Model Output Discussion 06Z, 13 Sep. 2013 ---->

[Cloud 10]

Looks like a major pattern change is on the way as we head into next weekend and into the start of October.

 

The 500mb anomalies for the first half of September with low heights over Greenland and strong Azores ridging giving a positive NAO look to be on the way out....

 

       

 

 

....giving a much more unsettled pattern with a southerly tracking jet and negative NAO etc. hinted at by the NAEFS and ECM ensemble mean charts for day 7.

 

naefs..  ecm..

 

 

Some very pleasant weather to come over the next few days however,with some sunshine and temperatures in the low seventies for many areas. 

[johnholmes]

The output this morning from ECMWF-GFS shows yet another change, especially the EC version, now an upper low where it had a ridge yesterday. So no help from the anomaly charts that I use, NOAA does suggest, with a more stable output over the last few days, that a westerly 500mb flow is the most likely within the 6-15 day time scale?

ECMWF-GFS

http://www.meteo.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

and below is the NOAA version for 5-10 and 8-14 days

http://www.cpc.ncep.noaa.gov/products/predictions/610day/500mb.php

 

I have nothing against the NAEFS output but have never got round to doing similar checks on it to those I have done on the other 3.

Thus I remain on the fence really but tending to favour the NOAA version as being the most likely.

Edited September 21, 2013 by johnholmes

[Summer Sun]

Latest from Gibby

 

All models show a moist and warm SW flow across the UK with a weak warm front moving NE across most areas. Some brightness may develop in the lee of High ground to the West and SW such as the East of Scotland and East Wales with some warm sunshine possible. Then through the following days some more warm sunshine will develop as drier air gradually feeds over some Southern and Eastern areas while the North and West stay more cloudy and damp.

 

GFS then shows a slow decline in pressure through next week though any major rain bearing events are not shown by GFS operational run this morning this side of next weekend. However, it will become slowly cooler and stay quite cloudy with some showery rain in places by the end of the week. Then in the second half of the run the engagement of warm and cool air masses either side of the UK takes place spawning a deep Low pressure area which crosses the UK with rain and strong winds towards the end of the run when temperatures fall near to or a little below average.

 

UKMO today shows the UK in a void of pressure in among a multi centre bank of Low pressure which stretches between Russia, parts of Europe through the Atlantic and even out to Newfoundland. There is no major system at the Day 6 chart which affects the UK directly but the promise of cooler weather will be what is felt the most through next week rather than any major rain event.

 

GEM shows what does happen when colder Autumnal air from the Arctic engages the warmer Atlantic air out to the SW which as the early week High pressure dissolves away opens the door for this engagement to give rise to a deep Autumnal Low to spin across the UK towards next weekend and the week that follows with cool weather and rain and gales likely for all for a time.

 

NAVGEM is much more sedate towards changes next week with a gentler introduction to cooler weather from the North with rain limited to more Northern areas where a chilly North or NW wind will develop.

 

ECM shows a GEM and GFS type scenario as colder air from the North engages the milder air to the South with a deep and vigorous Low sweeping East across England at the start of the week after next with rain and gales sweeping East to all.

 

The GFS Ensembles show strong support for cooler conditions next week. It takes a long tome for though for conditions to become more unsettled with rainfall reserved for late in the run for many. The operational run was very much a cool outlier for the second half of the run with a more average level of temperature the more likely outcome.

 

The Jet Stream shows the flow migrating north away from the UK into next week before the flow weakens and edges South thereafter. Late in the output a new arm is shown exiting the States across the Atlantic on a course South of 50 deg North which could take it South of the UK in the second part of the run.

 

In Summary I yesterday talked about what could happen if the very cool air to the North of the UK next week engaged with the warm air still to the South of Britain. Today we have charts that show that very thing happening as GEM, ECM  and GFS all whisk up a deep Autumnal Low with gales and heavy rain in a week or so time. Other models appear to be sitting on the fence waiting for something noteworthy to happen and as a result show just benign conditions for much of next week with the only constant shown between all the models being the certainty that things will turn somewhat cooler as we move deeper into next week. Perhaps the weekend runs to come will begin to make things rather clearer on where the weather is trending later next week and onward.

