Model Output Discussion - 1st August 00z---------->

[knocker]

Afternoon everyone,

 

I've spent a little time lurking behind the curtains of this forum, and my science-obsessed mind has been drawn to mentions of teleconnections and analogue year composites which have recently become a subject of fascination on my part.

 

Indeed we see a nice example above, representing a classic 'enhanced Euro Ridge' response to a strong El Nino configuration in the latter stages of the summer season. I suspect this relates (at least partially) to increased atmospheric warmth piling up into a greater 'bulge' in the troposphere (I prefer to describe it that way to avoid detailing complicated dynamics!). In this way we get a glimpse of the rationale behind warmer, drier UK summers as a result of global warming... though it's unlikely to be that straight forward I'm afraid.

 

 

ECM seems to want to add more amplification to the pattern than suggested by the composite, digging low pressure southeast from the mid-Atlantic rather than firing it northeast.

 

At a glance (been busy this morning as usual), GFS seems more in line with the composite out to 7-8 days ahead, though the Polar/Arctic pattern does still allow for more of a Scandi High with lower heights S. of the UK than would otherwise be expected:

 

 

 

A case of 'heat from the east' on that run, touching 30*C in CS England 

 

A little detail of the complicated dynamics would be useful as I'm not understanding what you mean by "increased atmospheric warmth piling up into a greater 'bulge' in the troposphere". Or for that matter ,"we get a glimpse of the rationale behind warmer, drier UK summers as a result of global warming"

 

The heat from the east on that run was due to a shallow low travelling NE from France.and was very temporary..

Edited August 7, 2015 by knocker

[phil nw.]

We still can't seem to get a nationwide decent Summery spell and it looks like a very average outlook remains with some very mixed conditions north to south during the next week to 10days.

Some images from the 12z GFS run and a UK fax chart at day4 show that even with a shallow Azores ridge across the south we have a lot of cloud inbedded in the Atlantic flow.

 

A shallow upper trough continues to plague Nw Europe and the E.Atlantic.The jet although rather weak continues to feed weak frontal systems across the UK.

 

keeping the Azores high suppressed and the heat unable to get north of the Channel.

It really is a case of taking things day to day,noting forecasts of any associated patchy cloud and rain, as there will be some brighter periods with some warmth either side of the straddling fronts,

 

[summer blizzard]

GFS and GEM both move a low in for days 8-10..

 

[ANYWEATHER]

Is the front slipping southeast across southern Britain on Sunday, going to give us nuisance value rain or a decent soaking? a nightmare for forecasters!

[Singularity]

A little detail of the complicated dynamics would be useful as I'm not understanding what you mean by "increased atmospheric warmth piling up into a greater 'bulge' in the troposphere". Or for that matter ,"we get a glimpse of the rationale behind warmer, drier UK summers as a result of global warming"

 

The heat from the east on that run was due to a shallow low travelling NE from France.and was very temporary..

 

Good questions and points knocker, I'll do what I can to answer/explain them;

 

First quote, I was referring to the way 500mb heights are influenced by temperature as well as surface pressure. This is due to the fact that pressure falls more slowly with height in warmer air relative to cooler (as it's less dense). I must admit that the idea of this leading to stronger, more expansive areas of high pressure being possible is pretty much paraphrased from various comments I've read online over the past few years (I remember it being linked with the Russian heatwave in 2010 I think it was), but it seems logical enough to me.

 

The link with warmer, drier summers as a result of global warming is then a case of supposing that, if the amount of heat in the atmosphere in a 'neutral' ENSO year was to become as high as in an 'El Nino' year at this point in time, then unusually strong and expansive ridges of high pressure over Europe would become more common.

 If anyone on this site (and I'm sure there are plenty with enough expertise) knows of stats/theory/facts that take this proposed link apart, please don't hesitate to correct me!   

