Model Output Discussions 12z 08/03/17

[Frosty.]

Where did next weeks warm spell go? The Ecm 00z for example looks much cooler than last evenings 12z.

[knocker]

The ecm has the front approaching Cornwall Sunday morning and slowly tracking north east in the next 24 hours petering out as it goes. Probably the main section of the rain moving east over France.

Then comes the pattern change and it too is centering the high cell to the north with the easterly component. But just to complicate matters it swings the high/trough on it's axis so ending with HP to the NW and LP to the SW. So certainly a dry scenario with temps around average but the door is ajar to various possibilities as we lose the Canadian lobe.

Edited April 26, 2017 by knocker

[Andover]

That Jay Wynne will have some egg on his face after his forecast was last night, looks a good deal cooler for next week going by what I've seen this morning.

[Frosty.]

I think it's best not to have knee jerk reactions to the 00z output as a day is a long time in model watching and the 12z could be a different story. Today's MO update will be interesting as to whether it sticks with the summery outlook or not..I hope we see a warm / very warm early-mid May.

Edited April 26, 2017 by Frosty.

[northwestsnow]

1 hour ago, Frosty. said:

Where did next weeks warm spell go? The Ecm 00z for example looks much cooler than last evenings 12z.

It was 168hrs and beyond mate.Trust nothing beyond 120 would be my advise,  we may have seen a couple of cool outlier solutions but i wouldnt be suprised if we end up with huge Northern blocking at the ecm/ gfs ops suggest..

[DR(S)NO]

2 hours ago, Frosty. said:

Where did next weeks warm spell go? The Ecm 00z for example looks much cooler than last evenings 12z.

 

1 hour ago, Frosty. said:

I think it's best not to have knee jerk reactions to the 00z output as a day is a long time in model watching and the 12z could be a different story. Today's MO update will be interesting as to whether it sticks with the summery outlook or not..I hope we see a warm / very warm early-mid May.

Yeah Frosty, best to not have any knee jerk reactions........

[stodge]

Morning all

As I've said in my In Depth analysis (shameless plug), there's a good deal of agreement across models this morning.

As I said yesterday, the source of the air flow would be crucial and the idea of an E'ly or SE'ly sourced from warmer regions has been diluted somewhat in favour of a more ENE'ly flow from west Russia which will obviously be cooler.

There are more differences in the orientation and position of the trough than the heights which look remarkably similar into next week.

[Frosty.]

9 minutes ago, DR(S)NO said:

 

Yeah Frosty, best to not have any knee jerk reactions........

HAHA yes but I'm not writing it off, just saying the 00z looks cooler than yesterday's runs regarding next week.

[Methuselah]

5 minutes ago, Frosty. said:

HAHA yes but I'm not writing it off, just saying the 00z looks cooler than yesterday's runs regarding next week.

Indeed. But, if you live in either NE England or E Scotland, 'haar haar' might be an apter response. However, that said, don't 'fret' it! 

Edited April 26, 2017 by Ed Stone

[Frosty.]

Just now, Ed Stone said:

Indeed. But, if you live in either NE & or E Scotland, 'haar haar' might be an apter response. However, that said, don't 'fret' it! 

Very witty Pete

[Singularity]

Slight differences in jet stream orientation in the N. Atlantic having big impacts on the location and movement with time of the big ridge next week.

This is an occasion where we could do with a little of the northern jet steam arm remaining in place to keep lower heights between Greenland and Iceland and so allow the ridge across the UK to remain largely independent of the blocking highs across the Arctic.

This year is displaying a propensity for extensive high-latitude blocking which would be if some concern for the summer season except that it's still only April and a big shake-up is fairly common by late May to set the stage for June and much or all of July.

The other day I mentioned some similarities in the overall global picture to 2007 - this was not the same as saying that the summer will be extremely wet as some inferred; rather that there is an increased chance of an unusually wet outcome. Research since that summer has identified unusual Indonesian rainfall patterns as a key contributing factor to what could otherwise have been a reasonable summer with plenty of warmth on offer. Hopefully we'll avoid that this year. Another big question is whether Arctic blocking continues or not, and in what configuration. I have yet to find convincing evidence either way with respect to whether low Arctic sea ice extent or area encourages such blocking; the low-ice summer of 2012 was very blocked for example, but 2016 was not. There is a tricky-to-resolve interplay between altered jet stream patterns and increased heat and moisture availability to low pressure systems.

Given the Arctic blocking being modelled for May 2017, it sure does appear likely that low sea ice extent and/or area will be a present factor for the summer, and quite likely record low. Fascinating times ahead - if a bit worrying from a broader climate perspective.

[knocker]

Significant points with the EPS this morning

• Weakening of the Canadian lobe as the high pressure builds adjacent to the UK and surges north west. Thus cutting off the energy feed into the Atlantic.

• Simultaneously intensifying the Russian arm and tracking it west.

• Thus with the surface high cell over Iceland by day ten and the low pressure WSW of Ireland around 25W an easterly component over the UK veering south east over the eastern Atlantic.

