Model Output Discussion - 1st July Onwards 18z--->

[Frosty.]

I'm really optimistic about August weather prospects with high pressure building in from the southwest and bringing a largely settled and warmer spell to most of the UK which is exactly what the experts are saying and the gfs 6z is hinting at. Now that early August is within gfs range, it will be fascinating to see the change to anticyclonic conditions evolve. The south has had a good summer so far whilst in the north/northwest of the UK it's been abysmal but I think we will all see a good deal of fine and warm / very warm / occasionally hot weather for the majority of the final month of this meteorological summer.

Edited July 20, 2015 by Frosty.

[Tamara]

i dont get the mjo.... i get the theory, but i dont find the mjo phase is a very good indicator as to what we are supposed to get. ill stick to the noaa anomaly charts as they seem to be most accurate for predicting the upper air pattern.

 

 

indeed, a westerly flow out to two weeks ahead looks likely, whilst not great its probably the only way to return to possible high pressure dominance close to the uk. as i see it, theres no quick way back so a gradual upper air pattern shift is worth watching for if we desire a decent lasting settled spell. currently high pressure dominance is always in deep fi.

its fairly safe now to write off the rest of july in terms of heat. the anomaly charts predicted a trough to our northeast, high to our west, leaving the uk in a cool northerly sourced airmass. thats what we are going to get this week, very poor for those of us who desire heat, very good for those who dont, plenty of mainly dry weather too which i like and feeling pleasant in any sunny intervals. so not bad weather, just suppressed temps.

 

A large portion of the global circulation variability in the upper troposphere is accounted for through heating directly related to MJO convection passage through the tropics.

 

MJO teleconnection from the tropics to the extra tropics occurs in the form of a Rossby wave train - characterised by the northwards and eastward propagation of these waves from the vicinity of the heating source in the tropics.

 

With such knock-on effects through ever increasing wave activity transport to the extra tropics, the MJO becomes an increasing forcing on our NH weather patterns, the further east it heads towards the dateline. In this way, the extra tropical signal, the Global Wind Oscillation (which acts as a measure of the direction of travel, upwards or downwards, of Atmospheric and Angular momentum tendency) reacts according to the extent of eastward movement and amplitude strength of tropical convection - and as a consequence of this, atmospheric circulation effects on weather patterns will vary according to whether they are imprinted and coupled to an ocean signal which is deferred to either an El Nino or La Nina signature.

 

During El Nino phases, such as we are currently seeing increasingly strengthen and imprint on atmospheric circulation patterns, eastward propagation of wave activity is much greater than during Nina phase response when MJO convection is retracted to the Western Pacific. The latter, much as was seen through all last winter and much of the Spring - a period when the atmosphere and ocean signals were actually de-coupled

 

Described thus far, it merely touches the surface of the principles involved. Its too complex a relationship to describe for these pages, but for the reasons given in answer to your post, atmosphere/ocean coupling signals and their combined effect on global AAM tendency tell us a lot about how global synoptic weather patterns will be modelled - and as such are a very important and useful guide as to how the upper air pattern, in turn, as depicted in the anomaly charts, may evolve

 

Previously, over a week back, suggestions were made that a warming trend and more widespread settled conditions would follow the present westerly changeable and flat pattern which is more especially a bane for northern parts. Southern and eastern parts of the UK have fared well so far this summer from the predominant N/S split and only this week sees any departure from that but with temperatures still close to average in real terms.

 

Such more general improvement has been anticipated to eventually arrive based on the current state of both the ocean tropical, and extra tropical atmospheric signals becoming more conducive to slowing the upstream Asian-Pacific jet stream, which, in tandem with a +PNA pattern over the US, is supplying us downstream with an active flat sub tropical jet profile - dividing the warm humid air to the south (and extreme heat over southern and parts of central europe) and the cool summer arctic air spilling south over the North Atlantic and Northern Europe.

