Model Output Discussion

[Glacier Point]

Interesting to read comparisons and people's views on how the summer of 2009 is panning out at the mid point.

Reanalysis of the H5 anomalies for the last three years identifies the location of the mean trough to our west whereas in the past two years it was centred over NW Europe. This year's anomaly pattern looks to be consistent with the underlying SSTA signal.

2007

2008

2009

http://weather.unisys.com/surface/sst_anom.html

Of late, we have seen the mean trough shift east which is attributable to a plunge in total angular momentum since late June driving a more Nina like pattern. One of the reasons why the jet has intensified (therefore preventing any trough development to our west) is that a mean positive (westerly) wind anomaly has been working its way through the sub-tropics. This has strengthened the Azores ridge but it is flat as a pancake due to a substantial -ve zonal wind anomaly over the pole (consistent with summer time low angular momentum conditions):

http://www.cpc.ncep.noaa.gov/products/stra...ALL_NH_2009.gif

Herein lies the very tentative signs that the end July will feature some improvement.

The positive zonal wind anomaly is likely to propagate poleward as a result of the normal dispersal of winds and also a slight signal for pressure to fall over the North Pole as we head towards August.

I find this interesting as the reversal in polar index (AO) has seemed to happen during late July, if only for a short 7-10 days during the last few summers at least. This summer the AO has been solidly negative so the reversal in polarity should be for +AO conditions to prevail for a little while. Remember it was this time last year that we enjoyed our most settled spell of weather.

Latest stratospheric zonal mean data identifies that the mean easterly wind anomaly has reversed over the Pole which will lead to less support for blocking to our north in the 10-20 day horizon as the atmopshere upwells positive wind anomalies (AO index nuetralising and becoming positive):

http://www.cpc.ncep.noaa.gov/products/stra...ALL_NH_2009.gif

GFS AO Ensembles are trending upwards from a very low base:

http://www.cpc.ncep.noaa.gov/products/prec...ndex_ensm.shtml

This should allow the tropics to respond with more westerly wind flow addition although the magnitude of this is open to question and we may continue along a low angular momentum base state for some time yet.

A feature of the last few operational GFS runs has been for some reduction in heights to our north allowing the jet to be deflected further north and pressure to build over NW Europe although the ECM ensembles aren't backing this just yet.

So some very tentative signals that we may see a more settled phase late July into 1st week August. Whether this manifests itself into a longer shift or return back to the pattern for the summer so far is a case for ongoing monitoring of the tropics.

Edited July 13, 2009 by Glacier Point

[Nick.F]

Perceptions of this summer are clearly very localised, in this particular location this year so far has borne no relation to 2007/2008 and has been very, very nice, generally speaking. If memory serves the teleconnections are quite different this year, any way. Resultant synoptics may possess superficial similarities, but causes are different.

In such an extremely complex chaotic system, the chances of one year following the previous one, pattern-wise, are inordinately slim, let alone the last two.

[johnholmes]

So some very tentative signals that we may see a more settled phase late July into 1st week August. Whether this manifests itself into a longer shift or return back to the pattern for the summer so far is a case for ongoing monitoring of the tropics.

sensible constructive post as always from Stewart.

I agree, see my previous post, re the tentative signs for the lead into early August-currently just less than 50/50 in my book but promising nevertheless.

Also very true about where the main upper trough is this year compared to last year.

Edited July 13, 2009 by johnholmes

[William of Walworth]

I always read GP's points with close attention. and I even understand parts of them, and try to learn from the rest ....

If GP and John are suggesting an improvement in late July, even on currently fairly tentative signals, then those tempted to write off the rest of the summer should take note I think.

Mixed, with room for 'up' periods (warmer, with more settled spells) as well as 'down' periods (Jet dominated) would be a safer default prediction surely.

So far any real general improvement not all that likely before (just?) too late in July for my personal wishes though

[chionomaniac]

Looking at the last 3 years H5 anomaly comparison charts that GP has posted the main difference this year is the more westerly positioning of this years Atlantic trough- surely the lower SST's have influenced this. And with these persisting surely they can continue to steer this pattern again when any increase in positive AAM and change in MJO orbit occurs.

