Model Output Discussion 30/06/2012

[OldMetMan]

And so it goes on - how can there BE so much rain?

The models are offering little hope of any change, in fact, the GFS seems to be emphasising more strongly in recent runs a renewal of a strong, low-latitude jet heading in our direction in the mid-term, basically repeating the pattern we are in now - slow moving upper low on top of the UK.

There are a few variations on this theme amongst the other models, the UKMet latest run is suggesting a weaker flow and the ECM is building pressure across us at the end of the run.

As I see it, the only real chance for this pattern to break down is for the new jet to propagate further south still than the models show with the main LP activity heading much further S into Spain and the Mediterranean, with HP building further N across the UK. I keep on about the strong upper high over the US and it is really remarkable in its persistence. At present, it does seem to be retrogressing somewhat into the W and NW States and W Canada, but, as I said before, we are still left with all the jet energy heading across Canada and SE into the Atlantic, then on to us.

I notice a fairly strong upper low developing in the Pacific NW which could perhaps start to erode the US ridge, maybe enough to disrupt the static wave pattern and give the downstream flow a chance to re-arrange itself in our favour - with the possibility of a more significant mid-Atlantic upper ridge finally blocking off the endless train of LPs coming our way.

But we still have the next few days to get through, with the current LP doing a cyclonic loop and further troughs and minor lows adding to the soggy mix. I notice we have a rare red alert for the SW of England from the Met Office - not good. The short-term model forecast seem to be shifting the rain emphasis further south in the next day or two - yet more flooding likely - until the whole sorry cyclonic mess finally moves off to the east.

A couple or three more days from now we should begin to see in the model output if this cyclonic pattern really is going to continue until at least mid-July.

[Cloud 10]

This evening's ECM operational run is looking like a stinker,however i have found summer in the form

of GEFS member 12 at 360hrs.

The true meaning of FI

[Frosty.]

There are some positives on the Gfs 12z run (albeit very FI) for an improving picture beyond mid month with high pressure perhaps getting a foothold in the southeast of the uk but with nw britain becoming more generally unsettled as the jet pushes further north and we see something more typical but into next week it looks like becoming cooler with N'ly to NW'ly winds and some showers but probably not the deluges we are currently having, maybe a bit drier and brighter for a time after midweek but all going downhill again towards next weekend with more heavy rain piling in from the southwest but maybe something more summery beyond next week?

[Thundery wintry showers]

Hats off to you, in the end you were right about it being bright rather than grey and wet this week (at least in my part of the world).

Thanks for the words of support, but I must admit that I was right only over a limited area of the country. Given the gloominess of the first two days I'd have considered my projections successful if England and Wales had reached at least 80% of normal sunshine for 1st-5th July, but Philip Eden has it at a mere 50% of normal. That said, it does show that even a generally dull wet week can have notable regional exceptions, supporting my view that it's worth looking at specifics rather than just writing off anything that looks unsettled.

Re. OldMetMan's post, the scenario of the jet heading further south allowing high pressure to establish over the top worked remarkably well for sun and warmth at the back end of May, but it relied upon the jet stream being weak, resulting in only shallow depressions tracking across to the south. I think in July/August it will be a lot harder to get the jet to be as weak as that, and thus any ridges from the main Azores anticyclone would be likely to land to our NW feeding in rather cool cloudy north-easterlies. Remember also that when we have a southerly tracking jet, deeper lows have a habit of tracking further north.

The latter stages of the GFS do look somewhat more "summery" for eastern and southern areas with a belt of relatively high pressure extending up from the Azores to central Europe and giving south to south-westerlies over Britain (this is the pattern which gave a warmer sunnier first half of July following the often-mentioned June of 1987 for instance). However it's well out in fantasy island with the outputs from T+144 to T+180 showing slow moving low pressure and the cloud and precipitation outputs implying a lot of frontal activity.

[Frosty.]

The Ecm 12z tonight has not really built on the promise of the 00z towards T+240 hours and high pressure is more supressed to the south but I don't think it would take much of a shift for the azores high to have much more influence on our weather beyond next week. Both the main models are now hinting at a relaxation of the recent/current dreadful weather with all the flooding to something drier just after mid july and hopefully a sustained warm and dry spell during the last 10 days of the month but i'm straw clutching a bit there. The first step would be for the very southerly tracking jet to be forced much further north due to height rises from the south but unfortunately the next week looks cooler and remaining on the unsettled side and some of the charts next week would not be out of place in autumn or winter, the opposite of summerlike springs to mind for another 6-8 days at least.

[OldMetMan]

Re. OldMetMan's post, the scenario of the jet heading further south allowing high pressure to establish over the top worked remarkably well for sun and warmth at the back end of May, but it relied upon the jet stream being weak, resulting in only shallow depressions tracking across to the south. I think in July/August it will be a lot harder to get the jet to be as weak as that, and thus any ridges from the main Azores anticyclone would be likely to land to our NW feeding in rather cool cloudy north-easterlies. Remember also that when we have a southerly tracking jet, deeper lows have a habit of tracking further north.

