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

[Captain Shortwave]

Day 6 charts

 

GFS

 

UKMO

 

ECM

 

GEM

 

This sort of highlights the uncertainty going on in the mid-range. Can the heights over Scandinavia back westwards to allow a drier and warmer picture to develop. Or will we see more shallow systems develop, potentially a thundery low from France over the coming days. The extended range doe suggest a build of heights from the south west, merging with the heights to the east. Trouble is whether it is a false signal given how the summer has panned out.

ECM ens

 

Overall a reasonable output for some, not so good for others, usual winners and losers I'm afraid.

Edited August 11, 2015 by Captain shortwave

[damianslaw]

UK very much at the battleground of competing airstreams at the moment. Strong heights to the SW and NE, low heights to the NW and SE doing battle over the country. Its all a bit messy, with no overall winner. The SE seeing the warmest conditions, NW locked in cool conditions in the main - the theme of the summer.

 

One notable aspect of the weather all year so far has been the propensity for very 'stuck' patterns with little overall variability bar the odd shortlived spell (think start of July). The dominant force has been the atlantic trough - far too close to our shores for any sustained settled spell/ridge to develop and take hold.

[johnholmes]

A word of caution about what the anomaly charts show, see below for the link.

They continue to show the major feature is the trough over/close by the UK. They show today a small, note small, +ve anomaly off France and Iberia and including parts of the UK. The ridge and +ve heights N Norway into Spitzbergen continue as they have for several days. yes it is slight change but not to me enough to warrant one or two of the comments about it this evening on here.

IF they show an increase in +ve heights tomorrow and the day after then we can start to feel that a change is looking more likely. But not before in my view.

I may be wrong of course but several years checking them closely every day makes me reluctant to jump on a major change band waggon.

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

 

this from my earlier post and apologies for quoting from my own post but it does give my feeling about how likely any change is this evening.

This is for both the 6-10 and 8-14 day time scales. The output at 8-14 has been as consistent as the 6-10 in showing no sign of any +ve heights of any significance along with no sign of any ridging in the UK area.

The ECMWF-GFS output has been less consistent with NOAA (6-10 day) or with one another. For several days they have both toyed with the idea of a ridge and +ve heights being fairly close to the UK (E or NE) to perhaps lend some credence to one or two synoptic model outputs. Neither has been totally consistent with this and this morning they broke ranks with EC showing more of an influence from the ridging to the E/NE than GFS. Unless NOAA 6-10 this evening shows some indication of any leaning towards this idea I think we can dismiss this idea. Indeed I would be surprised if this did happen based on a good many years of daily checking these outputs.

Edited August 11, 2015 by johnholmes

[knocker]

Michael Ventrice â€@MJVentrice 2h2 hours ago

Hey Europe... Omega Block setting up this week formed in another major El Nino during August.. good old Super 1997.

 

[William of Walworth]

Re those charts posted by knocker at the foot of page 16 :

 

Not sure I really understand those charts in that format.

 

Is the above a threat to HP influence in the UK (especially South) next week? 

Edited August 11, 2015 by William of Walworth

[knocker]

Re those charts posted by knocker at the foot of page 16 :

 

Not sure I really understand those charts in that format.

 

Is the above a threat to HP influence in the UK (especially South) next week? 

 

I don't know about a threat The UK is sitting between the trough and the HP so the surface detail will probably depend on how far south the trough reaches. The most likely scenario I feel is that you will keep the HP influence in the south whilst further north the trough may be the victor.

Edited August 12, 2015 by knocker

[mushymanrob]

A word of caution about what the anomaly charts show, see below for the link.

They continue to show the major feature is the trough over/close by the UK. They show today a small, note small, +ve anomaly off France and Iberia and including parts of the UK. The ridge and +ve heights N Norway into Spitzbergen continue as they have for several days. yes it is slight change but not to me enough to warrant one or two of the comments about it this evening on here.

IF they show an increase in +ve heights tomorrow and the day after then we can start to feel that a change is looking more likely. But not before in my view.