There is also a great amount of similarity in these charts though and that is the positive anomaly seen around Greenland and the NP remains, and with this the southerly based jet stream has been dominant. Whether the positive zonal wind anomaly propagating to the pole can disrupt this, early August remains to be seen, but if it does and other factors fall into place then we could look at a more settled spell. Also at what point is the developing El Nino going to overide the current La Nina like pattern we are in presently?

[johnholmes]

tks ch

yes lots to watch for and ponder on what might happen-interesting few weeks coming up-and pretty evenly balanced.

[Jezzer]

I've just taken a look at GFS for this weekend and it looked very hot in the continent. I'm heading to Paris on Sunday 19th for my birthday on Monday 20th July and it looks like it could be a scorcher over there.

I wish we could get a bit of their heat over here at some point!

[mushymanrob]

I always read GP's points with close attention. and I even understand parts of them, and try to learn from the rest ....

If GP and John are suggesting an improvement in late July, even on currently fairly tentative signals, then those tempted to write off the rest of the summer should take note I think.

Mixed, with room for 'up' periods (warmer, with more settled spells) as well as 'down' periods (Jet dominated) would be a safer default prediction surely.

So far any real general improvement not all that likely before (just?) too late in July for my personal wishes though

yep i agree, i think many of us ought to listen more to what the more knowlegable say, theres alot to be learned .

hope thats not too psychophantic!

[TonyH]

Still detecting an over-simplistic "low pressure therefore despair" similar to the "northerly therefore despair" in April or "south-westerly therefore despair" in January. The ranting about "where's our summer" isn't especially constructive.

The outlook through to Thursday is looking fairly showery/convective still, with a fair amount of warm sunshine likely towards the SE, always more cloud and showers towards the NW, and temperatures near average in the NW, above in the SE.

However in fairness it does look like developing into a washout towards the weekend as the trend is increasingly for the jet to speed up and large depressions to start moving in perhaps making it rather "autumnal". Friday could have some significant thundery activity although in my experience that kind of thunder setup is usually downgraded into rain closer to the time.

Yes, a lot of time wasted reading such simplistic and gloom laden posts. As I often have stated and observed, the reality often sees much fair and warm conditions, as even with lows in proximity, some days will be mainly dry and even quite sunny and warm. Best to enjoy the sunny interludes and get out in them, and then stay in and enjoy the showers/ rain events out of the window/ virtual chasing!

[BLAST FROM THE PAST]

Late July for decent warmth still is plausible in my books and also don't forget that i think too we should look out for torrential, thundery downpours 28/31 Jul period into beginning of Aug. Even yesterday and today it doesn't take much to achieve what I call are decent summery temps [here in SE for sure] of 25c. If we look for them sort of temps an not low to mid 30s we will be fine.

BFTP

Edited July 13, 2009 by BLAST FROM THE PAST

[Eugene]

http://www.wetterzentrale.de/pics/Rtavn841.png

http://www.wetterzentrale.de/pics/Rtavn901.png

http://www.wetterzentrale.de/pics/Rtavn961.png

http://www.wetterzentrale.de/pics/Rtavn1021.png

lol an area of low pressure pushing up from the SW for thursday night seems to be getting deeper by each run, GFS Op's seem to be the warmest for thursday, other runs aren't as warm, i expect the plume to miss us and for us to be cool and wet come friday.

This July looks like getting worse after such a promising start.

Edited July 13, 2009 by Eugene

[Eugene]

http://91.121.94.83/modeles/gfs/run/gfs-0-228.png?12

Oh dear, after looking at GFS 12Z and the GFS 06Z ensembles i am starting to write off July now, can August save this summer, my opinion is NO it can't as the lows will start to get even more vigourous esp the second half as autumn begins in earnest.

[NorthernRab]

yep i agree, i think many of us ought to listen more to what the more knowlegable say, theres alot to be learned .

hope thats not too psychophantic! :lol:

I think the word you're looking for is sycophantic, although pyschophantic might not be too far removed for some folk on here :lol:

[johnholmes]

for those posting August off on the basis of 06z and 12z data is really pretty laughable to any newcomers to this forum.

