In Depth Model Discussion, Analysis and Summaries

[picog]

I'll drop my ideas in here for late June into July later this week.

In the meantime in the pdf is the first of 6 checks with GFS and ECMWF on how good either of them are at providing forecast guidance for 10 days ahead.

comment into Net Wx so far 16 June 2010.pdf

Very interesting John. In view of some of the comments that appear quite regularly on the forum about this model, I'm somewhat surprised at the very clear result — albeit a tiny sample!

[jonboy]

Jonboy's post now amended to read how it should have.

With Glastonbury now starting to get into the reliable weather time frame, what chances of the High Pressure managing to last through next week, and my summations that SW areas may escape the worst of the Western if winds do come from the NE are suggested by some models over the past couple of days.

Thoughts welcome here and in the Glastonbury thread.

Thanks Jackone and apologies for mucking up my response. I always find GP's posts excellent and so informative on the wider global front. Understanding how patterns in one part of the world knocks into our own weather is absolutly fascinating.The one area that I want to try and understand better is what effect increased low level cloud cover over the equatorial/tropics may have on the various global weather systems as I think this could be the key to how we may switch between hotter and cooler patterns and to some extent how long or large those patterns become.

[BLAST FROM THE PAST]

La Nina won't take hold until at least Autumn, we are barely out of weak El Nino territory.

Don't be too sure about that SB, the drop from El Nino grace has been like a bomb and tentative signs of La Nina forming. I too suggested early autumn but it may come sooner.

BFTP

[johnholmes]

I'll post my overall ideas of end of June into mid July probably tomorrow evening perhaps over the weekend.

[MR EXTREMES]

Don't be too sure about that SB, the drop from El Nino grace has been like a bomb and tentative signs of La Nina forming. I too suggested early autumn but it may come sooner.

BFTP

drop in el nino is an understatment its gonna be intresting into autumn and winter very intresting.

looking forward to your thoughts jh.

and cheers gp more of the same

[Thundery wintry showers]

Again I think the teleconnections have done quite well over the last couple of months- they may have only sufficed to predict broad generalisations of the upcoming weather pattern, but given that constraint they've continued to be accurate. For instance the mid-Atlantic ridge suggested for mid June has certainly come to fruition.

I must admit that I've been sufficiently convinced by them that I've added teleconnections analysis as one of the factors that I use in my own month-ahead forecasts, and I built the mid-Atlantic ridge scenario into my forecast at the start of the month.

[damianslaw]

Again I think the teleconnections have done quite well over the last couple of months- they may have only sufficed to predict broad generalisations of the upcoming weather pattern, but given that constraint they've continued to be accurate. For instance the mid-Atlantic ridge suggested for mid June has certainly come to fruition.

I must admit that I've been sufficiently convinced by them that I've added teleconnections analysis as one of the factors that I use in my own month-ahead forecasts, and I built the mid-Atlantic ridge scenario into my forecast at the start of the month.

Agree and the teleconnections support continued mid atlantic ridge and no azores ridging north weast scenario, nor necessarily a return to extensive northern blocking..

[Thundery wintry showers]

Although the charts may superficially appear the same as on earlier runs, there are strong hints from GFS that over the next few days we'll be seeing a "dirty" high, with cloud circulating around its periphery and cloud from weak Atlantic systems trapped within.

Tomorrow will have a weak band of drizzle slipping south with a fair amount of cloud, but it should be sunny and warm early on in the south, and bright and cool in Scotland. Saturday looks like being sunny in the west, but cloudy in eastern areas with a stiff northerly, probably with light drizzly showers rather than continuous precipitation. On Sunday there should be a window of brighter weather, but a weak front looks like slipping SE on late Sunday into Monday which should keep most parts cloudy.

From Tuesday onwards there should be more in the way of sunshine, but I am envisaging a slow breakdown from the south-west. Having looked at Glacier Point's latest teleconnections analysis, the outputs point to a scenario with low pressure to the SE and NE winds. I think the last week of June will see an evolution towards something along those lines, as low pressure attacks from the SW and eventally drifts eastwards to our south. The most likely result is a recurrence of the pattern we saw in the second week of the month- bright with thundery showers in the south, cool dry and cloudy in N Scotland, but dull cold wet weather establishing by the last few days in S Scotland and N England.