 

guilty... my post (311) overstated the change, maybe i was letting desire get in the way of objectivity, maybe id been drinking , a-hem. there does appear to be uncertainty though on both the ops and anoms with some caution that conditions might improve once we get tomorrows/fridays thundery wet spell out the way by saturday.

[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 WEDNESDAY AUG 12TH 2015.

 

THE CURRENT GENERAL SITUATION. A ridge of High pressure will lie across Central areas of the UK today a thundery low will develop over Biscay and move slowly North towards Southern England later tonight and tomorrow.

 

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

 

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

 

THE GFS JET STREAM FORECAST The GFS Jet Stream Forecast shows the flow to the NW of Scotland at the moment with a new arm extending SE from Newfoundland to Northern Spain from the weekend with a returning arm North over the North Sea. After several days of this arrangement the flow to the South weakens and the flow becomes a generally cyclonic one around Low pressure close to northern Britain later.

 

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

 

GFS OPERATIONAL The GFS Operational Run today loks a very changeable affair over the two week period. The thundery Low moves North over the coming days to be absorbed by Low pressure to the North with a Westerly flow at the weekend with sunshine and showers in less warm and humid air. A blocking High pressure forms over NE Europe next week preventing Low pressure crossing east to the North and eventually sending them on a SE track across parts of the UK with further rain at times. This collapses late in the run and a Westerly flow with rain at times is shown to return to all areas by the end of the two week period.

 

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

 

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

 

THE GFS CONTROL The GFS Control Run is very similar to the operational this morning and any major differences between them is reserved for the very end of the run when High pressure is shown to build strongly across Southern Britain from the SW ensuring a warm and sunny spell here while the North stays a little more changeable under slack Westerly winds.

 

THE GFS CLUSTERS(14 Days) The GFS Clusters this morning are not quite as good as yesterday with a few more members going for more unsettled conditions from off the Atlantic in 14 days while those that show better conditions under a ridge show the ridge not quite as pronounced and well positioned for the British Isles 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 the thundery Low having moved North to the Northern Isles by the weekend leaving behind a spell of slack and unstable airflows across the UK, first from the West and then East as pressure builds over NE Europe. Occasional showers look likely almost anywhere perhaps becoming more focused towards the South and SW only later.

 

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

 

THE FAX CHARTS The Fax Charts this morning show the same thundery Low moving North with it's attendant warm and humid unstable airmass ahead of a very complex system of fronts introducing fresher air from the West for the weekend and start to next week.

 

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

 

GEM GEM today shows an equally changeable period with the main features being the build of pressure to the NE with a trough stalled near SE Britain early next week with a continuation here of the weekend showers which in itself follows the thundery rain of the coming days. Then as the High to the NE collapses a familiar North/South split under Westerly winds is shown to end the run with any rain most likely to the North then.

 

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

 

NAVGEM NAVGEM too shows a pressure rise across NE Europe behind the coming days thundery Low moving North. This sets up a trough stretching from Newfoundland through the UK to Italy next week with slack unstable air across the UK promoting some showery activity especially towards the SE and NW.

 

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

 

ECM ECM this morning also follows the route in promoting a pressure rise to the NE after the coming days thundery Low heads to the North which unfortunately shows little benefit to the UK as it just serves to stall Atlantic Lows and troughs close to the UK with just brief dry and more settled interludes in occasionally cyclonic winds. It could become quite warm and humid at times though as Southerly winds ahead of fronts make the following rain heavy and thundery at times before fresher air moves in late in the period.

 

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

 

ECM 10 DAY MEAN The ECM 10 Day Mean Chart  from last evening shows a split between members with many opting for that rise of pressure to the NE of the UK and some with it well to the SW. This will probably result in the UK being in nomansland between the two High pressure areas with lower pressure to both the NW and SE promoting at least some shower activity.

 

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

 

NOTABLE TREND CHANGES FROM PREVIOUS RUNS The models are trending towards  a strong build of pressure over NE Europe which on this morning's charts show little better influence to the weather over the UK.

