it departs. Some snow is suggested as colder air cuts in behind, due to the sheer intensity of the precipitation... but unless that's still being shown in a couple of days time, salt is probably best of taken with that output rather than put on the roads.

 

Longer term, we continue to see the dry theme strongly represented out to at least 17th, with cool nights (perhaps cold with a touch of frost in parts) and mild to very mild days (10 to 16*C) - unless fog develops widely and lingers through the morning. 

After that comes the increasing Arctic Heights and the chance of our block being drawn north. I consider GFS' application of pressure on the blocking system from the Atlantic to be rather dodgy given the background signals. Given that the falling AO looks to be well timed to throw some very cold air west from Siberia, I am seeing a not inconsiderable risk of an exceptionally cold blast of air from the NE/E in the third week of March. Trying to force low pressure over the top of blocking highs, in the face of great resistance, is a classic foible of the GFS model. 

With GFS having increased the -ve AO signal compared to the previous few runs (with precursor adjustments from around +120), the 12z ECM needs watching for such a trend.

[Guest]

Since my updates yesterday (see my posts on pages 57 and 58) there are some further slight upgrades on today’s charts (March 6th) in the mid-month AO and MJO trends with plenty to keep the "coldies" interested.

AO Ensemble Charts: 

Apart from one ensemble member, all the other members are continuing to trend down.  Most move into positive territory later this week but peak around next weekend before falling back to neutral early next week and then progressively into negative territory from around March 14th/15th.  By March 17th/18th they are trending downwards quite strongly with the AO index looking likely to remaining negative for at least a few days and may be rather longer.  

MJO Ensemble charts:

Here are todays MJO ensemble charts for the big 3 and Kyle MacRitchie’s for March 6th.  

UKMO:   http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/CLIVAR/ukme.shtml

ECM:   http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/CLIVAR/ecmm.shtml

NCEP/GEFS:  http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/CLIVAR/ncpe.shtml

Kyle MacRitchie:  http://www.kylemacritchie.com/real-time-maps/realtime-mjo/

UKMO have moved back to a slightly improved state, with most ensemble members now keeping the MJO out of the circle of death and moving it into phase 1 today, albeit with low amplitude. They then take it quickly into phase 2 but several members stay in phase 1 slightly longer and go for slightly greater amplitude.

ECM is very much in line with UKMO in terms of timing through the phases but with a slightly greater spread of ensemble members with a few more passing through the circle of death but one or two at much greater amplitude.

NCEP/GEFS take quite a different view. They keep the MJO in phase 1 for longer but then most of its ensemble members enter the circle of death with almost a complete stall. There are signs from the very confused looking chart that a few members look like they might re-enter phase 8 or phase 1 again! It was only about a week ago that this model was consistently much more bullish than UKMO and ECM with a more extended period in phases 8 and 1 and at much greater amplitude.

Overall, the big 3 show a very slight upgrade on yesterday’s charts.

Kyle MacRitchie continues to take a more positive view. He actually held the MJO back in phase 7 for longer – this was when the big 3 had taken it into phase 8, stalled at that point, then moved back into phase 8 several days ago and then downgraded their predictions showing much less amplititude. Kyle has the MJO only moving into phase 8 tomorrow (March 7th) and then pushing through phase 8 and on into phase 1 on March 11th/12th and eventually through to phase 2 on March 16th/17th. All 4 of his ensemble members retain good amplitude throughout this period.

So, Kyle has the MJO in the key phases 7/8/1 through to and just beyond mid-March. I believe that this is highly significant as it coincides with the predicted peak in the current SSW event with the stratospheric vortex already having split by then, we should have all the ingredients in place for some strong HLB. This is supported with the AO index trending negative. 

My view is that there remains a huge amount of uncertainty among all the main models (the ones that we usually refer to on this thread) and they are really struggling with the timing and impacts of the SSW, the negative AO and the MJO. The continuing trend is for these events to start impacting around mid-March. In fact, several experts feel that the current SSW will impact much more quickly than a mid-Winter event. If Kyle MacRitchie is right about the MJO then this, together with the AO going strongly negative should favour significant HLB by mid-month. Perhaps we will see a dramatic pattern change in about 10 days’ time.

This is purely my take on things and perhaps I am being overly optimistic. I hope that Judah Cohen’s AO report, due out later tomorrow, continues to show the trop vortex or a major lobe of it moving down into Europe around mid-month.

As I said yesterday, the AO charts come from NOAA. So, I would expect that their 8-14 anomaly charts start moving towards the HLB pattern during the next few days. There may already be signs of it but remember the “mean” chart will take longer to adjust with the earlier flatter flow and/or higher pressure nearer the UK to come first. Do NOAA publish any anomaly charts showing the daily changes or a chart showing the general trend?

While we continue to be in this very unusual set-up under the influence of the major impacting factors (a late/mature ENSO; a strong SSW event with a probable full split of the strat vortex and a complete strat/trop coupling;  the MJO in phases 8 and 1, possibly at decent amplitude and the negative AO reflecting the HLB pattern) then I shall continue to produce similar updates.

Feedback Noted: I see that several fellow posters have remarked about my comments regarding the negative AO. I can see how my wording in my paragraph above beginning..."My view"...caused the confusion. I realise that the AO indices that I have been publishing and commenting on in several recent posts are a predicted measure of HLB and are not another teleconnection. If you check my words in other paragraphs in this post or in my recent posts you will see that there is no confusion. I am sorry that I muddled up the wording in the offending paragraph and I hope that other readers of this post have not been misled.

