Model Output Discussion 01/06/2012

[William of Walworth]

Thanks for those summaries folks.

For summer preferrers, the signals continue to be broadly albeit moderately reassuring in the most recent output which I've just skimmed (I don't have much time). My own expectations are actually very modest -- just some more HP influence even if weakish, some more sunshine and pleasanter-feeling warmth here in the S will do fine. 17 or 18 or even 19C and mostly dry would seem a whole lot nicer by contrast to what we're getting/going to get right now, over this coming weekend!

If the predominant current consensus for next week's trends continues and verifies from about Tuesday or Wednesday, it'll all be about the contrast from now of weather-feel on the ground, even if temps never rise above 20C. I'm a pragmatist here!

Have a rainy cool weekend all. I'm away from this site til Monday**, just hoping the models play ball/behave and don't wildly go into Jet driven reverse over the next 3 days ...ulp.

. (**Luckily where we're going -- Builth Wells -- most of our 'entertainment' and beer will be under shelter!)

[Summer Sun]

Not a bad run from ECM, yes it could be better but after the past 3 weeks its better than nothing, also the good news is pressure stays low over Greenland and Iceland

http://www.null/ds/ecm.htm

[johnholmes]

Just watching the 500mb anomaly charts and the issue from ECMWF-GFS this morning continues with a variable picture. By that I mean they do not agree with one another. One(GFS) has a largish +ve area and an upper ridge in the Iceland//Greenland area the other(ECMWF) has a cut off low over western UK and little sign of any of the GFS ridging. With such differences the pattern for 10-15 days ahead is far from clear in my view.

Much as I posted in the technical thread yesterday=probably a short spell of more settled weather but the overall tendency is still more unsettled than settled.

Only if the 3 anomaly charts show very similar patterns over the same time scale and do this consistently for 2-3 days do I have any confidence to give my idea on the upper air pattern 10-15 days or more down the line.

Edited June 15, 2012 by johnholmes

[shedhead]

Just watching the 500mb anomaly charts and the issue from ECMWF-GFS this morning continues with a variable picture. By that I mean they do not agree with one another. One(GFS) has a largish +ve area and an upper ridge in the Iceland//Greenland area the other(ECMWF) has a cut off low over western UK and little sign of any of the GFS ridging. With such differences the pattern for 10-15 days ahead is far from clear in my view.

Much as I posted in the technical thread yesterday=probably a short spell of more settled weather but the overall tendency is still more unsettled than settled.

Only if the 3 anomaly charts show very similar patterns over the same time scale and do this consistently for 2-3 days do I have any confidence to give my idea on the upper air pattern 10-15 days or more down the line.

Regrettably I have to agree with you John and to be fair that's pretty much what GFS shows across it's full 384hrs timeframe. Rising pressure next week does look set to bring some welcome respite, but it's very easy to see how we could and probably will slip back to a cool, unsettled pattern once again, as heights build to the north and LP's gets attracted to us like lumps of metal to a magnet.

[joggs]

Just watching the 500mb anomaly charts and the issue from ECMWF-GFS this morning continues with a variable picture. By that I mean they do not agree with one another. One(GFS) has a largish +ve area and an upper ridge in the Iceland//Greenland area the other(ECMWF) has a cut off low over western UK and little sign of any of the GFS ridging. With such differences the pattern for 10-15 days ahead is far from clear in my view.

Much as I posted in the technical thread yesterday=probably a short spell of more settled weather but the overall tendency is still more unsettled than settled.

Only if the 3 anomaly charts show very similar patterns over the same time scale and do this consistently for 2-3 days do I have any confidence to give my idea on the upper air pattern 10-15 days or more down the line.

Thanks John keep us updated with your non biased views. Cheers

[Thundery wintry showers]

The current model outputs suggest to me that after a cloudy and breezy weekend with showery rain and then a much brighter week ahead with declining shower activity, there will be a breakdown of some kind from the west during next Friday-Sunday.