 

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 95.7 pts followed by UKMO at 95.4 pts and GFS at 94.65pts. At 5 days ECM is stll king at 85.8 pts followed by UKMO at 84.4 and GFS at 83.8 pts. Then at 8 Days ECM still leads at 59.2 pts over GFS's 55.3 pts. Finally at Day 10 ECM leads GFS at 40.5 pts to 35.0 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 Things look like trending very changeable across the UK over the coming two weeks with some changes in the basic synoptic pattern not really benefiting the UK weather over the two weeks in a big way. What we have is a ridge across Central Britain declining soon as a thundery Low moves North from Biscay up the spine of Britain to the northern isles by the end of Friday. This could deliver some copious disruptive weather locally before a shift to fresher Atlantic westerly winds sweep the humidity and thundery weather away for the weekend when sunshine and scattered showers looks likely. A strong build of pressure is then indicated over NE Europe, too far east to benefit us much other than to stall any progression of Atlantic Lows and troughs coming up against it from the west meaning the UK looks like being under a stalled slack and sometimes low pressure gradient promoting further outbreaks of rain or showers at times which incidentally also helps develop rather cooler weather at long last over Southern Europe. thereafter we have to pick up the crumbs of what the longer term output shows us today and there is still some hope that pressure will rise across the UK with some warm and sunny conditions across the South late in the period. However, shuffling around rather slack synoptics is always difficult for the models to handle and credence on any one specific outcome should not be taken too seriously at this range. So still a rather changeable outlook I'm afraid and with the Summer clock ticking away I get the feeling that any long term Summer UK wide weather is still some way in the distance of at all.  

 

Next update from 09:00 Thursday Aug 13th 2015

[DR(S)NO]

So still a rather changeable outlook I'm afraid and with the Summer clock ticking away I get the feeling that any long term Summer UK wide weather is still some way in the distance of at all.

I think your probably right Gibby......

After all , some of us have been waiting almost a year for Summer conditions..☔☔☔

[Vorticity0123]

With troughing residing to the northwest of the UK, and a ridge of high pressure located over central-eastern Europe and Scandinavia, the dominant pressure pattern throughout the summer still seems to be intact. In fact, the pattern itself allows perfect designation of some classic synoptic features often seen in the midlatitudes (like the polar front).

 

However, a surprise seems to be underway for Thursday and Friday, in the shape of a small-scale low pressure area approaching the UK from the south. This low pressure will bring somewhat warmer subtropical air and possibly a few thunderstorms along with it. Given that quite a bit has been said about the far-future synoptics in here, in this post I will dive into the classical characteristics of the current synoptics and also go into some detail about the warmth-bringing low pressure system that will pass on Friday.

 

Troughing to the northwest, ridging to the northeast

 

For the analysis we will begin by analysing the current synoptic pattern as shown by the GFS:

 

GFS 06Z 500 hPa heights and surface level pressure, 06Z analysis.

 

A few main things can be discerned here. The first is an area of troughing (green colours) from the USA towards Norway along with some rather deep low pressure activity for the time of the year (sub-990 hpa) just south of Greenland. Next to this feature, high pressure activity associated with 500 hPa ridging (red colours pointing poleward) can be seen over Eastern Europe and Eastern Scandinavia towards Svalbard. Also, weak ridging along with high pressure activity is evident over the UK itself (an extension from the Azores high)

 

If we look somewhat further south, we can see a couple of weak cut-off troughs (troughs that are not directly associated with, therefore cut-off from, a main trough to the north) over Sicily and just west the northwestern tip of the Iberian Penninsula (the last one being the one that will bring the warmer weather and possible thundery showers towards the UK - more about that later). These troughs are the lighter orange colours seen in the 500 hPa field.