 

This set-up is exacerbated through the combination of troughing over Scandinavia and heights over Greenland and NE Canada which act to both suppress the jet stream, and also create a temperature gradient where the different air masses meet- which in turn is providing the secondary spawning lows which interact and phase in the jet stream with the main upper trough over Scandinavia.

 

Decreased amplitude GWO phase orbit 7/8/0/1 in line with a transitional incoherent MJO signal (ahead of the next MJO convection wave starting in the Indian Ocean to follow the previous seismic East Pacific wave activity the other week) fully advertises the NE upper trough, upstream flat jet pattern and consequent mobile westerly pattern which is impacting our weather patterns

 

The evolution towards upstream change as described in previous posts is still forthcoming, but is proving a more erratic and slower process than could have been anticipated. The GWO is, for now, set mired in that very low amplitude Phase 7/8/0/1 sequence...

 

http://www.atmos.albany.edu/student/nschiral/research/gwo/gfsgwo_1.png

 

It was caveated though in previous postings that changeable conditions would persist until this orbit sequence was spent.

 

Its a case of keep pressing Press F5.... while this rut persists. It will persist until the next MJO wave imprints on atmosphere/ocean coupling signals and forces a change in the current upper air pattern from upstream and our troughing is ejected and "warms out".

 

 

There is MJO model indication of initiation starting again towards the Indian Ocean - at expected low amplitude. This would be expected with time to increase amplitude in line with the prevailing Nino conditions once again at it orbits further and further east through the Pacific towards the dateline

 

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/CLIVAR/ECMF_phase_51m_small.gif

 

In simple synoptic weather pattern summary terms, as an interpretation of all this - the anticipated more widespread improvement previously suggested for the last week of July is delayed for the next 10 days or so most probably.

 

Assuming signals start emerging soon enough from the Global Wind Oscillation of an  increasing amplitude away from changeable and cool Phases 0/1 to warmer and more settled Phase 3 to 5 ( as a result of renewed eastward MJO convection stimulating and changing the upstream pattern closer and closer towards us) there is good reasons for optimism regarding an eventual improvement from the south and west as the troughing relaxes away from us and the retracted Azores High to our west adjusts back eastwards towards the UK and Europe.

 

Good enough reason perhaps to eventually envisage quite a turn-about with pressure ridging towards Scandinavia as we head through the first week, perhaps more likely the second week, of August, to replace the stubborn upper trough

 

This will no doubt all appear to smack of jam tomorrow in terms of finding some more real summer weather for the majority, but most especially for areas further north who have been very short changed in terms of the predominantly very good weather enjoyed in southern and south eastern parts so far this summer.

 

However, hopefully some grounds for optimism for the turn of the new month  providing better fortunes for greater numbers, before the longest days and lightest evenings start properly drawing out from the last third of August and thereafter.

[fat chad]

Thank you for the thorough answer Tamara..... I am very sorry that your knowledge of this did not commute into my brain as you lost me on the second paragraph... But a proper sincere thankyou for the excellent posts you do all year round....

Edited July 20, 2015 by fat chad

[Frosty.]

The Gfs 12z looks rather more summery into early August than the 6z with a spell of warm anticyclonic weather and becoming very warm in the south with the promise of much more widespread settled weather once that trough fills and drifts away north. The met office seem very confident that a large part of August will be much more like most of us on here are hoping for and I expect we will be seeing lots of very summery low res charts in the days ahead.

[knocker]

This evenings GEFS anomalies are continuing the theme that it and the ECM have bee running for a few days now. To wit weakening of the upper trough and more influence from the Azores by the beginning of August with a distinct possibility of all of the UK getting some pleasant weather albeit not that hot. The weak trough shunted to Iceland and it could look something like this.

http://www.tropicaltidbits.com/

Edited July 20, 2015 by knocker

[Andy Bown]

Ian Fergusson on BBC Points West highlighted the uncertainty at just 96 hours this evening, showing a weak HIGH over Southern UK on Thursday with a pretty deep LOW to the SW. His warning (of course for the West Country region) was that Friday could go one of 2 ways, either very wet or dry and warm, and he would need to see the next model runs to see what the latest projection is.

