In Depth Model Discussion, Analysis and Summaries

[johnholmes]

Without getting too far ahead, and thanks as others have said GP for the long term outlook.

Turning to the shorter range I really see no reason, as some have been doing over the past 7-10 days, to write off summer for the southern half of the country. My own view is that the weather split is likely to carry on much as it has, both in terms of major synoptics and the north-south split as a result through into August.

My bet would be that areas south of ROUGHLY Morecambe Bay to Newcastle will end the official summer with above average temps and near or below average rainfall continuing. The rainfall dependent to an extent on the showery type weather hitting some and missing others quite close. Areas further north, and the further north west the more likely are going to have had (including much of Ireland) what could be described as a poorish summer which seems set to continue..

Just when or rather IF the overall weather pattern that has given these distinctions, even back into the last winter, will change is impossible to say. The most likely time is during August into September when the hurricane season along with La Nina is likely to set the Atlantic into a much more disturbed phase than many in the south have seen apart from the relatively small hiccup a week or so ago in the south.

What then happens is obviously linked to La Nina and the various parameters so well described by GP.

Interesting outlooks both for the remainder of summer let alone into the autumn and winter.

Edited July 25, 2010 by johnholmes

[Cheshire Freeze]

No blowtorch January for me, just can't see it. I have a feeling that the atmosphere may have a few surprises for us which may not be trademark of a typical strong la nina pattern for northwest Europe. ↲GP could you clarify the mentioned bit in bold as if there is a cold stratosphere and strong polar vortex then surely the cold will have real problems being displaced to mid latitudes?↲I'm a bit of a novice but the feeling i'm getting is that we may have a stab at a negative CET monthly return this year.↲Many thanks

[MP-R]

No blowtorch January for me, just can't see it. I have a feeling that the atmosphere may have a few surprises for us which may not be trademark of a typical strong la nina pattern for northwest Europe. ↲GP could you clarify the mentioned bit in bold as if there is a cold stratosphere and strong polar vortex then surely the cold will have real problems being displaced to mid latitudes?↲I'm a bit of a novice but the feeling i'm getting is that we may have a stab at a negative CET monthly return this year.↲Many thanks

I tend to agree. As we saw last winter, once the cold had become embedded through December, it really struggled to disappear through January and any Atlantic attack didn't succeed until the 16th and the cold kept coming back after that.

I was thinking that perhaps a La Nina and the southerly tracking jet associated with the solar minimum would promote more lows undercutting rather than going north which would keep us in the cold and heighten snow chances too. All too far out to say of course.

[johnholmes]

as promised my view for August, link below, its a pdf file

apologies for how its lined itself up with most of the charts beneath each other rather than side by side as I intended them to be.

lrf-August on 27 july 10.pdf

[Cheshire Freeze]

I tend to agree. As we saw last winter, once the cold had become embedded through December, it really struggled to disappear through January and any Atlantic attack didn't succeed until the 16th and the cold kept coming back after that.

I was thinking that perhaps a La Nina and the southerly tracking jet associated with the solar minimum would promote more lows undercutting rather than going north which would keep us in the cold and heighten snow chances too. All too far out to say of course.

Yes I hold this view too. I think there may be a powerful jet but I have a feeling it may end up directing Atlantic storms to the south. For me, January will be a month of cold zonality with frequent deep snowfalls to high ground and lower levels at times or the lows will be pushed far enough south for entrenched cold to manifest itself once again.

Aaron

[Paul]

I think it would be good if we can pull this back to model related discussion rather than winter based conjecture

Thanks

Paul

[BLAST FROM THE PAST]

Thanks GP.

More immediatly, would it be fair to say summer now looks likely to slowly ebb away? Or could we still see a late August/early September heatwave?

Hi Gav

There is still a shout for some 'rather warm' conditions for the south to develop but nothing spectacular, high 70s should be readily achievable particularly for the south. Interesting thoughts of GP, I mooted the rapid decline of El Nino and a La Nina to be in place by Sept if not sooner. This in turn will imply a cool/cold autumn which in turn IMHO implies no late August heatwave to develop as the global temps and set up get Nina driven.