 

 

Finally, I realise I didn't clarify that I was referring to the 'heat from the east' for that date in particular, not the run as a whole. Up the learning curve I go 

[I remember Atlantic 252]

Is the front slipping southeast across southern Britain on Sunday, going to give us nuisance value rain or a decent soaking? a nightmare for forecasters!

 

That's what I'm thinking, washout Sunday and monday for north midlands, maybe a lull Sunday night

[Singularity]

Is the front slipping southeast across southern Britain on Sunday, going to give us nuisance value rain or a decent soaking? a nightmare for forecasters!

 

I real headache this one, as there's ample moisture but the extent to which the frontal system can engage with that is highly uncertain - check out the precipitable water values (mm) from WRF-NMM:

 

 

 

Yet precipitation amounts are actually very low or nil:

 

 

...which is more or less what the BBC forecast this evening was in support of. GFS is not that far away this evening so perhaps the picture is finally becoming clearer - unlike for next week when it looks like the proximity and precise dynamics of a shallow low to the SE will make all the difference.

The GFS 12z was unfortunate for large parts of England, and ECM is worryingly similar, though who's to say whether the rain would be so persistent as GFS has come up with. Warm and showery is a possibility I think.

 

For some of the kindest output tonight, we can look to UKMO - as has often been the case in recent days:

 

 

 

I sure do like how images work in here 

[knocker]

A quick look at the GEFS anomalies tonight and they are not greatly different to 24hrs ago

 

The middle of next looks fine but by Saturday the trough to the NW has linked to the one near Spain which with the Scandinavian ridge could produce an interesting surface analysis. Far too early to go into that.

 

The trough doesn't hang around too long and by the 19th it has retracted to the Greenland/Iceland area leaving a zonal flow along the Azores ridge bring about a return of the fine weather

 

From there to the end of the run it builds on this scenario.

 

So generally speaking not a bad outlook according to the book of GEFS

 

http://www.tropicaltidbits.com/

Edited August 7, 2015 by knocker

[knocker]

Good questions and points knocker, I'll do what I can to answer/explain them;

 

First quote, I was referring to the way 500mb heights are influenced by temperature as well as surface pressure. This is due to the fact that pressure falls more slowly with height in warmer air relative to cooler (as it's less dense). I must admit that the idea of this leading to stronger, more expansive areas of high pressure being possible is pretty much paraphrased from various comments I've read online over the past few years (I remember it being linked with the Russian heatwave in 2010 I think it was), but it seems logical enough to me.

 

The link with warmer, drier summers as a result of global warming is then a case of supposing that, if the amount of heat in the atmosphere in a 'neutral' ENSO year was to become as high as in an 'El Nino' year at this point in time, then unusually strong and expansive ridges of high pressure over Europe would become more common.

 If anyone on this site (and I'm sure there are plenty with enough expertise) knows of stats/theory/facts that take this proposed link apart, please don't hesitate to correct me!   

 

 

Finally, I realise I didn't clarify that I was referring to the 'heat from the east' for that date in particular, not the run as a whole. Up the learning curve I go 

 

Singularity

 

With the best will in the world I think you are confusing a number of things. The 500mb heights are a function of temperature. Yes the variation of surface pressure comes into the equation which is why the 1000mb-500mb thickness is often used as a more useful measure of the air mass. If you take the 'height', measured in geopotential metres of the temperature profile between the various pressure levels of two air massess, one cold and one warm, then the heights in the colder air will all be less than the warmer air so the 500mb height will be correspondingly lower. Thus the 500mb contour chart is an indicator warm/cold or low and  high pressure. I'm afraid I haven't a clue what this has to do with a bulge in the troposphere. I apologise if I'm reading you incorrectly.

 

I think we will leave the drier summers and global warming issue as it's not relevant here anyway.

 

EDIT

So in an attempt to connect to your point. Yes pressure will 'fall' more slowly in warm air because the pressure levels will be higher.