 

It reminds me very much of the uncertainty for yesterday which in forecasting and modelling terms initially looked warm/dry then at 48 hours in advance turned into looking very wet before reverting to the former after a brief splash of rain.

 

IMO it's fairly pointless looking beyond T96 because the conditions after that will be hugely influenced by where that LOW goes, if it develops!

[mushymanrob]

Thanks for the reply tamara, i and others i dare say are also srruggling understanding the complexities of the mjo and other data, appreciates your explaination. Cheers.

[mushymanrob]

Ian Fergusson on BBC Points West highlighted the uncertainty at just 96 hours this evening, showing a weak HIGH over Southern UK on Thursday with a pretty deep LOW to the SW. His warning (of course for the West Country region) was that Friday could go one of 2 ways, either very wet or dry and warm, and he would need to see the next model runs to see what the latest projection is.

It reminds me very much of the uncertainty for yesterday which in forecasting and modelling terms initially looked warm/dry then at 48 hours in advance turned into looking very wet before reverting to the former after a brief splash of rain.

IMO it's fairly pointless looking beyond T96 because the conditions after that will be hugely influenced by where that LOW goes, if it develops!

See this is where i respectfully disagrees.

As i posted on the ramps/moans thread, the uncertainty is temporary detail. All data sources agree on the general pattern over the next ten days or so. So it matters not whether that little low develops or not, itll be a temporary blip in the general pattern not a pattern changing event. So it remains largely unsettled, and rather cool probably for the rest of the month.

Ps.. I hope im spectacularly wrong!!!

Edited July 20, 2015 by mushymanrob

[knocker]

Ian Fergusson on BBC Points West highlighted the uncertainty at just 96 hours this evening, showing a weak HIGH over Southern UK on Thursday with a pretty deep LOW to the SW. His warning (of course for the West Country region) was that Friday could go one of 2 ways, either very wet or dry and warm, and he would need to see the next model runs to see what the latest projection is.

 

It reminds me very much of the uncertainty for yesterday which in forecasting and modelling terms initially looked warm/dry then at 48 hours in advance turned into looking very wet before reverting to the former after a brief splash of rain.

 

IMO it's fairly pointless looking beyond T96 because the conditions after that will be hugely influenced by where that LOW goes, if it develops!

 

Yes I was looking at this little fella earlier.

Edited July 20, 2015 by knocker

[johnholmes]

See this is where i respectfully disagrees.

As i posted on the ramps/moans thread, the uncertainty is temporary detail. All data sources agree on the general pattern over the next ten days or so. So it matters not whether that little low develops or not, itll be a temporary blip in the general pattern not a pattern changing event. So it remains largely unsettled, and rather cool probably for the rest of the month.

Ps.. I hope im spectacularly wrong!!!

 

your comment seems about right mushy, the anomaly charts, all 3 main ones, all suggest quite solidly a westerly atlantic flow with the strongest of the flow in the southern half of the UK. The air at 500mb starts life over nne Russia, crossing over the far south of Hudson Bay and then over the far south of England. No sign on any of them of risges or any +ve heights near the UK. I persistent signal for +ve heights off/over the southern part of the Aleutian Isles.

Unsettled or changeable whichever word you prefer seems to sum up the weather for 6-15 days, perhaps longer. The heights shown for 500mb suggest, other than an isolated day that our temperatures are not going to be raising any more heat about jet eflux effects at Heathrow!

links as usual below

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

http://mp1.met.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

Edited July 20, 2015 by johnholmes

[Woollymummy]

Thank you for the thorough answer Tamara..... I am very sorry that your knowledge of this did not commute into my brain as you lost me on the second paragraph... But a proper sincere thankyou for the excellent posts you do all year round....