[johnholmes]

In the hope of dragging some away from the football farce this evening!

latest ideas into mid July-bit better than the England performance but then that is not too doifficult, Im suggesting the forecast is but it may end up just as ---p as that, anyway read on.

lrf update late june-mid july on 18 june-fri.pdf

[phil nw.]

In the hope of dragging some away from the football farce this evening!

latest ideas into mid July-bit better than the England performance but then that is not too doifficult, Im suggesting the forecast is but it may end up just as ---p as that, anyway read on.

lrf update late june-mid july on 18 june-fri.pdf

Thankyou John.

Latest output shows some fine weather at first then low pressure approaching from the North West later.

Maybe a further pressure build from the South West after that,so indeed mixed.

We are touring Scotland over the next 2weeks,starting today,so it could be a lot worse for sightseeing,i guess.

[Glacier Point]

The eagle eyed will note that the Global Wind Oscillation has not shifted towards phase 4 and has instead moved into high amplitude phase 1:

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

This is a result of a large negative tendency in relative angular momentum working its way through the sub-tropics and tropics.

Angular momentum looks to continue at low levels for the forseeable future which should see the GWO maintain orbits in phase 1-2-3 into July.

Composites for June phase 1 are a good match on the present pattern:

However, as we change the month we change the wavelengths. Composites for GWO July phases 2-3 bring back our mid Atlantic ridge with avengence:

[Gavin P]

Thanks GP. So make the most of the next few days, is the message?

[geoffw]

hi gp what are the ideal GWO phases for heatwave condition in July and August?

[BLAST FROM THE PAST]

This shows the obliteration of the El Nino and a strong -ve PDO and likely La Nina developing. This summer is developing into what I suggested it would, a transient summer...meaning that very warm spells will be passing in nature with no prolonged 'hot spells' as pattern to cooler conditions return.

It may be signalling the effects GP posts but for sure signals an early and cold autumn to come.

BFTP

[summer blizzard]

Agreed Blast, however for the moment La Nina does'nt really exist and i see a signal for early-mid Jult to see a more positive AO encouraging the Azores High to ridge into Europe.

I do think that there will be a change to much cooler conditions, however this is likely to occur sometime in August or September.

Looking into the longer term and the cold pool in the Atlantic currently split in two (stronger on the left, weaker on the east), is likely to diminish esspecially in its eastern segment promoting a stronger and more displaced Azores High, however as we progress into Autumn the main cold pool will likely transfer east towards the Azores promoting a stronger signal for the mid-Atlantic ridge.

A very northerly Autumn could be on the cards in my opinion.

[chionomaniac]

The eagle eyed will note that the Global Wind Oscillation has not shifted towards phase 4 and has instead moved into high amplitude phase 1:

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

This is a result of a large negative tendency in relative angular momentum working its way through the sub-tropics and tropics.

Angular momentum looks to continue at low levels for the forseeable future which should see the GWO maintain orbits in phase 1-2-3 into July.

Composites for June phase 1 are a good match on the present pattern:

However, as we change the month we change the wavelengths. Composites for GWO July phases 2-3 bring back our mid Atlantic ridge with avengence:

This looks like another good call Stewart. And with the strong possibilty that the negative tendency in angular momentum coupled with a stalled phase 3 MJO in July we could see that mid Atlantic Ridge elongate over the BI giving us more fine warm and dry sunny weather once the west placed troughing heads north.

Hosepipe bans very much the theme later this summer I reckon.

c

[Methuselah]

I may wery well be wrong here????? But, are some folks mistaking a positive pressure anomaly in the Atlantic for a persistant N. Atlantic ridge?

IMO, it is quite possible for the North Atlantic to spawn eastward-moving HP cells that can perpetuate warm/hot conditions in the UK? If I remember correctly, the summer of 1989 had many HP cells drifting from west to east across the UK maintaining warm or hot conditions for much of the time...

I may be wrong??? But an anomaly is only anomaly. It is not a persistent feature???

Help me out here, guys???

[summer blizzard]

I may wery well be wrong here????? But, are some folks mistaking a positive pressure anomaly in the Atlantic for a persistant N. Atlantic ridge?