 

http://www.norton-radstockweather.co.uk/Model-Analysis%282859336%29.htm

[Frosty.]

The Ukmo 00z indicates that changes could occur later next week with a gradual trend to cooler and unsettled weather, at least across the north but a weak ridge could hold across more southern areas, not before we have another very late burst of summery, anticyclonic weather with temps into the low 20's celsius, maybe nearer mid 20's for the more southern/se areas for a time, especially from monday until around midweek but then I think confidence in the forecast drops away, still, I think we should enjoy the upcoming fine and warm weather instead of worrying when it ends, after all, it's not summer anymore.

Edited September 21, 2013 by Frosty.

[Frosty.]

There is no denying that unsettled and cooler weather is on the way, it looks like by next weekend it will have turned into proper autumn weather with the polar front jet heading south for longer than last time, there is a very cool unsettled plunge sweeping down across scandinavia and unsettled weather pushing in from the southwest and they look like clashing over the uk in about a week, give or take a day or two but in the meantime we have a very decent spell of pleasant anticyclonic weather to look forward to according to the latest Ecm 00z ensemble mean with increasing sunshine and warmth in the days ahead until around midweek or possibly as far as thursday, at least across the south of the uk but the fine spell looks like it's not going to last, neither is the warmth, at least that is the impression I get from this run.

[Skeggy Winter Storm]

There is no denying that unsettled and cooler weather is on the way, it looks like by next weekend it will have turned into proper autumn weather with the polar front jet heading south for longer than last time, there is a very cool unsettled plunge sweeping down across scandinavia and unsettled weather pushing in from the southwest and they look like clashing over the uk in about a week, give or take a day or two but in the meantime we have a very decent spell of pleasant anticyclonic weather to look forward to according to the latest Ecm 00z ensemble mean with increasing sunshine and warmth in the days ahead until around midweek or possibly as far as thursday, at least across the south of the uk but the fine spell looks like it's not going to last, neither is the warmth, at least that is the impression I get from this run.

good post frosty it does look like its going to turn autumnal i for one am happy we've had a decent summer this year

[Severe Siberian icy blast]

Looks like a major pattern change is on the way as we head into next weekend and into the start of October.

 

The 500mb anomalies for the first half of September with low heights over Greenland and strong Azores ridging giving a positive NAO look to be on the way out....

 

1sthalfsep.gif        nao.fcst.gif

 

 

....giving a much more unsettled pattern with a southerly tracking jet and negative NAO etc. hinted at by the NAEFS and ECM ensemble mean charts for day 7.

 

naefs..naefsnh-0-0-168.png  ecm..EDH101-168.GIF

 

 

Some very pleasant weather to come over the next few days however,with some sunshine and temperatures in the low seventies for many areas. 

I wonder how long it is since we saw such negative NAO values heading into winter? 2010? I know last winter came in with a week +NAO , despite the snowy spells . If this were six weeks from now we would have a very interesting scenario on our hands , but it's stil a fanctaistc profile to see such northern blocking around, I remember last sept/oct we had something similar ?

[Summer Sun]

NAO heading to its lowest point for several months

 

 

If your seeking cold weather you need to hope this hasn't peaked at its lowest too early

Edited September 21, 2013 by Summer Sun

[bluearmy]

discrepancies between ecm and naefs anomolys days 7 thru 10. ecm is unsettled whilst naefs is weakly negative.  

[Mark Neal.]

GFS 6Z Run. Showing next week, settled start with warmer conditions, becoming breezier towards end of week with lower heights closeby. Should be pleasant for much of the week. 

   

 

    

Edited September 21, 2013 by Mark Neal.