I was trying to read up it again, to clear things in my mind a bit, this helped, although it is aimed at Southern Hemisphere thinking so the clockwise/counterclockwise thing is opposite for us.

http://www-das.uwyo.edu/~geerts/cwx/notes/chap12/pot_vort.html

Hope that is useful

[Woollymummy]

Yes, yes, charts discussion. We could play a party game: pin the Rossby-wave-tails on the chart!

[knocker]

The ext ECM is also going for the decline of the upper trough to a weak affair north of the UK giving a broad band of HP across the Atlantic to eastern Europe. This zonal flow would bring more settled and dry weather to the UK but only average temps.

[damianslaw]

Reliable timeframe it remains preety changeable with troughs moving down from the NW - cool air over the north distinctly unsummery, average temps in the south. Longer term - secondary low development set to spawn and develop over the country ushering in a more general cool NW airflow for all. So nothing particularly warm for the time of year on the horizon nor settled and in this respect very disappointing for what is now 'high summer', a time when we should be reaping the maximum benefits summer can deliver in terms of heat.

[mushymanrob]

The ext ECM is also going for the decline of the upper trough to a weak affair north of the UK giving a broad band of HP across the Atlantic to eastern Europe. This zonal flow would bring more settled and dry weather to the UK but only average temps.

Ill settle for average temps, especially if theres some humidity as that makes it feel warmer.

[mushymanrob]

your comment seems about right mushy, the anomaly charts, all 3 main ones, all suggest quite solidly a westerly atlantic flow with the strongest of the flow in the southern half of the UK. The air at 500mb starts life over nne Russia, crossing over the far south of Hudson Bay and then over the far south of England. No sign on any of them of risges or any +ve heights near the UK. I persistent signal for +ve heights off/over the southern part of the Aleutian Isles.

Unsettled or changeable whichever word you prefer seems to sum up the weather for 6-15 days, perhaps longer. The heights shown for 500mb suggest, other than an isolated day that our temperatures are not going to be raising any more heat about jet eflux effects at Heathrow!

links as usual below

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

http://mp1.met.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

Cheers john, nice to know i dont talk nonsense all the time lol

[knocker]

The latest EC32 update has the upper trough weakening and away to the east by the 5th August and the Azores ridging into the UK. This broadly speaking is the scenario until the 21st with weak low pressure Iceland eastwards which possible may impinge on occasion on N. Scotland. Thus no established HP cell over the UK but a westerly/north westerly zonal flow. No sign of any great warmth with temps around average but little precipitation.

[knocker]

Regarding this morning's GFS run suffice it to say it has the Friday low running along northern France and then not too bad until the middle of next week at which I decided to abandon ship and wait for the next run which is always a wise move.

http://www.tropicaltidbits.com/

 

[knocker]

Not a day to venture outside Nouska.

Chart weatherbell

 

[Gibby]

HERE IS MY LATEST ANALYSIS USING DATA SUPPLIED BY THE NWP OUTPUT COVERING 5 OF THE WORLDS MOST POWERFUL WEATHER COMPUTERS ISSUED AT 08:00 ON TUESDAY JULY 21ST 2015

 

THE CURRENT GENERAL SITUATION. A WSW flow across the UK will generally persist for the next 24-48hrs delivering scattered showers and bright conditions.

 

http://www.wetterzentrale.de/pics/Rtavn001.gif 

 

MODELS-2 WEEK HEADLINE Still rather changeable with some dry and bright conditions mixed with occasional rain or showers. Becoming drier and warmer everywhere later in the period.

 

THE GFS JET STREAM FORECAST The GFS Jet Stream Forecast keeps the flow blowing West to East across the South of the UK this week albeit quite lightly. Towards the start of next week it strengthens and if anything troughs further South than the UK for a time before it finally breaks up or shifts North in much lighter conditions by the end of the period.