Edited August 7, 2015 by knocker

[ANYWEATHER]

Well its Friday Night , so shall we have a laugh   :rofl:  

[Frosty.]

The Ecm 12z shows the Azores high ridging in nicely next week and the midweek period looks very good with high pressure bringing dry, warm and sunny weather for most areas. The s/e becomes very warm / hot and increasingly humid with a chance of thunderstorms breaking out and also a risk of Storms pushing up from the near continent later next week. After an unsettled blip it's also looking good at the end of the run with high pressure building east across the uk. I think the south and east of England will hot up through the second half of next week with hazy sunshine and a growing chance of catching a T-Storm with temperatures into the 80's F.

Edited August 7, 2015 by Frosty.

[Polar Maritime]

A few hopeful posts have been moved here https://forum.netweather.tv/topic/82655-model-banter-moans-and-ramps-springsummer-2015/page-70#entry3243442. 

[Gibby]

My interpretation of ECM is a little different to some in that while I acknowledge warmth and humidity is a strong feature in the South next week cloud cover and the threat of thundery outbreaks will not permit very high temperatures per se. Thereafter a cooler unsettled phase develops in a cool NW flow before a pressure rise from the NW returns warmer and drier conditions SE across the UK late next weekend.

[Man With Beard]

My tuppence tonight - next week looking warm, occasionally gorgeous, and often messy. I imagine everyone will get at least a couple of decent days out of it, even up in the highlands. Perhaps the messiest place will be down here in the south. STILL the potential for more or less heatwave conditions (26C or more daily, is that OK for a definition?) starting, well, now and carrying on until next weekend - but some weird complications rising up from the south - GFS has almost permanent rain from Weds to Fri - I would have thought hot and thundery myself. But nowhere looks like getting a bad week - one or two iffy days at worst. And at least average or above throughout. Not bad.

[Vorticity0123]

Where the UK continues to be affected by periods of unsettled weather associated with active troughing and over the eastern Atlantic ocean, parts of central and northern Europe are experiencing much hotter and drier weather. In fact, Germany touched upon its national heat record from 2003 (40.3*C). This weather is associated with anomalous ridging (high pressure activity) both near the surface and at 500 hPa over Eastern Europe. On the last few pages of this thread an interesting discussion has been going on about this ridge and the connection to El Nino. In order to explore this link, and (hopefully) find a few answers, I will examine some teleconnections, as well as have a look at the general circulation pattern.

 

Bridging the gap

 

A nice bridge to my previous post (discussing the ocean and the NAO in connection with troughing over the UK), and the current topic is that we are now not looking at the Eastern Atlantic trough and small sea surface temperature anomalies in the Atlantic, but the neighboring ridge and a much greater phenomenon - ENSO. Here is the link to my previous post:

 

https://forum.netweather.tv/topic/83477-model-output-discussion-1st-july-onwards-18z/page-47

 

Furthermore, on the same page, Knocker posed a key question for the current discussion, and a first start in our search for an answer:

 

 

Vorticity.

 

Is the heat in Central and Eastern Europe and our cooler temps linked to the current El Nino?

 

Michael Ventrice â€@MJVentrice 5h5 hours ago

It's interesting other El Nino states similar to the current event saw more heat waves o/central-eastern Europe

Attached Thumbnails

• 

 

To clarify: Michael Ventrice is a leading scientist in the field of teleconnections related to weather. And the image shown in the quote is an ECMWF forecast for 30 days out of surface temperature anomalies, NOT a representation of average surface temperatures during an El Nino event.

 

Link real or nonsense?

 

Validating the link is crucial here, so to test that below are 500 hPa height anomalies during El Nino events in summer:

 

500 hPa height anomalies during an El Nino summer, composed by averaging over various El Nino years. Courtesy: NOAA.