IMO, it is quite possible for the North Atlantic to spawn eastward-moving HP cells that can perpetuate warm/hot conditions in the UK? If I remember correctly, the summer of 1989 had many HP cells drifting from west to east across the UK maintaining warm or hot conditions for much of the time...

I may be wrong??? But an anomaly is only anomaly. It is not a persistent feature???

Help me out here, guys???

True, provided it was weak enougth you could have a permanent trough in central Atlantic pumping up warm air over the UK and still have a positive pressure anomoly.

[chionomaniac]

I may wery well be wrong here????? But, are some folks mistaking a positive pressure anomaly in the Atlantic for a persistant N. Atlantic ridge?

IMO, it is quite possible for the North Atlantic to spawn eastward-moving HP cells that can perpetuate warm/hot conditions in the UK? If I remember correctly, the summer of 1989 had many HP cells drifting from west to east across the UK maintaining warm or hot conditions for much of the time...

I may be wrong??? But an anomaly is only anomaly. It is not a persistent feature???

Help me out here, guys???

You are right Pete in suggesting that an anomaly is not a persistent feature, however when looking at trends, it can be seen that the same pattern reestablishes itself time and time again over a season such as you have suggested above for summer 1989. In that case whereas the feature is not persistent, the fact that it reoccurs almost cyclically the end result being that the overall anomaly is reinforced.

The latest 30 day 500 hPa geopotential height and anomaly comparison charts highlight the point that I think you are trying to make Pete, but to my mind, where we see the greatest anomalies, either positive or negative, we are likely to see subsequent ridging or troughing and the extent and duration of these anomalies determines the persistence of any such ridging or troughing. So with the MJO predicted to stall in phase 3 we could very well see a persistent Azores high ridging towards the UK. The SST's would also encourage this.

[Glacier Point]

Tonight's CPC 8-14 day outlook for 500hPa mean height anomaly looks just about bang on the money depicting a longwave trough centred just to the west of the UK and positive anomaly centred over the western Atlantic.

http://www.cpc.ncep.noaa.gov/products/predictions/814day/814day.03.gif

Global Angular Momentum has fallen to such a degree that it looks very likely that July will feature just three phases of the Global Wind Oscillation, those being the low angular momentum base states 1-2-3.

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

The composites as posted above depict a trough over the UK and NW Europe with a notable positive height anomaly centred in the western / central North Atlantic. This is slightly in conflict with the MJO composites for phase 3. As always, the GWO provides much the more likely longwave response.

The only question marks for me here are the shallowness of the trough and exact location of the axis. A definate pattern change on the cards which will not likely revert to what we have seen in the last 7-10 days.

hi gp what are the ideal GWO phases for heatwave condition in July and August?

For heatwave pattern, the GWO would need to be in the El Nino phases 5-6-7 which features a mid Atlantic trough.

[Gavin P]

Thanks GP. So once we get rid of the heat in the opening days July 2010 looks to be a pretty poor month?

Edited June 26, 2010 by Gavin P

[Cecil Hogmanay Melchett]

Thanks GP. So once we get rid of the heat in the opening days July 2010 looks to be a pretty poor month?

You are writing off the whole of July as a pretty poor month?

[Solar Cycles]

Would you say that once locked in, this pattern could persist right through the summer GP?

[BLAST FROM THE PAST]

You are writing off the whole of July as a pretty poor month?

I don't think he is but certainly believes the set up won't be conducive to prolonged heat or dryness. The ALL important sentence is the 'shallowness and axis of the trough'. As we know some parts could be pretty pleasant under those circumstances and others very poor.

BFTP

Edited June 27, 2010 by BLAST FROM THE PAST

[Iceberg]

Not trying to poo-poo long range forecasts of any description as GP has had some very good successes. This pattern matching can though be very easily put off track, I just went through the last few pages for April/May to see what it was predicting for June and came across a reference that June would be unsettled and cool.

I ma not sure we should really write anything off, remember these are just possibilities some higher, some lower of what might happen and a trough placed slightly differently can give us some very nice hot and thundery weather as opposed to cool NWerlys.

Cheers