 

http://www.netweather.tv/index.cgi?action=jetstream 

 

GFS OPERATIONAL The GFS Operational Run today is not dissimilar to yesterdays morning's output in that this weeks slack and benign weather pattern becomes replaced by a deep Low early next week with rain and showers in abundance then as well as some quite cool weather. It then becomes replaced by High pressure from the West, on this run across northern Britain while the South sees the remains of a cut off Low pressure area just to the South possibly delivering some thundery showers in the extreme South.

 

http://www.wetterzentrale.de/pics/Rtavn1441.gif

 

http://www.wetterzentrale.de/pics/Rtavn3841.gif 

 

THE GFS CONTROL The GFS Control Run is fairly similar in many respects, certainly in the early to mid run while the end of the period is less clear cut in detail as the High pressure build shown by the operational run at the end of the period being a little more ragged with an eventual pull of it back West out into the Atlantic with some showery rain in the NE on a cool NW flow again.

 

THE GFS CLUSTERS(14 Days) The GFS Clusters at 14 days still indicate a lot of support for High pressure to be lying close by, most likely just to the West with a lot of fine weather suggested for most areas. As always there is some conflicting charts to this pattern in the shape of Atlantic Low pressure towards the North but only amounting to around 20% of members today.

 

http://www.weatheronline.co.uk/cgi-bin/expertcharts?LANG=en&MENU=0000000000&CONT=euro&MODELL=gefs&MODELLTYP=2&BASE=-&VAR=cpre&HH=372&ZOOM=0&ARCHIV=0&RES=0&WMO=&PERIOD=

 

UKMO UKMO today shows benign conditions over the weekend as Fridays threat of Low pressure looks restricted to showers in the South before a fine weekend develops with some pleasant sunshine for many. By the start of next week though Low pressure steams in from the West with rain and showers for all in cooler and breezier conditions overall.

 

http://www.wetterzentrale.de/pics/Rukm1441.gif 

 

THE FAX CHARTS The Fax Charts this morning show a somewhat showery theme between now and Friday with the impending Low pressure to the SW on that day pulled further South on this morning's run leaving much of the UK unaffected. The weekend then shows a weak High pressure area near the South with fine and dry conditions likely as a result.

 

http://www.weathercharts.org/ukmomslp.htm#t120.

 

GEM GEM today shows showery Westerly flow with Friday's Low a little more influential to the South than other models suggest with some rain and cool conditions Friday. A quiet and largely dry weekend is then shown under a ridge with next weeks Low further North than other output, this time being most influential to the North where the most wind and rain from this falls while the South sees little. Then all areas become fine, warm and settled later next week as High pressure builds strongly across the UK.

 

http://www.wetterzentrale.de/pics/Rgem2401.gif 

 

NAVGEM NAVGEM today shows slack Westerly breeze, sunshine and showers for the remainder of this week with Friday's Low amounting to nothing before a ridge gives a decent weekend for many. next week's Low on this run though looks a fairly potent feature given the time of year crossing the UK and delivering rain, showers and cool conditions for all for a time.

 

http://www.wetterzentrale.de/pics/Rnvg1681.gif.

 

ECM ECM is encouraging longer term again today with High pressure building across the UK late in it's run following a spell of cool and unsettled conditions in West then NW winds next week, all this following the rest of this week's rather benign and slightly changeable conditions..

 

http://www.wetterzentrale.de/pics/Recm2401.gif

 

ECM 10 DAY MEAN The ECM 10 Day Mean Chart from last night shows Low pressure over Scandinavia with winds from between West and North across the UK with a typical pattern of sunshine and showers in average temperatures at best most likely by Day 10.

 

http://www.wetterzentrale.de/pics/Reem2401.gif 

 

NOTABLE TREND CHANGES FROM PREVIOUS RUNS There is a growing trend with cross model support from those models that look aheadthat far that High pressure is likely to build across the UK as we enter August.