 

Unexpectedly (at least for me), there are negative rather than positive height anomalies present over central and eastern Europe.This means that on avearge, during an El Nino summer, the 500 hPa heights are lower than usual. This would coincide with more low pressure activity than usual. In short, this is contradicting what I initially expected (namely that an El Nino summer correlates positively with 500 hPa height anomalies over central Europe).

 

Does this mean the answer is that there is no link? It is good to realize that we are currently facing a rather strong summer El Nino, and in the plot above also weak El Ninos are taken into account. Therefore, it might pay off to look only at strong El Nino events (although one could question the value of comparing only one year). Below are the 500 hPa height anomalies for the summer of the El Nino event of 1997:

 

500 hPa height anomalies during 1997 between June and August. Courtesy: NOAA.

 

In this particular El Nino event, we do see strong positive 500 hPa height anomalies covering the whole of Europe. However, does one year's match make the link to be true? This is a difficult question, where further examination of other strong El Nino years could be very valueable.

 

Finding an explanation for a phenomenon that may or may not be there is even more hazardous. Therefore, for the remainder of this post I will attempt to explain the current anomalous ridging over central Europe without looking at past analogues.

 

A rather amplified atmospheric state

 

In order to explain the current ridging over central Europe, it is good to take a look at the big picture. As such, below are the 100 hPa heights of the Northern Hemisphere (in order to retain the most clean view):

 

ECMWF height analysis at 100 hPa as of 06-08 12 UTC.

 

Note that even though the given level is near the stratosphere, the general pattern nicely matches the pattern at 500 hPa. The red lines indicate the position ridges, whereas the blue lines indicate the position of troughs.

 

What can be seen is that, if one follows the 1648 dam line, the pattern is rather wavy/amplified. In other words, there are a lot of rather deep troughs (isolines pointing towards the equator) and strong ridges (isolines pointing towards the poles) present. In my post on the 25th of June, I treated that subject in somewhat more detail, that post can be found here.

 

If we look into somewhat more detail (towards our region) we can see a deep trough extending southward just west of mainland Europe, while a potent ridge is positioned all the way up from central Europe to Siberia. This is a pattern that has been observed a lot during this summer.

 

One key conclusion can be driven from this is that the ridge over central and eastern Europe is present throughout the troposphere, and that it may be seen as a blockade in the atmosphere. The same applies for the trough just west of Europe.

 

Arctic oscillation as a measure: high pressure over the poles

 

Another way to look at this 'waviness' is the arctic oscillation. When this oscillation is positive, little 'waves' are present in the atmosphere resulting in a generally east-west circulation with weak to no dominant ridges or troughs. On the other hand, when the AO turns negative, lots of meanders (visualized by troughs and ridges) are present, resulting in lots of blockades and north/south orientated flow.

 

During a large part of the summer, the AO has been negative:

 

Arctic oscillation trends over the past few months (courtesy: NOAA)

 

What can be seen is that the AO has been negative a lot, indicative of a rather amplified flow. Therefore, anomalous ridges and troughs are more often than not occurring. Linking back to the ridge over Europe, the negative AO nicely coincides with the anomalous ridge present over central Europe.

 

In terms of the 500 hPa pattern over the pole itself, this pattern could be explained by the fact that the North Pole has seen higher than average heights (so higher than average pressure) during most of summer. This acted as a catalyst of the amplified flow. More about this can be found here:

 

https://www.aer.com/science-research/climate-weather/arctic-oscillation

 

What can be seen in the AO forecast in the image and the article above (the red lines are a forecast ensemble of the GFS model), is that the AO is going to turn positive. In other words, the flow at the midlatitudes is forecast to become more zonal (east-west oriented, with less strong ridges/troughs)

 

Europe ridge not responding

 

So that would mean easing of the ridge over central and eastern Europe? Well, this is not the case. In fact, the ridging only seems to stubbornly maintain itself, only changing some in shape. This is illustrated in the GFS ensemble 500 hPa heights chart below:

 

GFS ensemble 500 hPa heights and surface level pressure as of 18Z 07-08 T+240.