 

Nice example of polar front

 

Turning our eyes more towards the surface features, below is the pressure and frontal structure forecast for 12Z today (which will be treated here as an analysis):

 

KNMI surface synoptics and front identification forecast for 12Z 12-08

 

The low pressure system to the south of Greenland is nicely evident here with the warm front and cold front visible. However, more interestingly, a frontal system is identified running all the way from west of the Iberian Penninsula over southern England through the Netherlands over Finland. This is indeed the polar front.

 

Referring to the low pressure of Thursday and Friday, it can be seen here as well, as a ‘wave’ (disturbance) in the polar front just west of the Iberian Penninsula.

 

From above the feature can be nicely identified over Europe as well:

 

Eumetsat Airmass satellite image of 06UTC 12-08.

 

The black line indicates the position of the polar front per KNMI. The red circle denotes the location of the low pressure area important for the UK, while the blue circle defines the location of another upper-level disturbance near Sicily (which can be identified on the 500 hPa charts of the GFS analysis above as well).

Looking at Western Europe, one can see more blueish colours (polar air) to the northwest of the front, while more greenish (subtropical air) exists to the southeast of the frontal system. The rest of the polar front does not show this clear distinction in airmasses (perhaps blue in eastern Scandinavia/warm and red in western Scandinavia/cold).

 

Visualizing with potential wet bulb temperature

Another great way of visulaizing and identifying the position of fronts is by using the potential wet bulb temperature. To keep things simple, you can take the (potential) wet bulb temperature as being a measure for the type of airmass one is located in. High potential wet bulb temperatures generally indicate a relatively warm and humid airmass, while low potential wet bulb temperatures indicate a relatively cool and dry airmass. Here is a more in-depth explanation to the wet bulb temperature from Wikipedia. One important thing here is that we are talking about the potential wet bulb temperature, which means that this temperature, given adiabatic conditions (no influence of the environment) would be the same for any height. This makes it easier to compare the change in type of airmass with height. The same principle works for potential temperature.

 

Here is the chart illustrating the current potential temperature at 850 hPa:

 

WRF 06Z 850 hPa potential temperature (colours) and pressure (isolines), 06Z analysis.

 

Steep gradients of potential temperature (large change in potential temperature over short distance) usually denote changes in airmass type, and this is also a location where fronts are often seen.

 

We will follow the strong gradient in potential temperature here over southern UK. What can we identify here if we follow the gradient? Right, the position of the polar front! This gradient runs from sweden all the way through Denmark and the UK southwestward towards the Iberian penninsula and then further westward through the Atlantic.

 

Furthermore, here we can much more clearly identify the differences in airmass. To the southeast of the polar front mostly red and orange colours reside, indicative of subtropical air. To the norhtwest, on the other hand, more yellow/green colours dominate, indicative of polar air.

Finally, to the northwest of the UK we can see a large band of high potential air temperatures extending towards the low pressure are to the south of Greenland (see GFS analysis at the beginning of this post). This looks like a warm conveyor belt, or a river of subtropical moist air being transported northeastward away from the subtropics.

 

Finally, we can see ‘our’ low pressure area located at the border of the polar front. This low pressure area will undergo rapid development.

 

Low pressure area with very warm air

 

Only 24 hours later, the low pressure area noted above has developed rapidly and also acquired frontal characteristics:

 

WRF 06Z 850 hPa potential temperature (colours) and pressure (isolines), 06Z T+24. (for Thursday)

 

One can still see the polar front from Ireland via Denmark towards the Baltic States (black line). However, further inspection shows more is going on. We can see a tongue of even warmer and more moist air (red colours) advancing their way towards the UK and the Benelux (red arrow), indicative of a warm front. This is the moist and potentially unstable subtropical air that will herald an increased risk of thunderstorms by Thursday evening.

 

Next to this, we can see that another area of polar air (orange and green colours; denoted by the blue arrow) has started invading Europe from the southwest, circling towards the center of the low pressure area. On the gradient between this polar air and the humid subtropical air one can identify a cold front.