Read and take note of some of the rational folk on here, there are plenty.

[BLAST FROM THE PAST]

for those posting August off on the basis of 06z and 12z data is really pretty laughable to any newcomers to this forum.

Indeed it is John and very misguided to 'new' weather enthusiasts too. There is every chance that Aug could be the best summer month this year. [My own little LRF punt is for elongated warmth into September eminating from an overall decent August]. None really know yet but one or two model runs certainly don't

BFTP

[Stu_London]

for those posting August off on the basis of 06z and 12z data is really pretty laughable to any newcomers to this forum.

Read and take note of some of the rational folk on here, there are plenty.

The most rational forecast for August in my opinion would be one where the forecaster has no idea what it will be like

Teleconnections are an interesting read and might provide a hint of what to come but in the context of weather forecasting they are barely past the experimental stage and as we have seen previously the weather will do what it wants to despite any upstream signals.

Equally it would be wrong to write off August based on poor short term modelling in mid-July.

There are just too many variables at play with maritime climates at this latitude for any degree of certainty beyond a few days with the current level of knowledge and equipment, although if the same progress is made in the next 30 years as the last 30 years, then I believe we may start to achieve better mid range forecasts

[PB22]

The end of the week is still giving the models big problems, thus we really cannot take potential developments beyond this seriously at the moment.

The operational GFS 12z brings a wet and windy picture:

http://91.121.94.83/modeles/gfs/run/gfs-0-90.png?12

But the control run is rather different:

http://91.121.94.83/modeles/gens/run/gens-0-1-90.png?12

The ensemble mean backs up the control run:

http://91.121.94.83/modeles/gens/run/gens-21-1-90.png?12

So it seems the operational is an outlier, but given that it is run at the highest resolution then we cannot dismiss it by any means.

The 12z UKMO coming out goes with the GFS control run and ensembles. It will be interesting to see what the 12z ECm shows later, as it has, at various stages, brought a deep low (ala 12z operational) GFS across the country.

So uncertainty for the end of the week, let alone worrying about the rest of the summer!

[Snowyowl9]

I just going to enjoy all these showers for the time being, the outlook will change in time like late July.

After today I would think tomorrow could bring the best thundery showers of the week here.

http://91.121.93.17/pics/brack0.gif

[Timmytour]

If you read what I suggested, I said that chances of a settled spell look like being put back. That is not writing it off Also if you read within the general context of the post you will see why I think it is looking less likely, But there is a difference between that and dismissing any potential changes completely. I also suggested that it would need a big change in the modelling in the next week or so to change the current pattern and jet stream trajectory. That gives a week or so at least for things to change. As unlikely as imo that is atm - it is not writing it off. At least yet.

But I have to say there is no real evidence of the jet moving northwards imo - indeed ECM suggests a reload of the current pattern this morning with a new low next week approaching from the south west and setting up another UK/atlantic trough to follow. With heights still firmly in control over Greenland.

Hi, I think I'm a little guilty of using your a quote of your post as an intro to mine that is intended to relate to more than just yours....hence my comments about people writing off July were not specifically aimed at you......apologies!

That said I use the term "writing off July" in the sense that a poster is writing the chances of a nice prolonged setled spell of heat. It's not something I would accuse anyone of doing in a negative sense....indeed I think that there's a lot of evidence in the models that would lead someone to that conclusion. Anyone saying that they are "writing off July" in relation to how they see the models is of course relating to how they portray things in FI, but is doing so with probably more justification then anyone, like me, who is half sensing and half hoping that the models are pushing the worst of the weather at the end of the month towards the north and providing the south with a chance of that fine settled warm spell.

Edited July 13, 2009 by Timmytour

[Frosty.]

This July looks like getting worse after such a promising start.