 

As can be seen here, there is still a strong ridge present at 500 hPa (orange and red colours) over Scandinavia.

 

Concluding, the decreased 'waviness' of the atmosphere does not seem to lead to a relaxation of the ridge over central Europe. The 'waviness' of the atmosphere can therefore not be seen as a lead contributor to the ridge.

 

Taking a different approach: Atmospheric Angular Momentum linked to El Nino as a key player?

 

For a further search towards an answer, we might want to turn our eyes on the AAM budget, reflected in the Global Wind Oscillation (GWO). The AAM is, in short, the velocity of the movement of the atmosphere relative to the earth.

 

It is well-known that during an El Nino event, there are often higher than usual AAM values. This is also the case as of speaking, and will remain the case for the next weeks:

 

GWO analysis and forecast (in green). Courtesy: University of Albany.

 

The upper part of the diagram indicates high values of AAM, while the lower part of the diagram indicates lower values of AAM. As can be seen here, the AAM is currently positive, and will remain positive, despite the GWO making some orbits.

 

Unfortunately, this is as far as my knowledge allows me to go. Possibly somebody else can make or break the theory that this ridging over central Europe is associated to El Nino via the AAM budget, of course assuming that the link exists at all. It would be greatly appreciated!

 

Conclusion

 

In this post I came to the conclusion that the anomalous ridge over central Europe may not be directly coupled to El Nino, despite me initially thinking otherwise. Furthermore, we have seen that a rather amplified flow has been associated to the ridge, yet this waviness of the atmosphere did not seem to be directly linked. This was because even though forecasts pointed towards less 'waviness' in the atmosphere, the ridge over central Europe was not weakening as would be expected. Finally, I touched upon the atmospheric angular momentum and the link with El Nino as being a possible driver.

 

And yet, the only thing this post seems to do is raise more questions, rather than a definite answer to the question whether El Nino is related to anomalous ridging over Europe. This is the interesting part of science, though, as unveiling one aspect of a phenomenon reveals even more parts to discover! Hopefully, despite the lack of a definite answer, this post is an interesting read, and more contributions/theories/corrections are greatly appreciated as always .

 

Sources:

http://www.earthgauge.net/wp-content/CF_Arctic_Amplification.pdf

https://www.aer.com/science-research/climate-weather/arctic-oscillation

http://www.cpc.ncep.noaa.gov/products/predictions/814day/500mb.php

https://twitter.com/MJVentrice

http://www.wetterzentrale.de/topkarten/fsavneur.html

http://www.atmos.albany.edu/student/nschiral/gwo.html

http://www.esrl.noaa.gov/psd/enso/compare/

http://www.geo.fu-berlin.de/en/met/ag/strat/produkte/winterdiagnostics/

http://www.usclivar.org/working-groups/mjo/science/mjo-atmospheric-angular-momentum-length-of-day

http://www.iers.org/SharedDocs/Publikationen/EN/IERS/Publications/tn/TechnNote26/tn26.pdf?__blob=publicationFile&v=1

Edited August 7, 2015 by Vorticity0123

[knocker]

500 hPa height anomalies during 1997 between June and August. Courtesy: NOAA.

 

In this particular El Nino event, we do see strong positive 500 hPa height anomalies covering the whole of Europe. However, does one year's match make the link to be true? This is a difficult question, where further examination of other strong El Nino years could be very valueable.

 

Finding an explanation for a phenomenon that may or may not be there is even more hazardous. Therefore, for the remainder of this post I will attempt to explain the current anomalous ridging over central Europe without looking at past analogues.

 

Thanks for another interesting analysis. Regarding the connection with El Nino I think your comment quoted below, interesting and quite important as Michael Ventrice did say "similar to the current event". So I agree that until a further examination is carried out El Nino is still very much in the frame.