Good point, TWS, but I have seen past similar occasions in summer of a fairly deep LP in Biscay or over and to the W of Portugal spiral around for a day or two and finally move off to the E, as pressure builds over us - yes cool NE winds to start but then the jet re-establishes itself nearer it's normal position well to the NW, with HP finally settling over us.

Bit of a long shot I know, clutching at straws really! Much depends on whether the jet really does set out from N America as per the GFS - the Atlantic flow is quite weak at present.

[J10]

Interesting points made by Philip Eden over on weather online, about the June Monsoon and how it is often misunderstood.

http://www.weatheronline.co.uk/cgi-app/reports?LANG=en&MENU=Extra&FILE=extra_ne&DAY=20120629

This year it does that the June Monsoon hasn't arrived, hopefully it will do soon, as at least with a faster moving Atlantic, at least any rain moves away quicker and stick around for days on end.

[Gavin P]

Rank: Advanced Member

Joined: 05/04/2006

Posts: 15,621

Check out the ECM/GFS 8-10 day means;

http://www.meteo.psu.edu...i/ECMWF_12z/hgtcomp.html

If theres ever been a worst mean for "high summer" I'd like to see it

[Thundery wintry showers]

The first paragraph reminds me of what happened into the last third of August 2000- an instance of it where we didn't even get much of a north-easterly in the transition. However, the cyclonic spell that preceded it had much shallower depressions and an emphasis on sunshine and slow-moving thundery showers.

http://www.wetterzen...00120000821.gif

http://www.wetterzen...00120000822.gif

http://www.wetterzen...00120000823.gif

http://www.wetterzen...00120000824.gif

Re. return of the westerlies, those are traditionally associated with depressions tracking close to their usual position and a strong Azores High. June 2012 was comparably mobile to many "westerly" summer months, but crucial factors were the fact that the lows tracked much further south than usual and there was a near-relentless succession of them. Most Atlantic lows have fronts trailing around their cores, and often on the southern flank of them you may see just one or two fronts quickly push through. Hence, with southerly tracking lows we are more likely to find ourselves sat under trailing fronts until the lows clear off into the North Sea. Such trailing fronts have also been an issue with the present slow-moving low as most of us have seen for ourselves today.

The "return of the westerlies" pattern tends to see slow moving fronts largely confined to northern Scotland, whereas rain belts elsewhere tend to pass through somewhat more quickly, though as westerlies bring a lot of moisture off the Atlantic a strongly westerly type will often still be predominantly cloudy and moist especially in the west. This pattern characterised most of the last two-thirds of August 2011 if I remember rightly. If we get gaps in between lows, though, there is usually more scope in that case for the Azores High to throw up ridges into Europe which may form into separate anticyclones, instead of the rather tentative drier brighter interludes that we saw on occasion in June 2012. I think given the current atmospheric signals we're going to struggle to get that far in the next couple of weeks though!

Edited July 6, 2012 by Thundery wintry showers

[Gavin P]

LOL! Dreadful 8-10 day means from ECM/GFS;

http://www.meteo.psu.edu/~gadomski/ECMWF_12z/hgtcomp.html

Blocking over Greenland, trough over UK and W. Europe and jet down into south of France. Can it get any worse in high summer?

[johnholmes]

not quite as simplistic as you appear to suggest Gavin.

this copied from the 500mb thread

both (6-10 and 8-14) outlooks do take up the idea floated this morning by ECMWF-GFS. A quite different upper air pattern from all 3 for 7-15 days time to what we have had for some considerable time. That is IF it verifies. I personally need to see 2-3 days with the same pattern showing before I will feel confident in the pattern.

thanks to TH the 8-14 day NOAA outlook below

sorry won't do what I want but take a look in the 500mb thread or click on the link provided by Gavin for the 12z version from ECMWF-GFS?

The flow really is quite different to what all 3 models have shown for a long time. 2 do still have some +ve/ridge over Greenland but gone is the marked upper trough in the UK area with a marked flow n of west. Replaced by a fairly broad wly type pattern.

IF it is still being predicted by ALL THREE in 3 days time then its a fair bet a pattern similar to that will occur in the time scale 7-15 days.

Edited July 6, 2012 by johnholmes

[Bobby]

Looks like our weekly Thursday/Friday washout low is appearing on time

GFS 18z

Edited July 6, 2012 by Barb-

[bluearmy]

Looks like our weekly Thursday/Friday washout low is appearing on time

GFS 18z

indeed Barb but i have a feeling that this will trend a bit further nw this time.

[Backtrack]

Out of interest, was the jet stream in a similar position to what it's in now at the end of May when we had almost 2 weeks of cloudless skies? I can't remember, seems like it was ages ago!