 

31 DAY HISTORICAL VERIFICATION STATS FOR GFS, UKMO & ECM The Verification Statistics of GFS, UKMO and ECM. This morning's verification statistics show ECM leading the way at 3 days with 95.4 pts followed by UKMO at 94.9 pts and GFS at 94.0 pts. At 5 days ECM is stll king at 84.2 pts followed by UKMO at 80.7 and GFS at 80.5 pts. Then at 8 Days ECM still leads at 53.1 pts over GFS's 46.9 pts. Finally at Day 10 ECM leads GFS at 33.9 pts to 28.3 pts from GFS.

 

http://www.emc.ncep.noaa.gov/gmb/STATS_vsdb/allmodel/daily/cor/cor_day3_PMSL_MSL_G2NHX.png 

 

http://www.emc.ncep.noaa.gov/gmb/STATS_vsdb/allmodel/daily/cor/cor_day5_PMSL_MSL_G2NHX.png

 

http://www.emc.ncep.noaa.gov/gmb/STATS_vsdb/allmodel/daily/cor/cor_day8_PMSL_MSL_G2NHX.png

 

http://www.emc.ncep.noaa.gov/gmb/STATS_vsdb/allmodel/daily/cor/cor_day10_PMSL_MSL_G2NHX.prig

 

MY THOUGHTS The main theme of this morning's runs are the trend towards a different pattern synoptically showing up across the UK on a UK wide basis from later next week. In the meantime there is still a lot of days to come of indifferent conditions, often benign and quiet with sunny spells and the odd shower but occasionally rather wetter for some. The models have backed away from this Friday's earlier predicted Low pressure with only a glancing blow likely if any across the far South before a decent weekend turns up within rising pressure. It's next week when the interest begins with a deepening Low supported by most output crossing the UK and away to the NE through the early days of next week with a cool NW flow in it's wake giving rise to cool conditions along with sunshine and showers. Thereafter a pattern change is signified as High pressure builds into the UK from the Atlantic, settling over the top of us and bringing the best chance for some considerable time of a nationwide spell of fine and warm weather. My only worry is that the high centre may stay a little too far to the West or SW always maintaining something of a North or NW feed across the UK hence lower temperatures but this is speculation at the moment. Of course at this range there is a lot of water to cross under the bridge anyway before definintive certainties can be applied but the signs are encouraging with good support from ensembles, clusters etc. So while we have a week or so to go with weather as mixed as ever we should all look forward to something much more universally better across the UK from later next week. 

 

Next update from 09:00 Wednesday July 22nd 2015

Edited July 21, 2015 by Gibby

[johnholmes]

There is nothing on the anomaly charts in my view to give any hope of high pressure and heat in the next 2 weeks or so.

[knocker]

An example of the flat HP zonal patter that has been indicated of late.

http://www.tropicaltidbits.com/

[Man With Beard]

Signs of the long-anticipated Azores High (which I am going to rename "Knocker's High" if it happens) beginning to appear on our ops and ens for the start of August:

 

Still a good few weeks available for "height of summer" heat from that point.

[Summer Sun]

Hints from some of the models for a rise in pressure towards month's end and early August which the met office have been talking about for some time now

 

 

I say some because GFS is a bit different at day 10........

 

 

GFS does get there in the end just a bit slower

 

[Glacier Point]

If I could interject here....

 

The upper level divergence signal in the Indian Ocean (MJO related) is slowly edging across the Indian Ocean towards the Tropical Maritimes. That is a region where the GEFS frequently struggles and shows negative bias, so given the importance of this tropical driver, I would not be in a rush to back the GEFS means here - this is not the model to show us out of next weeks rather large trough dominating north and north-west Europe.

 

With the tropical signal migrating through the Indian Ocean, we should see a fall in pressure to the east of the Himalayas and pretty rapid spike in tendency in relative angular momentum and the Global Wind Oscillation move towards phase 4. That's a decent signal for Rossby wave influence for rising pressure over NW Europe within a 10-15 day timeframe.

 

EC EPS 00z going for a pretty impressive turnaround in pressure end next week into the following week, with the longwave trough replaced by a moderate strength +ve height anomaly centred to our east. So much more settled and becoming warmer again in the extended outlook period.