 

In this particular El Nino event, we do see strong positive 500 hPa height anomalies covering the whole of Europe. However, does one year's match make the link to be true? This is a difficult question, where further examination of other strong El Nino years could be very valueable.

Edited August 8, 2015 by knocker

[johnholmes]

Another interesting post from Vorticity, thank you, and knocker PLEASE do not repeat a whole post from other folk, just a link is good enough?

[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 SATURDAY AUG 8TH 2015

 

THE CURRENT GENERAL SITUATION A ridge of High pressure lies NE across the UK today. The ridge collapses SE tonight and tomorrow to lie in the English Channel while a fresh SW flow develops over the UK with troughs weakening as they move SE over Britain tonight and tomorrow.

 

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

 

MODELS-2 WEEK HEADLINE Remaining rather changeable with a little rain at times. Some dry and at times warm conditions are likely for all areas as well.

 

THE GFS JET STREAM FORECAST The GFS Jet Stream Forecast shows the flow moving NE across Northern Britain with the axis gradually feeding further SE over the coming days. The flow then steadily weakens close to Southern Britain before becoming generally quite slack though still troughed well South over the Atlantic and later towards the UK once more..

 

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

 

GFS OPERATIONAL The GFS Operational Run today shows the ridge across the far South of the UK weakening as the fronts moving down from the NW on Sunday and Monday weaken too and the accompanying SW flow lightens. occasional rain and drizzle will largely break up into showers by Tuesday. at the same time pressure falls from the South and a thundery spell of weather develops across Southern and Eastern Britain with a drier spell in the North. Then Westerly winds with rain at times looks likely as Low pressure to the North and NW returns with the best of the drier and warmer weather  back towards Southern Britain late in the run. 

 

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

 

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

 

THE GFS CONTROL The GFS Control Run looks broadly similar, certainly in the first week with the ridge of High pressure developing across the North towards midweek and a thundery low to the SE. The weather turns changeable generally at the end of Week 1 before week 2 shows a mix of a High pressure ridges followed by a Low pressure cell moving slowly North-east or North over the UK to leave the UK in a NW flow at the end of the run.

 

THE GFS CLUSTERS(14 Days) The GFS Clusters this morning for 14 days are not quite as good as yesterday morning's today as they indicate High pressure likely to be parked out over the Atlantic with a ridge only towards Southern Britain but with more influence from a West or NW flow over all areas with rain at times particularly towards the North and West.

 

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 increasingly thundery conditions developing next week as the SW flow weakens from all but Scotland by Tuesday with warm and humid air in place. Wednesday sees Low pressure edge into Southern Britain from Europe continuing in situ up to the end of the week with thundery showers in warm and close conditions while the North sees the best of the drier weather and just occasional rain on Thursday from an Atlantic trough.

 

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

 

THE FAX CHARTS The Fax Charts this morning show a series of troughs weakening as they move SE into Southern Britain over the coming days. They remain active enough to give cloud, occasional light rain and eventually thundery showers as humid and unstable air reinvigorates them by midweek when the North sees drier and brighter conditions.

 

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

 

GEM GEM today shows a SW flow with embedded troughs too moving SE into Southern Britain early next week. A ridge then develops across Central Britain but the old troughs get reinvigoration from thundery instability moving up from Europe close to the SE. So thundery showers become a risk in the South from midweek with the best weather in the North before a gradual change to cooler and more changeable conditions with rain at times look likely from later next weekend as Low pressure feeds slowly East over the UK from the West.

 

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

 

NAVGEM NAVGEM follows a similar route in bringing a thundery continental Low North close to SE Britain midweek with warm and close conditions developing after the innitial days of cloud and a little rain early next week. After the first few days the best of the drier and brighter conditions transfer to the NW of the UK close to a ridge from the SW..

 

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

 

ECM ECM this morning shows the thundery Low further to the East and as a result probably only affecting SE Britain with dry and bright weather elsewhere and pleasantly warm in any sunshine. Then as winds settled NW'ly for a time it will likely become a little cooler with just a few showers in the East before a North/South split in the weather gradually returns with rain at times for all but more especially in the North and West with longer dry spells for the South and SE.