[DTHFCJ]

Well if the ECM verified then the metoffice would have to rewrite pretty much all their forecast, though it's not the first time this week that's happened.

Lets hope the ECM is off on one 

Good call Sir...looks like its downhill quicker than arsenal's slip down the prem league

[Frosty.]

The GFS 06z operational run shows a spell of increasingly warm & sunny weather from tomorrow until tuesday, monday is the pinnacle of the warmth and sunshine with the 564 dam line an unusually long way north for this time of year, however, by tuesday the 564 dam is shrinking away southeastwards very quickly with the very warm air going with it but conditions at the surface look very similar for at least the southern half of the uk, by midweek a definate cooling from the north with more cloud and slowly turning more unsettled but the south still looks on the warm side of average by midweek but significantly cooler than mon/tues..by thursday and friday any residual warmth in the south drains away to the far southwest and then it looks cooler than average by the end of the week across the whole country, it trends very cool and unsettled with the 528 dam line spreading south towards northern scotland with a very cool unsettled N'ly/NEly airflow and becoming cold enough for snow on the scottish mountains and higher hills, a real chill eventually on the 6z op run but it just doesn't quite pull the trigger to unleash a freakishly early cold spell, it gets cut off as high pressure begins to nudge in from the southwest..BUT..this run has huge potential to unleash a very early cold blast with a retrogressing pattern which would be EPIC in the winter months, main message appears to be..make the most of the warmth during the next 4 days or so, it looks like a BIG change is on the way from later next week.

[snowking]

MJO Phase 6 signature (increasingly unsettled) beginning to be reflected in the days 5-10 NWP output. Expect some further swings for a couple of days yet as I imagine NWP is probably still having a little difficulty in resolving the energy fusing in to the jet stream from Humberto. Hopefully in to Monday/Tuesday a more consistent signal should begin to appear...and unfortunately that consistent signal looks as though it will be an unsettled one.

 

The next shot at something more settled currently around days 15-25, with little coherent MJO or GWO signal as both tropical convection and global angular momentum fall to average levels...this is not a guarantee of settled conditions, merely the best chance of such conditions.

 

Beyond that there is a growing trend from OLR plots to introduce something around phases 1/2/3 through the second half of October - all three of which suggest something rather unsettled.

 

So as a rough timetable based upon current projections:

 

27th Sept - 5th October - Unsettled

6th-16th October - Something more settled?

17th October Onwards - Unsettled once again

 

Timings are of course approximate

 

SK

[Summer Sun]

MJO Phase 6 signature (increasingly unsettled) beginning to be reflected in the days 5-10 NWP output. Expect some further swings for a couple of days yet as I imagine NWP is probably still having a little difficulty in resolving the energy fusing in to the jet stream from Humberto. Hopefully in to Monday/Tuesday a more consistent signal should begin to appear...and unfortunately that consistent signal looks as though it will be an unsettled one.

 

The next shot at something more settled currently around days 15-25, with little coherent MJO or GWO signal as both tropical convection and global angular momentum fall to average levels...this is not a guarantee of settled conditions, merely the best chance of such conditions.

 

Beyond that there is a growing trend from OLR plots to introduce something around phases 1/2/3 through the second half of October - all three of which suggest something rather unsettled.

 

So as a rough timetable based upon current projections:

 

27th Sept - 5th October - Unsettled

6th-16th October - Something more settled?

17th October Onwards - Unsettled once again

 

Timings are of course approximate

 

SK

 

Met office update backs you up for the next possible settled spell

 

 

UK Outlook for Saturday 5 Oct 2013 to Saturday 19 Oct 2013:

 

After a relatively unsettled start to October, most places can expect to see some more in the way of settled periods of weather through the month. These most frequent in southern and eastern UK. Further north and west there is a greater risk of seeing more changeable weather with showers or more prolonged rain at times. Temperatures should remain close to average but it may be warm at times in the south and east.