So even before winter the chill will be apparent and I agree with GPs assessment, there is likely to be another autumn winter where arctic air will readily spread equatorward to mid lats.

BFTP

[Gavin P]

Thanks Blast.

Edited July 28, 2010 by Gavin P

[tcc]

Hi Gav

There is still a shout for some 'rather warm' conditions for the south to develop but nothing spectacular, high 70s should be readily achievable particularly for the south. Interesting thoughts of GP, I mooted the rapid decline of El Nino and a La Nina to be in place by Sept if not sooner. This in turn will imply a cool/cold autumn which in turn IMHO implies no late August heatwave to develop as the global temps and set up get Nina driven.

So even before winter the chill will be apparent and I agree with GPs assessment, there is likely to be another autumn winter where arctic air will readily spread equatorward to mid lats.

BFTP

Thanks BFTP, just a general thought from me, when does the QBO go positive? Isn't that during the winter period? Doesn't that encourage a strong polar vortex? I know not necessarily in the Greenland area but knowing our luck it will do!

[summer blizzard]

Thanks BFTP, just a general thought from me, when does the QBO go positive? Isn't that during the winter period? Doesn't that encourage a strong polar vortex? I know not necessarily in the Greenland area but knowing our luck it will do!

Looking at the data, since 1979 the QBO has taken between 3-6 months to go from peak (recorded in May this year) to recording a positive value, this means that the change this year will occur in the September-November period (assuming nothing unusual). Yes, it does normally mean a stronger than normal Polar Vortex, however the winter of 2009 also saw a +QBO, so there are other factors which influence the general weather pattern as well.

[BLAST FROM THE PAST]

Thanks BFTP, just a general thought from me, when does the QBO go positive? Isn't that during the winter period? Doesn't that encourage a strong polar vortex? I know not necessarily in the Greenland area but knowing our luck it will do!

This is where the jetstream shifting south comes in and the effects of the perturbation cycle. I think teles have signals but are driven by solar and lunar phases. As in 08/09 the jet's positioning will overrule the QBO. If the QBO changes as SB predicts [and the timings seem right] then expect lots of southerly tracking LPs to crash over the UK....cold and wet and rough autumn....sounds about right to my initial thoughts.

BFTP

[tcc]

This is where the jetstream shifting south comes in and the effects of the perturbation cycle. I think teles have signals but are driven by solar and lunar phases. As in 08/09 the jet's positioning will overrule the QBO. If the QBO changes as SB predicts [and the timings seem right] then expect lots of southerly tracking LPs to crash over the UK....cold and wet and rough autumn....sounds about right to my initial thoughts.

BFTP

Thanks Blast & SB, I think this winter is going to be tough to call!

[Weather-history]

I think this winter is going to be tough to call!

Which begs the question why is this being discussed anyway this far out?!?

[Cloud 10]

Which begs the question why is this being discussed anyway this far out?!?

Is that a small pool of -15 850's i see before me over greenland? :lol: :lol:

[summer blizzard]

Is that a small pool of -15 850's i see before me over greenland? :lol:

I would be suprised if we saw the -15C isotherm occur before September, however the -10C isotherm is already present, and has been since July 30th..

http://www.wetterzentrale.de/pics/Rhavn002.gif

Having just looked, the archives for the northern hemisphere as a whole go back to 1998, and July 30th is the earliest occurance of the -10C isotherm that i can see, assuming we do not lose it, this is an extremely good sign for a more sotherly tracking Jet Stream in the coming months.

[BLAST FROM THE PAST]

I would be suprised if we saw the -15C isotherm occur before September, however the -10C isotherm is already present, and has been since July 30th..

http://www.wetterzentrale.de/pics/Rhavn002.gif

Having just looked, the archives for the northern hemisphere as a whole go back to 1998, and July 30th is the earliest occurance of the -10C isotherm that i can see, assuming we do not lose it, this is an extremely good sign for a more sotherly tracking Jet Stream in the coming months.

That IMO is a given. The solar and lunar signal is for the jet to remain on its southerly holiday.

BFTP

[Gavin P]

Is it on holiday or has it taken up a new permanant residence?