• Ergo weather continuing dry but temps hovering around the average

• Moving into the 10-15 period the pattern continues to develop with high pressure in the southern Greenland area and the cut off low pressure way to south with the Atlantic becoming very much an inactive zone. The key here may well be the trough to the east edging ever closer which may just put the UK back into a cooler northerly.

• Still much to be resolved and the next two or three days should be quite interesting

Edited April 26, 2017 by knocker

[Frosty.]

A cool breezy and cloudy Gfs 6z next week with even some rain around, high pressure gets sucked NW and the run ends with another chilly Northerly as a result of retrogression.

[northwestsnow]

10 minutes ago, Frosty. said:

A cool breezy and cloudy Gfs 6z next week with even some rain around, high pressure gets sucked NW and the run ends with another chilly Northerly as a result of retrogression.

Aye a dreadful 6z with temps really struggling, still time for a switch back karl but lets face it, for our grotty climate what can go wrong will go wrong..

[Frosty.]

18 minutes ago, northwestsnow said:

 karl but lets face it, for our grotty climate what can go wrong will go wrong..

Aye, not just in winter.

Whilst the runs so far today have been a disappointment in comparison to yesterday..The latest update from Exeter is only delaying the good weather by an extra day or two with a significant improvement from later next week with high pressure, increasing amounts of sunshine and warmth which continues into the extended outlook too.

Edited April 26, 2017 by Frosty.

[Tamara]

I think we need to be cautious of  comparisons heading through Spring and towards Summer between 2007 and 2017. There are some similarities for sure in a few respects, but also subtle and important differences

1) In 2007 at this time we were progressing quickly into a moderate La Nina event with global atmospheric angular momentum falling significantly into the summer. In mid late Spring 2017 we are firmly in neutral ENSO conditions with a slight bias towards official El Nino conditions developing from later this summer

http://ggweather.com/enso/oni.htm

 

2)  QBO

Easterly (negative) downwelling phase much more progressed in 2007 than 2017

2007
hPa  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC
10   -226 -318 -326 -338  -368   -208  -15   50    107   111  180   213
12   -253 -313 -318 -336   -353   -371 -142 -15    60    109  172  226
15   -266 -296 -317 -321   -320   -330 -329 -245 -70    42    115  192
20   -231 -226 -250 -278   -304   -318 -324 -333 -343 -319   02  125
25    -89  -69   -115 -233    -285   -292 -324 -332 -339 -331 -296  -28
30     54   53    14    -147    -253    -297 -313 -316 -321 -316 -320 -265
35     82   90    80     22      -184    -262 -293 -288 -298 -289 -290 -306
40    97  107   111    90       -71     -204  -242 -260 -265 -263 -262 -278
45  107  111   109   120      49      -126 -171  -212 -221 -218 -230 -249
50   96  111  103     128       92      -39  -100    -151 -162 -175 -204 -200
60   55   91   78       114        109      56   -13    -40   -33    -51  -98 -100
70   41   34   55        91         99       79      21    -08    12     28   04  -30
80   33  -09   37       26          69       51      16     13   21     16   22   -33
90   35  -17   17      -17          35      -10     -11    -39  -20    -80  15 -115
100   08  -20  -10    -29         00        -60    -61    -106 -117 -204  -61 -210

2017
hPa  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC
10    2   10      -162
12   76   75     -40
15  112  123   73
20  142  159  131
25  161  169  145
30  171  177  153
35  169  185  155
40  165  170  158
45  155  166  141
50  132  145  107
60   77   94   28
70   15   36   10
80  -22   21   11
90  -55  -21   -1
100 -150  -80  -38
 

3) Taking 1) and 2) together, progressively tanking -ve GLAMM and QBO teleconnected strongly with (at the time) record low arctic sea ice to favour anomalous arctic heights and a southerly tracking jet in 2007.  The risk of those synoptics happening again this year cannot of course be completely ruled out in times that are more and more unprecedented year on year in terms of looking at previous analogues, but suffice to say residual +QBO at the surface *probably* lasting well into the summer should align well with relative angular momentum propped up by the expected ENSO state in the Pacific (quite unlike 2007) to produce at least some periods of Western European ridging (fine warm summer conditions) rather than any predominating higher latitude blocking and UK/European trough.

In that regard, nothing untoward should be read into the present attempts by the models to programme northern blocking into the new month. It should be expected that negative zonal winds across the polar field in conjunction with the final warming of the stratosphere should produce at least one or two phases of HLB at this time of year, but without the wider background ingredients in place such as were present in summers like 2007, little more at this time should be read into trying to extrapolate these months ahead.