 

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

 

ECM 10 DAY MEAN The ECM 10 Day Mean Chart from last evening shows a Westerly feed across the Atlantic towards the British Isles with no doubt some influence across the UK given Low pressure lies to the NW and High pressure near the Azores. The likely result is a familiar tone of rain at times, chiefly in the North and West with longer drier, warmer and brighter weather towards the South and SE..

 

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

 

NOTABLE TREND CHANGES FROM PREVIOUS RUNS The models trend changeable today with various options between the models desiring a return to Atlantic airflow domination in the longer term.

 

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 95.9 pts followed by UKMO at 95.5 pts and GFS at 94.7 pts. At 5 days ECM is stll king at 85.9 pts followed by GFS at 83.9 and UKMO at 83.8 pts. Then at 8 Days ECM still leads at 58.3 pts over GFS's 53.5 pts. Finally at Day 10 ECM leads GFS at 39.7 pts to 34.0 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 Details of large scale changes are non apparent again this morning as the models serve up yet another cocktail of options on specific weather events over the coming two weeks, none of which have major implications for any one area in particular. In sequential order it looks like a SW flow will develop across the UK over the next three days with a series of troughs moving SE across the UK, weakening as they do and becoming slow moving over the South early next week but delivering occasional rain and drizzle where they lie. Behind them a ridge builds across the North but humid and thundery air over Europe looks like reinvigorating the troughs in the South to increase the risk of heavy and thundery showers for the rest of next week. While warm or locally very warm cloud amounts will deter the very highest temperatures but it is likely to feel close and humid. The North at this time look at long last likely to have some reasonable if not memorable conditions at this time. Then all models seem to then want to use this thundery Low to the SE as a catalyst to return a more Atlantic influence back across the UK through week 2 to a greater or lesser degree depending on which model you look at. What this would likely mean at the surface is a fall back in temperature to nearer average, less humidity but dare I say it a more North/South split in the weather again with rain at times for all but a lot of dry and bright weather in between especially for the South. The models seem to be really struggling at the moment which is quite a common occurrence when pressure conditions are generally quite slack as they look like being over the second half of next week meaning long term projections come with a lower than normal degree of confidence. I will say though that the ECM longer term projection illustrated by it's 10 day mean chart each day has been consistent in maintaining a loose westerly bias across the UK at the 10 day time point for several weeks now and this continues this morning. It's verification statistics listed above have shown this to be the right call and alone has not been sucked in by High Summer synoptics occasionally thrown out by some of the other output only to be watered down in later runs. So where that leaves us is in a continuing changeable theme of weather which looks much better than recently for the North but much the same for the South as occasional rain or showers looks the order of the next two weeks for many and while warm and humid but typical August conditions look likely there may well end up a more even distribution between amounts of rainfall having fallen North to South at the end of the next two weeks than has been the case so far this Summer.

 

Next update from 09:00 Monday Aug 10th 2015

[Man With Beard]

ECM has upped the temperatures again for coming week by a degree or two at times. I would expect at least 6 of the next 7 days to exceed 80F somewhere in the country.

Edited August 8, 2015 by rjbw

[Nouska]

With regard to the ENSO forcings discussed here, did anyone notice MV has a tweet about verification of their July analogue forecast for the USA.

 

https://twitter.com/MJVentrice/status/629658217400922112

 

 

Notice that '97 is not included in the five years (top left of pic) - is this because '98, as now, is a second year Nino season or for some other reason. Are we comparing like for like?

 

Recretos had an interesting comment on the state of the stratosphere...

 

Well, so far, the strat seems to be doing the opposite of what is supposed to be the main signal from a positive ENSO3.4.