 

The KNMI itself has a slightly different frontal analysis (note that the map of the KNMI is for six hours later):

 

KNMI surface synoptics and front identification forecast for 12Z 13-08

 

Although in general the setting is the same, the KNMI has the polar front connected to the warm front. The low pressure area itself is not very deep, with a central pressure of above 1010 hPa.

 

Warm & moist air advancing northward

 

24 hours later (Friday 06Z), the low pressure area has moved further northward, as can be seen below:

 

WRF 06Z 850 hPa potential temperature (colours) and pressure (isolines), 06Z T+48. (for Friday)

 

We can see that the warm humid air has advanced further northward, by then located somewhere near the border of Scotland and England (red arrow). Furthermore, the polar air from the south behind the cold front has also moved further northward (blue arrow). Near this cold front (blue line) some thunderstorms could be expected as well. Note that the frontal structures are based on own analysis, no synoptic analysis from KNMI is available for this timeframe.

 

Dynamic situation -  what about thunderstorms themselves?

 

Now that we have analyzed the synoptic situation, it is clear that we will  see dynamically interesting times. But what about the risk of thunderstorms themselves? I will (for brevity reasons) not go into too much detail on this, but as a short illustration below is a chart of CAPE for Thursday evening:

 

WRF 06Z MUCAPE values 06Z T+37. (for Thursday 21 UTC)

 

CAPE can be seen as a measure of the potential of formation of a thunderstorm. While CAPE is only a small part of the story, it can tell a little bit about where to and where not to expect them.

 

Especially southeastern parts of England seems to be at risk for this timeframe, with CAPE values exceeding 1500 J/Kg. However, also southern and southwestern parts may expect some thunderstorms at this timeframe judging from the WRF output. Note that this is just a single run, so the true allocation of thunderstorms, let alone the potential itself, may still change radically over the next day or so. The synoptic situation however suggests that some kind of thunderstorms are possible especially over southern parts of the UK.

 

Finally, if we take a look at the ‘modellwetter’ (which roughly is the condition a model expects at a given timeframe for a given location) we can see that at about the same timeframe as given above, the GFS expects very little in the way of thunderstorms, only heavy showers and frontal rain. This can be seen below:

 

GFS ‘Modellwetter’ for Thursday 18 UTC (06Z run).

 

Note how the Benelux is expected to see quite some thundery activity, while the UK appears to be relatively lacking in terms of thunderstorm potential.

 

Summary

 

Over the next few days an interesting synoptical situation will develop, with a low pressure area moving over the UK from the south. This system will bring warm, humid air along with it, and possibly a few thunderstorms. Although the potential is not very large for the UK, it definitely is worthwile watching. This weather type is at least something totally different than we have seen over the past month or so .

 

Sources:

http://www.knmi.nl/waarschuwingen_en_verwachtingen/extra/guidance_meerdaagse.html

http://www.knmi.nl/waarschuwingen_en_verwachtingen/weerkaarten.php

http://www.meteociel.fr/modeles/wrfnmm.php?ech=3&mode=28&map=5

http://eumetrain.org/eport/euro_06.php?width=1366&height=768&date=2015081206&region=euro

http://www.modellzentrale.de/WRF-medrange/index.php#

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

https://en.wikipedia.org/wiki/Wet-bulb_temperature

Edited August 12, 2015 by Vorticity0123

[BlueHedgehog074]

@Vorticity0123: Yet another brill post from you, and an excellent breakdown regarding frontal disturbances and thundery weather. Bravo Vorticity, Bravo!

Certainly some excitement for the Southern UK storm enthusiasts for the next few days. And although this will likely become a nowcasting situation keeping guard of the window, hopefully those who have not seen any proper thundery weather yet will get a storm. Though does look as though it could be a hit and miss situation. Flooding will certainly be something to watch as well (which could cause some travel disruption for places, particularly towards the South).

Quite like, also, that it looks as though the deep Atlantic Low and the shallow French Low are going to be racing each other to see who can reach the UK first:

But there can only be one winner:

(To be fair, though, both Low Pressure systems do end up joining forces with each other towards the weekend).