[Gavin P]

The BCC 500mbr height anomaly (the model I based my improving July forecast on) now looks pretty dreadful for the next 30 days;

http://cmdp.ncc.cma.gov....2/MD2012072GL_H5M1_1.GIF

Has to be big doubts on a general imrpvement for July now?

[k19]

The BCC 500mbr height anomaly (the model I based my improving July forecast on) now looks pretty dreadful for the next 30 days;

http://cmdp.ncc.cma....72GL_H5M1_1.GIF

Has to be big doubts on a general imrpvement for July now?

Not too sure gavin, the greenland high although not weakening within the foreseeable future has been showing tentative signs of shifting, even in the chart you posted, the anomaly over greenland doesn't seem to be what it was earlier in the month. Once the Greenland high is removed, it may not guarantee different weather, but it make a pattern change more accessible.

[TonyH]

My preliminary observations regarding this coming week show a definite trend away from the brief ridge and dry interlude midweek, to a cool/ very cool week with further showers or longer spells of rain on virtually every day. A quite horrendous outlook for July! Another low set to slowly cross the UK Friday and Saturday.

Edited July 7, 2012 by TonyH

[summer blizzard]

http://62.89.145.4/gefs/gefsens850London0.png

Ensembles say it all really, the mean is supposed to be near enough 10C at this time of year (just shy as it peaks in about a month) but it is pretty much just above 5C throughout.

ECWMF0z is abysmal for warmth, a northerly until late next week should be pleasant enough with cool minima before another washout.

[bluearmy]

Not too sure gavin, the greenland high although not weakening within the foreseeable future has been showing tentative signs of shifting, even in the chart you posted, the anomaly over greenland doesn't seem to be what it was earlier in the month. Once the Greenland high is removed, it may not guarantee different weather, but it make a pattern change more accessible.

those anomolys fit in with the meto extended which had likelihood of rainfall totals higher in the south than the north.

[Snowyowl9]

Seriously? I'm going next week too, Monday 9th till Friday 14th, madness!

Models looks quite good last time I checked, warm, sunny spells with the Azores high in charge for the week! No severe weather in sight for the week we go.

The AH is in charge of the azores only.

A fleeting ridge only now,this S-ly jet is destroying this high.

http://www.wetterzen...ics/brack2a.gif

http://www.wetterzen...ics/Recm961.gif

http://www.wetterzen...cs/Recm1201.gif

http://www.wetterzen...cs/Recm1441.gif

2 dry days if your lucky.

[Bobby]

The ensembles show a picture of a jet stream still much further south than it should be at this time of year with a lot of the ensembles showing low after low crossing us from the Atlantic. There might be some ridging but it doesn't look too robust.

[Frosty.]

IMO the models have taken a step backwards in terms of looking forward to better weather in the second half of july and the pattern is now looking pretty flat with more low pressure rolling in off the atlantic at regular intervals but with short lived ridges bringing some temporary relief from the downpours, no sign of high pressure settling down over the uk in the next few weeks and the coming week looks autumnal cool with N'ly winds and showers with temps in the mid to high teens celsius which in such a poor summer so far, is just adding insult to injury..this summer is gradually turning into one of the worst in many years and when the pattern change does come, it could be into august.

[Frosty.]

The latest meto update fully reflects the gfs and ecm op runs today with an unsettled outlook although perhaps not as desperately bad as it has been and currently is...the jet does look like remaining southerly tracking but probably migrating a little further north meaning the main core of awful weather will probably transfer to nw britain instead of the southeast, the south and east of england will probably see most improvement but still remain generally unsettled but at least the rain bands will move through more quickly rather than stagnating for many hours and causing all the flooding chaos..so there is a bit of light at the end of the tunnel but looking further ahead, even the idea of a protracted hot and sunny spell into august seems like pie in the sky according to the current model trends.

[swebby]

Hello from a soggy south west.

MJO has apparently staggered into phase 3.

I'm a total novice on these things so i would not like to offer an opinion on what bearing it will have. There have been posts (Chino or bluearmy i think ), that have suggested this is where we need it to be heading in July but i would guess there are plenty of other drivers to what weather we will get over the next month.

What i would like to comment on, is that i've been watching the forecasts for this over the past week and i feel their accuracy has been poor. Many have been very keen to reverse the movement in the short and long term back into phase 1.

The above are illustrative and the ECMF outputs have not been so bullish regarding a reversal into phase 1 but even they have to some extent underestimated the motion towards phase 3. I know these plots are effectively a snap shot of broad tropical convection but i'm wondering that if they are regularly struggling to forecast this correctly a day in advance, how much confidence should we have with the mid range model output being shown for the northern hemisphere?

Cheers

S

Edited July 7, 2012 by swebby

[johnholmes]

i share your reserve about accepting the MJO forecasts as gospel. Like any other forecast tool they can be wrong at times.