[azores92]

still looking pretty unsettled on tonights ecm, with a low stuck over us from 168+, before that though, things stay fairly changeable, with plenty of dry and bright weather.

Edited August 3, 2010 by azores92

[summer blizzard]

That IMO is a given. The solar and lunar signal is for the jet to remain on its southerly holiday.

BFTP

The Jet Stream has certainly become more amplified and on a more southerly track over the past month or so, however solar activity is increasing (absolute minima was November 2008).

[Glacier Point]

Brief posting .....

Easterly winds are now deeply ensconsed across large parts of the tropical and sub-tropical oceans in the northern hemisphere and dynamical processes such as torques and poleward eddies are constructively interferring with this development to such an extent that we are seeing the global circulation acting as an 'out-rider' for the La Nina event. The Global Wind Oscillation has spent the last 40 days in high amplitude phases 1-2-3, reflecting a low angular momentum ( Nina ) base state.

http://www.esrl.noaa.gov/psd/map/images/gcm/gwo_40d.gif

Tendency in angular momentum is falling once more, driven in part by large negative (east) wind anomalies across 30N and 30S. This is only serving to assist the upwelling of anomalously cold waters in the central and eastern tropical Pacific driving us towards a strong Nina event in the Autumn. Current data (as per Australian Met. Bureau) indicates region 3.4 with temperatures -1.18 C below normal.

http://www.bom.gov.au/climate/enso/indices.shtml

(you need to scroll down for region 3.4).

Th bottom line is that I can see no way the atmosphere can resurrect itself from this low angular momentum base state and we will continue to see orbits of the GWO and MJO through phases 1-2-3 for the remainder of the summer and autumn at least.

Composites for GWO phases 1-2-3 are a little tricky to interpret but broadly high amplitude phase 2 best describes the most likely pattern ahead for August:

The key features here are the strong ridge in the north-east / central Pacific setting up a series of downstream ridges and troughs, one of these mean ridges occuring in the central Atlantic as depic ted in the composite (notice how the composite also captures the Russian heat ridge nicely).

Phase 1 composites do hint at a cut off low developing close to the UK so I can see where current modelling, in particular the ECM, is going. However, unless angular momentum crashes significantly (going to be hard given gthat we are already well in advance of this Nina), I would see the ridge the Atlantic holding sway with a relatively cool and showery type weather pattern coming in along winds from the north-west and west. Hopes for sustained heat to develop, are, as they were a few weeks ago, unealistic given the overall set-up with pressure always likely to be higher further west.

[BLAST FROM THE PAST]

The Jet Stream has certainly become more amplified and on a more southerly track over the past month or so, however solar activity is increasing (absolute minima was November 2008).

The 11 year cycle is of little relevance inasmuch its the larger cycle that is the driver. However, even though we head towards maximait will be a low maxima.

GP, thanks for that update I mentioned on the model thread that we seem already to be in a Nina driven pattern. GFS heads towards ECM in deep FI so both are heading towards your composite.

-1.18 is pretty cold and certainly there appears to be no 'milding' out as GW would put it. This is certainly heading towards a strong Nina event.

BFTP

[johnholmes]

my latest idea for into September, as a pdf link below

lrf issued 13 august 2010.pdf

[azores92]

my latest idea for into September, as a pdf link below

lrf issued 13 august 2010.pdf

hmm please not another dreaded nw/se split!

[Winter Monsoon]

Im wondering if all of this is leading to another good winter like the one gone. Probably in the wrong post but im still learning and find this fascinating stuff.

[Glacier Point]

Latest IR satellite and low level wind analysis is showing a considerable slab of the tropical atmosphere shifting eastwards in the Indian Ocean.

Click on the link and review the last 30 hours and not how the cloudiness develops south-west of Sri Lanka as the westerly winds in the western Indian Ocean buckles and fades.

http://cimss.ssec.wisc.edu/tropic/real-time/wavetrak/winds/wavetrkP.html

A clear signal for angular momentum to continue to fall and lock us in to an unsettled passage of weather as the mean trough shifts over the UK. Meantime, the Southern Oscillation Index is tanking and an inter-seasonal issue we will have to see how far angular momentum falls in response.