Edited August 12, 2015 by DiagonalRedLine
To correct image attachment error

[DavidHamble57]

@Vorticity0123: Yet another brill post from you, and an excellent breakdown regarding frontal disturbances and thundery weather. Bravo Vorticity, Bravo!

Certainly some excitement for the Southern UK storm enthusiasts for the next few days. And although this will likely become a nowcasting situation keeping guard of the window, hopefully those who have not seen any proper thundery weather yet will get a storm. Though does look as though it could be a hit and miss situation. Flooding will certainly be something to watch as well (which could cause some travel disruption for places, particularly towards the South).

Quite like, also, that it looks as though the deep Atlantic Low and the shallow French Low are going to be racing each other to see who can reach the UK first:

image.jpg

(Charts used from latest GFS 06Z run)

But there can only be one winner:

(To be fair, though, both Low Pressure systems do end up joining forces with each other towards the weekend).image.jpg

 

 

Still has warm air over the UK though so it will probably be storms and not frontal rain I would of thought.

[BlueHedgehog074]

Still has warm air over the UK though so it will probably be storms and not frontal rain I would of thought.

Yeah, hopefully.

Edited August 12, 2015 by DiagonalRedLine

[stodge]

http://modeles.meteociel.fr/modeles/gfs/runs/2015081212/gfs-0-168.png?12

 

Well now, a significant Scandinavian HP - the first for some time and an ESE'ly flow over the North Sea. The British Isles in a classic col between the pressure systems.

 

There are probably two ways from this - one is for lower pressure to squeeze through from NW and SE to create a new LP over the British Isles - the other is for the two HP areas to win out with perhaps the Azores HP becoming the more dominant feature with a ridge to Scandinavia.

 

The 12Z OP goes down the latter route but by no means a done deal at this stage.

[summer blizzard]

GFS and GEM have high pressure gaining ground through days 5-10.

 

Euro has low pressure winning out by day 9.

 

[johnholmes]

The NOAA output this evening does lend some indication of +ve heights to NE of UK perhaps developing into something more settled. Just where any surface high would settle IF the trend continues is not that easy to pin down. I would imagine NE of the UK and how much ridging into the UK would not be clear for a week or so? link to NOAA below

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

Also it needs all 3 anomaly charts to show similar ideas before it is a 'done thing'. By Saturday we should know one way or the other for the following weekend or rather 2-3 days before the weekend.

[legritter]

The NOAA output this evening does lend some indication of +ve heights to NE of UK perhaps developing into something more settled. Just where any surface high would settle IF the trend continues is not that easy to pin down. I would imagine NE of the UK and how much ridging into the UK would not be clear for a week or so? link to NOAA below

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

Also it needs all 3 anomaly charts to show similar ideas before it is a 'done thing'. By Saturday we should know one way or the other for the following weekend or rather 2-3 days before the weekend.

Been following some north america /canada weather chat and low pressure seems like setting in around Hudson bay area so could very well see a rise of pressure to our N/east in about a weeks time ,thanks for posting the above link another good thing about our weather forum ,wish we had this 40 yrs ago , never realy boring this weather hobby ,take care all .

[knocker]

The NOAA output this evening does lend some indication of +ve heights to NE of UK perhaps developing into something more settled. Just where any surface high would settle IF the trend continues is not that easy to pin down. I would imagine NE of the UK and how much ridging into the UK would not be clear for a week or so? link to NOAA below

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

Also it needs all 3 anomaly charts to show similar ideas before it is a 'done thing'. By Saturday we should know one way or the other for the following weekend or rather 2-3 days before the weekend.

 

And some support for this

http://www.tropicaltidbits.com/

[knocker]

The GEFS anomalies this morning continue the theme of building heights to the NE. As JH has mentioned much depends on the position and orientation of the surface HP. And I might add the longevity of the position. Thus by Tuesday the HP is well established with cool stream lines from a southerly quadrant over the UK but dry.