It looks unlikely that particularly warm air will establish from the continent, despite a temporary spell of southerly winds, so I don't imagine the breakdown being particularly thundery- probably a bog-standard eastward transfer of Atlantic weather systems with maybe the odd rumble of thunder for a few. The low pressure system showing near the end of the ECMWF run is probably somewhat exaggerated but the ensemble mean again hints that we may see the "return of the westerlies" around then, backing down from hints of a longer quieter spell on yesterday's runs.

Next week may well have something for most of us I imagine, with convective activity and possible thunder quiet widespread on Monday and to a lesser extent on Tuesday, and mostly dry sunny weather for Wednesday, Thursday and possibly Friday. Temperatures will rise to the seasonal average, maybe slightly above in eastern and southern areas, which may be nothing spectacular but it may well feel markedly different to what we've been used to recently.

[Summer Sun]

06z from GFS shows no more deeps lows coming our way which is good, things should become better than of late as high pressure attempts to build although it never takes hold to give a prolonged settled period we should see temperatures around the seasonal average with the south seeing the best of the weather though all areas will be prone to rain at times

http://www.null/ds/gfs.htm

[Gavin P]

Here's today's model based video musing;

Improvements Next Week, but Will It Last?

http://gavsweathervids.com

Starts off with a few words about todays "one in fifty year event"

Edited June 15, 2012 by Gavin P

[phil nw.]

Here's today's model based video musing;

Improvements Next Week, but Will It Last?

Starts off with a few words about todays "one in fifty year event"

Yes a good summary of the next week or 2 Gavin.

My views on the latest outputs are fairly similar--improving from unsettled, to shall we say, changeable with some decent slightly warmer days next week but no signal for an extended settled period yet.

The 00z GFS/ECM ens mean heights for days 6-10 show the weakening and splitting of this persistent upper trough currently over the UK area.

However if we look further ahead-tenious i know at this range-at the days 11-15 anomolies we see lower heights again across the UK.

This later output reflects the forecasted MJO activity into Phase 1 as we enter July

So at the moment an improvement next week but unfortunately no real indications of a prolonged warm/dry period.

Edited June 15, 2012 by phil n.warks.

[Gavin P]

Thanks Phil

Latest Met 30 day update actually sounds a lot worse than our Thoughts with a another very unsettled spell setting up from next week to the end of the month.

Edited June 15, 2012 by Gavin P

[Milhouse]

The 06z ens mean looks quite good for a more prolonged spell of high pressure persisting through the weekend into the following week. The 1020mb line is still lurking over southern England next monday.

[phil nw.]

Thanks Phil

Latest Met 30 day update actually sounds a lot worse than our Thoughts with a another very unsettled spell setting up from next week to the end of the month.

Certainly the 16-30 day outlook doesn`t look very settled Gavin.

http://forum.netweat...20#entry2317258

Some days around the middle of next week look OK as we get some ridging from the near continent but, as you showed in your Video,the Atlantic looks to pushing in again from time to time keeping things changeable.

Edited June 15, 2012 by phil n.warks.

[Bobby]

The NAEFS anomolies shows an attempt at settling things down but then troughing returns eventually

Edited June 15, 2012 by Barb-

[Summer Sun]

Not a bad run from GFS tonight, although high pressure never takes control the unsettled weather of the past few weeks shouldn't be repeated thanfully

http://www.null/ds/gfs.htm

[phil nw.]

Not a bad run from GFS tonight, although high pressure never takes control the unsettled weather of the past few weeks shouldn't be repeated thanfully

http://www.jp2webdes...o.uk/ds/gfs.htm

Yes it about sums the GFS output Gavin.Improving for a while as we can see the upper trough (green)shrinking and splitting allowing some ridging high pressure across the UK. early next week.

It should give a much drier and brighter few days and perhaps warmer in the south later if we get some drift off the continent.

UKMO goes with the improvement too but shows another low closer to the west by Thurs.-so some uncertainty on how long this will last.

Edited June 15, 2012 by phil n.warks.