Agreed, the models are taking on a more unsettled look in the coming days, even more so than the current showery but warm weather. The coming weekend into next week looks cooler and very unsettled with strong winds at times, about as unsummerlike as you can get in July. As a few others have mentioned, it could improve before the end of the month but the next few weeks don't look promising unless you like wet breezy weather.

Edited July 13, 2009 by Frosty039

[TEITS]

http://91.121.94.83/modeles/gfs/run/gfs-0-228.png?12

Oh dear, after looking at GFS 12Z and the GFS 06Z ensembles i am starting to write off July now, can August save this summer, my opinion is NO it can't as the lows will start to get even more vigourous esp the second half as autumn begins in earnest.

I wonder what your response would be if someone wrote off winter when there was still 6 weeks left.

As for LP becoming more vigorous. Well you do realise that Autumn LP systems do not usually become apparant until the latter half of Autumn and not late Aug/Sep. The rather simplified reason for this is due to the temperature differences between the Arctic and the Equator.

I do despair at times when I see posts writing off the next 6 weeks when only the next 7 days can be accurately modelled. You can at times find clues via teleconnections but these are just clues and IMO not very reliable.

[ANYWEATHER]

Agreed, the models are taking on a more unsettled look in the coming days, even more so than the current showery but warm weather we have right now. The coming weekend into next week looks cooler and very unsettled with strong winds at times, about as unsummerlike as you can get in July. As a few others have mentioned, it could improve before the end of the month but the next few weeks don't look promising unless you like wet breezy weather.

Yep, Frosty totaly agree, for those who want a repeat of hot summer conditions of those few days a few weeks ago will be sorely disappointed, from the models at the moment! Of course not all areas will be rain ,rain .rain, and the best of the weather is often in southeast England with these setups but even here thundery rain cannot be ruled out. A lot of weather to talk about in the next few days but nothing of the "illusive Summer" :o

[Alex95]

I agree some bad looking charts, but I have noticed the models trending towards a warm southerly and high pressure by next week. I know it is quite a long way off, but it is a possibility which is repeatedly being suggested.Before then though it looks to me like moderate rain will be predominant rather than heavy rain at the end of the week (bar some possible storms in the southeast on Friday), and temperatures will most likely be 12-15C in Scotland and 17 or 18C elsewhere, with the odd 20C in the southeast.

Edited July 13, 2009 by alza

[chionomaniac]

The MJO has now reached phase 4 in it's orbit and I wonder will the models respond to this increase of tropical convection that can be seen east of the Phillipinnes. There is also a new area of convection developing north of NZ in the SH.

http://www.bom.gov.au/bmrc/clfor/cfstaff/m...m/OLR/m.3d.html

The MJO forecast suggests the orbit remaining in phase 4 for the next week.

http://www.cpc.ncep.noaa.gov/products/peop...EFS_membera.gif

This could possibly translate as an increase in pressure over Scandinavia looking at the phase 4 MJO 500hPa anomaly composite although the signal is probably still weak presently. I think though, that looking at this chart the jet stream still undercuts this HP cell and with a greater trough possible in the Atlantic, ( due to the lower SST's), that the Scandinavian high may not exert as much influence as this chart suggests.

Looking towards the end of the month, I have picked up on an interesting CFS OLR forecast. The following forecast suggests an increase of tropical convection closer to the equator towards the end of this month. When one looks at the previous pattern we see that when this has occurred at around phase 6 of the MJO and could possibly be a precurser to some more settled weather in the first few weeks of August.

http://www.cpc.ncep.noaa.gov/products/peop...analf30dolr.gif

http://www.bom.gov.au/bmrc/clfor/cfstaff/m...Last90days.html

c

[NorthantsSnow]

With all the moaning I expected the 12z to be a lot worse than it was in the immediate term.

Next few days; mixture of sunshine & showers for most, on Thursday pleasant and warm away from the extreme west and north with temps up to 25C, followed by thunderstorms for some early on Friday as heavy rain clears eastwards.

To me there's something for everyone there and some classic summer variety instead of full blown relentless heat and sun which does take its toll after a while. If that's your preference then fair enough, but it's important to remember that it's not a terrible outlook by any means.