This continues until Friday with the added complication of an upper trough just to the west of the UK running south. This may well bring about a reversal of the norm and introduce the worst weather to the south.

 

Onwards to Sunday and the HP flattens out, a weak trough France and the UK in no mans land. Best wait and see how this develops.

 

All in all not bad news even if it just breaks the dead lock and gives the north a chance.

http://www.tropicaltidbits.com/

Edited August 13, 2015 by knocker

[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 WEDNESDAY AUG 12TH 2015

 

THE CURRENT GENERAL SITUATION. A thundery Low will move North up the eastern side of the UK today and tomorrow with a fresher Westerly flow following late tomorrow.

 

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

 

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

 

THE GFS JET STREAM FORECAST The GFS Jet Stream Forecast shows the flow mving North over the UK cutrrently before the main arm runs SE towards Northern Spain in a couple of days time. It then weakens and becomes almost non existent for quite a while mid run before reverting to crossing the Atlantic to lie close to Western and Southern Britain late in the period.

 

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

 

GFS OPERATIONAL The GFS Operational Run today shows a thundery Low moving North to become absorbed by a Low to the North of the UK before the weekend. A Westerly but slack airflow becomes established for a time as High pressure builds strongly to the NE of Britain with winds switching SE. Low pressure is then forced SE towards SW areas of the UK keeping the most unsettled conditions here while the North and East close to the HIgh to the NE stay quite dry and occasionally warm. Late in the run the situation remains very benign with further Low pressure close to Southern England with rain or showers at times here with the best weather still in the North.

 

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

 

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

 

THE GFS CONTROL The GFS Control Run today also shows High pressure developing to the North and NE next week replacing the existing Low pressure with new ones to the West and SW for much of the period. The best and driest conditions look most likely in the North and NE while the SW and South in general become most at risk of rain or showers in average temperatures though by the same token some short warmer and drier interludes too.

 

THE GFS CLUSTERS(14 Days) The GFS Clusters this morning are generally quite poor today if it's fine and warm weather your looking for two weeks from now. The majority of members opt for the UK to lie under a trough of one sort or another fed down from the NW with High pressure favoured to lie to the East or NE of the UK.

 

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 is rather better than GFS in as much as once the current thundery Low expires to the North pressure builds across the UK from both the NE and SW. This finger of slack winds known as a 'col' area will most likely maintain benign conditions with any rain restricted to the far NW and showers to the far SE.

 

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

 

THE FAX CHARTS The Fax Charts this morning show the same thundery Low moving North with it's attendant warm and humid unstable airmass ahead of fresher air moving in from the West with airflow patterns becoming slack over the weekend and early next week with sunny spells and just a scattering of showers in places.

 

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

 

GEM GEM today shows an equally strong build of pressure to the North and NE of the UK once this thundery Low fills up and moves away North by the weekend. Slack winds for a time settle SE for many areas next week with Low pressure fed down into the SW approaches at times and delivering a stronger risk of rain or thundery showers to Southern and Western areas later next week.

 

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

 

NAVGEM NAVGEM prefers to hold on to a very slack pattern next week with High pressure to the NE and light winds and weak Low pressure close to the West with the risk of scattered showers maintained across the UK in luke warm conditions at times.

 

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

 

ECM ECM this morning also shows a lot of slack pressure gradients in the vicinity of the UK over the next 10 days. The current thundery Low moves away North and pressure builds then to the NE and from the SW. As with UKMO a finger of High pressure will likely lieacross the UK ensuring a lot of dry weather and just scattered light showers. With time some erosion of High pressure into slack Low pressure is shown with a greater threat from rain and showers likely to develop towards the end of the run.

 

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

 

ECM 10 DAY MEAN The ECM 10 Day Mean Chart  from last evening gives little clue as to where we will lie synoptically in 10 Days time as the chart itself shows hardly an isobar in sight no doubt made up of a lot of indecision between members between where and  how High or Low pressure will lie in relation to the UK. The most likely scenario thous is a benign pattern similar to what the operationals of many mebers show this morning.