 

https://forum.netweather.tv/topic/81567-stratosphere-temperature-watch-20142015/?p=3243289

[Man With Beard]

12Zs coming out. I still hold to my prediction of 6 days out of 7 reaching 80F in some locations. I also think favourable areas in the north could see 80F reached at some point in the week.

 

However, when in comes to any particular location, I'm not actually sure it's possible to make any prediction from Tuesday to Saturday next week. The scenario is a little like September in the Mediterranean - lots of heat around but also lots of disturbances. Places that avoid showers will see temperatures soar, whilst where the atmospheric disturbances are centralised - possibly even just 50 miles away - cloud, rain and temperatures up to 10C lower could be the result.

 

The following chart is an absolute minefield - uppers nearly 18C, but low pressure just to the south and not going anywhere quick. There'd be some pretty bizarre contrasts across the nation on this:

 

[Singularity]

I'd go so far as to say that this year has often behaved strangely, one way or another. I suppose it can in theory be a second-year El Nino depending on how you look at the SSTs, though it's only really this year that upwelling/reduced downwelling has really manifested in the W. Pacific to bring things in line with the typical El Nino pattern. In fact - assuming I'm recalling this accurately - the delay in that behavior was enough to keep the atmosphere in a more La Nina type arrangement during much of the first half of this year.

 

 

- - - - - - - 

 

Looking at the 12z GFS today, it appears that as early as Monday, a significant adjustment has occured over NW Europe regarding the position of the shallow low that goes on to become a significant player in our weather later in the week. Here's the 06z version of events followed by the 12z, for comparison:

 

 

 

A glance at the UKMO 12z op run reveals a similar adjustment as of T+96, yet the focal point for development still turns out to be about as far east as it was come T+120 (dubious in my humble opinion!). It will be interesting to see which way ECM goes tonight - I'd surprised if the low wasn't initially further west, but will the main development still occur to our SE then E or will it be something more to our S?

 

With that LP developing notably further west than seen in the previous few operational GFS runs, there are interesting results by Thursday:

 

As much as I feel UKMO is a bit dubious in how it evolves, it still fits in better with recent model consistency than this GFS outcome, so arguably it's more sensible to expect something closer to UKMO at this stage. At least that still involves what could be a very warm easterly next Thursday. I would post images but the last time I did that they had to be from another site and my post disappeared...

 

 

The most positive interpretation I can think of is that we've now had two GFS runs in a row which have avoided the 'stalled frontal boundary' situation for England, instead allowing for very warm conditions for at least Wed-Fri and possibly Tue-Sat if the 12z GFS turns out to be close to the actual outcome.

 

 

Looking further ahead, that GFS 12z produces a strong Scandi High as the Atlantic trough doesn't extend SE and 'scoop out' the low pressure over Central/Eastern Europe. A very interesting outcome and one of my favourite runs of recent days 

[Frosty.]

The Gfs 12z shows a nice influx of very warm and increasingly humid weather through the second half of next week although the first half looks warm too, from Thursday,temps rise into the 80's F quite widely across southern UK with sunny periods but an increasing chance of thundery showers both home grown and imported from France. Looking further ahead, it stays on the warm side with a lot of fine weather but with a few sharp showers around and then a spell of very warm anticyclonic weather during low res. It's good to see warmer temps and more summery synoptics again after what happened in most of July...plenty of warmth on the way, at least for England and Wales.

[Polar Maritime]

The GFS continues to show a nice pleasant week ahead, With temps showing touching 28c for the Midlands South by Friday, And the North also fairing some pleasant and warmer temps than of recent Wks/Month's. Out into day 10 and High Pressure continues to sit over the UK.

Edited August 8, 2015 by Polar Maritime

[Polar Maritime]

Back to the Models please. If your post is missing it's here https://forum.netweather.tv/topic/82655-model-banter-moans-and-ramps-springsummer-2015/page-71#entry3243685

 

Thanks, PM.

Edited August 8, 2015 by Polar Maritime