[Bobby]

The GEM and UKMO are quite different at +144 to the GFS with another low rolling in from the Atlantic

[Cloud 10]

UKMO and GEM showing yet another low heading our way towards the end of next week.

http://modeles.meteo...em-0-144.png?12

http://www.meteociel...44-21.GIF?15-18

The GFS has the low stalling to the west of us against an area of high pressure,and fits in well

with the MJO forecast.

http://modeles.meteo...fs-0-144.png?12

Lets see what the ECM churns out.

lol,barb ^^

Edited June 15, 2012 by Cloud 10

[PubliusEnigma]

Ok so looking further ahead in search of summer, it would appear the ensembles move away from the long term troughing over the UK, so whist they hit at a westerly or flat jet as we enter July, it surely will be less wet and have more sunny days than we've seen in a very long time. Next weeks warm and sunny weather seems to be shrinking in duration with each run and the MO are now hinting at a 48 hour window in the unsettled weather before rain and unsettled conditions return to see out the month of June with more of the same likely to be case as we move into July. The ensembles show low pressure establishing over greenland at last

but the Azores high beginning to root itself mid atlantic. If this is the case expect an unsettled start to

July which may well persist for some considerable time, as this set up is often difficult to shift. The

Met office paints a bleaker outlook with its 16-30 day outlook updated today, calling for cooler and wetter

conditions the further we go into July, with the South prone to higher rainfall and below average temps.

In a word more of the same since we've seen since April. Im not sure if we have any growers amongst us here

but almost everything in my greenhouse has rotted away or been consumed by mould this summer, tomatoes have no

fruit at all. Haven't seen anything like this in living memory not even in 2007.

MO UK Outlook for Saturday 30 Jun 2012 to Saturday 14 Jul 2012:

Periods of unsettled weather are likely to continue although these may be interspersed with drier conditions at times. Temperatures are expected to start off a little below the seasonal average, but possibly recovering to nearer normal later in the period. Rainfall amounts are generally expected to be close to the seasonal average, but may still be above normal in the south.

[Summer Sun]

ECM showing things becoming slightly more settled than of late during next week before a low pressure system begins to move into the south west worth keeping an eye on to see if it deepens further

Pressure falls over Greenland and Iceland which is a start it should alow the Jet to head northwards again

[OldMetMan]

I am finding this summer especially interesting in terms of contrasts and extremes and, at the moment, the models seem to be in a sort of no-mans-land as to what is likely to happen following this current LP, that is, after the next 3-4 days. The consensus at the moment puts the UK in a slack vaguely low pressure field after the current low fills with a weak HP possible settling things down temporarily but I have seen some hints of another significant weather event within the next 7-10 days.

Given that the jet is still way south, and there is still likely to be a broad upper trough over much of the E Atlantic for some days yet, what I am looking at is a steady increase in thickness values, and thus surface temperatures over W Europe and I have seen this pattern produce "Spanish Plume" events in the past, with hot, humid air heading N very close to the SE of the UK and engaging the upper trough and jet. This is being shown at intervals in the GFS and especially the ECM today. The previous unusually deep LPs this month have not had this added element and they produced more than enough rain!

The significance of this is clearly the threat of a major thundery LP crossing the UK, most likely the S and E, but accompanied by very high rainfall amounts with the cool Atlantic air undercutting the hot, humid continental air. If this is going to happen, we should see the models picking up on it within the next 2-3 days.

2 previous instances of this happening that I remember most vividly at July and September 1968.

In the meantime, the weakish HP looks likely as per the GFS early next week, but I can't see anything yet to suggest a longer settled spell. The upper pattern is very meridional but, like I said in an earlier post, there has been alternating upper high/upper low blocking for much of this year so we need to see the models suggesting a more zonal flow, with the jet moving back to where it usually is and the Azores HP being given a chance to push in. At the moment, that is conspicuous by its absence.

One last point, the slack pressure field early next week, with fairly low thickness values gives a significant risk of some local heavy - and slow moving - downpours.

[Bobby]

The Atlantic seems to be pretty strong for the time of year, it has a 'return of the westerlies' look about it. There are signals for pressure builds and ridging but will it hold against all those troughs and LPs...

Looks marginal to say the least I would say.