 

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

 

NOTABLE TREND CHANGES FROM PREVIOUS RUNS The models are trending towards  a strong build of pressure over NE Europe which on this morning's charts show varying degree of influence to the weather over the UK.

 

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 95.7 pts followed by UKMO at 95.3 pts and GFS at 94.4pts. At 5 days ECM is stll king at 85.4 pts followed by UKMO at 84.4 and GFS at 83.5 pts. Then at 8 Days ECM still leads at 58.9 pts over GFS's 55.3 pts. Finally at Day 10 ECM leads GFS at 39.5 pts to 35.8 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 biggest concistency between all of the output this morning is the build of pressure to the NE next week. One would think this would give us a very good chance of bringing the UK into a sustained period of very warm and settled weather but alas this one looks to be rather different. The problem is that synoptic pressure patterns elsewhere in the Northern hemisphere do not permit it to build a substantial ridge SW across the UK to link to our Azores High without intervention from lower pressure either feeding down from the NW and linking with other lower pressure to the SE leaving the UK under the technical term when we're between two High's and two Low's known as a 'Col' area. These are notoriously difficult to pin down actual weather details under as influences from both the High and Low pressure can occur within them. On this occasion I have looked at the whole output as a whole and I think I can determine that there will be a lot of dry weather around over the next few weeks as that High to the NE doesn't look like going anywhere fast. The problems lie in determining the extent and influence Low pressure has either from the SW later or NW as the blocking High to the NE sends them on a SE trajectory close to the UK and I'm afraid the jury is out on that one at present. One thing I can note is 850 temperatures are never overly high through the next few weeks so we have to rely on surface heating from prolonged sunshine to warm things up and that should happen on occasion for many so while I can't foresee any particularly hot late Summer weather coming up again this morning the conditions could well be acceptable for many much of the time with just scattered showers within a generally benign picture overall far more likely.

 

Next update from 09:00 Friday Aug 14th 2015

[summer blizzard]

Days 8-10 undecided at the moment. Euro and GFS have low pressure just about winning, GEM has the high standing firm.

[Northern Sky]

I'd like to order the GFS 06z run for my trip to the highlands next week . Certainly no heatwave but compared to the dreadful weather they have experienced up there most of the summer it's a definite improvement.  Having followed the output closely for a while I think I'm right in saying (the EC32 Knocker?) that the relaxing of the trough to the north west has been signposted for a while for next week. Difficult to predict sunshine amounts but hopefully no deluge and fingers crossed for some useable outdoor weather at least.

[cheeky_monkey]

Looks set fair after Friday right to the end of the month...for me the GFS is almost perfection for this time of the year..dry and warm with low humidity

[knocker]

I'd like to order the GFS 06z run for my trip to the highlands next week . Certainly no heatwave but compared to the dreadful weather they have experienced up there most of the summer it's a definite improvement.  Having followed the output closely for a while I think I'm right in saying (the EC32 Knocker?) that the relaxing of the trough to the north west has been signposted for a while for next week. Difficult to predict sunshine amounts but hopefully no deluge and fingers crossed for some useable outdoor weather at least.

 

Yes correct NS but not really with this evolution but this could be better for your hols. fingers crossed. Not that hot but settle for warm and dryish/

[knocker]

The GEFS anomalies tonight on the 18th have the HP cell orientated virtually N/S over Scandinavia with the trough relegated west and a weak low pressure area France  So Scotland should be fine and dry in the SE airflow but the weather far more uncertain in the south..

 

Thereafter there is some juggling for position with the trough moving a tad east but much the same surface scenario applies by the 21st.

 

By the 24th the HP to the NE is considerable weaker with the trough to the west stretching down to the SW approaches. Surface wise quite a confused picture with weak HP to the NE and weak LP to the NW and the Azores HP shunted away to the south west.

 

All a bit messy really but temps not bad and pretty dry and under this scenario the north could well a few days of decent weather.

http://www.tropicaltidbits.com/

 

Edited August 13, 2015 by knocker