 

 

Looks a good call to me SK

 

[draztik]

How things can change. I haven't been watching the models for any length of time, but the recent output, the changes etc, I haven't seen anything like it before. Even at t96, the changes between gfs runs back to back have been eye popping. The ensembles have certainly nosedived recently, and its now all but certain we are readying for an unsettled period. Autumn lovers, rejoice! I'm only thankful i wont be reading "epic, sensational" et al, in relation to warm periods... gosh, that got old awful fast!

[Frosty.]

The GEFS 06z mean is not quite as gung ho as the 6z op run about the cold and very unsettled outlook but it does gradually turn cooler and more unsettled with winds swinging into a NEly quarter for a while so it would still be a shock to the system following the more summerlike spell, through FI the mean shows high pressure migrating to the southeast across the near continent and a large complex trough swinging down from the northwest, so a nw/se split eventually with the driest, brightest and relatively warmer weather across the south & east, most unsettled, coolest and windiest across the north and west of the uk but that's all in FI..for the time being it's an increasingly warm and sunny spell ahead, especially through the first half of next week and the warmth persists until the end of next week across the far south of the uk but becoming progressively cooler and more unsettled further north, especially across the northeast of the BI. The charts become much more autumnal then and although there is then a recovery for the east and south, the northwest of the uk looks like descending into proper autumn weather with gales and heavy rain interspersed by clearer, showery weather through early october with the PFJ very close to the northwest of scotland.

Edited September 21, 2013 by Frosty.

[Captain Shortwave]

How things can change. I haven't been watching the models for any length of time, but the recent output, the changes etc, I haven't seen anything like it before. Even at t96, the changes between gfs runs back to back have been eye popping. The ensembles have certainly nosedived recently, and its now all but certain we are readying for an unsettled period. Autumn lovers, rejoice! I'm only thankful i wont be reading "epic, sensational" et al, in relation to warm periods... gosh, that got old awful fast!

You think the summer is bad?

If you don't like freezing cold and furious blizzards then you are in for a world of pain once winter arrives 

[Frosty.]

Have to say i'm surprised the met office don't think we will eventually engage that unusually cold air or at least very cool air to the northeast with a N'ly/NE'ly flow as the mean shows, more of a westerly or sw'ly instead so only feeling relatively on the cool side with stronger winds at times and unsettled at times but nothing below average, very surprising indeed in my opinion, i'm actually disappointed, I was looking forward to an early cold plunge with wintry ppn to northern hills.

Edited September 21, 2013 by Frosty.

[Captain Shortwave]

Well the warm air clears from the south Wednesday,  but

 

The GFS gets the flow coming from the south again a day later and the warmth pushes northwards again

Edited September 21, 2013 by Captain shortwave

[Tim Bland]

Going by the ensembles I would say a good chance of snow over Scottish hills and mountains around the turn of the month

[Summer Sun]

Nothing overly cold on this afternoon's GFS run

 

This is the coolest it gets

 

 

Very short lived

 

 

The bulk of the colder uppers are staying in eastern europe

Edited September 21, 2013 by Summer Sun

[Summer Sun]

UKMO once again shows pressure becoming lower through next week

 

[Summer Sun]

ECM is showing pressure falling away but remaining mild out to t144 this evening as per GFS colder uppers are building over eastern Europe whilst the UK remains in the milder Atlantic air

 

[Captain Shortwave]

Well the ECM agrees with the GFS in throwing one last gasp of warm air towards the UK Friday in Saturday

 

It could produce something interesting in the rain/thunder department.

Interestingly the ECM isn't too far off keeping the south warm or very warm throughout next week.

Breakdown next weekend looks the form horse (as in proper breakdown). The output looks distinctly westerly based which would pretty much be average for the time of year.

Edited September 21, 2013 by Captain shortwave

[Summer Sun]

+10 uppers pushing northwards again next Saturday

 

 

Cooler uppers push in at t192