Edited June 15, 2012 by Barb-

[Summer Sun]

Final Run's from ECM show pressure rising slowly

Only concern could be that pressure is to rise over Greenland again

Edited June 15, 2012 by Gavin D

[Thundery wintry showers]

In the meantime, the weakish HP looks likely as per the GFS early next week, but I can't see anything yet to suggest a longer settled spell. The upper pattern is very meridional but, like I said in an earlier post, there has been alternating upper high/upper low blocking for much of this year so we need to see the models suggesting a more zonal flow, with the jet moving back to where it usually is and the Azores HP being given a chance to push in. At the moment, that is conspicuous by its absence.

That latter description reminds me a lot of the August 1998 pattern- a strong ridging Azores HP, the jet in its usual position, and a broad scoop of westerly winds in between, giving dry sunny weather for the south and somewhat cloudier and breezier weather further north.

Thus I think particularly for northern areas it helps if the jet is relatively weak and/or displaced further north than its usual position at our end of the Atlantic, which introduces greater scope for those ridges of high pressure to establish further to the north and east, perhaps forming breakaway anticyclones over western Europe which can prove pretty hard to shift.

We're always going to struggle for much "summery" weather though when the default track of low pressure systems is over central and southern Britain.

I agree with OldMetMan's point about heavy slow-moving downpours- on the basis of UKMO/GFS, these will be most likely early and late next week (as pressure falls from the west towards next Friday) with most places staying dry and sunny around midweek. Both UKMO and GFS suggest a lull in the jet, allowing high pressure to develop quite widely as far north as Scandinavia. The ECMWF outputs look somewhat dodgier for "summery" prospects with the temporary weak high pressure giving way to an active low pressure system by Thursday/Friday which could well bring some organised rain north-eastwards (rather than the thundery showers indicated by the GFS), as well as introducing a rather chilly north-westerly type afterwards.

[Carl46Wrexham]

I am finding this summer especially interesting in terms of contrasts and extremes and, at the moment, the models seem to be in a sort of no-mans-land as to what is likely to happen following this current LP, that is, after the next 3-4 days. The consensus at the moment puts the UK in a slack vaguely low pressure field after the current low fills with a weak HP possible settling things down temporarily but I have seen some hints of another significant weather event within the next 7-10 days.

Given that the jet is still way south, and there is still likely to be a broad upper trough over much of the E Atlantic for some days yet, what I am looking at is a steady increase in thickness values, and thus surface temperatures over W Europe and I have seen this pattern produce "Spanish Plume" events in the past, with hot, humid air heading N very close to the SE of the UK and engaging the upper trough and jet. This is being shown at intervals in the GFS and especially the ECM today. The previous unusually deep LPs this month have not had this added element and they produced more than enough rain!

The significance of this is clearly the threat of a major thundery LP crossing the UK, most likely the S and E, but accompanied by very high rainfall amounts with the cool Atlantic air undercutting the hot, humid continental air. If this is going to happen, we should see the models picking up on it within the next 2-3 days.

2 previous instances of this happening that I remember most vividly at July and September 1968.

In the meantime, the weakish HP looks likely as per the GFS early next week, but I can't see anything yet to suggest a longer settled spell. The upper pattern is very meridional but, like I said in an earlier post, there has been alternating upper high/upper low blocking for much of this year so we need to see the models suggesting a more zonal flow, with the jet moving back to where it usually is and the Azores HP being given a chance to push in. At the moment, that is conspicuous by its absence.

One last point, the slack pressure field early next week, with fairly low thickness values gives a significant risk of some local heavy - and slow moving - downpours.

I vaguely recall the storms of July 1st and 2nd 1968. What stands out in my memory about them , was the coloured rain (contamination from Saharan dust?)...the large hail, and that there were so many storms...one after another after another, that and how dark it was during the day. Most of all though...the explosion from an electricity substation a quarter mile from my house having taken a direct hit from a CG bolt.

Edited June 15, 2012 by Carl43Wrexham

[Methuselah]

I vaguely recall the storms of July 1st and 2nd 1968. What stands out in my memory about them , was the coloured rain (contamination from Saharan dust?)...the large hail, and that there were so many storms...one after another after another, that and how dark it was during the day. Most of all though...the explosion from an electricity substation a quarter mile from my house having taken a direct hit from a CG bolt.

I remember that, too...Late June or early July, and 33C in London? Was that the year when the Macclesfield game was called-off after several players were struck by lightning?