Edited March 7, 2016 by Guest
sluggish links - hopefully improved

[Frosty.]

The Gfs 12z shows a lovely spring like spell on the way with pressure and temperatures rising, low teens possible next Friday and then widely low to mid teens celsius next weekend until the middle of the following week with an anticyclone centred over the UK, the high then slowly drifts further north by north west in response to an arctic plunge through Scandinavia and colder air filters across the UK later in week 2 which increases the risk of night frosts but really, I'm liking these charts which show an early taste of pleasant spring weather..I mean, what's not to like about this after the abysmal winter we have endured!

[TomDav]

Cold pool very close at 300hrs on the GFS 12z

 

[knocker]

The GEFs anomalies this evening continuing the transitional theme of the last few days. The 6-10 has the Canadian vortex.Atlantic trough still in situ with a HP cell very adjacent to the UK. Thus a period of settled weather with temps above average that has already been well sign posted. Then in the later period the Canadian vortex is no more and the Siberian namesake takes centre stage (well partly).  The trough associated with this stretches south over eastern Europe and the UK HP cell retrogresses to become a ridge to the west. This results in an upper flow N of west which brings the temps over the UK to around average. Where we go from here is open to various interpretation, including the possible amplification of the HP to the west, but this is way above my pay grade.

Await the EPS and NOAA with some anticipation

Oh and I'm not spotting very cold air anywhere close.

Edited March 6, 2016 by knocker

[A.J]

not sure if there's any other model support, but the GFS output in the short range (T60) throws up a very interesting low pressure with was touched on earlier.......it wouldn't be beyond the realms of possibility for parts of Northern England, the midlands and maybe even central southern england to get a serious dumping of snow.........unlikely I know, but certainly something of interest, you never know!

subsequent runs might make nothing of it, for sure but worth keeping an eye on

 

[Gael_Force]

1 hour ago, Bring Back1962-63 said:

My view is that there remains a huge amount of uncertainty among all the main models (the ones that we usually refer to on this thread) and they are really struggling with the timing and impacts of the SSW, the negative AO and the MJO. The continuing trend is for these events to start impacting around mid-March. In fact, several experts feel that the current SSW will impact much more quickly than a mid-Winter event. If Kyle MacRitchie is right about the MJO then this, together with the AO going strongly negative should favour significant HLB by mid-month. Perhaps we will see a dramatic pattern change in about 10 days’ time.

I'm wondering how the models are "struggling" with the AO. The index forecast you posted is just a reflection of how the various ensemble members model the increasing heights in the Arctic region; it is not another separate teleconnection for them to have to resolve.

[I remember Atlantic 252]

no ECM tonight folks? or is it hour later now

[Gowon]

Nice JMA tonight, it disrupts the trough and an Easterly sets up after the high nudges further north.

[chris55]

25 minutes ago, ajpoolshark said:

not sure if there's any other model support, but the GFS output in the short range (T60) throws up a very interesting low pressure with was touched on earlier.......it wouldn't be beyond the realms of possibility for parts of Northern England, the midlands and maybe even central southern england to get a serious dumping of snow.........unlikely I know, but certainly something of interest, you never know!

subsequent runs might make nothing of it, for sure but worth keeping an eye on

 

There is a small risk i would say, the models today certainly do ramp it up and ECM has it centred in the channel at T72.

GFS highlights how heavy the ppn could be as well,

Lots and lots of variables needed to fall into place to get some snow out of it, though not impossible.

 

 

[chris55]

Following that ECM begins to build in the high pressure from the south and by Monday we are all basking in the warmer settled spell

Edited March 6, 2016 by chris55

[Frosty.]

The GEFS 12z mean shows high pressure domination from next weekend onwards...becoming settled and spring like!

[SMU]

Well despite checking out of winter I would happily take the JMA as last chance saloon !

216 would see that -10c line in England !

[chris55]

And then we finish off with this....

 

Easterly incoming anyone lol! Certainly lots going on out to day ten tonight!

Edited March 6, 2016 by chris55

[nick sussex]

Could be a dramatic switch between some warmer weather and a bitter ne flow if that chunk of the PV drops south into Scandi.

The ECM shows that type of scenario being possible, its all about getting any block aligned favourably to draw the flow in from the ne.

Without the major SSW I'd be very dubious but with that we are likely to see some unusually cold conditions drop further south in the NH.

It might just tease and hit the UKs cold and snow forcefield and head down towards eastern Europe but its impossible to rule anything out, we'll see over the next few days.

 

[Purga]

As they say on a question of sport - what happens next??

[Cloud 10]

The GEFS control run really going to town with the scandi trough!

 

[knocker]

52 minutes ago, Gael_Force said:

I'm wondering how the models are "struggling" with the AO. The index forecast you posted is just a reflection of how the various ensemble members model the increasing heights in the Arctic region; it is not another separate teleconnection for them to have to resolve.

Quite. It's just an index of surface atmospheric pressure patterns.

Edited March 6, 2016 by knocker

[Frosty.]

Looking beyond the upcoming Anticyclonic spell with above average temperatures, the GEFS 12z mean shows a change to colder and more unsettled weather later in the month with a large scandi trough extending it's influence across the UK but that's a long way off and after the unsettled conditions in the week ahead it's looking very nice with high pressure settling things down and warming things up.