4) Of the here and now:

Both total and relative angular momentum have responded to tropical activity passage through the Pacific with westerly winds added to the global circulation

Tropical convection patters are the engine of future pattern changes it is true, but as applies in winter and any other time of year, this is not a stand alone phenomenon and it is always wiser to look at the whole atmospheric circulation budget which includes the extra tropics and reflects total global wind-flow. This is measured and reflected by the Global Wind Oscillation (GWO)

The amount of total "westerlyness" in the global circulation determines the predominance of downstream amplified ridges when angular momentum is higher under these conditions

The atmosphere is in not too different a place to where it was in February. This was the last time we saw a notable spike in angular momentum tendency and which coincided with attempts to build higher latitude blocks early in that month. This time, the FW of the stratosphere has augmented that process and the tropical signal in the Pacific has been a little more durable.

Accordingly, the GWO has mirrored the phase progression seen in February but with a marginally stronger and slightly slower amplitude orbit into the Nino type Phases 5,6,7.

We should expect angular momentum to start falling back as the current tropical wave fades from the eastern Pacific.

   

Caution though should be taken in terms of how the models programme the mid and higher latitudes over the coming first half of May period because there is a highly likely absolute floor limit to the fall-back of AAM in terms of the evolving ENSO background.

In this respect, another litmus test of where the atmospheric/ocean circulation is jiving is the Southern Oscillation Index (SOI). In association with tropical and extra tropical signals, whilst still officially neutral this has been tanking negatively once again with El Nino type westerlies being injected into the global circulation and rossby waves transferring polewards from the tropics.

Looking further ahead, if we take into account the periodicity of the MJO (up to 60 days) and the general ENSO trends in the Pacific, then it is not unrealistic to expect another eastward progressing MJO wave as we usher in official summer

In the absence of the -QBO wave prematurely downwelling as occurred in Summer 2007, and no La Nina descent signal in the Pacific expected to allow angular momentum to fall too far, then the effects of the seasonal stratospheric break-up should be able to diffuse in a way to favour at least some summertime mid-latitude ridging with phases of migrating Atlantic troughs re-setting the pattern, rather than heights displaced to the west and north and a downstream trough over UK,/W Europe and into Scandinavia.

So what will be key to watch will be how far the return tide mark of angular momentum is through May as the tropical progression fades and then renews. If this is higher, or at least no lower than seen early March following the previous wave, then this will bode more favourably as one important ingredient for a decent opening to summer.

 

Edited April 26, 2017 by Tamara

[Eugene]

5 hours ago, Andover said:

That Jay Wynne will have some egg on his face after his forecast was last night, looks a good deal cooler for next week going by what I've seen this morning.

Didn't see the forecast so i assume he was forecasting a very warm week next week which is absolutely crazy with even the UKMO runs never going for it and many other runs the day before showing cooler easterlies. 

[Eugene]

6 hours ago, Frosty. said:

Where did next weeks warm spell go? The Ecm 00z for example looks much cooler than last evenings 12z.

Sorry frosty but a warm spell for next week has never had any consistent model output, models have swung back and forth between cooler easterlies and warm southeasterlies for days, i keep a close eye on GFS ensembles and even when OP's were showing the possibility of mid 20's C a decent number of ensemble runs didn't, there has just never been any conclusive evidence of a very warm spell next week, i feel too many posters get carried away with warmth and let it cloud their judgement.

Edited April 26, 2017 by Eugene

[Frosty.]

50 minutes ago, Eugene said:

i feel too many posters get carried away with warmth and let it cloud their judgement.

I don't think that's true, even the met office updates in the last few days have been painting a summery picture through the first half of May and still is.

[Fourty Point Three Degrees]

MO have been promising summery warmth for the early part of May for some time now. Even ensembles is showing dryer and above average temps following Bank holidays washout. I think more runs are needed for next week.

[Scorcher]

3 hours ago, Eugene said:

Didn't see the forecast so i assume he was forecasting a very warm week next week which is absolutely crazy with even the UKMO runs never going for it and many other runs the day before showing cooler easterlies. 

They also have access to a lot more data than we do, so I don't think you can call it 'absolutely crazy'. I still think that locally it could get warm midweek, particularly further west.

[Scorcher]

In any case, it's looking like it will be a good deal warmer than this week, except perhaps on North Sea coasts. Although the runs have been a bit disappointing after what we had the other night, it is going to be a big improvement on this week temperature-wise for most.

[Frosty.]

The Gfs 12z looks a lot clearer and sunnier than the 6z next week and becoming pleasantly warm, especially sheltered from the occasionally fresh to strong Easterly breeze..so..an anticyclonic spell looks to be on the way after BH Monday.

Edited April 26, 2017 by Frosty.

[Eugene]

Could be alot of cloud cover left over from an atlantic frontal system from the southwest next tuesday/wednesday leaving miserable dank conditions, a freshening easterly breeze should start to clear it by thursday, max temps near average for early May (15C) .

[Neilsouth]

3 minutes ago, Eugene said:

Could be alot of cloud cover left over from an atlantic frontal system from the southwest next tuesday/wednesday leaving miserable dank conditions, a freshening easterly breeze should start to clear it by thursday, max temps near average for early May (15C) .

Maybe but as that wind strengthens there's going to be alot of cloud coming into eastern counties and it will not feel warm at all in that wind, something the east as suffered from throughout the last few years on and off.